Risk Assessment: Release of Anthrax in an IRS Building

Team Members:

Amanda H., Claudia R., Kyle E., Meghan M., Oliver B., Phares O, Stephanie L.T., Yin H.

Outline What is anthrax?

Case Study Scenario

Transport of Particles

Dose Response

Exposure Assessment Decision tree Acceptable risk

Outline cont’d Sampling

Sites Recovery Protocols Detection Methods

Stakeholders Remediation

Decontamination Procedure (explain method and acceptable limit

Problem

What is Anthrax?

Bacillus anthracis Gram positive spore forming rods Very resistant spores Survive in the environment for extended periods of time Used as a biological weapon

Mortality Inhalation → ~75% Cutaneous → ~20% Ingested → ~25 – 60%

Weaponized Anthrax Spores

http://cryptome.org/anthrax-powder.jpg

particle of zinc sulfide coated with silica. The zinc sulfide particle is about 2 microns across (similar in size to an anthrax spore), and thesilica particles are about 100 nanometers

Aerosolized Anthrax

Radiographic examination of the chest often reveals characteristic mediastinal widening, indicative of hemorrhagic mediastinitis

http://www.youtube.com/watch?v=WNRgLkjaRlY

Scenario

Package containing anthrax spores opened in office with 5 desks

Quickly aerosolized & dispersed

30 min before hazard recognized & personnel evacuated

Environmental sampling is needed

Transport Zones

Coffee

Printer& Copier

40 feet

30 feet wide13 feet high

Air Vent

Air Vent

Plant

Plant

window

Break Area with chairs

Not-to-scale

Air Vent

Air Vent

Air flow

ZONE 1

10 feet 10 feet 10 feet 10 feet

ZONE 2ZONE 3ZONE 4

Scenario

Particle Transport

Total Room Volume: V = 441 m3

Zone Volume: Vzone = 110 m3

Air Flow conforms to ASHRAE Standard 62 – requires 6 air exchanges per hour 0.7 m3/s

First order decay based on air flow Neglect settling due to gravity (for 30 minute duration)

settling due to particle size

Calculate the Concentration (# particles/m3) based on time

Range in particle concentration (#particles/m^3) in room after 1 air exchange

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

7.00E+07

8.00E+07

9.00E+07

1.00E+08

0 10 20 30 40

Distance in Room (10 ft Zones)

# p

art

icle

s/m

^3

ZONE 1 Instant ZONE 2 ZONE 3 ZONE 4

Explosion Zone

Particle concentration Range reaching each Zone during 1 Air Turnover

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

7.00E+07

8.00E+07

9.00E+07

1.00E+08

0.00 0.00 2.63 5.26 7.89

ZONE 1 Instant ZONE 2

Receives Max Concentration spores diluted in room volume

SENIOR MANAGER

1e10 colonies - 9e7 colonies

ZONE 3 ZONE 4

Log Scale - 1e10 particles in explosion for Zone 1

1.00E+001.00E+011.00E+021.00E+031.00E+041.00E+051.00E+061.00E+071.00E+081.00E+091.00E+10

0

2.63

5.26

7.89

10.5

2

13.1

5

15.7

8

18.4

1

21.0

4

23.6

7

26.3

28.9

3

31.5

6

Time (minutes)

# pa

rticl

es/m

3

Removal of Particles by ventilation in Office ZONE 4

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

7.00E+07

8.00E+07

9.00E+07

0

2.63

5.26

7.89

10.52

13.15

15.78

18.41

21.04

23.67 26

.3

28.93

31.56

Time (minutes)

# par

ticles

/m3

Removal of Particles by ventilation in Office ZONE 3

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

7.00E+07

8.00E+07

9.00E+07

0

2.63

5.26

7.89

10.52

13.15

15.78

18.41

21.04

23.67 26

.3

28.93

31.56

Time (minutes)

# par

ticles

/m^3

Removal of Particles by ventilation in Office ZONE 2

0.00E+00

1.00E+07

2.00E+07

3.00E+07

4.00E+07

5.00E+07

6.00E+07

7.00E+07

8.00E+07

9.00E+07

0

2.63

5.26

7.89

10.52

13.15

15.78

18.41

21.04

23.67 26

.3

28.93

31.56

Time (minutes)

# part

icles

/m3

Dose-Response: Data LD50 = ED50

In the literature, LD50 ranges several orders of magnitude (2500 to 155,000)

Frequently cited human estimates ranging from 4100 to 8000.

LD5 = 14 -28 LD2 = 4-7 LD1 = 1-3

Even a single spore results in a risk of 1/100

Dose-Response: Model

P(d) = 1/100 d=1075-1813

spores

P(d) = 1/10,000 d=11-18 spores

Dose Response

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

10 1̂ 10 2̂ 10 3̂ 10 4̂ 10 5̂ 10 6̂ 10 7̂ 10 8̂ 10^9

Dose

P(d

)

LD50 = 74100

LD50=94320

LD50 = 125060

Bartrand et al. 2008

Dose-Response: Assumptions

Human potency information can be extrapolated from animal data

Uniform strain

Uniform size - small

Time does not have a significant effect on cumulative dose

Human response is uniform

Model assumptions ‘k’ parameter for exponential model

Triangular dist.; min 5.54e-6, mean 7.00e-6, max 9.35e-6 (Bartrand et al. 2008)

Inhalation rate, m^3/h Normal dist.; mean 5.6, SD 0.114 (Adams 1993)

Attempted to randomly distribute, but failed due to technical problems: Number of spores released (1e10) Ventilation rate of room (assumed accurately measured)

Modeling approach Given room air turnover rate, size of room, and # of

spores released: Determined # of spores in each room section, on

average, over 30m Given the above, with inhalation rate:

Determined # of spores inhaled per person in each zone of room

Given the above, with ‘k’ parameter: Determined risk using the exponential model for

each zone of room

Initial exposure risk results

Zone of room

Risk of death:

Mean

Risk of death:

SD

1 1.00 0.00

2 0.56 0.08

3 0.26 0.05

4 0.11 0.02

‘k’ contributed 20% of the variation;

Inhalation rate contributed 80% of the variation.

There were 1000 Monte Carlo trials.

Prophylaxis by Doxycycline

Yes

No

Yes q=80%p

No 1-q=1-80%p

No 1-p=10%

Yes p=90%

$0

$52

$6milion(VSL)+$52

$6milion(VSL)

Death

Death

Decision Tree

Acceptable Risk

E [prophylaxis] = E [no prophylaxis]

E [prophylaxis] = (value of statistical life + cost of doxycycline + cost of prescription) × q + (cost of doxycycline + cost of prescription) ×(1-q)

E [no prophylaxis] = value of statistical life × p + 0 × (1-p)

P= 4.33 × 10-5

CLINICAL SYMPTOMS / TRANSMISSION ROUTE

Form Symptoms Frequency Route of acquisition

Ulceroglandular or glandular

Skin ulcer, lymph node enlargement, fever, chills, headache

75-85%

65%

Vector-borne and direct contact

Oculoglandular Fever, conjunctivitis, photophobia, glaucomatous lesions

<1%

4%

Touching the eye with contaminated fingers or possibly from infective dust

Oropharyngeal Ulcerative-exudative stomatitis, pharyngitis, lymphadenitis, vomiting, diarrhea

1% Ingesting contaminated food or water

Respiratory Cough, chest pain, increased repiratory rate, fever, nausea, vomiting

17% Inhaling contaminated dust or laboratory-acquired infection

Typhoidal Fever, weight loss, diarrhea and pain

12% Unknown (probably oral or respiratory)

Fonte: WHO,2007; Staples, 2006

Surface Sampling Method

40% 93%

D.L.=12 CFU/cm2

(4 papers-Surfaces)

D.L.=430 CFU/mL (18 papers-Instrument)

Air Sampling Method

The ASD features an air sampler, a thermal lysis unit, a syringe pump, a time-gated spectrometer, and endospore detection chemistry comprised of dipicolinic acid (DPA)-triggered terbium ion (Tb3+) luminescence

D.L.=50 spores/L (2 papers)

Sampling Zones

Coffee

Printer& Copier

Senior Manager

40 feet

30 feet

Air Vent

Air Vent

Plant

Plant

Air flow

window

Break Area with chairs

Not-to-scale

Air Vent

Air Vent

10 feet 10 feet 10 feet 10 feet

30 million surface samples (95% confidence)

=surface sampling =air sampling

Who Cares???

Remediation

H2O2 gas effective in inactivating Bacterial spores Vegetative bacterial cells Viruses Prions

Less toxic than other fumigants Chlorine dioxide Ethylene oxide Formaldehyde

Breaks down to O2

H20

Remediation

Uses: decontamination

Lab & medical equipment Pharmaceutical facilities Hospital rooms Animal holding rooms

Remediation

Acceptable overall Risk 4.33*E-5

30 years/260d/8hrs

Assumption: cumulative

1 – (1-DR)260 x 30 = 4.33*E-5

DR = 5.55E-9

Remediation cont’d

H2O2 Gas

1000ppm, 20 Pa for 20 min

Cycle reduction of 10E3

Target # spores in room: 0.000793 spores

Total # of cycles needed: ~1.5

Number of spores in room as a function of remediation time

Time (min) # Spores in Room

0 5.00E+05

20 500

40 0.5

60 0.0005

80 0.0000005

100 5E-10

120 5E-13

Number of spores in room as a function of remediation time

1.00E-13

1.00E-12

1.00E-11

1.00E-10

1.00E-09

1.00E-08

1.00E-07

1.00E-06

1.00E-05

1.00E-04

1.00E-03

1.00E-02

1.00E-01

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

0 20 40 60 80 100 120

Time (minutes)

Nu

mb

er

of

sp

ore

s in

ro

om

Communication

Avoid disparities in treatment on the basis of race or social class

Tell the public What is anthrax? What are the symptoms? How is it transmitted? How can infection be prevented? How is anthrax treated? How likely a harmful biological or chemical substance in

the mail? What should people do if receiving an Anthrax threat by

mail?

Communication cont’d

Avoid frequent changes to recommendations lack of significant prior experience with anthrax

Inform public what has been done & what will be done to secure their safety in the future

To treat the public with respect, listen to their opinion and make them decision making partners.

Questions???