application for the reassessment of a hazardous substance

www.epa.govt.nz

Application for the reassessment of a hazardous substance under Section 63 of the Hazardous Substances and New Organisms Act 1996

Name of substance: Dichlorvos and its formulations

Application number: APP202097

Applicant: Chief Executive, Environmental Protection Authority

SUPPLEMENTARY REPORT B

Human Health Risk Assessment

Supplementary Report B – Human Health Risk Assessment (APP202097) Page 2

Contents

Toxicological endpoints for human health risk assessment ............................................................ 4

Acceptable operator exposure level (AOEL) ...................................................................................... 4

Dermal absorption factor ..................................................................................................................... 5

Inhalation absorption factor ................................................................................................................. 5

Risk quotients ...................................................................................................................................... 5

Agricultural, horticultural and biosecurity uses ................................................................................. 5

Uncertainties associated with the operator risk assessment of dichlorvos......................................... 6

Operator exposure for ground boom and airblast application ............................................................ 6

Operator exposure for aerial application ............................................................................................. 7

Outdoor re-entry worker exposure ...................................................................................................... 8

Bystander risks for ground boom, airblast and aerial application ..................................................... 13

Operator exposure to fogging application in greenhouses, mushroom houses and for biosecurity

purposes ........................................................................................................................................... 18

Operator exposure to pesticides manually sprayed in greenhouses ................................................ 20

Operator exposure to pesticides sprayed by fully automatic equipment in a greenhouse ............... 21

Operator exposure from greenhouse application using a trolley boom sprayer ............................... 21

Operator exposure to pesticides sprayed by semi-automatic equipment in a greenhouse .............. 21

Operator exposure to pesticides sprayed by fully automatic equipment in mushroom houses ....... 25

Operator exposure when using dichlorvos for treating cut flowers ................................................... 26

Operator exposure when using dichlorvos for post-harvest treatment of asparagus ....................... 27

Operator exposure when dipping flowers for biosecurity purposes .................................................. 29

Re-entry worker risks in treated greenhouses and mushroom houses ............................................ 30

Re-entry worker risks in treated greenhouses .................................................................................. 31

Re-entry worker risks in mushroom houses ..................................................................................... 38

Re-entry worker risks when using dichlorvos for post-harvest treatment of asparagus ................... 41

Re-entry worker risks when using dichlorvos for treating cut flowers ............................................... 42

Bystander exposure to dichlorvos from application in greenhouses ................................................ 43

Bystander and resident exposure and risk assessment following application to mushroom houses

and other buildings where dichlorvos has been used ....................................................................... 45

Dichlorvos human health risk assessment – public health and residential use scenarios ......... 47

Application in closed industrial spaces ............................................................................................. 47

Enclosed space fogging using ready to use (RTU) aerosol cylinders with automatic/remote

application ......................................................................................................................................... 47

Enclosed space fogging using RTU aerosol cylinders with manual application ............................... 52

Enclosed space fogging using EC solutions with automatic/remote application (exposure only at

mixing/loading) .................................................................................................................................. 60

Enclosed space fogging using EC solutions with manual application .............................................. 62

Enclosed space applications of EC solutions with high pressure handwand ................................... 68

Enclosed domestic space applications of RTU aerosol cans ........................................................... 72

Domestic application of RTU spray mixes to surfaces and crevices ................................................ 73

Public space manual fogging applications ........................................................................................ 75

Re-entry worker risk assessment – indoor use scenarios ................................................................ 79

Re-entry worker risk assessment for enclosed industrial spaces ..................................................... 79

Bystander and resident exposure and risk assessment ................................................................... 85

Bystander and resident risks from treatment of enclosed industrial buildings .................................. 85

Resident risks from enclosed space application of RTU aerosol cans ............................................. 85

Bystander and resident risks from outdoor domestic application of dichlorvos ................................ 88

Bystander risks from outdoor application of dichlorvos in public spaces.......................................... 91

References………. ................................................................................................................................ 95

Toxicological endpoints for human health risk assessment

Acceptable operator exposure level (AOEL)

The human health risk assessment is based on a comparison of predicted exposures of operators, re-

entry workers, bystanders and residents with a health based exposure guideline value which is not

expected to result in adverse health effects.

For pesticides, the relevant exposure guideline value is the acceptable operator exposure level

(AOEL). The AOEL is intended to define a level of daily exposure throughout a spraying season, year

on year, below which no adverse health effects would be expected. It is also appropriate to use the

AOEL to assess risks to re-entry workers, bystanders and residents where there is a potential for

repeated exposures to occur.

The AOEL is normally derived by applying an uncertainty factor to a no observed adverse effect level

(NOAEL) from a toxicological study in which experimental animals were dosed daily for 90 days or

longer, or from relevant human epidemiological data. The uncertainty factor is intended to take into

account the variability and uncertainty that are reflected in possible differences between test animals

and humans and variability within the human population.

For dichlorvos, the most relevant toxicological endpoint for risk assessment is inhibition of

cholinesterase (ChE) activity. EPA staff have adopted the Australian Pesticides and Veterinary

Medicine Authority (APVMA)’s approach and based the AOEL on a 28 day oral study in human

volunteers (Rider, 1967; original not sighted; APVMA, 2008). The NOAEL in this study was 1.0

mg/day, based on toxicologically significant inhibition of plasma ChE active at doses of 1.5 mg/day

and higher. This study was considered highly suitable by the APVMA because it demonstrated both a

NOAEL and a lowest observed adverse effect level (LOAEL) for plasma ChE inhibition and was

performed with human subjects, eliminating uncertainty associated with extrapolating from findings in

experimental animals.

Assuming an average body weight (bw) of 70 kg and 100% oral absorption of dichlorvos, the NOAEL

is 0.014 mg/kg bw/day. An uncertainty factor of 10 is applied to the NOAEL to account for individual

variability. Therefore the AOEL is:

𝑁𝑂𝐴𝐸𝐿×𝐴𝐹

𝑈𝐹 =

0.014×1.0

10 = 0.0014 mg/kg bw/day

Where:

AF = absorption factor (1.0 [100%])

UF = uncertainty factor

More detail on the selection of the AOEL can be found in the Review of Toxicology and HSNO

Classifications 6 and 8 conducted for the original dichlorvos application (Supplementary Report A).

Dermal absorption factor

The APVMA (2008) and European Food Safety Authority (EFSA; 2006) both identified a dermal

absorption factor of 30% for dichlorvos, based on in vivo rat data. In a study by Jeffcoat (1990;

original not seen; APVMA, 2008), the level of skin absorption of dichlorvos in rats was 22-30% when

dichlorvos was applied to 12 cm2 of skin at 3.6, 36 or 360 µg in a total volume of 100 µL. Absorption

occurred within the first 10 hours of exposure and a substantial proportion (28-55%) of dichlorvos was

found to evaporate from the skin surface following application. The APVMA noted that in the absence

of this evaporation it is plausible that close to 100% of the applied dose would have been absorbed,

but this scenario was considered unlikely under actual use conditions.

Inhalation absorption factor

The APVMA concluded that a 70% inhalation absorption factor would be used for risk assessment.

This was based on a study (Kirkland, 1971; original not seen) that demonstrated that at dichlorvos

concentrations of 0.1-2.0 mg/m3, pigs retained 15-70% of the inhaled dichlorvos (APVMA, 2008).

However, the US EPA used an inhalation absorption factor of 100%. Based on the lack of available

information, an absorption factor of 100% has been applied in the risk assessment.

Risk quotients

The human health risks from exposure to dichlorvos are evaluated through the calculation of Risk

Quotient (RQ) values. RQs are calculated by dividing the estimated exposure by the AOEL value. An

RQ value of > 1 indicates that exposure is above the AOEL and potentially of concern. The greater

the RQ the greater the exceedance of the AOEL.

Agricultural, horticultural and biosecurity uses

Quantitative estimates of exposure are needed in order to carry out a risk assessment. The EPA has

previously requested that stakeholders submit any operator, re-entry and bystander exposure data

that are available for the use of dichlorvos. None has been provided to the EPA, so the EPA has used

models and studies used by other regulators to determine the predicted exposure for New Zealand

use patterns.

The EPA request that anyone with quantitative exposure data for operators, re-entry workers

and bystanders provide this to the EPA

Uncertainties associated with the operator risk assessment of dichlorvos

The EPA note that due to the volatile nature of dichlorvos, the inhalation estimates for the operator

exposure for outdoor application may be underestimates. It is noted that in its review of dichlorvos the

APVMA considered this issue and increased the inhalation component of one of the Pesticide Handler

Exposure Database (PHED) exposure scenarios to account for this. The EPA has not done this for

the agricultural use scenarios for dichlorvos as we are not able to quantify how much the inhalation

component should be increased for these use patterns.

The EPA have also assumed that operator exposure would be reduced by 95 % due to wearing

chemical resistant coveralls and study footwear (this is the default value in the operator exposure

model used by the EPA). This is a higher percentage than that assumed by the APVMA, who

assumed that coveralls reduce exposure by 80 % based on empirical studies. The coveralls

considered by the APVMA appear to represent polyester coveralls which could be expected to be less

protective than other chemical resistant coveralls. Despite this, the EPA do have concerns about

assuming that chemical resistant coveralls would offer a 95 % exposure reduction factor for dichlorvos

given its physico chemical properties.

Any results of the operator risk assessment should therefore be viewed with caution as they may

potentially underestimate both inhalation and dermal exposure.

Operator exposure for ground boom and airblast application

The UK Chemicals Regulation Directorate (CRD) version of the German Federal Biological Research

Centre for Agriculture and Forestry (BBA) operator exposure model was used to calculate exposure

(Chemicals Regulation Directorate, 2011). All of the exposure data and assumptions for this model

are published online (Chemicals Regulation Directorate, 2011a). The EPA estimated the exposure of

an operator and evaluated the impact of wearing different forms of Personal Protective Equipment

(PPE) using exposure reduction factors which have been empirically derived (Chemicals Regulation

Directorate, 2011a). Where possible the work rates (ha/day) were taken from feedback received from

the call for information in September 2011 and a further request in July 2014. Where this information

was not provided, the following work rates were assumed for boom, airblast and knapsack spraying:

Boom 20 ha/day

Airblast 8 ha/day

Knapsack 1 ha/day

Exposure was estimated during mixing/loading and application assuming the following PPE levels:

Full PPE (chemical resistant coveralls, sturdy footwear (95 % protection), hood and visor (95

% protection) and gloves (90 % protection)) during mixing, loading and application (excluding

respirator);

Full PPE (chemical resistant coveralls, sturdy footwear, hood and visor and gloves) during

mixing, loading and application (same protection factor as above) including either a FFP2SL

or P2 respirator (95 % protection).

These protection factors are the default values for this model. The exception is that the protection

factor for gloves has been changed from 99 % to 90 % to account for the physico chemical properties

of dichlorvos. This is the same protection factor as has been used by the APVMA. Due to the

relatively high toxicity of dichlorvos only these higher protection levels have been included in the risk

assessment as clearly the risks from lower levels of protection will be higher. Predicted exposures are

compared to the Acceptable Operator Exposure Level (AOEL).

Operator exposure for aerial application

This was estimated using the same approach used for ground boom/airblast application but only

considering mixing and loading exposure, as it was assumed that exposure of the pilot during

application would be minimal. Predicted exposures are compared to the Acceptable Operator

Exposure Level (AOEL).

Table 1 Results of the operator risk assessment for ground boom, airblast, knapsack and aerial application

Crop Application

method

Application

(g /ha)

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

Persimmons Airblast 2400 3 7 3 19

Persimmons Airblast 3078 4 7 3 24

Tamarillos Airblast 2000 4 7 8 41

Tamarillos Airblast 1600 5 2 8 33

Berryfruit Airblast 798 4 7 8 16

Clover seed

Boom 220 2 7 50 12

Ornamentals Boom 800 4 7 20 18

Brassica Boom 855 1 3 3

Silver beet and

spinach

Boom 855 1 3 3

Cucurbits Boom 855 1 10 9

Crop Application

method

Application

(g /ha)

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

Salad leaf Boom 855 1 5 5

Asian greens Boom 855 1 5 5

Berryfruit Boom 798 4 7 20 18

Brassica Boom 750 4 7 20 17

Strawberry Boom 800 1 3 3

Kumara Boom 570 1 40 25

Herbs Boom 855 1 5 5

Lettuce Boom 855 1 5 5

Onions Boom 912 2 5 55 55

Cucurbits Aerial 855 1 50 31

Lettuce Aerial 855 1 50 31

Brassicas Aerial 855 1 50 31

Passionfruit Knapsack 1026 1 1 72

Passionfruit Knapsack 1000 3 7 1 71

Conclusions on the operator risk assessment for ground boom, airblast, knapsack and aerial

application

The results of this risk assessment indicate that even with full PPE and RPE operator exposure is

always in exceedance of the AOEL. This is of particular concern given the uncertainties that exist in

the risk assessment.

Outdoor re-entry worker exposure

The re-entry worker exposure for outdoor application is based on dermal exposure through contact

with foliar residues only; inhalation exposure or exposure to other contaminated surfaces (e.g. soil) is

not accounted for. It is recognised that this may underestimate the exposure of re-entry workers;

however, the EPA was not able to determine how this exposure should be assessed. Therefore,

caution should be applied when interpreting the risk quotient values as these may be potential

underestimates.

Dermal exposure following re-entry intervals are calculated using the formula below which was

developed by other regulators (Chemicals Regulation Directorate, 2010b EUROPOEM, 2002).

Re-entry worker dermal exposure = DFR x TC x WR x AR x DA

These parameters with default values where they exist are:

DFR is the Dislodgeable Foliar Residue (0.5 µg/cm2 per kg a.i./ha)

TC is the Transfer coefficient for the anticipated activity being performed (cm2/hr, defaults in

Table 1)

WR is the work rate per day (8 hrs/day)

AR is the Application rate (kg/ha)

BW is the Body weight (70 kg)

DA is the dermal aborption, expressed as a proportion (0.3 i.e. 30 %).

The DFR value of 0.5 µg/cm2 per kg a.i./ha was calculated based on the study of Casida et al (1962)

which found that only 5 % of the application rate remains on the treated leaf surface 20 minutes after

application. It is recognised that there are some limitations in using data from one study; however, this

study was the only one available to the EPA. It is noted that data from this study were used by the

Australian Pesticides and Veterinary Medicines Authority (APVMA) in their risk assessment of

dichlorvos. Again caution should be used when interpreting the results of the risk assessment and any

results should be viewed as potential underestimates.

Transfer coefficients

Transfer coefficients refer to the amount of contact between a re-entry worker and foliage. These are

regarded as independent of the active ingredient/product used and depend on the crop type and the

activity that the re-entry worker is carrying out (EUROPOEM, 2002). In the absence of data, the EPA

used the values in Table 2 which have been obtained from overseas regulators.

Table 2 Default transfer coefficients used for the re-entry worker risk assessment

Crop Activity

Transfer

coefficient

(cm2/hr)

Source of transfer coefficient

Vegetables Reach/Pick 2500 (EUROPOEM, 2002)

Fruit from

Search/Reach/Pick 4500 (EUROPOEM, 2002)

Crop Activity

Transfer

coefficient

(cm2/hr)

Berries Reach/pick 3000 (EUROPOEM, 2002)

Ornamentals Cut/Sort/Bundle/Carry 5000 (EUROPOEM, 2002)

These transfer coefficients all assume that re-entry workers are wearing long trousers and long

sleeved T shirts and are not wearing gloves. It is recognised that re-entry workers may not always

wear this level of clothing therefore; caution should be applied when interpreting the results of the risk

assessment.

Impact of wearing gloves

When appropriate information is available, the transfer coefficients suggested in the EUROPOEM

document have been divided between hand exposure and rest-of-body exposure. From this

information the exposure of re-entry workers wearing chemical resistant gloves was estimated. In the

absence of other information, the EPA assumed that chemical resistant gloves reduce hand exposure

by 90 %, a default used by other regulators (California Environmental Protection Agency, 2010). Such

revised TC are shown in Table 3. The impact of wearing gloves cannot be calculated for some

crops/activities since TC attributable to hands only are not available.

Table 3 Impact of gloves on re-entry worker transfer coefficients

Transfer

coefficients for

workers not

wearing gloves

(cm2/hr)

Transfer

coefficients

attributable

to hand

exposure

(cm2/hr)

attributable to hand

exposure assuming

90% reduction in hand

exposure due to

wearing gloves

(cm2/hr)

Transfer

coefficients

for re-entry

workers

wearing

gloves

(cm2/hr)

Vegetables 2500 2200 220 520

Ornamentals 5000 4000 400 1400

Berries 3000 2500 250 750

Fruit trees 4500 2500 250 2250

Multiple applications

The effect of multiple applications on re-entry worker exposure was estimated. The DFR is the only

parameter that is altered by multiple applications. The EPA estimated the DFR immediately following

the nth application (DFRn(a)) by assuming first order dissipation and using the following equation

derived from the FOCUS guidance (FOCUS, 2010):

DFRn(a) = DFRsingle-application x (1-e

-nki)/(1-e

Where n is the number of applications

k is the rate constant for foliar dissipation (4.07734 based on a half-life of 0.17 days) from US EPA RED (also cited in APVMA, pp 72-73 of APVMA review). i is the interval between applications (days)

The reduction in DFRn(a) over time after last application is then given by:

DFRn(a)+t = DFRn(a) x e

where t is days since last application. It should however, be noted that due to the short half-life of

dichlorvos on foliage including the impact of multiple applications did not have any significant impact

upon predicted exposure.

Risks to re-entry worker after 24 hours

The risks to re-entry workers 24 hour after the final treatment was estimated using the following

equations.

when t = 1 (24 h post-treatment)

The absorbed dose is calculated by:

DFRn(a) x e

-k x C x D

Where C = TC x WR x AR/BW D = Dermal absorption Therefore the risk to re-entry workers 24 h after the final application is given by the following equation:

RQ = DFRn(a) x e

-k x C x D/AOEL

Where AOEL = Acceptable Operator Exposure Level

Table 4 Results of the re-entry risk assessment for ground boom, airblast and aerial application

Crop Application

method

Application

(g /ha)

Frequency

Interval

(days)

RQ re-entry

worker 24 h after

application

(no gloves)

RQ re-entry

worker 24 h

application

(gloves)

Persimmons Airblast 2400 3 7 2.2 1.1

Persimmons Airblast 3078 4 7 2.9 1.4

Tamarillos Airblast 2000 4 7 1.9 0.9

Tamarillos Airblast 1600 5 2 1.5 0.7

Berryfruit Airblast 798 4 7 0.5 0.1

Clover seed

Boom 220 2 7 0.0 0.0

Ornamentals Boom 800 4 7 0.8 0.2

Brassica Boom 855 1 0.4 0.1

Silver beet

and spinach

Boom 855 1 0.4 0.1

Cucurbits Boom 855 1 0.4 0.1

Salad leaf Boom 855 1 0.4 0.1

Asian greens Boom 855 1 0.4 0.1

Berryfruit Boom 798 4 7 0.5 0.1

Brassica Boom 750 4 7 0.4 0.1

Strawberry Boom 800 1 0.5 0.1

Kumara Boom 570 1 0.3 0.1

Herbs Boom 855 1 0.4 0.1

Lettuce Boom 855 1 0.4 0.1

Onions Boom 912 2 5 0.5 0.1

Cucurbits Aerial 855 1 0.4 0.1

Lettuce Aerial 855 1 0.4 0.1

Crop Application

method

Application

(g /ha)

Frequency

Interval

(days)

RQ re-entry

worker 24 h after

application

(no gloves)

RQ re-entry

worker 24 h

application

(gloves)

Brassicas Aerial 855 1 0.4 0.1

Passionfruit Knapsack 1026 1 1 0.5

Passionfruit Knapsack 1000 3 0.9 0.5

Conclusions on the re-entry risk assessment for ground boom, airblast and aerial application

The results of the risk assessment indicate that for the majority of use scenarios a 24 hour re-entry

interval is sufficient to manage the risks. The exception is use at higher rates e.g. on persimmons and

tamarillos where gloves would be required to be worn for re-entry after 24 hours. Exposure to re-entry

workers from use on persimmons at both rates is still marginally above the AOEL even when wearing

gloves 2 days after the application, however, given the conservative nature of the dermal risk

assessment, the short half-life of dichlorvos in the environment and the magnitude of the exceedance,

wearing gloves on the second day after application should be sufficient to manage any risks for

persimmons. Caution should however; be taken when interpreting these results as they do not

consider any impacts from inhaling volatised dichlorvos, which means any results are potential

underestimates.

Bystander risks for ground boom, airblast and aerial application

The bystander risk assessment is based on exposure of a toddler to surfaces contaminated with

dichlorvos residues 8 m (default) away from the edge of the area to which the substance was applied

(i.e. exposure is to surfaces on which spray has deposited; not through direct contact with the spray).

Exposure to airborne dichlorvos was not estimated. It is recognised that this may underestimate

exposure, however, the EPA was not able to determine how this should be modelled. Therefore,

caution should be used when interpreting the risk quotient values as these may be potential

underestimates.

Exposure is estimated using the equations from the UK Chemical Regulation Directorate (CRD) which

account for dermal exposure, hand-to-mouth exposure and object-to-mouth exposure (Chemicals

Regulation Directorate, 2010a). In addition, incidental ingestion of soil is taken into account using a

modified exposure equation from the United States Environmental Protection Agency (USEPA)

(USEPA, 2007).

Spray drift was estimated using models specific to the type of application equipment. For pesticides

applied by ground boom or airblast sprayer, the AgDrift model is used. The model is based on data

from a series of field trials carried out in the United States (APVMA, 2009b) in which the percentage

of the application rate deposited is plotted against distance from the area of application. These

deposition curves were taken from the Australian Pesticides and Veterinary Medicines Authority

(APVMA) website (APVMA, 2010). For ground boom applications there are deposition data for the

following scenarios which represent the 90th percentile of the spraydrift data collected:

High boom (1.27 m above the ground) fine droplets

Low boom (0.5 m above the ground) fine droplets

For airblast application the EPA has used the sparse orchard dataset on the APVMA website (Sparse

orchards or small trees) which represents the 95th percentile of the spraydrift data collected.

Spraydrift deposition from aerial application of dichlorvos to cucurbits, lettuce and brassicas is

estimated using the AGDISP model along with appropriate New Zealand input parameters obtained

through prior discussion with the New Zealand Agricultural Aviation Association (NZAAA). The

specific inputs used in the AGDISP model can be seen in Annex 1.

Children’s dermal exposure

Systemic exposures via the dermal route were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE (d) = AR x DF x TTR x TC x H x DA BW

Where: SE(d) = systemic exposure via the dermal route AR = field application rate (input into this equation as ug/cm

DF = spray drift value TTR = turf transferable residues – the USEPA default value of 5 % was decreased by 95 %

(5 % x 0.05 = 0.25 % or 0.0025 as a fraction) to account for the rapid volatisation of dichlorvos based on the study by Casida et al (1962).

TC = transfer coefficient – the standard USEPA value of 5200 cm2/h was used for the

estimate H = exposure duration for a typical day (hours) – this was assumed to be 2 hours which

matches the 75th percentile for toddlers playing on grass in the USEPA Exposure

Factors Handbook DA = percent dermal absorption (0.3 i.e. 30 %) BW = body weight – 15 kg which is the average of UK 1995-7 Health Surveys for England

values for males and females of 2 and 3 yrs

Children’s hand-to-mouth exposure

Hand-to-mouth exposures were calculated using the following equation (Chemicals Regulation

Directorate, 2010a):

SE(h) = AR x DF x TTR x SE x SA x Freq x H

BW Where: SE(h) = systemic exposure via the hand-to-mouth route AR = field application rate (input into this equation as ug/cm

DF = spray drift value

TTR = turf transferable residues – the USEPA default value of 5% derived from transferability studies with wet hands was decreased by 95 % (5 % x 0.05 = 0.25 % or 0.0025 as a fraction) to account for the rapid volatisation of dichlorvos based on the study by Casida et al (1962).

SE = saliva extraction factor – the default value of 50% will be used SA = surface area of the hands – the assumption used was that 20 cm

2 of skin area is

contacted each time a child puts a hand in his or her mouth (this is equivalent to the palmer surface of three figures and is also related to the next parameter (Freq))

Freq = frequency of hand to mouth events/hour – for short term exposures the value of 20 events/hour was used, this is the 90

th percentile of observations that ranges from 0 to

70 events/hour H = exposure duration (hours) – this was assumed to be 2 hours (as above) BW = body weight - 15kg (as above)

Children’s object-to-mouth exposure

Object to mouth exposures were calculated using the following equation (Chemicals Regulation

SE(o) = AR x DF x TTR x IgR

Where: SE(o) = systemic exposure via mouthing activity AR = field application rate (input into this equation as ug/cm

DF = spray drift value TTR = turf transferable residues – the default value of 20% transferability from object to

mouth(from the UK CRD) was decreased by 95 % (20 % x 0.05 = 1 % or 0.01 as a fraction) to account for the rapid volatisation of dichlorvos based on the study by Casida et al (1962) .

IgR = ingestion rate for mouthing grass/day – this was assumed to be equivalent to 25 cm2 of

grass/day BW = body weight - 15kg (as above)

Children’s incidental ingestion of soil

The approach that was used to calculate doses attributable to soil ingestion is (US EPA, 1997):

ADOD = AR (μg/cm

2) x DF x F (cm) x IgR (mg/day) x SDF (cm

BW (kg)

Where: ADOD = oral dose on day of application (μg/kg/day) AR = field application rate (input into this equation as ug/cm

DF = spray drift value F = fraction or residue retained on uppermost 1 cm of soil (%) (Note: this is an adjustment from

surface area to volume) SDF = soil density factor - volume of soil (cm

3) per milligram of soil

IgR = ingestion rate of soil (mg/day) BW = body weight (kg) Assumptions: F = fraction or residue retained on uppermost 1 cm of soil is 100 percent based on incorporation into top 1 cm of soil after application (1.0/cm)

IgR = ingestion rate of soil is 100 mg/day SDF = soil density factor - volume of soil (cm

3) per milligram of soil; to weight 6.7 x 10

cm3/mg soil

BW = body weight of a toddler is 15 kg (as above)

Total exposure

Total exposure will be calculated as the sum of the above equations:

∑ Exposure = SE (d) + SE (h) + SE (o) + ADOD

The impacts of multiple applications were quantitatively included by considering the half-life of dichlorvos and including the FOCUS calculations for predicting the impact of multiple applications. It should, however, be noted that this had no impact upon the predicted exposure due to the very short

half-life of dichlorvos. Risk quotients were estimated by comparing predicted exposure to the AOEL.

Table 5 Bystander risks from for ground boom, airblast and aerial application

Crop Application

method

Application

(g /ha)

Frequency Interval

(days)

Bystanders

Persimmons Airblast (sparse

orchard)

2400 3 7 3

Persimmons Airblast (sparse

orchard)

3078 4 7 4

Tamarillos Airblast (sparse

orchard)

2000 4 7 2

Tamarillos Airblast (sparse

orchard)

1600 5 2 2

Berryfruit Airblast (sparse

orchard)

798 4 7 1

Clover seed

Low ground boom

220 2 7 0.03

Ornamentals High ground boom

800 4 7 0.3

Brassica High ground boom

855 1 0.4

Silver beet and

spinach

High ground boom

855 1 0.4

Crop Application

method

Application

(g /ha)

Frequency Interval

(days)

Bystanders

Cucurbits Low ground boom

855 1 0.1

Salad leaf Low ground boom

855 1 0.1

Asian greens Low ground boom

855 1 0.1

Berryfruit High ground boom

798 4 7 0.3

Brassica High ground boom

750 4 7 0.3

Strawberry Low ground boom

800 1 0.1

Kumara High ground boom

570 1 0.2

Herbs Low ground boom

855 1 0.1

Lettuce Low ground boom

855 1 0.1

Onions High ground boom

912 2 5 0.4

Cucurbits Aerial 855 1 0.7

Lettuce Aerial 855 1 0.7

Brassicas Aerial 855 1 0.7

Conclusions on the bystander risk assessment for ground boom, airblast and aerial

application

The results of the risk assessment indicate that the predicted exposure to bystanders from ground

boom, airblast and aerial application are typically less than the AOEL. The exceptions are airblast

application to persimmons and tamarillos where controls such as downwind buffer zones could

potentially be used to manage the risks. Caution should be applied to these conclusions as they do

not consider the impact of volatisation of dichlorvos on exposure and hence are likely to

underestimate risks.

Operator exposure to fogging application in greenhouses, mushroom houses and for

biosecurity purposes

It was assumed that mixing and loading exposure for liquid concentrates for fogging would be the

same as mixing and loading exposure of a handheld sprayer using the UK version of the BBA model

(CRD, 2011). Data from the Pesticide Handler Exposure Database (PHED) were used to estimate

applicator exposure (see table 6) (data taken from the APVMA report). The protection factors of PPE

were assumed to be, sturdy footwear (95 % protection), hood and visor (95 % protection), gloves (90

% protection) and respirator (95 % protection) during mixing, loading and application.

Table 6. Exposure of an applicator to dichlorvos emulsifiable concentrates which are fogging

Dermal mg/kg a.s. Inhalation mg/kg a.s.

Head Hands Body

0.018 2.68 0.26 0.174

For Ready To Use (RTU) dichlorvos aerosol cylinders, the approach to estimating exposure has been

taken from the Australian Pesticides and Veterinary Medicines Authority (APVMA) review of

dichlorvos. For use of RTU aerosol cylinders in greenhouses or mushroom houses the EPA has

assumed that there will be no exposure apart from connection of cylinders i.e. that application of

dichlorvos is completely automatic. The EPA seeks feedback about the appropriateness of this

assumption.

The APVMA estimated dermal exposure to be 0.001 mL of dichlorvos per cylinder (equivalent to

0.0014 g dichlorvos; relative density, 1.425). Inhalation exposure could also result if some of the

dichlorvos evaporated into the 1 m3 personal air space around the operator’s breathing zone. If 0.005

ml of dichlorvos (wt. 7.1mg) was available for inhalation for 1 minute, then they would inhale 0.12mg

or 0.0017 mg/kg b.w. (70kg).

The estimated absorbed dose from dermal exposure after 1 cylinder change was estimated using the

following equations (assuming that gloves are worn)

SE(d) = CR x WR x DA x P BW SE(d) = 1.4 x 1 x 0.30 x 0.1 = 0.0006 mg/kg b.w.

Where: SE(d) = systemic exposure via the dermal route

CR = contamination rate [1.4 mg/cylinder change] WR = Work Rate [cylinder changes/day] DA = percent dermal absorption [30%] P = Penetration Factor for Clothing [gloves, 10%]

BW = body weight [70kg]

Inhalation exposure from cylinder changing

The estimated absorbed dose from inhalation exposure after 1 cylinder change would be:

SE(i) = CR x WR x IA x P BW SE(i) = 0.12 x 1 x 1 x 0.05 =0.000085 mg/kg b.w.

Where: SE(i) = systemic exposure via the inhalation route CR = contamination rate [0.12 mg/cylinder change] WR = Work Rate [cylinder changes/day, 1 and 5 respectively] IA = percent inhalation absorption [100%] P = Penetration Factor for RPE [0.05- i.e. assume that a respirator would reduce exposure by 95 %]

BW = body weight [70kg]

Therefore total exposure to an operator changing 1 cylinder wearing gloves and a respirator would be

0.0006 + 0.000085 = 6.85 x 10-4

mg/kg bw/day.

The EPA also estimated exposure for changing 5 cylinders as

6.85 x 10-4

mg/ kg bw/day x 5 = 3.425 x 10-3

mg/ kg bw/day

Risk quotients (see table 7) were estimated by comparing predicted exposure to the AOEL.

Table 7 Results of the operator risk assessment from fogging application in greenhouses, mushroom house

and for biosecurity purposes

Crop Formulation

Application

(g /ha)

unless

otherwise

specified

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

Cymbidium Liquid 1000 1 1 64

Mushrooms RTU aerosol

cylinder

1250 2 7 1.25

Mushrooms Liquid 1250 1 1.25 100

Crop Formulation

Application

(g /ha)

unless

otherwise

specified

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

Capsicum Liquid 1900 7 7 3 363

Tomatoes Liquid 1900 6 7 3 363

Aubergine Liquid 1900 6 7 1.25 151

Biosecurity Liquid 100 g/day 1 n/a 6.4

Greenhouse

crops - clean

Liquid

600 1 3

Conclusions of the operator risk assessment from fogging application in greenhouses,

mushroom house and for biosecurity purposes

The results of the risk assessment show that operator exposure to dichlorvos for fogging of the liquid

concentrate for all uses is above the AOEL. This is of particular concern given the uncertainties that

exist relating to this risk assessment.

Operator exposure to pesticides manually sprayed in greenhouses

Risks from spraying pesticides in greenhouses were estimated using the Dutch greenhouse model

(EFSA, 2008b). Where possible the work rates (ha/day) were taken from feedback received from the

call for information and a further request in July 2014. Where this information was not provided, it was

assumed that an operator would treat 1.25 hectare per day. Risks were assessed assuming that full

PPE (coveralls and gloves) would be worn by an operator with a respirator (it was assumed that a

respirator would reduce the inhalation exposure by 95 %). For dermal exposure it was assumed that

PPE (coveralls and gloves) would reduce operator exposure by 90 %. It should be noted that this is

different from the assumptions made about PPE for the other risk assessments, this is because 90 %

is the default used in the model and cannot easily be changed). Risk quotients were estimated by

comparing predicted exposure to the AOEL.

Operator exposure to pesticides sprayed by fully automatic equipment in a

greenhouse

Risks from automated spraying were estimated by using the mixing and loading component of the UK

version of the German BBA model (assuming that the operator won’t be in the greenhouse while the

product is being sprayed). This assumes that mixing and loading dichlorvos into a tank in a

greenhouse would be equivalent to exposure obtained from mixing and loading pesticides into a

sprayer mounted or pulled on a tractor. Where possible the work rates (ha/day) were taken from

feedback received from the call for information and a further request in July 2014. Where this

information was not provided, it was assumed that an operator would mix enough spray to treat 1.25

hectare per day. Risks were assessed assuming that full PPE (coveralls (providing 95 % protection)

and gloves (providing 90 % protection)) would be worn by the mixer/loader with a respirator (providing

95 % protection). PPE exposure reduction factors were the same as those used for outdoor

application. Risk quotients were estimated by comparing predicted exposure to the AOEL.

Operator exposure from greenhouse application using a trolley boom sprayer

The EPA were unable to obtain any exposure models for this application method. To assess operator

exposures the EPA used the exposure reduction factors suggested by Nuyttens et al. (2009) for novel

application equipment in a greenhouse assuming that use of a trolley boom sprayer would reduce

operator dermal exposure of an operator in a greenhouse by a factor of 60. Risk quotients were

estimated by comparing predicted exposure to the AOEL. PPE exposure reduction factors were the

same as those used for outdoor application. Risk quotients were estimated by comparing predicted

exposure to the AOEL.

Operator exposure to pesticides sprayed by semi-automatic equipment in a

greenhouse

In New Zealand, some greenhouses use application methods which are best described as semi-

automated. This kind of application method is largely automated during the pesticide release, as the

machinery travels up and down individual rows of crops. However, the machinery is required to be

moved manually between rows. Although an operator is not present when pesticide is being released

from the machinery, the operator will be exposed (through inhalation and dermal exposure) when

entering a confined location where pesticide has recently been released and moving the spray

equipment between crop rows.

There were no suitable models or datasets that the EPA was able to use to assess exposure for this

method of application. Exposure can be estimated for mixing and loading but not the application

phase. Exposure will lie somewhere between the values for fully automated application and trolley

boom application, but the EPA are not able to quantify where in this range this method of application

would be. Entering a greenhouse where this equipment has recently been used even for short periods

of time could potentially be a problem because of the low AOEL value. Since the EPA are not able to

carry out a risk assessment for this application method it is not currently possible to determine

whether this method of application is safe or not and what controls should be applied to manage risks.

Given the toxicity of dichlorvos the EPA would have very serious concerns about this method of

application continuing without additional data being provided to the EPA to confirm whether

exposures will be acceptable or not. In practice this data would have to be collected through

monitoring of occupational exposure. This would have to be carried out using an appropriate sampling

strategy, for example, following the USEPA test guidance for operator exposure studies, and any

analytical monitoring should also be carried out using a suitable analysis method, for example,

Occupational Safety and Health Administration (OSHA) method 62 (USEPA, 1996) (OSHA, 1986).

EPA staff note that monitoring of employees exposure to hazardous substances in the workplace is a

requirement under the HSE Act 1992 (S10(2)c) so it is possible that data may already be available.

The EPA requests that any relevant exposure monitoring data are submitted to inform the evaluation.

Results of the operator risk assessment for application in greenhouses using manual, trolley

boom and fully-automated equipment

Table 8 Results of the operator risk assessment for application in greenhouses using manual, trolley boom and fully-automated equipment

Crop Formulation

Application

(g /ha)

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

(Manual)

Quotient

with PPE

and RPE

(Trolley

Quotient with

PPE and RPE

(Fully

automated)

Glasshouse

flowers

(cymbidium)

Liquid

1000 1 1

62 1.8

Glasshouse

flowers

(cymbidium)

Liquid

1800 2 7 1

111 3.2

Capsicum Liquid 1320 7 7 3 245 7 2.9

Capsicum Liquid 1900 7 7 3 352 10 4

Tomatoes Liquid 1900 6 7 3 352 10 4

Tomatoes Liquid 1320 6 7 3 245 7 2.9

Aubergine Liquid 1320 6 7 3 245 7 2.9

Aubergine Liquid 1900 6 7 3 352 10 4

Lettuce Liquid 100 1 1 6 0.2 0.07

Conclusions of the operator risk assessment for application in greenhouses using manual,

trolley boom and fully-automated equipment

The results show that the predicted exposure of operators to manual application of dichlorvos in

greenhouses (using a handgun) is significantly above the AOEL. This is of particular concern given

the uncertainties that exist in the risk assessment. Given the magnitude of the exceedance, staff do

not believe that there is any way that risks from manual application could be managed through

controls.

Risks from application using a trolley boom, were also found to be unacceptable apart from at the

lower application rates (less than 200 g/ha). Risks from fully automatic application were generally

significantly lower provided full PPE and RPE are worn but predicated exposure was not necessarily

below the AOEL. Risks from fully automatic application could be managed, if the users were required

to wear full PPE and RPE, plus there were some limitation on how much they were allowed to handle

per day at approximately 1400 g/day.

Operator exposure to pesticides sprayed by fully automatic equipment in mushroom

houses

Risks from automated spraying were estimated by using the mixing and loading component of the UK

version of the German BBA model (assuming that the operator won’t be in the greenhouse while the

product is being sprayed). It was assumed that an operator would mix enough spray to treat 1.25

hectares per day. Risks were assessed assuming that full PPE (coveralls and gloves) would be worn

by the mixer/loader with a respirator. PPE exposure reduction factors were the same as those used

for outdoor application. Risk quotients were estimated by comparing predicted exposure to the AOEL.

Results of the operator risk assessment for application in mushroom houses using fully

automated equipment

Table 9 Results of the operator risk assessment for application in mushroom houses using fully automated

equipment

Conclusions of the operator risk assessment for application in mushroom houses using fully

automated equipment

The results indicate risks from application through fully automated equipment where operators are

wearing full PPE and RPE during mixing and loading could be managed through limiting the amount

of active ingredient that an operator is allowed to use per day to 1400 g.

Operator exposure when using dichlorvos for treating cut flowers

Risks from application to cut flowers were estimated using the mixing and loading component of the

UK version of the German BBA model (assuming that the operator only mixes and loads the product

and that they won’t be in the building while the product is being sprayed). PPE exposure reduction

factors were the same as those used for outdoor application. Risk quotients were estimated by

comparing predicted exposure to the AOEL.

Table 10 Results of operator risk assessment for cut flowers

Crop Application method Application rate

(g/application)

Quotient

with full

PPE and

Cut flowers Automatic fogging 23 0.02

Crop Formulation

Application

(g /ha)

Frequency Interval

(days)

Application

area (ha)

Quotient

with PPE

and RPE

(Fully

automated)

Mushrooms Liquid 1250 1 1.25 1.2

Mushrooms Liquid 1250 2 7 1.25 1.2

Conclusions on the operator risk assessment for cut flowers

The results of the risk assessment indicate that operator exposure is significantly lower than the

AOEL, provided that full PPE and RPE are worn. While some caution should be applied when

interpreting these results due to the uncertainties in the EPA’s risk assessment, the fact that the

predicted exposure is significantly lower than the AOEL is reassuring.

Operator exposure when using dichlorvos for post-harvest treatment of asparagus

It was assumed that post-harvest use of dichlorvos would occur in containers where the gas is applied

through a hole in the container via a spray gun fitted to a RTU aerosol cylinder. The EPA have

assumed that the only exposure here would occur when connecting the cylinder to the spray gun and

that an operator would only use one cylinder per day. The EPA seek feedback about the

appropriateness of this assumption.

Exposure values were based on those estimated by the APVMA. The APVMA considered that

operators may be exposed to dichlorvos when changing cylinders, through contact with small

amounts of liquid dichlorvos deposited in the connector fittings or on the nozzle.

Dermal exposure

The APVMA estimated dermal exposure to be 0.001 mL dichlorvos/cylinder used, equivalent to

0.0014 g (as the relative density of dichlorvos is 1.425).

Assuming that gloves are worn during cylinder changing, the estimated amount of dichlorvos

absorbed from dermal exposure (mg/day) can be calculated using the following equation:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑜𝑙𝑙𝑜𝑤𝑖𝑛𝑔 𝑑𝑒𝑟𝑚𝑎𝑙 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒 = 𝐶𝑅 × 𝑊𝑅 × 𝐷𝐴 × 𝑃

Where:

CR = contamination rate [1.4 mg/cylinder change]

WR = work rate [cylinder changes/day (1)]

DA = dermal absorption [0.3 (i.e. 30%)]

P = penetration factor for clothing [gloves, 0.1 (i.e. 10%)]

On a body weight basis, the systemic dose is calculated using the following equation:

𝑆𝐸(𝑑) =𝐶𝑅×𝑊𝑅×𝐷𝐴×𝑃

𝐵𝑊

Where:

SE(d) = systemic exposure via the dermal route [mg/kg bodyweight (bw)/day]

BW = bodyweight [70 kg]

Inhalation exposure

For inhalation exposure, the APVMA assumed that dichlorvos may be present within the cylinder

fittings and connections and that this would evaporate into the atmosphere when a cylinder is

removed. It was assumed that if 0.005 ml of dichlorvos (weight 7.1 mg) evaporated into the 1 m3

personal air space around an operator’s breathing zone, and the operator was exposed for 1 minute

at an inhalation rate of 1.0 m3/hour (light activities), they would inhale 0.12 mg dichlorvos).

The estimated inhalation exposure during cylinder changing can be calculated using the following

equations:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑜𝑙𝑙𝑜𝑤𝑖𝑛𝑔 𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 = 𝐶𝑅 × 𝑊𝑅 × 𝐼𝐴 × 𝑃

Where:

WR = work rate [cylinder changes/day (1)]

IA = inhalation absorption [1 (i.e. 100%)]

P = penetration factor for RPE [full face respirator: 0.05 (95% protection)]

𝑆𝐸(𝑖) = 𝐶𝑅×𝑊𝑅×𝐼𝐴×𝑃

𝐵𝑊

Where:

SE(i) = systemic exposure via the inhalation route [mg/kg bw/day]

Estimated exposures for changing one cylinder are summarised below.

Table 11 Total operator systemic exposure for an operator changing 1 cylinder

Level of PPE/RPE Exposure mg/kg bw/day

With gloves (90 % protection factor) and a

respirator (95 % protection factor)

0.00069

Table 12 Results of the operator risk assessment for post-harvest use on asparagus

Crop Application method Application rate

(g/m3)

Quotient

gloves

and RPE

Asparagus Spray gun attached to a cylinder 1 0.49

Conclusions on the operator risk assessment

The results of the operator exposure assessment indicate that the predicted exposure is less that the

AOEL, provided that operators wear gloves and RPE. Caution should however; be taken when

interpreting these results as they may be underestimates of exposure.

Operator exposure when dipping flowers for biosecurity purposes

Operator exposure was estimated for mixing and loading of the dipping solution using the UK version

of the BBA model. Exposure to applicators was estimated using values from the Dutch Dipping model

which were reported in an EFSA Draft Assessment Report (DAR) (EFSA, 2008a). It was assumed

that dipping would use a dichlorvos formulation of 1000 g/L, mixed with water to a concentration of 2

This assumed that an applicator would mix and load 300 litres of dipping solution into a dipping bath

and carry out dipping (i.e. physically placing the flowers into the dipping solution and removing them)

for approximately 10 minutes per day. During dipping it was assumed that an applicator would get

exposed to 0.0278 ml of dipping solution per minute. Exposure was estimated assuming that an

operator would wear full Personal Protective Equipment (PPE) and a respirator.

It was assumed that penetration of dichlorvos through a full face respirator would be 5 % (i.e.

inhalation exposure would be reduced by 95 %), penetration of dichlorvos through gloves would be 10

% (i.e. exposure via the hands would be reduced by 90 % by wearing gloves) and that penetration

through chemical resistant coveralls and study footwear would be 5 % (i.e. operator exposure would

be reduced by 95 %).

Table 13 Results of the operator risk assessment for dipping flowers

Crop Application method

Amount of

dichlorvos handled

per day

Quotient

with full

PPE and

Dipping flowers Dipping 600 g 0.5

The results indicate that provided an operator was using full PPE and RPE at these use patterns, the

predicted operator exposure would be less than the AOEL. The EPA note that the results of this risk

assessment are highly dependent on the assumptions made about how the mixing and loading

occurs. The EPA have assumed that mixing and loading would be similar to mixing and loading of

dichlorvos into a large tank similar to that on a tractor mounted or pulled sprayer. This is similar to the

assumptions used by European regulators about the mixing and loading of dipping material to dip

bulbs (EFSA, 2008a). Staff note that the conclusion of the risk assessment would be different if mixing

and loading were assumed to be more similar to that of a backpack or knapsack sprayer. The smaller

tank and hole for pouring material would produce much higher dermal exposures. It is, therefore,

important that the EPA receive more information about the treatment process to confirm the above

conclusion. This should also include information about the current procedures for disposing of dipping

liquid. It is also important to note that the volatility of dichlorvos was not taken into account which may

underestimate inhalation exposure.

The EPA seeks feedback about the validity of all these assumptions and whether they

accurately reflect use. Information on procedures for disposal of dipping liquid is also

requested.

Re-entry worker risks in treated greenhouses and mushroom houses

Separate re-entry risk assessments were carried out for greenhouses and mushroom houses due to

the different rates of degradation of dichlorvos in these structures. The approaches and studies used

by the EPA largely mirror those used by the APVMA.

Re-entry worker risks in treated greenhouses

Inhalation exposure during re-entry to a greenhouse

Inhalation exposure from re-entry activity in a treated greenhouse was estimated using information

from a study carried out by Brouwer et al (1992) and used by the APVMA for their risk assessment.

Re-entry exposure was calculated for two separate time periods. The first was exposure for a worker

entering a treated greenhouse to carry out ventilation for 30 minutes 12 hours after the application.

For this activity it was assumed that the worker would not contact treated plants (i.e. dermal exposure

was considered to be minimal) and that they would be wearing full PPE. The exposure with a

respirator was considered as the EPA have assumed that someone re-entering a treated greenhouse

would always wear a respirator to account for the uncertainties associated with degradation of the

dichlorvos.

The second time period was for a re-entry worker in a greenhouse who would be entering for an eight

hour shift following ventilation 24 hours after application. It was assumed that they would be also

exposed dermally and not wearing a respirator.

Inhalation exposure during ventilation

The EPA used the study by Brouwer et al to estimate the concentration of dichlorvos in air 12 hours

after the application (Brouwer et al, 1992). This study was published in a peer reviewed publication

and has also been used by the APVMA in their review of dichlorvos. EPA staff consider that the study

by Brouwer et al appears to have been carried to a satisfactory standard. Caution should, however,

be taken when interpreting these results as while there is some conservatism in some of the

assumptions in this risk assessment the predicted concentrations of dichlorvos in air are estimated

from this study and involve significant extrapolation of data beyond the time periods when they were

collected.

This risk assessment was carried out by accounting for the different application rates used in New

Zealand compared to those overseas. An example of how the concentration in air was estimated for a

rate of 1000 g/ha is shown below. The concentration for all other rates was estimated using the same

approach.

The EPA has assumed that greenhouses would have a volume of 25000 m3.

For rates at 1000 g/ha this would equate to a concentration of 50 mg/m3. The rate in the Brouwer et al

study was 33 mg/m3. Therefore in order to shift the dissipation curve from the Brouwer et al study the

regression plot intercepts have been adjusted upwards by a factor of 1.515 (50/33).

(Log10 [6900 x1.515]) = 4.02

Taking the slowest rate of decline from the Brouwer et al study (-0.0031 /minute) the following

equation estimates the concentration at 12 hours (720 minutes) to be

10 (4.02+ [-0.0031 x 720])

= 61.4 ug/m3 or 0.0614 mg/m

Re-entry exposure during ventilation was then calculated using the following equation =

Airborne concentration (mg/m3) x inhalation rate (m

3/hr) x duration (hours)

Body weight (kg)

= 0.0614 x 1 x 0.5

= 0.00044 mg/kg bw/day

Assuming inhalation exposure is reduced 95 % by using a suitable respirator; exposure wearing a

respirator would be 0.00044 x 0.05 =0.000022 mg/kg bw/day.

Inhalation exposure following ventilation

After ventilation has taken place for 12 hours, the inhalation exposure of a worker re-entering for an 8

hour work shift was estimated in a similar manner to the approach used by the APVMA. The

methodology below outlines the approach used for rates of 1000 g/ha, concentrations in air for all

other rates were estimated in the same manner.

Since the initial concentration just before ventilation was assumed to be 61.4 ug/m3 the regression plot

intercept was estimated as

Log10 61.4 = 1.79

The slope during the ventilation in the study by Bouwer et al was -0.018/minute, therefore the

concentration at 12 hours (720 minutes) after ventilation can be estimated using the following

equation.

10 (1.79+[-0.018 x 720])

= 6.8 x 10-12

ug/m3 or 6.8 x 10

-15 mg/m

Re-entry exposure following ventilation was then calculated using the following equation =

Body weight (kg)

= 6.8 x 10-15

x 1 x 8

= 7.8 x 10-16

mg/kg bw/day

Note that this concentration is insignificant; therefore it makes virtually no difference to the level of risk

when added to the dermal exposure.

The predicted exposure was then compared to the AOEL value to calculate the RQ value.

Dermal exposure to dichlorvos in a treated greenhouse

Re-entry exposure to dichlorvos in treated greenhouses considered both inhalation and dermal

exposure. Dermal exposure to a re-entry worker 24 hours after the application was calculated using

the formula below which was developed by other regulators (Chemicals Regulation Directorate,

2010b EUROPOEM, 2002).

Re-entry worker exposure = DFR x TC x WR x AR x DA BW

These parameters with default values where they exist are:

DFR is the Dislodgeable Foliar Residue (0.5 µg/cm

2 per kg a.i./ha)

TC is the Transfer coefficient for the anticipated activity being performed (cm2/hr, defaults in

Table 14)

AR is the application rate (kg/ha)

DA is the dermal aborption, expressed as a proportion (0.3 i.e. 30 %:).

The DFR value of 0.5 µg/cm2 per kg a.i. /ha was calculated based on the study of Casida et al (1962)

application. It is recognised that there are some limitations in only using data from one study,

however, this study was the only one available to the EPA. It is noted that these data were used by

the Australian Pesticides and Veterinary Medicines Authority (APVMA) in their risk assessment of

dichlorvos. Again caution should be used when interpreting the results of the risk assessment and the

Transfer coefficients refer to the amount of contact between a re-entry worker and foliage. These are

regarded as independent of the active ingredient/product used and depend on the crop type and the

activity that the re-entry worker is carrying out (EUROPOEM, 2002). In the absence of data, the EPA

used the values in Table 14 obtained from overseas regulators.

Table 14 Default transfer coefficients used for the re-entry worker risk assessment

Crop Activity

Transfer

coefficient

(cm2/hr)

Vegetables Reach/Pick 2500 (EUROPOEM, 2002)

Picking fruit Search/Reach/Pick 4500 (EUROPOEM, 2002)

Berries Reach/pick 3000 (EUROPOEM, 2002)

Ornamentals Cut/Sort/Bundle/Carry 5000 (EUROPOEM, 2002)

These transfer coefficients all assume that re-entry workers are wearing long trousers and long

sleeved T shirts and are not wearing gloves. It is recognised that re-entry workers may not always

wear this level of clothing; therefore caution should be applied when interpreting the results of the risk

assessment.

Impact of wearing gloves

When appropriate information is available, the transfer coefficients suggested in the EUROPOEM

document have been divided between hand exposure and rest-of-body exposure. From this

information the exposure of re-entry workers wearing chemical resistant gloves is estimated. In the

absence of other information, the model assumes that chemical resistant gloves reduce hand

exposure by 90 %, a default used by other regulators for worker re-entry risk assessment (California

Environmental Protection Agency, 2010). Such revised TC are shown in Table 15. Re-entry intervals

are calculated for workers wearing gloves and those not wearing gloves. The impact of wearing

gloves cannot be calculated for some crops/activities since TC attributable to hands only are not

available.

Table 15 Impact of gloves on re-entry worker transfer coefficients

Transfer

coefficients for

workers not

wearing gloves

(cm2/hr)

Transfer

coefficients

attributable

to hand

exposure

(cm2/hr)

attributable to hand

exposure assuming

90% reduction in hand

exposure due to

wearing gloves

(cm2/hr)

Transfer

coefficients for re-

entry workers

wearing gloves

(cm2/hr)

Vegetables 2500 2200 220 520

Ornamentals 5000 4000 400 1400

Berries 3000 2500 250 750

Picking fruit 4500 2500 250 2250

The effect of multiple applications on re-entry worker exposure was estimated. The DFR is the only

parameter that is altered by multiple applications. The EPA estimated the DFR immediately following

the nth application (DFRn(a)) by assuming first order dissipation and using the following equation

derived from the FOCUS guidance (FOCUS, 2010):

-nki)/(1-e

k is the rate constant for foliar dissipation (4.07734 based on a half-life of 4 hours from US EPA RED (also cited in APVMA pp 72-73 of APVMA review). i is the interval between applications (days)

The reduction in DFRn(a) over time after last application is then given by: DFRn(a)+t = DFRn(a) x e

where t is days since last application. It should however, be noted that due to the short half-life of dichlorvos on foliage, consideration of multiple applications did not have any impact upon predicted exposure.

Risks to re-entry worker after 24 hours

The risks to re-entry workers 24 hour after the final treatment was estimated using the following

equations.

when t = 1 (24 h post-treatment)

The absorbed dermal dose is calculated by:

DFRn(a) x e

-k x C x D

Where C = TC x WR x AR/BW D = Dermal absorption

Therefore the risk to re-entry workers 24 h after the final application is given by the following equation:

RQ = (DFRn(a) x e

-k x C x D)+ IE/AOEL

Where IE = inhalation exposure over an eight hour work period

Results of the re-entry worker risk assessment for greenhouse

Table 16 Results of the re-entry worker risk assessment for greenhouses

* Due to the uncertainties associated with how dichlorvos would degrade over time the EPA have assumed that anyone re-entering a treatment area which has not been ventilated would always be wearing a respirator.

Crop Formulation

Application

(g /ha)

Frequency Interval

(days)

Re-entry RQ for

ventilation 12

hours after

treatment (with

RQ re-entry worker

24 h after

application

(no gloves) assuming

first order

degradation

RQ re-entry worker 24 h after

application

(gloves) assuming first order

degradation

Glasshouse

flowers

(cymbidium)

Liquid

1000 1

0.02 1 0.3

Glasshouse

flowers

(cymbidium)

Liquid

1800 2 7

0.03 1.9 0.5

Capsicum Liquid 1320 7 7 0.02 1.2 0.6

Capsicum Liquid 1900 7 7 0.03 1.8 0.9

Tomatoes Liquid 1900 6 7 0.03 1.8 0.9

Tomatoes Liquid 1320 6 7 0.02 1.2 0.6

Aubergine Liquid 1320 6 7 0.02 1.2 0.6

Aubergine Liquid 1900 6 7 0.03 1.8 0.9

Lettuce Liquid 100 1 0.002 0.3 0.1

Conclusion of the of the re-entry worker risk assessment for greenhouse use

The results of the risk assessment indicate that risks to re-entry workers ventilating treated

greenhouses are acceptable provided that workers only re-enter the treated greenhouse for short

periods of time (up to 30 minutes) to ventilate 12 hours after application using a respirator. Risks to

re-entry workers carrying out other tasks are acceptable provided that 24 hours has passed since the

application, that ventilation occurs for 12 hours and that workers wear gloves when handling treated

material on the second day after application.

Re-entry worker risks in mushroom houses

Inhalation exposure

Inhalation exposure to dichlorvos for re-entry workers entering a mushroom house was estimated

using a similar approach to that taken by the APVMA who used the data from a study by Hussey and

Hughes (APVMA, 2008 original not sighted). The application rate in New Zealand is assumed to be

1250 g/ha equivalent to a rate of 50 mg/m3 (assuming that a mushroom house would be 2.5 m high)

which is 23.6 % of the rate used in the study by Hussey and Hughes. Therefore the regression plot

intercept is adjusted downwards to -0.494 (log 10 [1.358 x 0.236]).

Assuming that the degradation of dichlorvos is represented by a slope of -0.0558/hour the predicted

concentration 24 hours post application is predicted by the following equation

10(-0.494+[-0.0558 x24])

= 0.015 mg/m3

Therefore inhalation exposure over an eight hour time period can be calculated as follows

Body weight (kg)

= 0.015 x 1 x 8

= 1.71 x 10-3

mg/kg bw/day

Dermal exposure to a treated mushroom house

The EPA has assumed that dichlorvos is used in mushroom houses to treat mushrooms and that

dermal exposure could occur to re-entry workers who contact the mushrooms after application. The

EPA would appreciate feedback on whether this assumption is realistic or if dichlorvos would

only be used as a tool for cleaning up the mushroom house when there are no mushrooms

present.

Dermal exposure to a re-entry worker handling treated mushrooms 24 hours after application was

calculated using the formula below which was developed by other regulators (Chemicals Regulation

Directorate, 2010b EUROPOEM, 2002).

Re-entry worker exposure = DFR x TC x WR x AR x DA BW These parameters with default values where they exist are:

DFR is the Dislodgeable Foliar Residue (0.5 µg/cm2 per kg a.i./ha)

TC is the Transfer coefficient for the anticipated activity being performed (2500cm2/hr without

gloves 520 cm2/hr

with gloves see table 15 for more information)

AR is the Application rate (kg/ha)

DA is the dermal aborption, expressed as a proportion (0.3 i.e. 30 %).

The DFR value of 0.5 µg/cm2 per kg a.i. /ha was calculated based on the study of Casida et al (1962)

application. It is recognised that there are some limitations in only using data from one study,

however, this study was the only one available to the EPA. It is noted that these data were used by

the Australian Pesticides and Veterinary Medicines Authority (APVMA) in their risk assessment of

dichlorvos. Again caution should be used when interpreting the results of the risk assessment and any

The effect of multiple applications on re-entry worker exposure was estimated. DFR is the only

parameter that is altered by multiple applications. The DFR was estimated immediately following the

nth application (DFRn(a)) by assuming first order dissipation and using the following equation derived

from the FOCUS guidance (FOCUS, 2010):

-nki)/(1-e

k is the rate constant for foliar dissipation (4.07734 based on a half-life of 4 hours from US EPA RED (also cited in APVMA, pp 72-73 of APVMA review). i is the interval between applications (days)

The reduction in DFRn(a) over time after last application is then given by:

DFRn(a)+t = DFRn(a) x e-kt

where t is days since last application.

It should however, be noted that due to the short half-life of dichlorvos on foliage including

consideration of multiple applications did not have any impact upon predicted exposure.

Risks to re-entry workers after 24 hours

The risks to re-entry workers 24 hours after the final treatment was estimated using the following

equations.

When t = 1 (24 h post-treatment)

The absorbed dermal dose is calculated by:

DFRn(a) x e

-k x C x D

Where C = TC x WR x AR/BW D = Dermal absorption

Therefore the risk to re-entry workers 24 h after the final application is given by the following equation:

RQ = (DFRn(a) x e

-k x C x D)+ IE/AOEL

Where IE = inhalation exposure over an eight hour work period

Results of the re-entry exposure when re-entering a treated mushroom house

Table 17 Results of the re-entry worker risk assessment for greenhouses

Application rate

(g/ha) Frequency Interval (day)

Re-entry RQ after

24 hours ( no

gloves)

Re-entry RQ

after 24 hours

(gloves)

1250 1 1.9 1.4

1250 2 7 1.9 1.4

Conclusion of the of the re-entry worker risk assessment for mushroom houses

The results of this risk assessment indicate that if dichlorvos was used in a mushroom house and

workers were re-entering after 24 hours that the predicted exposure would be greater than the AOEL.

In this instance longer re-entry intervals similar to those required in other buildings would be

necessary to manage the risks.

Re-entry worker risks when using dichlorvos for post-harvest treatment of asparagus

The EPA have assumed that a worker would re-enter a treated container which had been treated with

dichlorvos to carry out tasks in the container or to unload the container. Exposure for workers re-

entering a container to perform these tasks has been assessed at 12 hours following treatment. The

concentration of dichlorvos to which a worker would be exposed on re-entry is estimated based on the

rate of dissipation measured by Schofield (1993) during the six hour period following application in an

industrial building and a one hour ventilation period.

The main application rate of 1 g/m3 is approximately 20 times higher than the rate used in the study

by Schofield (85 mg/m3). The regression plot intercept from the Schofield study has therefore been

adjusted upwards to 5.99 (Ln [20 x 20]) while it has been assumed that the same dissipation rate will

apply (-0.4207/h).

The airborne concentration of dichlorvos at 12 hours following treatment can therefore be calculated

3124207.099.5 /56.2 mmge

Assuming that a worker would spend a maximum of 1 hour in a building to perform tasks associated

with ventilation, and an inhalation rate of 1 m3 per hour, the predicted inhalation exposures at venting

with various levels of RPE can be calculated using the following formula:

𝑆𝐸(𝑖) =[𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠]×𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛×𝐼𝑅×𝐼𝐴×𝑃

𝐵𝑊

Where:

SE(i) = systemic exposure via the inhalation route [mg/kg bw]

[Dichlorvos] = airborne dichlorvos concentration [mg/m3]

Exposure duration = 1 hours

IR = inhalation rate [1m3/hour]

IA = inhalation absorption [1, i.e. 100%]

P = penetration factor for RPE [no RPE: 1 (no protection) and full face respirator: 0.05 (95%

protection)]

The APVMA considered that dermal exposure during this venting process would be negligible

compared to the inhalation exposures. Schofield (1993) measured dichlorvos in hand rinsates from

workers re-occupying treated buildings which indicated that dermal exposures were approximately

two orders of magnitude lower than inhalation exposure. Therefore dermal exposures were not

included in the calculation for this exposure scenario.

Results and conclusions of the worker re-entry risk assessment when using dichlorvos for

post-harvest treatment of asparagus

The predicted exposures using the above calculations were as follows: 0.04 mg/kg bw/day without

RPE (RQ =26.1) and 0.0018 mg/kg bw/day (RQ = 1.3) with RPE. The results indicate that predicted

exposure would be at an approximately acceptable level provided that

the container is enclosed for 12 hours after application.

there is a 1 hour ventilation period

re-entry workers are wearing RPE (providing at least 95 % protection)

re-entry workers only spend a maximium of 1 hour in treated containers

Staff have used the Schofield study to assess re-entry exposure in the absence of more suitable data.

However, it is important to note that there are a number of limitations and uncertainties involved in

using this study.

The building in the study was kept closed for 6 hours following application and was only

ventilated for one hour. There is considerable uncertainty in extrapolating the data to the

New Zealand use pattern, where a treated container is kept closed for 12 hours and then

ventilated.

Exposures have been extrapolated to time periods beyond where they were measured.

It is unclear whether the building in the study was ventilated mechanically (i.e. via an air

conditioning system) or passively during this period, or at other times during the study.

These estimates of exposure could be improved if the EPA were provided with air quality

information following application to asparagus. The EPA also requests that users inform the

EPA about whether the assumptions outlined in the risk assessment are appropriate.

Re-entry worker risks when using dichlorvos for treating cut flowers

For this use scenario, the EPA have assumed that exposure would be equivalent to exposure when

dichlorvos is used for post harvest treatment of asparagus. This means that exposure would be

expected to be acceptable, provided that

the building is enclosed for 12 hours after application.

there is a 1 hour ventilation period

re-entry workers are wearing RPE (providing at least 95 % protection)

re-entry workers only spend 1 hour indoors

These estimates of exposure could be improved if the EPA were provided with air quality

information following application to cut flowers. The EPA requests that any air quality data

available for this type of application be submitted to us.

Bystander exposure to dichlorvos from application in greenhouses

Bystander exposure to pesticides applied in a greenhouse can occur in two ways, either directly after

application through small cracks and crevices and later on when the greenhouse is ventilated (RIVM,

1998). Bystanders could be considered to be employees working around the greenhouse (not

wearing any respirator protection) or members of the public who either live nearby or are temporarily

close to the greenhouse. To assess exposure to bystanders the EPA have used an approach

proposed by Leistra et al. (2001) which is outlined in a document published by the RIVM (the National

Institute for Public Health and the Environment in the Netherlands) (RIVM, 2004). This approach

predicts bystander exposure in a leeside eddy 20 m away from the edge of a greenhouse by

predicting the impact that the greenhouse dimensions and wind speed will have upon ventilation,

deposition and volatilisation.

For this assessment the EPA have used the default greenhouse dimension values outlined in the

RIVM document (area of 10000 m2, 4.5 m high and a façade of 450 m

2). Exposure to a worker

(breathing 1 m3 of air per hour and weighing 70 kg) was estimated along with that of a toddler

(breathing 0.67 m3 of air per hour and weighing 15 kg). It was assumed that exposure would be for

one hour following application. The variables used in this assessment along with the results for an

application rate of 1900 kg/ha are outlined below in table 18. Input parameters were kept the same for

all other application rates. Wind speeds were assumed to be 1 m/s. It is recognised that this approach

is a tier 1 model (i.e. specifically designed to be conservative and highlight where more data is

required). It does, however, indicate the potential for there to be a problem and highlights the need for

further data to be collected in order to more accurately determine risks to bystanders.

Table 18 Input parameters used for bystander exposure assessment from a greenhouse

Variable Value Units

Application rate 1.9 kg/ha

Application rate 0.00019 kg/m2

Time (t) 1 h

Time (t) 0.042 d

K gh - greenhouse

coefficient referring to the

construction and the wind 0.5

Variable Value Units

direction

Area of the greenhouse

facade 450 m2

Area of the greenhouse

floor 10000 m2

Height of the greenhouse 4.5 m

Inner surface of a

greenhouse (floor, sides,

and roof) 21800 m2

Concentration in air in

greenhouse t=0 42222 ug/m3

greenhouse t=0 42 mg/m3

greenhouse over time t 4475 ug/m3

greenhouse over time t 4.5 mg/m3

K gh -ventilation rate

constant (within

greenhouse) 0.000167 s-1

K gh - ventilation rate

constant (within

greenhouse) 14.4 d-1

U - wind speed 1 m/s

Source strength of a

greenhouse over a period

(t) 63189

Concentrations in air

outdoors at time t 280 ug/m3

Concentrations in air

outdoors at time t 0.28 mg/m3

Results of the bystander risk assessment for indoor use in greenhouses

Table 19 Results of the bystander risk assessment for indoor use in greenhouses

Crop Application rate (g/ha) Risk Quotient

adult worker

Quotient

toddler

Lettuce 100 0.2 0.5

Clean up of greenhouses 600 0.9 2.8

Cymbidium 1000 1.5 4.7

Capsicum 1320 2.6 6.6

Tomatoes 1320 2.6 6.6

Aubergine 1320 2.6 6.6

Cymbidium 1800 2.7 8.5

Capsicum 1900 2.9 9

Tomatoes 1900 2.9 9

Aubergine 1900 2.9 9

Conclusions on the bystander exposure from indoor use in greenhouses

The results of the risk assessment indicate that bystanders would not be at risk from emissions from

greenhouses following application at rates less than 100 g/ha. For use at higher rates, however, it is

not possible to exclude the possibility that there may be risks to bystanders (both workers and other

members of the public). The only way to confirm whether or not this is an issue would be through

conducting air quality monitoring studies around these locations to examine predicted exposure.

Bystander and resident exposure and risk assessment following application to

mushroom houses and other buildings where dichlorvos has been used

Bystander exposure following treatment of enclosed buildings or other spaces (e.g. fumigation

chambers) could occur either as a result of leaking from the building if it cannot be completely sealed,

or once the building is opened up for ventilation.

EPA staff have not been able to locate any exposure models or monitoring data to enable

quantification of the potential bystander exposure following application of dichlorvos in these use

scenarios. However, it is noted that the exposure modelling for bystanders in the vicinity of

greenhouse indicates that there is a potential for bystander exposure that may be of concern if rates

of over 100 g/ha are used. In the absence of any specific information EPA staff have assumed that

application of dichlorvos in buildings is unlikely to result in potential risks for bystanders if small

quantities (e.g. less than 100 g per day in any sized area) are used. Staff have assumed that use of

quantities greater than 100 g per day may result in potential risks for bystanders.

Dichlorvos human health risk assessment – public health and residential use scenarios

The human health risk assessment was based on the approach previously outlined in the original

dichlorvos application (HRC08004), with some minor modifications for the purposes of clarification.

For the operator exposure scenarios, exposure has been assessed assuming that gloves (90%

protection factor) and a full face respirator (protection factor of 95%) are worn during mixing and

loading, and that chemical resistant clothes (protection factor of 95%), gloves and a full face respirator

are worn during application.

Due to the relatively high toxicity of dichlorvos only these higher protection levels have been included

in the risk assessment as clearly the risks from lower levels of protection will be higher. Predicted

exposures are compared to the Acceptable Operator Exposure Level (AOEL).

The EPA seeks feedback about the practicality of wearing this level of personal protective

equipment.

Application in closed industrial spaces

Enclosed space fogging using ready to use (RTU) aerosol cylinders with

automatic/remote application

The original application indicates that ready to use (RTU) aerosol cylinders containing 50 g

dichlorvos/L are available for sale in New Zealand in 7 litre (L) and 35 L cylinders.

In this use scenario a RTU aerosol cylinder is triggered remotely in enclosed spaces of 375, 3750 and

12500 m3. Therefore in these scenarios it is expected that operators will only be exposed to

dichlorvos when connecting and changing aerosol cylinders.

Application rates and number of cylinders required

At an application rate of 0.05 g a.i./m3, a total amount of 18.75, 187.5 and 625 g a.i. is required to

treat spaces of 375, 3750 and 12500m3, respectively.

At a dichlorvos concentration of 50 g a.i./L, the total amount of aerosol needed to provide the total

amount of dichlorvos required is 0.375, 3.75 and 12.5 L, respectively. Therefore only one 7 L cylinder

would be required to treat spaces of 375 and 3750 m3, while two cylinders would be needed to treat a

space of 12500 m3.

Product labels also recommend a higher application rate of 0.15 g a.i./m3 against certain pests. At this

rate a total amount of 56.25, 562.5 and 1875 g dichlorvos is required to treat spaces of 375, 3750 and

12500 m3, respectively.

At a dichlorvos concentration of 50 g a.i./L, the total amount of aerosol needed to provide the total

amount of dichlorvos required is 1.125, 11.25 and 37.5 L, respectively. Therefore one 7 L cylinder

would be required to treat a space of 375 m3, two cylinders would be need to treat a space of 3750 m

and six 7 L cylinders would be needed to treat a space of 12500 m3. Alternatively, one 35 L cylinder

would be needed to treat spaces of 375 or 3750 m3, and two cylinders would be needed to treat a

space of 12500 m3.

Worker/loader exposures during RTU aerosol cylinder changing

The EPA used a similar approach to that used in the APVMA assessment of dichlorvos.

The APVMA considered that operators may be exposed to dichlorvos when changing cylinders,

through contact with small amounts of liquid dichlorvos deposited in the connector fittings or on the

nozzle.

Dermal exposure

The APVMA estimated dermal exposure to be 0.001 mL dichlorvos/cylinder used, equivalent to

0.0014 g (as the relative density of dichlorvos is 1.425).

Where:

WR = work rate [cylinder changes/day (1, 2 or 6)]

𝑆𝐸(𝑑) =𝐶𝑅 × 𝑊𝑅 × 𝐷𝐴 × 𝑃

𝐵𝑊

Where:

Estimated dermal exposures are summarised below in table 20.

Table 20 Estimated dermal exposures from enclosed space fogging using ready to use (RTU) aerosol

cylinders with automatic/remote application

Application rate

(g a.i./m3)

Volume treated

Cylinders used

Dermal

absorbed dose

with PPE

(mg/day)

Systemic dose

from dermal

exposure with

PPE (mg/kg

bw/day)

0.05 375 1 0.042 0.0006

0.05 3750 1 0.042 0.0006

0.05 12500 2 0.084 0.0012

0.15 375 1 0.042 0.0006

0.15 3750 2 0.084 0.0012

0.15 12500

6 (if 7L cylinder

used; 2 if 35 L

cylinder used)

0.252 (6 cylinders)

0.084 (2 cylinders)

0.0036 (6

cylinders)

0.0012 (2

cylinders)

Inhalation exposure

at an inhalation rate of 1.0 m3/hour (light activities), they would inhale 0.12 mg dichlorvos).

equations:

Where:

WR = work rate [cylinder changes/day (1, 2 or 6)]

𝐵𝑊

Where:

Estimated inhalation exposures are summarised below in table 21.

Table 21 Estimated inhalation exposures from enclosed space fogging using RTU aerosol cylinders with

Application

rate (g

a.i./m3)

Volume

treated

Cylinders

Inhalation absorbed

dose when wearing

a full face respirator

(mg/day)

Systemic dose from

inhalation exposure

when wearing a full

face respirator

(mg/kg bw/day)

0.05 375 1 0.006 0.00009

0.05 3750 1 0.006 0.00009

0.05 12500 2 0.012 0.00017

0.15 375 1 0.006 0.00009

0.15 3750, 12500

cylinder for

3750 m3; 35

L cylinder

for 12500

0.012 0.00017

0.15 12500

6 (if 7 L

cylinder

0.036 0.0005

Risk quotients

Overall exposure is calculated by summing the exposure from the dermal and inhalation routes.

Exposure is then compared to the AOEL to derive a risk quotient (RQ).

𝑅𝑄 = 𝑆𝐸(𝑑)+𝑆𝐸(𝑖)

𝐴𝑂𝐸𝐿

SE(d) = systemic exposure via the dermal route [mg/kg bw/day]

AOEL = 0.0014 mg/kg bw/day

Table 22 Results of the operator risk assessment for enclosed space fogging applications with RTU aerosol

cylinders (automatic/remote application)

Operation/PPE/RPE

Application

dichlorvos/

Volume

treated

Cylinde

rs used

operator

systemic

exposure

(mg/kg

bw/day)

Quotient

Cylinder

connection/gloves/full

face respirator

0.05 375, 3750 1 X 7 L 0.000686 0.49

Cylinder

face respirator

0.05 12500 2 X 7 L 0.00137 0.98

Cylinder

face respirator

0.15 375 1 X 7 L 0.000686 0.49

Cylinder

face respirator

2 X 7 L,

2 X 35 L

0.00137 0.98

Cylinder

face respirator

0.15 12500 6 X 7L 0.0041 2.94

Conclusions from the operator risk assessment for enclosed space fogging applications with RTU

aerosol cylinders [automatic/remote application]

When the RTU dichlorvos aerosol is released through automatic spray systems, risks during cylinder

connection/disconnection, predicted exposures are less than the AOEL for operators using up to two

cylinders per day, provided gloves and a full-face respirator (providing a 95 % protection factor) are

The connection/disconnection of more than two cylinders per day (i.e. using six 7 L cylinders to treat

12500 m3 at 0.15 g dichlorvos/m

3) results in predicted exposures greater than the AOEL.

Enclosed space fogging using RTU aerosol cylinders with manual application

In this use scenario a RTU aerosol containing 50 g dichlorvos/L is applied using a manual pressure

gun in enclosed spaces of 375, 3750 and 12500 m3. The application rate is 0.05 or 0.15 g/m

3. The

estimated exposure during cylinder changing calculated for automatic application above is combined

with estimates of exposure during application. The approach taken is based on that used by the

APVMA.

The APVMA noted that when using a manual pressure gun, operators are directed to work away from

spray drift and move towards the exit, and to avoid wetting any surfaces. The pressure nozzle is likely

to be held at chest or head height as the operator moves through the treated building. Volatilisation of

dichlorvos was expected to be almost instantaneous and complete.

It is anticipated that operator exposure during application would primarily arise from inhalation, with

some additional dermal exposure from precipitation of dichlorvos from the spray or the vapour phase

on to the operator’s body or clothing.

Mixing and loading

Exposure during mixing and loading – Dermal exposure

The EPA estimated exposure as per the approach taken by the APVMA. The APVMA estimated

dermal exposure to be 0.001 mL dichlorvos/cylinder used, equivalent to 0.0014 g (as the relative

density of dichlorvos is 1.425).

Where:

WR = work rate [cylinder changes/day (1, 2: it was assumed that only the larger cylinder size would be used and that six 7 L cylinders would not be used for manual fogging)]

𝑆𝐸(𝑑) =𝐶𝑅×𝑊𝑅×𝐷𝐴×𝑃

𝐵𝑊

Where:

Estimated dermal exposures are summarised below in table 23.

Table 23 Estimated dermal exposure (mixing and loading) for enclosed space fogging using RTU aerosol

cylinders with manual application

Application rate

(g a.i./m3)

Volume treated

Cylinders used

Dermal

absorbed dose

with PPE

(mg/day)

Systemic dose

from dermal

exposure with

PPE (mg/kg

bw/day)

0.05 375 1 0.042 0.0006

0.05 3750 1 0.042 0.0006

0.05 12500 2 0.084 0.0012

0.15 375 1 0.042 0.0006

0.15 3750 2 0.084 0.0012

0.15 12500 2 0.084 0.0012

Exposure during mixing and loading: Inhalation exposure

at an inhalation rate of 1.0 m3/hour (light activities), they would inhale 0.12 mg dichlorvos (0.0017

mg/kg bw for a 70 kg individual).

equations:

Where:

WR = work rate [cylinder changes/day (1, 2: it was assumed that only the larger cylinder size would be used and that six 7 L cylinders would not be used for manual fogging)]

𝐵𝑊

Where:

Estimated inhalation exposures are summarised below in table 24.

Table 24 Estimated inhalation exposure (mixing and loading) for enclosed space fogging using RTU

aerosol cylinders with manual application

Application

rate (g

a.i./m3)

Volume

treated

Cylinders

Inhalation absorbed

dose when wearing

(mg/day)

Systemic dose

from inhalation

exposure when

wearing a full

face respirator

(mg/kg bw/day)

0.05 375 1 0.006 0.00009

0.05 3750 1 0.006 0.00009

0.05 12500 2 0.012 0.00017

0.05 375 1 0.006 0.00009

0.05 3750 2 0.012 0.00017

0.05 12500 2 0.012 0.00017

Application

Exposure during application – Dermal exposure

Exposure during application was assessed following the approach taken by the APVMA. The APVMA

used the Pesticide Handlers Exposure Database (PHED) exposure model for high pressure

handwand application, in the absence of specific study data for this exposure route. The PHED model

was modified to address the expectation that the efflux from a manual pressure gun would be

significantly less diffuse and more directional than that from a high pressure handwand sprayer. The

PHED dermal exposure estimates were therefore reduced to 10% of those estimated for a high

pressure handwand.

Exposure to the head/neck, exterior of clothing and hands were assumed to be 0.018, 2.68 and 0.26

mg/kg a.i. handled, 10% of the values from the PHED high pressure handwand model.

At an application rate of 0.05 g a.i./m3, a total amount of 18.75, 187.5 and 625 g dichlorvos is required

to treat spaces of 375, 3750 and 12500m3, respectively.

The estimated amount of dichlorvos absorbed from dermal exposure (mg/day) can be calculated by

the following formula:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑜𝑙𝑙𝑜𝑤𝑖𝑛𝑔 𝑑𝑒𝑟𝑚𝑎𝑙 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒 = 𝑎𝑚𝑜𝑢𝑛𝑡 𝑎𝑐𝑡𝑖𝑣𝑒 ℎ𝑎𝑛𝑑𝑙𝑒𝑑 [𝑘𝑔]× [(ℎ𝑒𝑎𝑑&𝑛𝑒𝑐𝑘 × 𝑃) + (𝑐𝑙𝑜𝑡ℎ𝑖𝑛𝑔 × 𝑃) + (ℎ𝑎𝑛𝑑𝑠 × 𝑃)] × 𝐷𝐴

Amount of active handled = 0.01875, 0.1875 and 0.625 kg to treat spaces of 375, 3750 and 12500m3,

respectively, at an application rate of 0.05 g a.i./m3; 0.05625, 0.5625 and 1.875 to treat spaces of 375,

3750 and 12500m3, respectively, at an application rate of 0.05 g a.i./m

Head and neck = 0.018 mg/kg active handled (adapted from the PHED model)

Clothing = 2.68 mg/kg active handled (adapted from the PHED model)

Hands = 0.26 mg/kg active handled (adapted from the PHED model)

P = penetration factor for protective equipment. With full body chemical resistant clothes, the penetration factor for head/neck and clothing was assumed to be 5% (0.05), with a penetration factor of 10% (0.1) for gloves.

The systemic dose following dermal exposure is calculated by the following formula:

𝑆𝐸(𝑑) =(𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑)

𝐵𝑊

Estimated dermal exposures are summarised below in table 25:

Table 25 Estimated dermal exposure (application) for enclosed space fogging using RTU aerosol cylinders

with manual application

Application

rate (g

a.i./m3)

Volume

treated

Active

handled

Dermal absorbed

dose with PPE

(mg/day)

Systemic Exposure

with PPE (mg/kg

bw/day)

0.05 375 0.01875 0.0009 0.00001

0.05 3750 0.1875 0.009 0.0001

0.05 12500 0.625 0.03 0.0004

0.15 375 0.01875 0.003 0.00004

0.15 3750 0.1875 0.03 0.0004

Application

rate (g

a.i./m3)

Volume

treated

Active

handled

Dermal absorbed

dose with PPE

(mg/day)

Systemic Exposure

with PPE (mg/kg

bw/day)

0.15 12500 0.625 0.09 0.001

Exposure during application: Inhalation exposure

When estimating inhalation exposure during manual fogging, the APVMA inferred the potential for

inhalation exposure from the recommended application rate and the length of time it would take an

operator to treat the types of premises for which the product is intended to be used.

The APVMA noted that as long as the operator did not walk back through the efflux stream then the

highest airborne concentration of dichlorvos to which they would be exposed should be the use rate.

The use rate in New Zealand is expected to be 50 or 150 mg/m3. However, at the start of treatment

the airborne concentration of dichlorvos would be zero and the maximum concentration would only be

reached at the end of application. Therefore exposure was estimated to be at a time weighted

average (TWA) of 50 % of the application rate (i.e. 25 mg/m3 at an application rate of 50 mg/m

mg/m3 at an application rate of 0.15 mg/m

The APVMA estimated the duration of exposure for treatment of larger industrial spaces based on the

application times from the manufacturer’s specification for the manual pressure gun (70 sec/300 m3).

This results in exposure durations of 87.5 seconds (375/300 x 70), 875 seconds (3750/300 x 70) and

2917 seconds (12500/300 x 70) for the use scenarios of treating 375, 3750 and 12500 mg/m3,

respectively. These values were rounded to 1.5, 15 and 50 minutes, equivalent to 0.025, 0.25 and

0.83 hour respectively. The operator’s inhalation rate was taken as 1 m3/hour for light activities

(APVMA, 2008).

Assuming that inhalation absorption is 100%, the absorbed dose of dichlorvos from inhalation can be

calculated using the following formula:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑜𝑙𝑙𝑜𝑤𝑖𝑛𝑔 𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛

= [(𝑎𝑖𝑟𝑏𝑜𝑢𝑟𝑛𝑒 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 × 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛) × 𝑃]

Where:

Airborne concentration = TWA (25 mg/m3 at an application rate of 50 mg/m

3, 75 mg/m

3 at an

application rate of 0.15 mg/m3).

Inhalation rate = 1 m3/hour

Duration = 0.025, 0.25 and 0.83 hour for spaces of 375, 3750 and 12500 m3, respectively

P = protection factor for RPE [full face respirator: 0.05 (95% protection)]

The systemic dose following inhalation exposure is calculated using the following equation:

𝑆𝐸(𝑖) =[(𝑎𝑖𝑟𝑏𝑜𝑟𝑛𝑒 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛×𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 ×𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛)×𝑃]

𝐵𝑊

Where:

BW = 70 kg

Estimated inhalation exposure is summarised below in table 26.

Table 26 Estimated dermal exposure (application) for enclosed space fogging using RTU aerosol cylinders

with manual application

Application rate

(g a.i./m3)

Volume

treated

Exposure

duration

Inhalation

absorbed dose

when wearing a

full face respirator

(mg/day)

Systemic

Exposure when

wearing a full face

respirator (mg/kg

bw/day)

0.05 375 0.025 0.03125 0.0004

0.05 3750 0.25 0.3125 0.004

0.05 12500 0.83 1.0375 0.015

0.15 375 0.025 0.09375 0.0013

0.15 3750 0.25 0.9375 0.013

0.15 12500 0.83 3.1125 0.044

Risk quotients

𝑆𝐸(𝑑)+𝑆𝐸(𝑖)

𝐴𝑂𝐸𝐿

SE(d) = systemic exposure via the dermal route [mg/kg bw/day]

AOEL = 0.0014 mg/kg bw/day

Table 27 Results of the operator risk assessment for enclosed space fogging applications with RTU aerosol cylinders with manual application

Operation/PPE/

Application rate

(g dichlorvos/m3)

Volume

treated

Amount of

dichlorvos

handled (g/day)

Cylinders

Total operator systemic exposure

(mg/kg bw/day)

Risk Quotient

Cylinder connection:

gloves and full face

respirator

Application: chemical

resistant clothes & gloves,

full-face respirator

0.05 375 18.75 1 X 7 L 0.0011 0.82

respirator

0.05 3750 187.5 1 X 7 L 0.005 3.8

respirator

0.05 12500 625 2 X 7 L 0.017 11.9

Operation/PPE/

Application rate

(g dichlorvos/m3)

Volume

treated

Amount of

dichlorvos

handled (g/day)

Cylinders

Total operator systemic exposure

(mg/kg bw/day)

Risk Quotient

respirator

0.15 375 56.25 1 X 7 L 0.002 1.47

respirator

0.15 3750 562.5 2 X 7 L 0.015 10.82

respirator

0.15 12500 1875 2 X 7 L 0.047 33.7

Conclusion for the operator risk assessment for enclosed space fogging applications with

RTU aerosol cylinders with manual application

The operator risk assessment for manual fogging of dichlorvos RTU aerosol cylinders results in the

following conclusions:

Predicted exposure is below the AOEL during treatment of 375 m3 spaces at an application rate of

0.05 mg dichlorvos/m3 provided the following PPE is worn:

Gloves and a full-face respirator (95 % protection) during cylinder changing

Chemical resistant clothing, gloves and a full-face respirator during application

Predicted exposures are greater than the AOEL during treatment of 3750 m3 and 12500 m

3 spaces at

the application rate of 0.05 mg/m3, and for all three spaces at the higher application rate (0.15 mg/m

Operator exposure would be acceptable if operators only handle approximately 19 g dichlorvos per

Enclosed space fogging using EC solutions with automatic/remote application

(exposure only at mixing/loading)

This use scenario represents a fogging solution triggered remotely into enclosed spaces of 375, 3750

and 12500 m3. Based on a formulation containing 1000g a.i./L and applied at 5 ml/100m

3 (i.e. a use

rate of 0.05 g a.i./m3), 18.75, 187.5 and 625 g dichlorvos are required respectively to treat each

space. The product labels also recommend a higher use rate of 0.15 g a.i./m3 against certain pests.

The higher rates would require 56.25, 562.5 and 1875 g dichlorvos for spaces of 375, 3750 and

12500 m3, respectively. In these scenarios, exposure to the operator is only expected to occur during

mixing and loading.

It was assumed that assumed that mixing and loading exposure for fogging would be the same as

mixing and loading exposure of a boom sprayer using the UK Chemicals Regulation Directorate

(CRD) version of the German Federal Biological Research Centre for Agriculture and Forestry (BBA)

operator exposure model (Chemicals Regulation Directorate, 2011). All of the exposure data and

assumptions for this model are published online (Chemicals Regulation Directorate, 2011a). The

model estimates the exposure of an operator and evaluates the impact of wearing different forms of

Personal Protective Equipment (PPE) (Chemicals Regulation Directorate, 2011a). The EPA have

used exposure reduction factors listed below which are different from the defaults in the CRD model

but consistent with those used for the other use scenarios included in this evaluation.

Gloves (90% protection factor) and a respirator (95% protection factor)

The following assumptions were included in the modelling for this scenario:

Application rate: 0.05 or 0.15 g a.i./m3

Amount of product used per hectare: 1.25 L product/ha (assuming a 2.5 m building height) at 0.05

g a.i./m3; 3.75 L product/ha at 0.15 g a.i./m

Dichlorvos concentration in product: 1000 g/L

Work rate: 0.015 ha/day for 375 m3, 0.15 ha/day for 3750 m

3, 0.5 ha/day for 12500 m

Table 28 Results of the operator risk assessment for enclosed space fogging with EC Solutions with

Operation/RPE/PPE

Application

dichlorvos/m3)

Volume

treated

Total operator

systemic

exposure

(mg/kg bw/day)

Quotient

Mixing/loading: A1P2

RPE & gloves

0.05 375 0.0000193 0.01

RPE & gloves

0.05 3750 0.000193 0.1

RPE & gloves

0.05 12500 0.0006 0.5

RPE & gloves

0.15 375 0.000058 0.04

RPE & gloves

0.15 3750 0.00058 0.4

RPE & gloves

0.15 12500 0.0019 1.4

Conclusion for the operator exposure assessment for enclosed space fogging with EC

Solutions with automatic/remote application

Predicted operator exposures from mixing/loading fogging solutions for application through automatic

spray systems into enclosed industrial spaces of 375 and 3750 m3 are below the AOEL at both

application rates provided a respirator (95% protection) and gloves are worn.

For the largest treatment volume, exposures from mixing and loading are below the AOEL at the

lower application rate (0.05 mg/m3), but slightly higher than the AOEL at the higher rate (0.15 mg/m

Enclosed space fogging using EC solutions with manual application

In this use scenario the fogger solution is applied manually into enclosed spaces of 375, 3750 and

12500 m3 (equivalent areas: 150, 1500 and 2500 m

2; APVMA, 2008b: assumes 2.5m building height).

Application rates are 0.05 and 0.015 g dichlorvos/m3.

Exposure during mixing and loading is calculated using the same approach as for the mixing and

loading of the EC solution prior to automatic application, as described above. For exposure during

application, inhalation and dermal exposure is calculated following the approach previously used for

fogging with RTU aerosol cylinders.

Mixing and loading

It was assumed that assumed that mixing and loading exposure for fogging would be the same as

mixing and loading exposure of a handheld sprayer using the UK Chemicals Regulation Directorate

(CRD) version of the German Federal Biological Research Centre for Agriculture and Forestry (BBA)

operator exposure model (Chemicals Regulation Directorate, 2011). All of the exposure data and

assumptions for this model are published online (Chemicals Regulation Directorate, 2011a). The

model estimates the exposure of an operator and evaluates the impact of wearing different forms of

Personal Protective Equipment (PPE) using exposure reduction factors (Chemicals Regulation

Directorate, 2011a). The EPA have used exposure reduction factors listed below which are different

from the defaults in the CRD model but consistent with those used for the other use scenarios

included in this evaluation.

Gloves (90% protection factor) and a respirator (95% protection factor)

The following assumptions were included in the modelling for this scenario:

Application rate: 0.05 or 0.15 g a.i./m3

Amount of product used per hectare: 1.25 L product/ha (assuming a 2.5 m building height) at 0.05

g a.i./m3; 3.75 L product/ha at 0.15 g a.i./m

Dichlorvos concentration in product: 1000 g/L

Work rate: 0.015 ha/day for 375 m3, 0.15 ha/day for 3750 m

3, 0.5 ha/day for 12500 m

Application

Dermal exposure

The APVMA used a Pesticide Handlers Exposure Database (PHED) exposure model for high

pressure handwand application, in the absence of specific study data for this exposure route. The

PHED model was modified to address the expectation that the efflux from a manual pressure gun

would be significantly less diffuse and more directional than that from a high pressure handwand

sprayer. The PHED dermal exposure estimates were therefore reduced to 10% of those estimated for

a high pressure handwand.

Exposure to the head/neck, exterior of clothing and hands were assumed to be 0.018, 2.68 and 0.26

mg/kg a.i. handled, 10% of the values from the PHED high pressure handwand model.

At an application rate of 0.05 g a.i./m3, a total amount of 18.75, 187.5 and 625 g dichlorvos is required

to treat spaces of 375, 3750 and 12500m3, respectively.

The estimated amount of dichlorvos absorbed from dermal exposure (mg/day) can be calculated by

the following formula:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑜𝑙𝑙𝑜𝑤𝑖𝑛𝑔 𝑑𝑒𝑟𝑚𝑎𝑙 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒

= 𝑎𝑚𝑜𝑢𝑛𝑡 𝑎𝑐𝑡𝑖𝑣𝑒 ℎ𝑎𝑛𝑑𝑙𝑒𝑑 [𝑘𝑔] × [(ℎ𝑒𝑎𝑑&𝑛𝑒𝑐𝑘 × 𝑃) + (𝑐𝑙𝑜𝑡ℎ𝑖𝑛𝑔 × 𝑃) + (ℎ𝑎𝑛𝑑𝑠 × 𝑃)]

× 𝐷𝐴

Amount of active handled = 0.01875, 0.1875 and 0.625 kg to treat spaces of 375, 3750 and 12500m3,

respectively, at an application rate of 0.05 g a.i./m3; At the higher application rate of 0.15 g a.i./m

total amount of 56.25, 562.5 and 1875 g dichlorvos is required to treat spaces of 375, 3750 and 12500 m

3, respectively.

P = penetration factor for protective equipment. This was assumed to be 10% (0.1) for gloves, with a penetration factor of 5 % (0.05) for head/neck and clothing, assuming full body chemical resistant clothes are worn.

𝐵𝑊

Table 29 Estimated dermal exposure for enclosed space fogging using EC solutions with manual

application

Application

rate (g

a.i./m3)

Volume

treated

Active

handled

Dermal

absorbed

dose with

(mg/day)

Systemic

Exposure

with PPE

(mg/kg

bw/day)

0.05 375 0.01875 0.0009 0.00001

0.05 3750 0.1875 0.009 0.0001

Application

rate (g

a.i./m3)

Volume

treated

Active

handled

Dermal

absorbed

dose with

(mg/day)

Systemic

Exposure

with PPE

(mg/kg

bw/day)

0.05 12500 0.625 0.03 0.0004

0.15 375 0.05625 0.0027 0.00004

0.15 3750 0.5625 0.027 0.0004

0.15 12500 1.875 0.091 0.001

Inhalation exposure

When estimating inhalation exposure during application of manual pressure gun, the APVMA inferred

the potential for inhalation exposure from the recommended application rate and the length of time it

would take an operator to treat the types of premises for which the product is intended to be used.

The APVMA noted that as long as the operator did not walk back through the efflux stream then the

highest airborne concentration of dichlorvos to which they would be exposed should be the use rate.

The use rate in New Zealand is expected to be 50 mg/m3. However, at the start of treatment the

airborne concentration of dichlorvos would be zero and the maximum concentration would only be

reached at the end of application. Therefore exposure was estimated to be at a time weighted

average (TWA) of 50 % of the application rate (i.e. 25 mg/m3).

The APVMA estimated the duration of exposure for treatment of larger industrial spaces based on the

application times from the manufacturer’s specification for the manual pressure gun (70 sec/300 m3).

This results in exposure durations of 87.5 seconds (375/300 x 70), 875 seconds (3750/300 x 70) and

2917 seconds (12500/300 x 70) for the use scenarios of treating 375, 3750 and 12500 mg/m3,

respectively. These values were rounded to 1.5, 15 and 50 minutes, equivalent to 0.025, 0.25 and

0.83 hour respectively. The operator’s inhalation rate was taken as 1 m3/hour for light activities (US

EPA, 1996; Original not sighted).

Assuming that inhalation absorption is 100%, the absorbed dose of dichlorvos from inhalation can be

calculated using the following formula:

= [(𝑎𝑖𝑟𝑏𝑜𝑢𝑟𝑛𝑒 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛 × 𝑖𝑛ℎ𝑙𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 × 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛) × 𝑃]

Where:

Airborne concentration = TWA (25 mg/m3 at an application rate of 50 mg/m

3; 75 mg/m

3 at an

application rate of 150 mg/m3).

Inhalation rate = 1 m3/hour

Duration = 0.025, 0.25 and 0.83 hour for spaces of 375, 3750 and 12500 m3, respectively

𝑆𝐸(𝑖) =[(𝑎𝑖𝑟𝑏𝑜𝑟𝑛𝑒 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛×𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 𝑟𝑎𝑡𝑒 ×𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛)×𝑃]

𝐵𝑊

Where:

BW = 70 kg

Table 30 Estimated inhalation exposure for enclosed space fogging using EC solutions with manual

application

Application

rate (g

a.i./m3)

Volume

treated

Exposure

duration

Inhalation

absorbed dose

when wearing a

full face respirator

(mg/day)

Systemic Exposure

when wearing a full face

respirator (mg/kg

bw/day)

0.05 375 0.025 0.03125 0.000445

0.05 3750 0.25 0.3125 0.0045

0.05 12500 0.83 1.0375 0.0148

0.15 375 0.025 0.09375 0.0013

0.15 3750 0.25 0.9375 0.0134

0.15 12500 0.83 3.1125 0.044

Risk quotients

Overall exposure is calculated by summing the exposure from mixing and loading with the exposure

from the dermal and inhalation routes during application. Exposure is then compared to the AOEL to

derive a risk quotient (RQ).

Table 31 Results of the operator risk assessment for enclosed space fogging with EC Solutions

Operation/RPE/

Application

dichlorvos/m3

Volume

treated

Amount of

dichlorvos

handled

(g/day)

Total operator

systemic

exposure

(mg/kg

bw/day)

Quotient

Mixing/loading:

gloves and full-face

respirator

Application:

chemical resistant

clothes and gloves,

0.05 375 18.75 0.0021 1.5

Mixing/loading:

respirator

Application:

chemical resistant

clothes and gloves,

0.05 3750 187.5 0.021 15

Mixing/loading:

respirator

Application:

chemical resistant

clothes and gloves,

0.05 12500 625 0.0702 50

Mixing/loading:

respirator

Application:

0.15 375 56.25 0.006 4.5

Operation/RPE/

Application

dichlorvos/m3

Volume

treated

Amount of

dichlorvos

handled

(g/day)

Total operator

systemic

exposure

(mg/kg

bw/day)

Quotient

chemical resistant

clothes and gloves,

Mixing/loading:

respirator

Application:

chemical resistant

clothes and gloves,

0.15 3750 562.5 0.063 45

Mixing/loading:

respirator

Application:

chemical resistant

clothes and gloves,

0.15 12500 1875 0.211 150

Conclusions for the operator exposure assessment for enclosed space fogging with EC

Solutions with manual application

Predicted operator exposures from manual application of dichlorvos fogging solutions into enclosed

spaces are above the AOEL for all use scenarios, regardless of the application rate or the protective

equipment used. The level of exposure is considerably higher than the AOEL (and therefore of

particular concern) when treating spaces of 3750 m3 or greater at either application rate, or when

treating a space of 375 m3 at the higher rate.

Enclosed space applications of EC solutions with high pressure handwand

In this use scenarios a spray is manually applied into enclosed spaces of 375, 3750 and 12500 m3 (equivalent to

150, 1500 and 2500 m2, respectively) at use rates of 0.1 or 0.3 g dichlorvos/m

Application at 0.1 g a.i./m2 would require 15, 150 or 250 g dichlorvos to be handled and applied to treat spaces of

150, 1500 and 2500 m2, respectively. At the higher application rate, the amounts of dichlorvos handled and

applied would be 45, 450 and 750 g dichlorvos, respectively.

Dermal exposure

The APVMA considered that there were no available exposure studies directly applicable to indoor space spray

application of dichlorvos. Instead, the PHED exposure model 35 (mixer/loader/applicators mixing liquid

formulations by open pour methods and applying the spraymix with high pressure handwand equipment) was

considered to be the most appropriate estimation method.

In the absence of protective clothing the predicted dermal exposure rates on head, body and hands were 1.155,

90.86 and 2.49 mg a.i./kg applied.

The amount of dichlorvos (mg/day) absorbed from dermal exposure is calculated using the following equation:

𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠 𝑎𝑏𝑠𝑜𝑟𝑏𝑒𝑑 𝑓𝑟𝑜𝑚 𝑑𝑒𝑟𝑚𝑎𝑙 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒

= ⌊𝑘𝑔 𝑎. 𝑖. ℎ𝑎𝑛𝑑𝑙𝑒𝑑 × {(ℎ𝑒𝑎𝑑&𝑛𝑒𝑐𝑘 × 𝑃) + (𝑐𝑙𝑜𝑡ℎ𝑖𝑛𝑔 × 𝑃) + (ℎ𝑎𝑛𝑑𝑠 × 𝑃)} × 𝐷𝐴⌋

Where:

P = penetration factor for protective equipment. With full body chemical resistant clothes and gloves the penetration factor was assumed to be 10% (0.1) for gloves, the penetration factor for head/neck and clothing was assumed to be 5% (0.05).

𝐵𝑊

Table 32 Estimated dermal exposure from enclosed space applications of EC solutions with high pressure

handwand

Application

rate (g

a.i./m2)

treated

Active

handled

Dermal absorbed

dose with PPE

(mg/day)

Systemic Exposure with

PPE (mg/kg bw/day)

0.1 150 0.015 0.022 0.0003

0.1 1500 0.15 0.218 0.003

0.1 2500 0.25 0.364 0.005

0.3 150 0.045 0.065 0.0009

0.3 1500 0.45 0.654 0.009

0.3 2500 0.75 1.09 0.016

Inhalation exposure

APVMA noted that the relevant PHED model was likely to underestimate inhalation exposure to

dichlorvos due to its high volatility. Therefore the APVMA applied a 50-fold uncertainty factor to the

PHED value (0.264 mg a.i./kg applied) to estimate an inhalation exposure estimate of 13.2 mg

dichlorvos/kg applied. This 50-fold factor was based on data from a study by Gold and Holcslaw

(1984). Inhalation exposures from mixing, loading and application of a liquid dichlorvos product using

low pressure hand sprayers in this study were 25-fold higher than the PHED prediction for exposure

using the same mixing and application methods. Given that the experimental data were from a single

study, a conservative 50-fold factor was applied to the PHED model estimate.

Assuming 100% absorption following inhalation, the absorbed dose of dichlorvos from inhalation can

be calculated using the following formula:

= 𝑎𝑚𝑜𝑢𝑛𝑡 𝑎. 𝑖. ℎ𝑎𝑛𝑑𝑙𝑒𝑑 (𝑘𝑔) × 𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒 (13.2 𝑚𝑔 𝑝𝑒𝑟 𝑘𝑔 ℎ𝑎𝑛𝑑𝑙𝑒𝑑) × 𝑃

Where:

𝑆𝐸(𝑖) =𝑎𝑚𝑜𝑢𝑛𝑡 𝑎.𝑖.ℎ𝑎𝑛𝑑𝑙𝑒𝑑×𝑖𝑛ℎ𝑎𝑙𝑎𝑡𝑖𝑜𝑛 𝑒𝑥𝑝𝑜𝑠𝑢𝑟𝑒×𝑃

𝐵𝑊

Where:

BW = 70 kg

Estimated inhalation exposure is summarised below.

Table 33 Estimated inhalation exposure from enclosed space applications of EC solutions with high

pressure handwand

Application

rate (g a.i./m2)

treated

Active

handled

Inhalation absorbed

dose when wearing

a full face

respirator (mg/day)

Systemic Exposure when

wearing a full face respirator

(mg/kg bw/day)

0.1 150 0.015 0.0099 0.00014

0.1 1500 0.15 0.099 0.0014

0.1 2500 0.25 0.165 0.002

0.3 150 0.045 0.0297 0.0004

0.3 1500 0.45 0.297 0.004

0.3 2500 0.75 0.495 0.007

Risk quotients

Table 34 Results of the operator risk assessment for enclosed space applications of EC solutions with high

pressure handwand

Operation/RPE/PPE

Application

dichlorvos/

treated

Amount of

dichlorvos

handled

(g/day)

operator

systemic

exposure

(mg/kg

bw/day)

Quotient

Mixing/loading/application:

chemical resistant clothes

and gloves, full-face

respirator

0.1 150 15 0.00045 0.32

respirator

0.1 1500 150 0.0045 3.2

respirator

0.1 2500 250 0.0076 5.4

respirator

0.3 150 45 0.00136 0.97

respirator

0.3 1500 450 0.014 9.7

respirator

0.3 2500 750 0.023 16.2

Conclusion on operator risk assessment for enclosed space applications of EC solutions with

high pressure handwand

Space spraying of EC dichlorvos products is generally associated with operator exposures greater

than the AOEL, even with the use of chemical resistant clothing and full face RPE. Treatment of the

smallest spaces (150 m2) results in exposures below the AOEL provided the following PPE/RPE is

Chemical resistant clothes and a full face respirator (95 % protection)

Operator exposure could potentially be acceptable by limiting the amount handed to 45 g dichlorvos

per day.

Enclosed domestic space applications of RTU aerosol cans

In this use scenario a RTU aerosol can is applied manually in a domestic enclosed space as a

surface/crevice application for the control of a range of pests including cockroaches, ants, fleas,

silverfish and carpet beetles. The use rate is 0.25 g dichlorvos/m2. The operator risk assessment is

based on the assumption that the user will be a non-professional without the use of PPE.

Information in the original dichlorvos application indicates that the available product in New Zealand is

sold in 600 mL cans containing 3.1 g dichlorvos/L. Each can therefore contains 1.86 g of dichlorvos,

enough to treat 7.44 m2 at the recommended use rate.

The UK Chemicals Regulation Directorate (CRD) has models available to estimate exposures during

amateur use of pesticides. These models include one for aerosol surface treatment. The model

assumes rates of dermal (hand and forearm; 0.0647 mL/min; legs, feet and face: 0.0357 mL/min) and

inhalation exposure per minute taken for the task (0.0006 mL/min), with a default duration of 300

seconds (5 minutes). Predicted exposures are based on the model’s 75th percentile values. The

model assumes a default 60 kg body weight, rather than the 70 kg body weight used in the exposure

assessment for professional operators. This is considered appropriate as domestic users may be

expected to include a broader range of the population than professional operators.

The model is based on 15 sets of data from two exposure monitoring studies during tasks such as

spraying a small room including sofa, 6 metres of skirting board, 2 dining chairs, and 6 m2 of carpet.

The specific parameters inputted into the model for the evaluation of dichlorvos are:

discharge over a period of 5 minutes of a 600mL RTU can containing 3.1 g dichlorvos/L

30 % dermal absorption of dichlorvos

100 % inhalation absorption

Five minutes could seem a long time to discharge a 600mL can, but if it is assumed that the total time

in the treated room(s) will be influenced by the time needed to spray sofa cushions and more complex

items then this can be seen as a realistic assumption. EPA Staff have compared the predicted

exposure to the AOEL to derive a risk quotient value, on the assumption that it is possible that a home

user may use the spray repeatedly. Staff note that the modelling has not been adjusted to account for

the high volatility of dichlorvos, and therefore inhalation exposure is likely to have been

underestimated.

Table 35 Results of operator risk assessment for application of RTU aerosol cans in an enclosed domestic

Operation/RPE/PPE

Application

dichlorvos/m2)

Area treated

Total operator

systemic

exposure

(mg/kg

bw/day)

Quotient

Enclosed space

applications of RTU

aerosol cans

0.25 7.44 0.0079 6

Conclusion on operator risk assessment for application of RTU aerosol cans in an enclosed

domestic space

Domestic application of dichlorvos by amateur users is assumed to be performed without the use of

PPE or RPE. Predicted exposures to dichlorvos for domestic users spraying RTU aerosol cans to

treat indoor surfaces and crevices are higher than the AOEL. This value is also likely to be an

underestimate given that it was not possible to adjust the predicted inhalation exposure to account for

the volatility of dichlorvos.

Domestic application of RTU spray mixes to surfaces and crevices

This use scenario is based on amateur users loading a RTU spray solution into a knapsack sprayer

for applications to larger areas such as patios and decks. The registered product contains 4.4 g

dichlorvos/L and is sold in 4 L packs, therefore containing 17.6 g dichlorvos in total. No application

rate is recommended beyond the label statement that treated surfaces should be damp. It is

considered that this use scenario is similar to the scenario for enclosed space applications of EC

solutions with a high pressure handwand, except the operators will be amateur users rather than

professionals. Therefore no PPE or RPE can be expected to be used, and smaller areas are likely to

be treated.

For modelling purposes it has been assumed that the complete 4 L pack will be used in one session,

but the available models require an application rate for calculations. The professional products

recommend application rates of 0.3 g a.i./m2 for the control of similar pests, cockroaches, fleas etc. At

0.3 g a.i./m2, 4L of product containing 4.4 g dichlorvos/L (17.6 g in total) would cover approximately 60

The UK CRD’s POEM_07 (UK CRD, 2007) has a model available to estimate exposures during

amateur use of pesticides through knapsack sprayers which the BBA model does not, so this model

was used for this use scenario. The model assumes that hand contamination may be higher than for

professional users. The model also requires inputs for mixing/loading. The worst-case for hand

contamination during mixing/loading is posed by containers with separate measuring caps, and the

least exposure is expected when using an "integral squeeze-to-fill measure". As the product is a

RTU, no mixing is anticipated but only loading of the solution into a knapsack sprayer. Therefore the

lowest mixing/loading exposure option was used.

The default assumptions are that 5 L of product is applied, the operator uses no gloves, wears a T-

shirt and shorts, and exposure lasts for 30 minutes. However, as only 4L of the RTU product is to be

applied 24 minutes has been used as an upper limit for the time needed to spray 4L in place of the

default. Staff note that the modelling has not been adjusted to account for the high volatility of

dichlorvos, and therefore inhalation exposure is likely to have been underestimated.

Table 36 Results of operator risk assessment for domestic application of RTU spray mixes to surfaces and

crevices

Operation/RPE/PPE

Application

dichlorvos/m2)

Area treated

Total operator

systemic

exposure

(mg/kg

bw/day)

Quotient

Surface/crevice

application of RTU

spray mixes

0.3 60 0.285 204

Conclusion on operator risk assessment for domestic application of RTU spray mixes to

surfaces and crevices

Domestic application of dichlorvos by amateur users is assumed to be performed without the use of

PPE or RPE. Predicted exposures to dichlorvos for domestic users spraying outdoor domestic spaces

with RTU spray mixes using a knapsack sprayer are substantially higher than the AOEL. This value is

also likely to be an underestimate given that it was not possible to adjust the predicted inhalation

exposure to account for the volatility of dichlorvos. Staff are particularly concerned by the magnitude

by which the estimated exposure exceeds the AOEL, particularly as home users may be expected in

include more vulnerable individuals than healthy workers.

Public space manual fogging applications

This use scenario relates to the fogging of public spaces. Labels indicate that this use covers the

treatment of parks, beaches, sports areas and other fly breeding sites to control flies and mosquitos.

Dichlorvos is applied as a cold fog to wet the top 5 to 8 cm of litter to control larvae. For products

containing dichlorvos at 1000 g/L the use rate has been assumed to be 10 ml product/2 L

spraymix/100 m2, based on the area coverage for other applications. This is equivalent to 0.1 g

dichlorvos/m2.

It has been assumed that the application area could be up to 1 ha. This would require 1000 g

dichlorvos to be handled and applied.

Exposure during mixing and loading – Dermal exposure

The APVMA estimated exposures and risks for similar uses using a PHED model (mixing/loading by

open pour) as the most appropriate method to predict dermal exposure (APVMA, 2008). The

predicted dermal exposure rates on the head/neck, clothing and hands are 0.0116, 0.6622 and 6.248

mg a.i./kg handled, respectively.

The amount of dichlorvos (mg/day) absorbed from dermal exposure is calculated using the following

equation:

Where:

1 kg dichlorvos is assumed to be handled

P = penetration factor for protective equipment. This was assumed to be 10% (0.1) for gloves. With full body chemical resistant clothes and gloves, the penetration factor for head/neck and clothing was assumed to be 5% (0.05).

𝐵𝑊

SE(d) = systemic exposure via the dermal route [mg/kg bodyweight (bw)]

Estimated dermal exposures during mixing/loading are summarised below in table 37:

Table 37 Estimated dermal exposures during mixing/loading for public space manual fogging application

Application rate

(g a.i./m2)

treated

Active

handled

Dermal absorbed

dose with PPE

(mg/day)

Systemic Exposure with

PPE (mg/kg bw/day)

0.1 10,000 1 0.198 0.0028

Exposure during mixing and loading – Inhalation exposure

As with enclosed space applications of EC solutions with a high pressure handwand, the APVMA

considered that the rate of inhalation exposure predicted by the relevant PHED model would be a

significant underestimate for dichlorvos due to its high volatility. Again, the APVMA increased the

predicted rate of inhalation exposure from the PHED model (inhalation exposure rate of 0.00264 mg

a.i./kg handled during mixing/loading by open pour) 50-fold to give 0.132 mg dichlorvos/kg used.

Where:

𝐵𝑊

Where:

BW = 70 kg

Table 38 Estimated inhalation exposures during mixing/loading for public space manual fogging application

Application

rate (g

a.i./m2)

treated

Active

handled

Inhalation absorbed

dose when wearing

(mg/day)

Systemic Exposure

when wearing a full

face respirator

(mg/kg bw/day)

0.1 10,000 1 0.0066 0.00009

Exposure during application – Dermal exposure

The APVMA used the PHED model 19 (high pressure handwand application) to predict dermal

exposures during application. Predicted dermal exposure rates on head/neck, clothing and hands

were 0.184, 26.8 and 2.55 mg a.i./kg handled respectively.

The amount of dichlorvos (mg/day) absorbed from dermal exposure is calculated using the following equation:

Where:

1 kg dichlorvos is assumed to be handled

P = penetration factor for protective equipment. This was assumed to be 10% (0.1) for gloves. With full body chemical resistant clothes and gloves, the penetration factor for head/neck and clothing was assumed to be 5% (0.05).

𝐵𝑊

SE(d) = systemic exposure via the dermal route [mg/kg bodyweight (bw)]

Estimated dermal exposures during mixing/loading are summarised below in table 39:

Table 39 Estimated dermal exposures during application for public space manual fogging application

Application

rate (g

a.i./m2)

treated

Active

handled

Dermal absorbed

dose with PPE

(mg/day)

Systemic

Exposure with

PPE (mg/kg

bw/day)

0.1 10,000 1 0.4813 0.0069

Exposure during application – Inhalation exposure

The APVMA also used the PHED model 19 to estimate inhalation exposure for outdoor application by

space spray. The estimated inhalation exposure rate is 0.174 mg a.i./kg handled.

Where:

𝐵𝑊

Where:

BW = 70 kg

Table 40 Estimated inhalation exposures during application for public space manual fogging application

Application

rate (g a.i./m2)

treated

Active

handled

Inhalation absorbed

dose when wearing

(mg/day)

Systemic Exposure

when wearing a full

face respirator (mg/kg

bw/day)

0.1 10000 1 0.0087 0.000124

Risk quotients

The combined dermal and inhalation exposures from mixing/loading and application are compared

with the AOEL to derive the risk quotient.

Table 41 Operator risk assessment for public space manual fogging applications

Operation/RPE/PPE

Application rate

dichlorvos/m2)

Area treated

Total operator

systemic

exposure

(mg/kg

bw/day)a

Risk Quotient

Mixing/Loading: chemical

resistant clothing, gloves

and full-face respirator c

resistant clothing, gloves

and full-face respirator c

0.1 10000 0.0099 7.1

Conclusion on operator risk assessment for public space manual fogging applications

Public space fogging application of dichlorvos by professional operators is associated with predicted

operator exposures that are greater than the AOEL, even when wearing chemical resistant clothing

and a full-face respirator during mixing, loading and application.

Re-entry worker risk assessment – indoor use scenarios

Re-entry exposures have been assessed for workers entering enclosed industrial spaces either to

carry out tasks associated with ventilation, or to undertake work in the building. For domestic uses

and uses in public spaces, estimates of re-entry exposure and risk are considered in the section on

bystanders and residents.

Re-entry worker risk assessment for enclosed industrial spaces

The risk assessment for re-entry into enclosed industrial spaces is based on the approach taken by

the APVMA. Re-entry risks have been assessed for workers re-entering a treated building to ventilate

it, and also for workers re-entering and working in treated industrial buildings. After indoor application,

the fate and behaviour of dichlorvos residues in the air and on surfaces are strongly influenced by a

number of environmental parameters. The most important of these are probably the rate of air

exchange, temperature and the amount of sunlight entering the structure. However, a proportion of

airborne dichlorvos becomes deposited on surfaces, where it may degrade or become adsorbed. A

significant proportion of deposited dichlorvos can subsequently re-enter the atmosphere. Although

dichlorvos decomposes rapidly if it contacts concrete or glass, it persists in carpet fabric and is highly

persistent on wood, which may act as reservoirs. Dichlorvos has been detected in the atmosphere of

buildings fumigated several weeks previously (APVMA 2008). Therefore it is considered appropriate

to compare predicted re-entry exposures to the AOEL rather than an acute exposure guidance value.

Exposure study used in the risk assessment

The APVMA used a study by Schofield (1993, original not seen), in which a large food manufacturing

building was fogged with dichlorvos, as the basis of the exposure assessment for re-entry to industrial

buildings. A brief summary of the study is provided below.

The study was quality assured and GLP certified but did not conform to all the conditions required for

GLP. The exceptions related to a failure to record pesticide use history and atmospheric conditions at

the application site, or to maintain SOPs for the pesticide application equipment. In addition, progress

inspections were not performed during laboratory analysis.

The study was conducted at a seven-storey baked food manufacturing facility in the USA to assess

exposure of workers following application of dichlorvos. Three processing areas were selected for

evaluation: a 3336 m3 packaging room (location 1), a 3021 m

3 room where final products were

received from other locations (location 2) and a 634 m3 ingredient mixing room (location 3).

Dichlorvos was applied at a target concentration of 85 mg/m3 using a single portable electric fogger

and multiple commercial wall-mounted fogging units. Six hours after application the building was

ventilated for approximately one hour before workers were allowed to re-enter. The half-life of

airborne dichlorvos during the period spanning application to the end of the venting was 1.6 hours.

The study author’s regression analysis of Ln concentration versus time gave a Y intercept of 2.996

(which is Ln [20.0 mg/m3]), a slope (i.e. the rate of loss of dichlorvos) of -0.4207/hour and an R

During the period following ventilation, mean time-weighted airborne dichlorvos levels fell

progressively at a much slower half-life than in the first period of the study, at 12.7 hours. The

regression analysis of Ln concentration versus time gave a Y intercept of 0.611, a slope of -

0.0544/hour and an R2 of 0.74 indicating considerably more variability and uncertainty in the

measurements made during this period than those in the pre-ventilation period.

Analysis of dichlorvos residues on the hands of workers participating in the study indicated that

dichlorvos was present on the hands of all workers on the morning of the first day post application.

Residue recovery during the afternoon of day 1 had decreased by approximately 20-73%, depending

on the location of the workers. The decline continued over the following two days and dichlorvos

residues at the final sampling time had fallen to 5.8-8.6% of the initial amounts recovered. The

dissipation half-life of dichlorvos residues recovered from the hands was estimated at 13 hours,

similar to the second-phase half-life of dichlorvos in the air. The APVMA calculated that the systemic

dose arising from dermal exposure would have been approximately two orders of magnitude lower

than intake via ventilation.

Limitations of the exposure study

Staff have used this study to underpin the re-entry exposure assessment for industrial buildings in the

absence of more suitable data. However, it is important to note that there are a number of limitations

and uncertainties involved in using this study.

The building was kept closed for 6 hours following application and was only ventilated for one

hour. There is considerable uncertainty in extrapolating the data to the New Zealand use pattern,

where a treated building is kept closed for 10-12 hours and then ventilated for a further 10-12

hours.

Due to the short ventilation period in the study it has not been possible to calculate separate half-

lives for airborne dichlorvos during the pre-ventilation phase, the ventilation phase and the post-

ventilation phase. As a worst case the slower half-life for the period following ventilation has been

applied to the time following the start of ventilation.

Exposures have been extrapolated to time periods beyond where they were measured.

It is unclear whether the building was ventilated mechanically (i.e. via an air conditioning system)

or passively during this period, or at other times during the study.

The EPA requests that anyone with additional information on dichlorvos exposure levels

following application in industrial buildings provides this to the EPA.

Re-entry risks for workers ventilating industrial buildings after treatment

Product labels recommend that treated enclosed spaces should be kept closed for 10-12 hours before

ventilation, and that the building should be ventilated for another 10-12 hours before people

recommence work in treated buildings. It is assumed that tasks associated with ventilation would

probably only take a few minutes and would seldom exceed 30 minutes.

Exposure for workers re-entering a building to perform tasks associated with ventilation has been

assessed at 12 hours following treatment. The concentration of dichlorvos to which a worker would be

exposed on re-entry for ventilation is estimated based on the rate of dissipation measured by

Schofield (1993) during the six hours following application and the one hour ventilation period.

The main New Zealand application rate of 50 mg/m3 is approximately 58.8% of the rate used in the

study by Schofield (85 mg/m3). The regression plot intercept from the Schofield study has therefore

been adjusted downwards to 2.465 (Ln [20 x 0.588]) while it has been assumed that the same

dissipation rate will apply (-0.4207/h).

The airborne concentration of dichlorvos at 12 hours following treatment can be calculated:

𝑒(2.465+[−0.4207×12]) = 0.076 𝑚𝑔/𝑚3

At the higher application rate of 150 mg/m3, the regression plot intercept is adjusted to 3.564 (Ln [20 x

1.7647]) and the airborne concentration of dichlorvos 12 hours following treatment would be:

𝑒(3.564+[−0.4207×12]) = 0.227 𝑚𝑔/𝑚3

Assuming that a worker would spend a maximum of 30 minutes in a building to perform tasks

associated with ventilation and an inhalation rate of 1 m3 per hour, the predicted inhalation exposures

at venting with various levels of RPE can be calculated using the following formula:

𝑆𝐸(𝑖) =[𝐷𝑖𝑐ℎ𝑙𝑜𝑟𝑣𝑜𝑠]×𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝑑𝑢𝑟𝑎𝑡𝑖𝑜𝑛×𝐼𝑅×𝐼𝐴×𝑃

𝐵𝑊

Where:

[Dichlorvos] = airborne dichlorvos concentration [mg/m3]

Exposure duration = 0.5 hours

IR = inhalation rate [1m3/hour]

IA = inhalation absorption [1, i.e. 100%]

The APVMA considered that dermal exposure during this venting process would be negligible

compared to the inhalation exposures. Schofield (1993) measured dichlorvos in hand rinsates from

workers re-occupying treated buildings which indicated that dermal exposures were approximately

two orders of magnitude lower than inhalation exposure. Therefore dermal exposures were not

included in the calculation for this exposure scenario.

Table 42 Risk assessment for re-entry into treated industrial buildings for venting 12 hours after application

Conclusion on re-entry to treated buildings for ventilation purposes

Exposure to dichlorvos during re-entry to treated buildings for ventilation purposes is acceptable at

both application rates, provided respiratory protective equipment (95 % protection) is worn. It is also

recommended that gloves are required to be worn to ensure that dermal exposure is minimised.

Re-entry risks for workers re-entering and working in industrial buildings after treatment and

ventilation

The APVMA approach to the exposure assessment for workers re-entering and working in buildings

following ventilation was also based on the study by Schofield (1993). As noted above, caution should

be taken when interpreting these results as the predicted concentrations of dichlorvos in air are

estimated from one study and involve significant extrapolation of data beyond the time periods when

they were collected. It is not possible to estimate a dissipation half-life for dichlorvos during the

ventilation period as the ventilation period in the Schofield study was just one hour. As a worst case

the slower dissipation half-life measured in the post-ventilation period has been applied to the

estimated airborne concentration of dichlorvos at the start of ventilation.

It was again considered that persons re-occupying a dichlorvos-treated building would be exposed to

dichlorvos mainly by inhalation. Schofield measured dermal exposure to dichlorvos on day 3 following

application as 0.0024 mg. In order for RQ values for exposure to remain below 1, it was calculated

that the maximum time weighted average (TWA) concentration of dichlorvos in the atmosphere over

an 8 hour work day should be 0.01 mg/m3 based on the following considerations. An individual

breathing a TWA of 0.01 mg/m3 for an 8 hour working day at an inhalation rate of 1 m

3/hour would be

exposed to 0.08 mg of dichlorvos per day. If the dermal exposure measured on day 3 following

application by Schofield is added to this, the total daily exposure would be 0.0824 mg/day. This

equates to a systemic exposure for individuals with a 70 kg body weight of 0.00118 mg/kg bw/day,

lower than the AOEL (RQ: 0.8).

Application rate

(mg/m3)

Airborne dichlorvos

concentration

(mg/m3)

Exposure

duration

Systemic

exposure

when wearing

a respirator

(mg/kg

bw/day)

Risk Quotient

50 0.076 0.5 0.000027 0.02

150 0.227 0.5 0.000081 0.06

In the study by Schofield, the dissipation half-life of dichlorvos during the post-ventilation period was

12.7 hours. The regression analysis of Ln concentration vs time data gave the slope as -0.0544/hour.

The time taken for the concentration of dichlorvos to decline to 0.01 mg/m3 can be calculated using

the following equation:

(𝐿𝑛 𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛−𝐿𝑛 𝐹𝑖𝑛𝑎𝑙 𝑐𝑜𝑛𝑐𝑒𝑛𝑡𝑟𝑎𝑡𝑖𝑜𝑛)

𝑆𝑙𝑜𝑝𝑒

Where:

Ln Initial concentration = Ln 0.076 (-2.577) at 50 mg/m3; Ln 0.227 (-1.4828) at 150 mg/m

Ln final concentration = Ln 0.01 (-4.6052)

Slope = 0.0544

The time required following commencement of ventilation for the dichlorvos concentration to reach the

acceptable level of 0.01 mg/m3 is:

37.3 hours at an application rate of 50 mg/m3

57.4 hours at an application rate of 150 mg/m3

Conclusion on re-entry to ventilated treated buildings for work purposes

At the lower application rate (50 mg/m3), the time required after the onset of ventilation for the

airborne dichlorvos concentration to decline to an acceptable level is estimated at 37.3 hours. At the

higher application rate (150 mg/m3) the time required following the onset of ventilation for dichlorvos

concentrations to decline to an acceptable level is estimated at 57.4 hours. In order to allow for

uncertainties in the characteristics of different buildings, and uncertainties relating to extrapolation of

data from a study with a lower application rate (85 mg/m3) to time points beyond those measured, it is

proposed that a re-entry interval of 4 days after the onset of ventilation would need to be applied. This

is consistent with that set by the APVMA.

Bystander and resident exposure and risk assessment

Bystander and resident risks from treatment of enclosed industrial buildings

Bystander exposure following treatment of enclosed industrial buildings could occur either as a result

of leaking from the building if it cannot be completely sealed, or once the building is opened up for

ventilation. EPA Staff have not been able to locate any exposure models or monitoring data to enable

quantification of the potential bystander exposure following application of dichlorvos in these use

scenarios. However, it is noted that the exposure modelling for bystanders in the vicinity of

greenhouse indicates that there is a potential for bystander exposure that may be of concern. In the

absence of any specific information EPA staff have assumed that application of dichlorvos in industrial

buildings could also result in potential risks for bystanders.

Resident risks from enclosed space application of RTU aerosol cans

When dichlorvos is applied in domestic buildings, individuals may have direct contact with

contaminated surfaces and objects. Children are expected to be most at risk due to their potential for

high amounts of contact and hand to mouth exposure, exploratory nature and low body weight. The

resident exposure assessment therefore assesses risks to toddlers. Given that dichlorvos has been

detected in the atmosphere of buildings fumigated several weeks previously it is considered

appropriate to compare predicted resident exposures to the AOEL rather than an acute exposure

guidance value. Exposure is estimated using the equations from the UK Chemical Regulation

Directorate (CRD) which account for dermal exposure, hand-to-mouth exposure and object-to-mouth

exposure (Chemicals Regulation Directorate, 2010a).

The modelling includes a number of assumptions and uncertainties. It was assumed that the toddler

would be exposed to the application rate which is expected to overestimate exposure (assumes spray

stays on the surface where it is applied and there is no dissipation before or during exposure) due to

lack of information on the behaviour of dichlorvos following treatment of residential houses with

furniture, soft furnishing etc. However it should also be noted that potential inhalation exposure from

volatilised dichlorvos has not been estimated which will mean that the results should be seen as

potential underestimates.

Children’s dermal exposure

Systemic exposures via the dermal route were calculated using the following equation (Chemicals

Regulation Directorate, 2010a):

SE (d) = AR x TTR x TC x H x DA

SE (d) = 25 x 0.05 x 5200 x 8 x 0.3 15

Where: SE(d) = systemic exposure via the dermal route AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues – the USEPA default value of 5 % was used in the absence of information on the behaviour of dichlorvos following treatment of residential houses with furniture, soft furnishing etc.

TC = transfer coefficient – the standard USEPA value of 5200 cm2/h was used for the

matches the average time in any one indoor space DA = percent dermal absorption (0.3 [i.e. 30%]) BW = body weight – 15 kg which is the average of UK 1995-7 Health Surveys for England

Children’s hand-to-mouth exposure

Hand-to-mouth exposures was calculated using the following equation (Chemicals Regulation

SE(h) = AR x TTR x SE x SA x Freq x H

SE(h) = 25 x 0.05 x 0.5 x 20 x 20 x 8 15

Where: SE(h) = systemic exposure via the hand-to-mouth route AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues – the USEPA default value of 5% derived from transferability studies with wet hands was used in the absence of information on the behaviour of dichlorvos following treatment of residential houses with furniture, soft furnishing etc.

2 of skin area is

Freq = frequency of hand to mouth events/hour – for short term exposures the value of 20 events/hour was used, this is the 90th percentile of observations that ranges from 0 to 70 events/hour

H = exposure duration (hours) – this will be assumed to be 8 hours (as above) BW = body weight - 15kg (as above)

Children’s object-to-mouth exposure

Object to mouth exposures was calculated using the following equation (Chemicals Regulation

SE(o) = AR x TTR x IgR

SE(o) = 25 x 0.2 x 25

Where: SE(o) = systemic exposure via mouthing activity AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues: the default value of 20% transferability from object to mouth assessments was used in the absence of information on the behaviour of dichlorvos following treatment of residential houses with furniture, soft furnishing etc.

IgR = ingestion rate for mouthing grass/day – this was assumed to be equivalent to 25cm2

of grass/day BW = body weight - 15kg (as above)

Children’s total exposure Total exposure was calculated as the sum of the above equations: ∑ Exposure = SE (d) + SE (h) + SE (o) Risk quotients were estimated by comparing predicted exposure to the AOEL.

Table 43 Risk assessment for residents exposure following indoor domestic application of dichlorvos

Exposure source Exposure

(mg/kg bw/day) Risk Quotient (RQ)

Child’s dermal

exposure 1.04

Child’s hand-to-mouth

exposure 0.133

Child’s object-to-mouth

exposure 0.00833

Child’s total exposure 1.182 844

Conclusion on residents exposure following indoor application of dichlorvos

Children’s exposure to dichlorvos following application in indoor domestic areas is predicted to be

substantially higher than the AOEL. It should be noted, however, that there are a number of

uncertainties in the exposure modelling. No dissipation of dichlorvos has been factored in due to a

lack of relevant information on the behaviour of dichlorvos after the treatment of residential houses

with furniture, soft furnishings etc. While this may be expected to overestimate dermal exposure, it

should also be noted that it has not been possible to estimate inhalation exposure to volatilised

dichlorvos in this scenario. EPA staff are particularly concerned by the magnitude by which the

estimated exposure level exceeds the AOEL.

Bystander and resident risks from outdoor domestic application of dichlorvos

A similar approach has been taken to assess bystander/resident risks from outdoor domestic

application of dichlorvos as was used for the risks to residents following indoor application, although

due to the outdoor use scenario potential exposure from incidental ingestion of soil has also been

assessed. Children are expected to be most at risk due to their potential for high amounts of contact

and hand to mouth exposure, exploratory nature and low body weight. The exposure modelling

therefore assesses risks to toddlers.

(USEPA, 2007).

would be exposed to the application rate which could potentially overestimate exposure (assumes

spray stays on the surface where it is applied and there is no dissipation before or during exposure). It

is not possible to factor in dissipation due, in part, to the fact that the treated surfaces are expected to

vary in terms of their characteristics. The surfaces could range from concrete, which is reported to

cause rapid degradation of dichlorvos, to wooden decks which may act as a reservoir (APVMA,

2008). It should also be noted that potential inhalation exposure from volatilised dichlorvos has not

been estimated.

Given that dichlorvos may be present for some time following application it is considered appropriate

to compare predicted bystander/resident exposures to the AOEL rather than an acute exposure

guidance value.

Children’s dermal exposure Systemic exposures via the dermal route were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE (d) = AR x TTR x TC x H x DA BW

SE (d) = 25 x 0.05 x 5200 x 2 x 0.3 15

Where: SE(d) = systemic exposure via the dermal route AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues – the USEPA default value of 5 % was used. TC = transfer coefficient – the standard USEPA value of 5200 cm

2/h was used for the

matches the 75th percentile for toddlers playing on grass in the USEPA Exposure Factors Handbook

DA = percent dermal absorption (0.3 [i.e. 30%]) BW = body weight – 15 kg which is the average of UK 1995-7 Health Surveys for England

Children’s hand-to-mouth exposure Hand-to-mouth exposures were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE(h) = AR x TTR x SE x SA x Freq x H BW

SE(h) = 25 x 0.05 x 0.5 x 20 x 20 x 2 15

Where: SE(h) = systemic exposure via the hand-to-mouth route AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues – the USEPA default value of 5% derived from transferability studies with wet hands was used.

2 of skin area is

Children’s object-to-mouth exposure Object to mouth exposures were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE(o) = AR x TTR x IgR BW

SE(o) = 25 x 0.2 x 25 15

Where: SE(o) = systemic exposure via mouthing activity AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

TTR = turf transferable residues: the default value of 20% transferability from object to mouth assessments was used.

Children’s incidental ingestion of soil

The approach that was used to calculate doses attributable to soil ingestion is (US EPA, 1997):

ADOD = AR (μg/cm2) x F (cm) x IgR (mg/day) x SDF (cm

BW (kg) ADOD = 25 x 1 x 100 x (6.7 x 10

Where: ADOD = oral dose on day of application (μg/kg bw/day) AR = field application rate (2.5 kg/ha [recommended rate is 0.25 g dichlorvos/m

2 = 25

µg/cm2])

F = fraction or residue retained on uppermost 1 cm of soil (%) (Note: this is an adjustment from surface area to volume)

SDF = soil density factor - volume of soil (cm3) per milligram of soil

IgR = ingestion rate of soil (mg/day) BW = body weight (kg) Assumptions: F = fraction or residue retained on uppermost 1 cm of soil is 100 percent based on soil

incorporation into top 1 cm of soil after application (1.0/cm) IgR = ingestion rate of soil is 100 mg/day SDF = soil density factor - volume of soil (cm

3) per gram of soil; to weight 6.7 x 10

soil) BW = body weight of a toddler is 15 kg (as above)

Children’s total exposure Total exposure was calculated as the sum of the above equations: ∑ Exposure = SE (d) + SE (h) + SE (o) + ADOD Risk quotients were estimated by comparing predicted exposure to the AOEL.

Table 44 Risk assessment for bystander and resident exposure from outdoor domestic application of

dichlorvos

Child’s dermal

exposure 0.26

exposure 0.033

exposure 0.00833

Child’s soil ingestion 0.0001117

Conclusion on bystander and resident exposure following outdoor domestic application of

dichlorvos

Children’s exposure to dichlorvos following application in outdoor domestic areas is predicted to be

substantially higher than the AOEL. It should be noted, however, that there are a number of

uncertainties in the exposure modelling. No dissipation of dichlorvos has been factored in due to the

variety of surfaces that may be treated. The treated surfaces could be anything from concrete, which

is reported to cause rapid degradation of dichlorvos, to wooden decks which may act as a reservoir

(APVMA, 2008). While this may be expected to overestimate dermal exposure, it should also be

noted that it has not been possible to estimate inhalation exposure to volatilised dichlorvos in this

scenario. EPA staff are particularly concerned by the magnitude by which the estimated exposure

level exceeds the AOEL.

Bystander risks from outdoor application of dichlorvos in public spaces

A similar approach has been taken to assess bystander risks for outdoor public space application of

dichlorvos as was used for the assessment of risks for bystanders following outdoor domestic

application. Children are expected to be most at risk due to their potential for high amounts of contact

and hand to mouth exposure, exploratory nature and low body weight. The exposure modelling

therefore assesses risks to toddlers.

(USEPA, 2007).

would be exposed to the application rate which could potentially overestimate exposure (assumes

spray stays on the surface where it is applied and there is no dissipation before or during exposure). It

is not possible to factor dissipation into the assessment due, in part, to the complexity of what

constitutes public spaces. These spaces include concrete, parks, beaches and playgrounds. However

it should also be noted that potential inhalation exposure from volatilised dichlorvos has not been

estimated.

Given that dichlorvos may be present for some time following application it is considered appropriate

to compare predicted bystander/resident exposures to the AOEL rather than an acute exposure

guidance value.

Children’s dermal exposure Systemic exposures via the dermal route were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE (d) = AR x TTR x TC x H x DA

SE (d) = 10 x 0.05 x 5200 x 2 x 0.3 15

Where: SE(d) = systemic exposure via the dermal route AR = field application rate (1 kg/ha = 10 µg/cm

TTR = turf transferable residues – the USEPA default value of 5 % was used. TC = transfer coefficient – the standard USEPA value of 5200 cm

2/h was used for the

matches the 75th percentile for toddlers playing on grass in the USEPA Exposure Factors Handbook

DA = percent dermal absorption (0.3 [i.e. 30%]) BW = body weight – 15 kg which is the average of UK 1995-7 Health Surveys for England

Children’s hand-to-mouth exposure Hand-to-mouth exposures were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE(h) = AR x TTR x SE x SA x Freq x H BW

SE(h) = 10 x 0.05 x 0.5 x 20 x 20 x 2 15

Where: SE(h) = systemic exposure via the hand-to-mouth route AR = field application rate (1 kg/ha = 10 µg/cm

TTR = turf transferable residues – the USEPA default value of 5% derived from transferability studies with wet hands was used.

2 of skin area is

Children’s object-to-mouth exposure Object to mouth exposures were calculated using the following equation (Chemicals Regulation Directorate, 2010a):

SE(o) = AR x TTR x IgR BW

SE(o) = 10 x 0.2 x 25

Where:

SE(o) = systemic exposure via mouthing activity AR = field application rate (1 kg/ha = 10 µg/cm

TTR = turf transferable residues: the default value of 20% transferability from object to mouth assessments was used.

Children’s incidental ingestion of soil The approach that was used to calculate doses attributable to soil ingestion is (US EPA, 1997):

ADOD = AR (μg/cm

2) x F (cm) x IgR (mg/day) x SDF (cm

BW (kg) ADOD = 10 x 1 x 100 x (6.7 x 10

Where: ADOD = oral dose on day of application (μg/kg bw/day) AR = field application rate (1 kg/ha = 10 µg/cm

F = fraction or residue retained on uppermost 1 cm of soil (%) (Note: this is an adjustment from surface area to volume)

SDF = soil density factor - volume of soil (cm3) per milligram of soil

IgR = ingestion rate of soil (mg/day) BW = body weight (kg) Assumptions: F = fraction or residue retained on uppermost 1 cm of soil is 100 percent based on soil

incorporation into top 1 cm of soil after application (1.0/cm) IgR = ingestion rate of soil is 100 mg/day SDF = soil density factor - volume of soil (cm

3) per gram of soil; to weight 6.7 x 10

soil) BW = body weight of a toddler is 15 kg (as above)

Children’s total exposure Total exposure was calculated as the sum of the above equations: ∑ Exposure = SE (d) + SE (h) + SE (o) + ADOD Risk quotients were estimated by comparing predicted exposure to the AOEL.

Table 55 Risk assessment for bystanders exposure from outdoor application of dichlorvos in public spaces

Child’s dermal

exposure 0.104

exposure 0.0133

exposure 0.0033

Child’s soil ingestion 0.000045

Conclusion on bystander/resident exposure following outdoor application of dichlorvos in

public spaces

Children’s exposure to dichlorvos following application in outdoor public spaces is predicted to result

in exposure substantially higher than the AOEL. It should be noted, however, that there are a number

of uncertainties in the exposure modelling. No dissipation of dichlorvos has been factored in due to

the variety of spaces in which dichlorvos may be applied. Treated surfaces could include concrete,

parks, beaches and playgrounds etc. While this may be expected to overestimate dermal exposure, it

should also be noted that it has not been possible to estimate inhalation exposure to volatilised

dichlorvos in this scenario. EPA staff are particularly concerned by the magnitude by which the

estimated exposure level exceeds the AOEL.

References

APVMA, 2008 Dichlorvos Occupational Health and Safety Assessment The reconsideration of approvals of the active constituent, registrations of products containing dichlorvos and approvals of their associated labels Available online at http://apvma.gov.au/sites/default/files/dichlorvos-phase-5-ohs.pdf Accessed 17/09/2014 APVMA, Standard Spray Drift Risk Assessment Scenarios, Available online at http://test.apvma.gov.au/archive/spray_drift/scenarios.php#ground Accessed 17/09/2014 Brouwer DH et al (1992) Dissipation of aerosols from greenhouse air after application of pesticides using a low-volume technique. Implications for safe re-entry. Chemosphere 24 (9); 1157 – 1169. California Environmental Protection Agency, Guidance for the preparation of human pesticide exposure assessment documents, Available online at http://www.cdpr.ca.gov/docs/whs/pdf/hs1612.pdf Accessed 13/10/2014 Casida, J.E., L. McBride, and R.P. Niedermeier, 1962. Metabolism of 2,2-dichlorvinyl dimethyl phosphate in relation to residues in milk and mammalian tissues. J. Agric. Food Chem. 10:370-377 Chemicals Regulation Directorate, Bystander Exposure Guidance, Available online at http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/B/Bystander-exposure-guidance.pdf Accessed 27/01/2010a. Chemicals Regulation Directorate, Guidance for post-application (re-entry worker) exposure assessment. Available at http://www.pesticides.gov.uk/guidance/industries/pesticides/topics/pesticide-approvals/pesticides-registration/data-requirements-handbook/guidance-on-post-application-re-entry-worker-exposure-to-pesticides Accessed 16/08/2010b Chemicals Regulation Directorate, PSD’s interpretation of the German Operator Exposure Model Available online at http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/G/German_Model_PSD1.xlsAccessed 27/01/2010c. EUROPOEM II project ,2002, Post application exposure of workers to pesticides in agriculture, report of the re-entry working group. FAIR-CT96-1406. EFSA, 2008a. Initial Risk assessment provided by the rapporteur member state The Netherlands for the existing active substance didecyldimethylammonium chloride of the fourth stage of the review programme referred to in Article 8(2) of the Council Directive 91/414/EEC Volume 3, Annex B, Part 6 EFSA, 2008b Project to assess current approaches and knowledge with a view to develop a Guidance Document for pesticide exposure assessment for workers, operators, bystanders and residents Available online at http://www.efsa.europa.eu/en/scdocs/doc/26e.pdf Accessed 18/09/2014 EFSA Scientific Report (2006) Conclusion on the peer review of dichlorvos, 77, 1-43.

Forum for the Co-ordination of pesticide fate models and their USe. Available online at http://focus.jrc.ec.europa.eu/ Accessed 18/09/2014 Jeffcoat R (1990) Dermal absorption of dichlorvos® in rats. RTI Study No. 4615-1. Lab: Research Triangle Institute, Research Triangle Park, North Carolina, USA. Sponsor: AMVAC Chemical Corporation, Los Angeles, California, USA. Unpublished [AMVAC; sub: 12161, Vol 69 of 85] [In APVMA, 2008; Original not sighted]

Kirkland VL (1971) Some aspects of acute inhalation pharmacology of dichlorvos in swine. Paper presented at: American Chemical Society for Pharmacology and Experimental Therapeutics and the Division of Medical Chemistry, Burlington, Vermont, 25 August 1971. [In APVMA, 2008; Original not sighted]

Occupational Safety and Health Administration, Chemical Sampling Chlorpyrifos (Dursban), DDVP

(Dichlorvos), Diazinon, Malathion Parathion Available online at

https://www.osha.gov/dts/sltc/methods/organic/org062/org062.html 18/09/2014

Rider JA (1967) Determination of the minimal incipient toxicity of dichlorvos in humans. Report and Study No.s unspecified. Lab: Gastrointestinal Research Laboratory, Franklin Hospital, San Francisco, CA, USA. Sponsor: Shell Chemical Company, Agricultural Chemicals Division, New York, New York, USA. Unpublished. [Kiwi Brands Pty Ltd; sub 11606, Vol 2 of 4] [In APVMA, 2008; Original not sighted]

RIVM Pesticide emissions from greenhouses Proposal for the risk assessment system USES RIVM report 601450014/2004 Available online at publicaties.minienm.nl/download-bijlage/22242/1m378.pdfAccessed 01/10/14 RIVM (1998) Airborne pesticides concentrations near greenhouses [acute exposure and potential effects to humans]. RIVM Report No.679102040. Available online at http://www.rivm.nl/bibliotheek/rapporten/679102040.htmlAccessed 01/10/14 Schofield CM (1993a) Exposure assessment of dichlorvos in a food handling establishment: Manufacturing facility. Study No. SARS – 92 – 15. Labs: Stewart Agricultural Research Associates, Inc., Macon, MO, USA and Horizon Laboratories Inc., Columbia, MO, USA. Sponsor: AMVAC Chemical Corporation, Los Angeles, CA, USA. Study Duration: 27 October 1992 – 30 April 1993. Report date: 30 April 1993. [AMVAC; submission to NOHSC, Volume 5 of 8] [In APVMA, 2008; Original not sighted]

Schofield CM (1993b) Confidential attachment to: Exposure assessment of dichlorvos in a food handling establishment: Manufacturing facility. Study No. SARS – 92 – 15. Labs: Stewart Agricultural Research Associates, Inc., Macon, MO, USA and Horizon Laboratories Inc., Columbia, MO, USA. Sponsor: AMVAC Chemical Corporation, Los Angeles, CA, USA. Study Duration: 27 October 1992 – 30 April 1993. Report date: 30 April 1993. [AMVAC; submission to NOHSC, Volume 6 of 8] [In APVMA, 2008; Original not sighted]

Soil persistence models and EU registration: Available online at http://ec.europa.eu/food/plant/protection/evaluation/guidance/soil_en.pdf Accessed 03/02/10

UK Chemicals Regulation Directorate. Operator exposure guidance for amateur (home use) pesticides. Available for download at http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/A/Amateur-use-guidance-2.pdf Accessed 10 October 2014.

UK Chemicals Regulation Directorate. UK POEM Operator exposure model. Available for download at http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/U/UK_POEM_07.xls

Accessed 10 October 2014

UK Chemicals Regulation Directorate. Exposure model for amateur (home use) pesticides. Available for download at http://www.pesticides.gov.uk/Resources/CRD/Migrated-Resources/Documents/A/Amateur-use-model2.xls Accessed 10 October 2014.

USEPA, 1996 OCSPP Harmonized Test Guidelines, Series 875 - Occupational and Residential

Exposure Test Guidelines Available online at

http://www.epa.gov/ocspp/pubs/frs/publications/Test_Guidelines/series875.htm Accessed 23/09/2014

USEPA, 2007, Standard Operating Procedures (SOPs) for Residential Exposure Assessments, Contract No. 68-W6-0030, Work Assignment No. 3385.102 USEPA, 2006, Reregistration Eligibility Decision for Dichlorvos (DDVP) http://www.epa.gov/oppsrrd1/REDs/ddvp_red.pdf Accessed 18/09/14

Annex 1 AGDISP Input Data Summary for application of dichlorvos to cucurbits, brassica and lettuce

This section summarises the input parameters that were used for the modelling of spraydrift from the

aerial application of dichlorvos to cucurbits, brassica and lettuce using the AGDISP model.

--General--

Title: Dichlorvos cucurbit 855g/ha

Notes:

Calculations Done: Yes

Run ID: AGDISP dichlorvos855gha.ag 8.15 02-21-2012 10:59:35

--Aircraft-- ----------------------------

Name Air Tractor AT-402B

Type User-defined

Boom Height (m) 3

Spray Lines 10

Optimize Spray Lines No

Spray Line Reps # Reps

Wing Type Fixed-Wing

Semispan (m) 7.79

Typical Speed (m/s) 59.16

Biplane Separation (m) 0

Weight (kg) 4000

Planform Area (m²) 26.02

Propeller RPM 2000

Propeller Radius (m) 1.33

Engine Vert Distance (m) 0

Engine Fwd Distance (m) 4.35

--Aerial Application Type-- ----------------------------

Aerial Application Type Liquid

--Drop Size Distribution-- ----------------------------

Name ASAE Fine to Medium

Type Reference

Drop Categories # Diam (um) Frac

1 10.77 0.0010

2 16.73 0.0003

3 19.39 0.0007

4 22.49 0.0003

5 26.05 0.0007

6 30.21 0.0010

7 35.01 0.0010

8 40.57 0.0020

9 47.03 0.0033

10 54.50 0.0053

11 63.16 0.0067

12 73.23 0.0090

13 84.85 0.0133

14 98.12 0.0223

15 113.71 0.0330

16 131.73 0.0393

17 152.79 0.0480

18 177.84 0.0647

19 205.84 0.0830

20 238.45 0.1147

21 276.48 0.1283

22 320.60 0.1380

23 372.18 0.1127

24 430.74 0.0640

25 498.91 0.0440

26 578.54 0.0317

27 670.72 0.0203

28 777.39 0.0093

29 900.61 0.0010

30 1044.42 0.0007

31 1210.66 0.0003

--Nozzle Distribution-- ----------------------------

Boom Length (%) 73

Nozzle Locations # Hor(m) Ver(m) Fwd(m)

1 -5.69 0 0

2 -5.49 0 0

3 -5.3 0 0

4 -5.11 0 0

5 -4.92 0 0

6 -4.72 0 0

7 -4.53 0 0

8 -4.34 0 0

9 -4.14 0 0

10 -3.95 0 0

11 -3.76 0 0

12 -3.57 0 0

13 -3.37 0 0

14 -3.18 0 0

15 -2.99 0 0

16 -2.8 0 0

17 -2.6 0 0

18 -2.41 0 0

19 -2.22 0 0

20 -2.02 0 0

21 -1.83 0 0

22 -1.64 0 0

23 -1.45 0 0

24 -1.25 0 0

25 -1.06 0 0

26 -0.8675 0 0

27 -0.6747 0 0

28 -0.4819 0 0

29 -0.2892 0 0

30 -0.0964 0 0

31 0.0964 0 0

32 0.2892 0 0

33 0.4819 0 0

34 0.6747 0 0

35 0.8675 0 0

36 1.06 0 0

37 1.25 0 0

38 1.45 0 0

39 1.64 0 0

40 1.83 0 0

41 2.02 0 0

42 2.22 0 0

43 2.41 0 0

44 2.6 0 0

45 2.8 0 0

46 2.99 0 0

47 3.18 0 0

48 3.37 0 0

49 3.57 0 0

50 3.76 0 0

51 3.95 0 0

52 4.14 0 0

53 4.34 0 0

54 4.53 0 0

55 4.72 0 0

56 4.92 0 0

57 5.11 0 0

58 5.3 0 0

59 5.49 0 0

60 5.69 0 0

--Swath-- ----------------------------

Swath Width 24 m

Swath Displacement 2 m

--Spray Material-- ----------------------------

Name Water

Type Reference

Nonvolatile Fraction 0.017

Active Fraction 0.017

Spray Volume Rate (L/ha) 50

--Meteorology-- ----------------------------

Wind Speed (m/s) 3

Wind Direction (deg) -90

Temperature (deg C) 21

Relative Humidity (%) 46

--Atmospheric Stability-- ----------------------------

Atmospheric Stability Overcast

--Transport-- ----------------------------

Flux Plane Distance (m) 0

--Canopy-- ----------------------------

Name 1013

Type Height

Height (m) 0.3

Canopy Roughness (m) 0.042

Canopy Displacement (m) 0.21

--Terrain-- ----------------------------

Upslope Angle (deg) 0

Sideslope Angle (deg) 0

--Advanced-- ----------------------------

Wind Speed Height (m) 2

Max Compute Time (sec) 600

Max Downwind Dist (m) 795

Vortex Decay Rate (IGE) (m/s) 0.56

Vortex Decay Rate (OGE) (m/s) 0.15

Aircraft Drag Coeff 0.1

Propeller Efficiency 0.8

Ambient Pressure (mb) 1013

Save Trajectory Files No

Half Boom No

Default Swath Offset 1/2 Swath

Specific Gravity (Carrier) 1

Specific Gravity (Nonvolatile) 1

Evaporation Rate (µm²/deg C/sec) 84.76

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