ohio state university extension human health risk assessment and chemical safety stephanie simstad...

OHIO STATE UNIVERSITY EXTENSIONOHIO STATE UNIVERSITY EXTENSION

Human Health Risk Assessment and Chemical Safety

Stephanie SimstadThe Ohio State University Extension Clermont County

AFCEE, 2002


Acknowledgements

U.S. EPA risk assessment documents including: – Risk Assessment Guidance for Superfund– Presenter’s Manual for “Superfund Risk

Assessment and How You Can Help”


What if . .

Your private water well has been sampled and results show that a commonly used pesticide is present in your drinking water.How would you determine whether this contaminant could be a health problem for your family?

Ohio EPA


OverviewDescription of risk assessment and how it is usedUse of human health risk assessment process to evaluate a contaminated family wellGroup exercise to identify source and pathways of pesticide into wellConsideration of exposure pathway analysis to identify Best Management Practices for protection of drinking water sources


Human Health Risk Assessment

A formalized process to evaluate risk posed to humans from exposure to an identified hazard

– Evaluation of both cancer and noncancer effects– Evaluation of risk to adult, child, or even prenatal

populations


Hazard versus RiskHazard

– Potential to do harm• tornado• hazardous chemical

Risk– Likelihood of defined harm to

occur from specific hazard• 1 additional cancer per 10,000 people

exposedIndividual

Lifetime Risk ofDeveloping

Melanoma is1 in 75.

(OEPA)

(NOAA)

(NIH)


How is Risk Assessment Used?To set drinking water standards for public water suppliesLicensing and regulation of pesticidesIdentification and clean-up of hazardous waste sitesIdentification of special handling requirements for chemicals


Back to the Well . . .

You’ve found that the family well is contaminated and you use this water for drinking, cooking, and bathing.How would the risk to those who use water from the well be evaluated?


Risk Assessment is a 4-Part ProcessHazard Identification

– What chemicals are present and are they likely to be toxic?Exposure Assessment

– Who is exposed, at what concentration, how often, and for how long?

Toxicity Assessment– How is it toxic and at what exposure levels?

Risk Characterization– What does the risk assessment tell us about this situation?


Risk Assessment Process (U.S. EPA)

Hazard Identification

Exposure Assessmen

t

Toxicity Assessment

Risk Characterization


Step 1:Hazard IdentificationCollect data on presence of chemical

– Sampling– Modeling– Chemical fate and transport

Determine if chemical may be toxicDevelop model of how chemical may move through environment

– Conceptual Site Model is used to organize information regarding chemicals and potential transport to people

© Vermont DPS, 2000

AFCEE, 2002

OHIO STATE UNIVERSITY EXTENSIONOHIO STATE UNIVERSITY EXTENSIONInput for Conceptual Site ModelModified from Oak Ridge (2002)

Conceptual Site Model

Who may be exposed?

How may they be

exposed?

How are chemicals transported

to receptors?

How does exposure change

through time?

What information is missing?

OHIO STATE UNIVERSITY EXTENSIONOHIO STATE UNIVERSITY EXTENSIONModeling of Chemicals in the Environment

Chemical characteristics– More or less soluble in water?

Soil and connections to surface and ground water – Type of soil– Likely paths to and through water sources

General Concept– Based on knowledge of the chemical, the soils, and local

water sources; predictions can be made about how that chemical will move through the environment.

OHIO STATE UNIVERSITY EXTENSIONOHIO STATE UNIVERSITY EXTENSIONConceptual Site Model(Oak Ridge National Lab, 2002)


Step #2: Exposure Assessment

Who is Exposed?– Adult, Child, Special Populations

How Are They Exposed? – Ingestion, Inhalation, Skin Contact

What is the Concentration of Chemical to Which They are Exposed?

– ppm in Water or SoilHow Often Are They Exposed?

– Days per year, Number of years


Exposure Pathway

Definition: The steps that a chemical takes from the source to an exposed individual

– Exposure is contact with a chemical through either swallowing, breathing, or direct contact on skin

SpilledContainer

Soil Groundwater WellIndividual Using Well

SOURCEExposed Individual

Path Traveled by Chemical


Exposure Pathway Diagram(ATSDR, 2002)


Complete Exposure Pathways

Key to Risk Assessment is Identifying Complete Exposure Pathways

– Individual must have contact with chemical for it to cause a health effect

Chemical

Receptor

Contact


Complete Exposure PathwaySteps in Complete Exposure Pathway

– Source– Chemical Transport and Transformation– Exposure Point– Receptor and Exposure Route

SpilledContainer

Soil Groundwater WellIndividualDrinksWater

SOURCE

RECEPTOR AND

EXPOSURE ROUTE

CHEMICAL TRANSPORTEXPOSURE POINT


Exposure Point and Exposure RouteExposure Point defines the place that an

individual comes into contact with the chemical– Home with lead-contaminated paint

Exposure Route describes the way a chemical enters the body

– Ingestion (Eating and Drinking)– Inhalation (Breathing)– Dermal (Skin Contact)


Exposure PathwaysAll exposure pathways are not obvious

– Ingestion of contaminated soil• Children during play (200 mg soil /day)• Children who deliberately ingest soil (1 gram soil/day)• Incidental ingestion by adults (100 mg soil/day)

– Inhalation of chemical vapors• During showering with contaminated water

– Volatile chemicals will vaporize into the air from the shower water, they can then be inhaled by person showering

• Vapor migration into homes from contaminated ground water or soil under homes


Identify Source and Potential Exposure Pathways

(Oak Ridge National Lab, 2002)


Back To Contaminated Well Example. . .

Who is exposed when family farm well is contaminated?What are their routes of exposure?

Drinking Water Well

?

Receptors

Routes of

Exposure

?


Exposure Assessment

Purpose is to calculate dose that individual receives – Dose represents a daily average intake per unit of body

weightUse information from conceptual site model and sampling to identify complete exposure pathwaysCalculate dose for each exposure pathway by using exposure assumptionsSum goes across all pathways to get total dose


Exposure Assumptions

Answer “how much” and “how often” people may be exposed to chemical in air, water, soil or dustExamples

– How much water does an adult drink in one day? – How many days per year is someone at their home? – How many years does someone live in the same house?


Why Calculate Dose?

Paracelsus (15th century scientist)– “Dose makes the poison”

For most chemicals, there is a threshold below which health effects are unlikely to occur

– HOWEVER for some cancer-causing chemicals, a threshold is not assumed to exist

Toxicity data can then be compared with dose to determine if health effect likely to occur

Courtesy of the National Library of Medicine


Dose-Response CurveDose – Chemical concentration per unit body weight

Response – Level of measured adverse effect


Putting it all together. . .

ATBW

EDEFCRCdaykgmgDoseIntake

)/(

Intake Equation for Drinking Water ExampleC= Chemical Concentration (Obtain from sampling)CR= Contact Rate (2 liters water/day)EF= Exposure Frequency (350 days/year)ED= Exposure Duration (30 years)BW=Body Weight (70 kg.)AT= Averaging Time (10,950 days)


Special Concerns During Exposure Assessment

Children– Children will often have a higher dose than adults

when exposed to the same chemical concentration in the environment

• Differences in children’s activities– Playing in dirt, infant mouthing of toys, formula-dominated

diet of young infants• Water, food, and air intake per pound of body weight can be

higher for children than adults


Step #3: Toxicity AssessmentWhat toxicity data are available?

– Acute or chronic effect? Or both?– Cancer or noncancer effect? Or both?

Consider effects of multiple chemicals – Similar to “Mode of Action” concept in pesticides but

broader since multiple nonlethal effects can still have an adverse impact on human health

Consider route of exposure– Effects can be route of exposure specific


Sensitive Subpopulations

Children– Rapid development and differing physiologies of

young children can result in potentially greater sensitivity to contaminants

• Lead exposure and the developing brain– Exposure to lead during prenatal or early childhood can cause

irreversible intelligence losses– What are potential sources on the farm for lead exposure to

children?


Sensitive SubpopulationsChildren or adults with health problems

– Compromised immune systems• Undergoing chemotherapy• Organ transplant patients• Diseases affecting immune system

– Other diseases that affect body system that chemical exposure may target

Children or adults with “hidden” sensitivities– Genes can increase or decrease susceptibility to

environmental factors and can therefore modify risk


Distinction between Cancer and Noncancer Effects

Calculation of dose and some exposure assumptions differLarge number of carcinogenic contaminants are assumed to have no threshold

What would dose-response curve look like if we did not assume a threshold existed?

Hint: An effect would be seen at any dose level.


Step #4: Risk CharacterizationThe risk characterization combines the information obtained on toxicity with the calculated exposure to provide an estimate of risk.

Purdue, 1997


Risk Characterization Answers

What is the likelihood of harm following exposure to this chemical in this specific situation?

– Provides a numerical estimate of risk – Identifies key uncertainties in this estimate– Compares numerical estimate of risk with a

previously determined risk goal


Risk GoalMost environmental programs have a specified risk goal which has gone through reviewRisk goal is a policy determination

– Risk goal is numerical estimate of acceptable risk for cancer or noncancer effects.

• 1 in 1,000,000 for cancer or the level of reference dose (threshold + uncertainty factor) for noncancer effect.

Compare numerical estimate of risk with risk goalIf risk goal is exceeded, risk management decision necessary


Risk Assessment is One Part of Decisionmaking Process to Manage

HazardsScience determines likelihood of effect but risk management determines whether and how the risk should be addressedPolicy decision


What Does Risk Assessment Not Tell Us?

Whether risk is “acceptable”Whether risk is equitably distributed across populationPredictions regarding personal or individual risk


Summary

Risk assessment is a 4-part process to evaluate risk from suspected hazards.

– Hazard Identification– Exposure Assessment– Toxicity Assessment– Risk Characterization

For a hazard to have an adverse impact on health, there must be contact between the receptor and the hazard. Exposure must occur. Children and other sensitive subpopulations can have greater exposure and toxicity to the same environmental conditions than other adults.


Summary contd.Risk goals are used as a comparison point with calculated risk values. These are policy, or nonscientific, determinations.Risk characterization

– defines the risk relative to the risk goal,– identifies uncertainties, and – identifies receptors and exposure pathways of

most concern.


Summary contd.

Risk management is the decisionmaking process to determine whether to take action for an identified risk.


Case Study Scenario


Case Study Review

Working back from the contaminated well– What are some possible sources and associated

pathways?– Which source and pathway do you believe to be

the most likely cause? Why?


BMP’s to Prevent Potential Well Contamination?

Pesticide Selection?Pesticide Storage?Pesticide Application Practices?Well Placement?Well Maintenance?Well Abandonment?


And How Can You Use Your New Risk Assessment Knowledge?

Think about the possible ways that chemicals stored or used at your farm could reach receptors, especially through drinking water pathways.

X


Consider Drinking Water Sources

Be aware of drinking water sources that could be affected by your use of agricultural chemicals

– Private family wells? Public Water Supply wells?– Nearby reservoirs used as public water sources?– Drinking water intakes in rivers or streams?

Take necessary steps to protect them


Consider Local Conditions When Selecting Pesticides

Be aware of geologic and hydrologic conditions when selecting pesticides

– Type of soils• Sand versus clay?

– Location of surface water bodies and runoff pattern of surface water

– Location and depth of ground waterThink:

If you have shallow groundwater and sand/gravel soils, what should you be concerned about if you choose to apply a highly water soluble pesticide?


Consider Local Surface Water Quality Conditions

Be aware of local water quality conditions when selecting pesticides– Are there any identified problems with pesticides in water,

sediment or fish in local streams or rivers?• See Ohio EPA’s web site and associated reports

– Join your local watershed group!• Most watersheds in the state have a watershed coordinator and

group working to improve water quality

OEPA


Consider and Use Appropriate BMPs

Be aware of BMPs when storing and applying pesticides

– Store properly and be prepared for spills– Read and follow the label!

• Drinking and surface water advisories (e.g., Atrazine)

– Use buffer strips and maintain streamside areas in natural state

U.S. EPA

NRCS

University of University of ArizonaArizona

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