Human Health Human Health Risk Assessment Risk Assessment

and Chemical and Chemical SafetySafety

Stephanie SimstadStephanie Simstad

The Ohio State University The Ohio State University Extension Extension

Clermont CountyClermont County

AFCEE, 2002

AcknowledgementsAcknowledgements

• U.S. EPA risk assessment documents U.S. EPA risk assessment documents including: including: – Risk Assessment Guidance for Risk Assessment Guidance for

SuperfundSuperfund– Presenter’s Manual for “Superfund Risk Presenter’s Manual for “Superfund Risk

Assessment and How You Can Help”Assessment and How You Can Help”

What if . . What if . .

• Your private water well has been Your private water well has been sampled and results show that a sampled and results show that a commonly used pesticide is present commonly used pesticide is present in your drinking water.in your drinking water.

• How would you determine whether How would you determine whether this contaminant could be a health this contaminant could be a health problem for your family?problem for your family?

Ohio EPA

OverviewOverview• Description of risk assessment and how it is Description of risk assessment and how it is

usedused

• Use of human health risk assessment Use of human health risk assessment process to evaluate a contaminated family process to evaluate a contaminated family wellwell

• Group exercise to identify source and Group exercise to identify source and pathways of pesticide into wellpathways of pesticide into well

• Consideration of exposure pathway analysis Consideration of exposure pathway analysis to identify Best Management Practices for to identify Best Management Practices for protection of drinking water sourcesprotection of drinking water sources

Human Health Risk Human Health Risk Assessment Assessment • A formalized process to evaluate risk A formalized process to evaluate risk

posed to humans from exposure to posed to humans from exposure to an identified hazardan identified hazard– Evaluation of both cancer and Evaluation of both cancer and

noncancer effectsnoncancer effects– Evaluation of risk to adult, child, or even Evaluation of risk to adult, child, or even

prenatal populationsprenatal populations

Hazard versus RiskHazard versus Risk

• HazardHazard– Potential to do harmPotential to do harm

•tornadotornado•hazardous chemicalhazardous chemical

• RiskRisk– Likelihood of defined harm to Likelihood of defined harm to

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

people exposedpeople exposed

IndividualLifetime Risk of

DevelopingMelanoma is

1 in 75.

(OEPA)

(NOAA)

(NIH)

How is Risk Assessment How is Risk Assessment Used?Used?• To set drinking water standards for To set drinking water standards for

public water suppliespublic water supplies

• Licensing and regulation of pesticidesLicensing and regulation of pesticides

• Identification and clean-up of Identification and clean-up of hazardous waste siteshazardous waste sites

• Identification of special handling Identification of special handling requirements for chemicalsrequirements for chemicals

Back to the Well . . .Back to the Well . . .

• You’ve found that the family well is You’ve found that the family well is contaminated and you use this water contaminated and you use this water for drinking, cooking, and bathing.for drinking, cooking, and bathing.

• How would the risk to those who use How would the risk to those who use water from the well be evaluated?water from the well be evaluated?

Risk Assessment is a 4-Part Risk Assessment is a 4-Part ProcessProcess

• Hazard IdentificationHazard Identification– What chemicals are present and are they likely What chemicals are present and are they likely

to be toxic?to be toxic?

• Exposure AssessmentExposure Assessment– Who is exposed, at what concentration, how Who is exposed, at what concentration, how

often, and for how long?often, and for how long?

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

• Risk CharacterizationRisk Characterization– What does the risk assessment tell us about What does the risk assessment tell us about

this situation? this situation?

Risk Assessment Process Risk Assessment Process (U.S. EPA)(U.S. EPA)

Hazard Identification

Exposure Assessmen

t

Toxicity Assessment

Risk Characterization

Step 1:Hazard IdentificationStep 1:Hazard Identification

• Collect data on presence of Collect data on presence of chemicalchemical– SamplingSampling– ModelingModeling– Chemical fate and transportChemical fate and transport

• Determine if chemical may be Determine if chemical may be toxictoxic

• Develop model of how chemical Develop model of how chemical may move through environment may move through environment – Conceptual Site Model is used to Conceptual Site Model is used to

organize information regarding organize information regarding chemicals and potential transport to chemicals and potential transport to peoplepeople

© Vermont DPS, 2000

AFCEE, 2002

Input for Conceptual Site Input for Conceptual Site ModelModelModified from Oak Ridge (2002)Modified 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?

Modeling of Chemicals in Modeling of Chemicals in the Environmentthe Environment• Chemical characteristicsChemical characteristics

– More or less soluble in water?More or less soluble in water?

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

• General ConceptGeneral Concept– Based on knowledge of the chemical, the soils, Based on knowledge of the chemical, the soils,

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

Conceptual Site ModelConceptual Site Model(Oak Ridge National Lab, 2002)(Oak Ridge National Lab, 2002)

Step #2: Exposure Step #2: Exposure AssessmentAssessment

• WhoWho is Exposed? is Exposed?– Adult, Child, Special PopulationsAdult, Child, Special Populations

• HowHow Are They Exposed? Are They Exposed? – Ingestion, Inhalation, Skin ContactIngestion, Inhalation, Skin Contact

• What is the What is the ConcentrationConcentration of Chemical of Chemical to Which They are Exposed?to Which They are Exposed?– ppm in Water or Soilppm in Water or Soil

• How How OftenOften Are They Exposed? Are They Exposed?– Days per year, Number of yearsDays per year, Number of years

Exposure PathwayExposure Pathway

• Definition: The steps that a chemical takes from the Definition: The steps that a chemical takes from the source to an exposed individualsource to an exposed individual– Exposure is contact with a chemical through either swallowing, Exposure is contact with a chemical through either swallowing,

breathing, or direct contact on skinbreathing, or direct contact on skin

SpilledContainer

Soil Groundwater WellIndividual Using Well

SOURCE Exposed Individual

Path Traveled by Chemical

Exposure Pathway DiagramExposure Pathway Diagram(ATSDR, 2002)(ATSDR, 2002)

Complete Exposure Complete Exposure PathwaysPathways

• Key to Risk Assessment is Identifying Key to Risk Assessment is Identifying Complete Exposure PathwaysComplete Exposure Pathways– Individual must have contact with Individual must have contact with

chemical for it to cause a health chemical for it to cause a health effecteffect

Chemical

Receptor

Contact

Complete Exposure PathwayComplete Exposure Pathway

• Steps in Complete Exposure PathwaySteps in Complete Exposure Pathway– SourceSource– Chemical Transport and TransformationChemical Transport and Transformation– Exposure PointExposure Point– Receptor and Exposure RouteReceptor and Exposure Route

SpilledContainer

Soil Groundwater WellIndividualDrinksWater

SOURCE

RECEPTOR AND

EXPOSURE ROUTE

CHEMICAL TRANSPORTEXPOSURE POINT

Exposure Point and Exposure Point and Exposure RouteExposure Route

• Exposure PointExposure Point defines the place that defines the place that an individual comes into contact with an individual comes into contact with the chemicalthe chemical– Home with lead-contaminated paintHome with lead-contaminated paint

• Exposure RouteExposure Route describes the way a describes the way a chemical enters the bodychemical enters the body– Ingestion (Eating and Drinking)Ingestion (Eating and Drinking)– Inhalation (Breathing)Inhalation (Breathing)– Dermal (Skin Contact)Dermal (Skin Contact)

Exposure PathwaysExposure Pathways• All exposure pathways are not obviousAll exposure pathways are not obvious

– Ingestion of contaminated soilIngestion of contaminated soil•Children during play (200 mg soil /day)Children during play (200 mg soil /day)•Children who deliberately ingest soil (1 gram Children who deliberately ingest soil (1 gram

soil/day)soil/day)• Incidental ingestion by adults (100 mg soil/day)Incidental ingestion by adults (100 mg soil/day)

– Inhalation of chemical vaporsInhalation of chemical vapors•During showering with contaminated waterDuring showering with contaminated water

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

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

Identify Source and Potential Identify Source and Potential Exposure PathwaysExposure Pathways

(Oak Ridge National Lab, 2002)

Back To Contaminated Well Back To Contaminated Well Example. . . Example. . .

• Who is exposed when family farm Who is exposed when family farm well is contaminated?well is contaminated?

• What are their routes of exposure? What are their routes of exposure?

Drinking Water Well

?

Receptors

Routes of

Exposure

?

Exposure AssessmentExposure Assessment

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

body weightbody weight

• Use information from conceptual site model Use information from conceptual site model and sampling to identify complete exposure and sampling to identify complete exposure pathwayspathways

• Calculate dose for each exposure pathway by Calculate dose for each exposure pathway by using exposure assumptionsusing exposure assumptions

• Sum goes across all pathways to get total Sum goes across all pathways to get total dosedose

Exposure AssumptionsExposure Assumptions

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

• ExamplesExamples– How much water does an adult drink in one day? How much water does an adult drink in one day? – How many days per year is someone at their How many days per year is someone at their

home? home? – How many years does someone live in the same How many years does someone live in the same

house?house?

Why Calculate Dose?Why Calculate Dose?

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

• For most chemicals, there is a threshold For most chemicals, there is a threshold below which health effects are unlikely to below which health effects are unlikely to occuroccur– HOWEVER for some cancer-causing chemicals, a HOWEVER for some cancer-causing chemicals, a

threshold is not assumed to existthreshold is not assumed to exist

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

Courtesy of the National Library of Medicine

Dose-Response CurveDose-Response Curve

Dose – Chemical concentration per unit body weightResponse – Level of measured adverse effect

Putting it all together. . .Putting it all together. . .

ATBW

EDEFCRCdaykgmgDoseIntake

)/(

• Intake Equation for Drinking Water ExampleIntake Equation for Drinking Water ExampleC= Chemical Concentration (Obtain from sampling)C= Chemical Concentration (Obtain from sampling)

CR= Contact Rate (2 liters water/day)CR= Contact Rate (2 liters water/day)

EF= Exposure Frequency (350 days/year)EF= Exposure Frequency (350 days/year)

ED= Exposure Duration (30 years)ED= Exposure Duration (30 years)

BW=Body Weight (70 kg.)BW=Body Weight (70 kg.)

AT= Averaging Time (10,950 days)AT= Averaging Time (10,950 days)

Special Concerns During Special Concerns During Exposure AssessmentExposure Assessment• ChildrenChildren

– Children will often have a higher dose than Children will often have a higher dose than adults when exposed to the same chemical adults when exposed to the same chemical concentration in the environmentconcentration in the environment•Differences in children’s activitiesDifferences in children’s activities

– Playing in dirt, infant mouthing of toys, formula-Playing in dirt, infant mouthing of toys, formula-dominated diet of young infantsdominated diet of young infants

•Water, food, and air intake per pound of body Water, food, and air intake per pound of body weight can be higher for children than adultsweight can be higher for children than adults

Step #3: Toxicity Step #3: Toxicity AssessmentAssessment• What toxicity data are available? What toxicity data are available?

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

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

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

• Consider route of exposureConsider route of exposure– Effects can be route of exposure specificEffects can be route of exposure specific

Sensitive SubpopulationsSensitive Subpopulations

• ChildrenChildren– Rapid development and differing Rapid development and differing

physiologies of young children can result physiologies of young children can result in potentially greater sensitivity to in potentially greater sensitivity to contaminantscontaminants•Lead exposure and the developing brainLead exposure and the developing brain

– Exposure to lead during prenatal or early Exposure to lead during prenatal or early childhood can cause irreversible intelligence childhood can cause irreversible intelligence losseslosses

– What are potential sources on the farm for lead What are potential sources on the farm for lead exposure to children?exposure to children?

Sensitive SubpopulationsSensitive Subpopulations

• Children or adults with health problemsChildren or adults with health problems– Compromised immune systemsCompromised immune systems

• Undergoing chemotherapyUndergoing chemotherapy• Organ transplant patientsOrgan transplant patients• Diseases affecting immune systemDiseases affecting immune system

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

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

environmental factors and can therefore modify environmental factors and can therefore modify riskrisk

Distinction between Cancer Distinction between Cancer and Noncancer Effectsand Noncancer Effects• Calculation of dose and some exposure Calculation of dose and some exposure

assumptions differassumptions differ

• Large number of carcinogenic contaminants Large number of carcinogenic contaminants are assumed to have no thresholdare 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 Step #4: Risk CharacterizationCharacterizationThe risk characterization combines the information obtained on toxicity with the calculated exposure to provide an estimate of risk.

Purdue, 1997

Risk Characterization Risk Characterization AnswersAnswers• What is the likelihood of harm What is the likelihood of harm

following exposure to this following exposure to this chemical in this specific situation?chemical in this specific situation? – Provides a numerical estimate of risk Provides a numerical estimate of risk – Identifies key Identifies key uncertaintiesuncertainties in this in this

estimateestimate– Compares numerical estimate of risk with Compares numerical estimate of risk with

a previously determined risk goala previously determined risk goal

Risk GoalRisk Goal

• Most environmental programs have a specified Most environmental programs have a specified risk goal which has gone through reviewrisk goal which has gone through review

• Risk goal is a policy determinationRisk goal is a policy determination– Risk goal is numerical estimate of acceptable risk Risk goal is numerical estimate of acceptable risk

for cancer or noncancer effects. for cancer or noncancer effects. • 1 in 1,000,000 for cancer or the level of reference dose 1 in 1,000,000 for cancer or the level of reference dose

(threshold + uncertainty factor) for noncancer effect. (threshold + uncertainty factor) for noncancer effect.

• Compare numerical estimate of risk with risk Compare numerical estimate of risk with risk goalgoal

• If risk goal is exceeded, risk management If risk goal is exceeded, risk management decision necessarydecision necessary

Risk Assessment is One Part of Risk Assessment is One Part of Decisionmaking Process to Decisionmaking Process to Manage HazardsManage Hazards• Science Science

determines determines likelihood of likelihood of effect but risk effect but risk management management determines determines whether and whether and how the risk how the risk should be should be addressedaddressed

• Policy Policy decisiondecision

What Does Risk Assessment What Does Risk Assessment NotNot Tell Us? Tell Us?

• Whether risk is “acceptable”Whether risk is “acceptable”

• Whether risk is equitably distributed Whether risk is equitably distributed across populationacross population

• Predictions regarding personal or Predictions regarding personal or individual riskindividual risk

SummarySummary

• Risk assessment is a 4-part process to evaluate Risk assessment is a 4-part process to evaluate risk from suspected hazards. risk from suspected hazards. – Hazard IdentificationHazard Identification– Exposure AssessmentExposure Assessment– Toxicity AssessmentToxicity Assessment– Risk CharacterizationRisk Characterization

• For a hazard to have an adverse impact on health, For a hazard to have an adverse impact on health, there must be contact between the receptor and there must be contact between the receptor and the hazard. Exposure must occur. the hazard. Exposure must occur.

• Children and other sensitive subpopulations can Children and other sensitive subpopulations can have greater exposure and toxicity to the same have greater exposure and toxicity to the same environmental conditions than other adults. environmental conditions than other adults.

Summary contd.Summary contd.

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

• Risk characterization Risk characterization – defines the risk relative to the risk goal,defines the risk relative to the risk goal,– identifies uncertainties, and identifies uncertainties, and – identifies receptors and exposure pathways identifies receptors and exposure pathways

of most concern.of most concern.

Summary contd.Summary contd.

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

Case Study ScenarioCase Study Scenario

• Smith family well was found to have Smith family well was found to have “herbex” contamination“herbex” contamination

• Both neighboring farms have used or Both neighboring farms have used or stored herbexstored herbex

• HandoutsHandouts– Risk Assessment Case Study MapRisk Assessment Case Study Map– Pesticide Application WorksheetPesticide Application Worksheet– Participant worksheet to complete Participant worksheet to complete – Herbex labelHerbex label

Case Study MapCase Study Map

Pictures of Storage ShedsPictures of Storage ShedsMr. Ulright’s ShedMr. Ulright’s Shed Mr. Sorong’s Mr. Sorong’s

Shed Shed

HintsHints

• Examine map closelyExamine map closely

• Environmental information from Environmental information from herbex labelherbex label

• Review Pesticide Application Review Pesticide Application WorksheetsWorksheets

• Complete participant worksheet to aid Complete participant worksheet to aid in identifying all parts of exposure in identifying all parts of exposure pathwaypathway

Case Study AnswersCase Study Answers

• Working back from the contaminated Working back from the contaminated wellwell– What are some possible sources and What are some possible sources and

associated pathways?associated pathways?– Which source and pathway do you Which source and pathway do you

believe to be the most likely cause? believe to be the most likely cause? Why?Why?

• Pesticide Selection?Pesticide Selection?

• Pesticide Storage?Pesticide Storage?

• Pesticide Application Practices?Pesticide Application Practices?

• Well Placement?Well Placement?

• Well Maintenance?Well Maintenance?

• Well Abandonment?Well Abandonment?

BMP’s to Prevent Potential BMP’s to Prevent Potential Well Contamination?Well Contamination?

And How Can You Use Your And How Can You Use Your New Risk Assessment New Risk Assessment Knowledge?Knowledge?

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

X

Consider Drinking Consider Drinking Water SourcesWater Sources•Be aware of drinking water sources Be aware of drinking water sources

that could be affected by your use that could be affected by your use of agricultural chemicalsof agricultural chemicals– Private family wells? Public Water Supply Private family wells? Public Water Supply

wells?wells?– Nearby reservoirs used as public water Nearby reservoirs used as public water

sources?sources?– Drinking water intakes in rivers or Drinking water intakes in rivers or

streams?streams?

• Take necessary steps to protect themTake necessary steps to protect them

Consider Local Conditions Consider Local Conditions When Selecting Pesticides When Selecting Pesticides • Be aware of geologic and hydrologic Be aware of geologic and hydrologic

conditions when selecting pesticides conditions when selecting pesticides – Type of soilsType of soils

•Sand versus clay?Sand versus clay?

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

– Location and depth of ground waterLocation and depth of ground water

Think:

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 Consider Local Surface Water Surface Water Quality Conditions Quality Conditions • Be aware of local water quality Be aware of local water quality

conditions when selecting pesticidesconditions when selecting pesticides– Are there any identified problems with Are there any identified problems with

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

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

coordinator and group working to improve water coordinator and group working to improve water qualityquality

OEPA

Consider and Use Consider and Use Appropriate BMPsAppropriate BMPs

• Be aware of BMPs when Be aware of BMPs when storing and applying storing and applying pesticidespesticides– Store properly and be prepared Store properly and be prepared

for spillsfor spills– Read and follow the label!Read and follow the label!

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

– Use buffer strips and maintain Use buffer strips and maintain streamside areas in natural statestreamside areas in natural state

U.S. EPA

NRCS

University of University of ArizonaArizona