BASELINE RISK BASELINE RISK ASSESSMENTASSESSMENT

OVERVIEW OVERVIEW

Dawn A. IovenDawn A. IovenSenior ToxicologistSenior Toxicologist

U.S. EPA – Region IIIU.S. EPA – Region III

4 April 20124 April 2012

WHAT IS RISK?WHAT IS RISK?

Definition: probability of harm or lossDefinition: probability of harm or loss Risk = Hazard x ExposureRisk = Hazard x Exposure Risk can be voluntary or involuntaryRisk can be voluntary or involuntary Interpretation of risk differs for each of usInterpretation of risk differs for each of us Predictive risk assessment (U.S. EPA) vs. Predictive risk assessment (U.S. EPA) vs.

health study (ATSDR, Health Department) health study (ATSDR, Health Department)

PURPOSE OF BASELINE RISK PURPOSE OF BASELINE RISK ASSESSMENTASSESSMENT

Characterize current Characterize current andand potential future potential future risks to human health and the environment risks to human health and the environment

Determine the need for remedial actionDetermine the need for remedial action Aid stakeholders in understanding Aid stakeholders in understanding

potential site-related riskspotential site-related risks Satisfy Federal regulations requiring the Satisfy Federal regulations requiring the

assessment of risk at Superfund sitesassessment of risk at Superfund sites

BASELINE RISK BASELINE RISK ASSESSMENT PROCESSASSESSMENT PROCESS

Hazard IdentificationHazard Identification Exposure AssessmentExposure Assessment Toxicity AssessmentToxicity Assessment Risk CharacterizationRisk Characterization Uncertainty AnalysisUncertainty Analysis

HAZARD IDENTIFICATIONHAZARD IDENTIFICATION

Gather and analyze relevant site dataGather and analyze relevant site data Identify Chemicals of Potential Identify Chemicals of Potential

Concern (CoPCs)Concern (CoPCs) CoPCs are chemicals that may contribute significantly CoPCs are chemicals that may contribute significantly

to site-related risksto site-related risks Determined by comparison to generic risk-based Determined by comparison to generic risk-based

screening levels or regulatory criteriascreening levels or regulatory criteria Identification process also considers essentiality, Identification process also considers essentiality,

frequency of detection, and background conditions frequency of detection, and background conditions

EXPOSURE ASSESSMENTEXPOSURE ASSESSMENT

Analyze contaminant releasesAnalyze contaminant releases Identify potentially-exposed populations Identify potentially-exposed populations

(current and future)(current and future) Identify potential exposure pathwaysIdentify potential exposure pathways Estimate exposure point concentrations for Estimate exposure point concentrations for

CoPCsCoPCs Estimate contaminant intake (dose) for Estimate contaminant intake (dose) for

each CoPCeach CoPC

EXPOSURE ASSESSMENT (cont.)EXPOSURE ASSESSMENT (cont.)

Common Land-Use ScenariosCommon Land-Use Scenarios

ResidentialResidential OccupationalOccupational

Commercial / IndustrialCommercial / Industrial ConstructionConstruction

RecreationalRecreational OtherOther

AgriculturalAgricultural TrespassingTrespassing Maintenance (Landscaping)Maintenance (Landscaping)

EXPOSURE ASSESSMENT (cont.)EXPOSURE ASSESSMENT (cont.)

Common Exposure PathwaysCommon Exposure Pathways

Surface soilSurface soil Subsurface soilSubsurface soil Ground waterGround water AirAir Surface waterSurface water SedimentSediment

EXPOSURE ASSESSMENT (cont.)EXPOSURE ASSESSMENT (cont.)

Common Exposure RoutesCommon Exposure Routes

IngestionIngestion SoilSoil Ground waterGround water Surface waterSurface water SedimentSediment

Dermal contactDermal contact SoilSoil Ground water (bathing)Ground water (bathing) Surface waterSurface water SedimentSediment

InhalationInhalation Soil (outdoor vapors, airborne particulate, vapor intrusion)Soil (outdoor vapors, airborne particulate, vapor intrusion) Ground water (showering, vapor intrusion)Ground water (showering, vapor intrusion) AirAir

EXPOSURE ASSESSMENT (cont.)EXPOSURE ASSESSMENT (cont.)

Generic Dose Equation - IngestionGeneric Dose Equation - Ingestion

Dose = (C x CR x EF x ED) / (BW x AT)Dose = (C x CR x EF x ED) / (BW x AT)where:where: C = contaminant concentration, media-dependentC = contaminant concentration, media-dependent

CR = contact rate, media-dependentCR = contact rate, media-dependentEF (days/yr) = exposure frequencyEF (days/yr) = exposure frequencyED (yrs) = exposure durationED (yrs) = exposure durationBW (kg) = body weightBW (kg) = body weightAT (days) = averaging timeAT (days) = averaging time

Generic Dose Equation - InhalationGeneric Dose Equation - Inhalation

Exposure Concentration = (CA x ET x EF x ED x CF) / ATExposure Concentration = (CA x ET x EF x ED x CF) / ATwhere:where: CA (ug/mCA (ug/m33) = contaminant concentration in air) = contaminant concentration in air

ET (hrs/day) = exposure timeET (hrs/day) = exposure timeEF (days/yr) = exposure frequencyEF (days/yr) = exposure frequencyED (yrs) = exposure durationED (yrs) = exposure durationCF (1 day/24 hrs) = conversion factorCF (1 day/24 hrs) = conversion factorAT (days) = averaging timeAT (days) = averaging time

TOXICITY ASSESSMENTTOXICITY ASSESSMENT

Collect qualitative and quantitative toxicity Collect qualitative and quantitative toxicity information for CoPCsinformation for CoPCs

Determine appropriate toxicity values for Determine appropriate toxicity values for CoPCs to estimate risksCoPCs to estimate risks Reference Dose (RfD)Reference Dose (RfD) Inhalation Reference Concentration (RfC)Inhalation Reference Concentration (RfC) Carcinogenic Slope Factor (CSF)Carcinogenic Slope Factor (CSF) Inhalation Unit Risk (IUR)Inhalation Unit Risk (IUR)

RISK CHARACTERIZATIONRISK CHARACTERIZATION

Combine Exposure Assessment with Combine Exposure Assessment with Toxicity Assessment to describe potential Toxicity Assessment to describe potential for adverse health effectsfor adverse health effects

RISK CHARACTERIZATION RISK CHARACTERIZATION (cont.)(cont.)

Cancer RisksCancer Risks

Risk = CSF x DoseRisk = CSF x Dosewhere:where: CSF (mg/kg/day)CSF (mg/kg/day)-1-1 = Carcinogenic Slope Factor = Carcinogenic Slope Factor

Risk = IUR x ECRisk = IUR x ECwhere:where: IUR (ug/mIUR (ug/m33))-1-1 = Inhalation Unit Risk, chemical-specific = Inhalation Unit Risk, chemical-specific

EC (ug/mEC (ug/m33) = exposure concentration) = exposure concentration

Non-Cancer RisksNon-Cancer Risks

HQ = Dose / RfDHQ = Dose / RfDwhere:where: HQ (unitless) = Hazard QuotientHQ (unitless) = Hazard Quotient

RfD (mg/kg/day) = Reference DoseRfD (mg/kg/day) = Reference Dose

HQ = EC / (RfC x 1000 ug/mg)HQ = EC / (RfC x 1000 ug/mg)where:where: HQ (unitless) = Hazard QuotientHQ (unitless) = Hazard Quotient

EC (ug/mEC (ug/m33) = exposure concentration) = exposure concentrationRfC (mg/mRfC (mg/m33) = Reference Concentration, chemical-specific) = Reference Concentration, chemical-specific

RISK CHARACTERIZATION RISK CHARACTERIZATION (cont.)(cont.)

Unacceptable RiskUnacceptable Risk Excess cancer risk greater than 1E-04Excess cancer risk greater than 1E-04

• probability of developing cancer from defined probability of developing cancer from defined exposure is greater than 1 in 10,000exposure is greater than 1 in 10,000

For non-cancer impacts, sum of HQs for For non-cancer impacts, sum of HQs for similar target organs is greater than 1similar target organs is greater than 1• ““safe” dose is exceededsafe” dose is exceeded

UNCERTAINTY ANALYSISUNCERTAINTY ANALYSIS

Describe assumptions and significant Describe assumptions and significant unknowns associated with risk unknowns associated with risk assessment processassessment process

Quantitative measure of variability and Quantitative measure of variability and sensitivity of each input parameter can be sensitivity of each input parameter can be performed via Monte Carlo Analysisperformed via Monte Carlo Analysis

NATIONAL RESEARCH COUNCIL NATIONAL RESEARCH COUNCIL RISK ASSESSMENT PARADIGMRISK ASSESSMENT PARADIGM

Risk AssessmentRisk Assessment

Risk ManagementRisk Management National Research Council, 1983National Research Council, 1983

Dose-Response Assessment

HazardIdentification

RiskCharacterization

ExposureAssessment

Statutory and LegalConsiderations

Public HealthConsiderations

RegulatoryDecisions

SocialFactors

EconomicFactors

ControlOptions

AsbestosAsbestos

Two mineral groupsTwo mineral groups SerpentineSerpentine

• Single asbestosform variety (chrysotile)Single asbestosform variety (chrysotile) AmphiboleAmphibole

• Several asbestosform varieties (crocidolite, Several asbestosform varieties (crocidolite, amosite, anthophyllite, tremolite, actinolite)amosite, anthophyllite, tremolite, actinolite)

Asbestos InvestigationsAsbestos Investigations

No method has been found that reliably No method has been found that reliably predicts asbestos concentrations in air predicts asbestos concentrations in air given concentrations at the source.given concentrations at the source.

Levels of asbestos in air from source Levels of asbestos in air from source disturbance are measured, not predicted.disturbance are measured, not predicted.

Activity-Based Sampling (ABS)Activity-Based Sampling (ABS)

Asbestos ABS SamplingAsbestos ABS Sampling

Potential limitationsPotential limitations Representativeness of samples over an area Representativeness of samples over an area

of concernof concern Generalizing snapshot findings to future Generalizing snapshot findings to future

exposuresexposures Engaging in dissimilar activitiesEngaging in dissimilar activities Differing environmental conditionsDiffering environmental conditions

Asbestos ABS Sampling (cont.)Asbestos ABS Sampling (cont.)

Remedy to limitationsRemedy to limitations Bias sampling towards most contaminated Bias sampling towards most contaminated

asbestos sourcesasbestos sources Perform aggressive soil disturbance (raking), Perform aggressive soil disturbance (raking),

to generate maximum air concentrationsto generate maximum air concentrations Sample when environmental conditions are Sample when environmental conditions are

favorable to maximum airborne release favorable to maximum airborne release Apply conservative exposure assumptions Apply conservative exposure assumptions

and tox criteria in Baseline Risk Assessmentand tox criteria in Baseline Risk Assessment

Asbestos RisksAsbestos Risks

InhalationInhalation CarcinogenicCarcinogenic

• Lung cancerLung cancer• MesotheliomaMesothelioma• Laryngopharyngeal cancerLaryngopharyngeal cancer• GI tumors (possibly)GI tumors (possibly)

Non-CancerNon-Cancer• AsbestosisAsbestosis• Pleural diseasePleural disease

Asbestos Risk EquationAsbestos Risk Equation

Generic Risk Equation - InhalationGeneric Risk Equation - Inhalation

ELCR = EPC x TWF x IURELCR = EPC x TWF x IUR

where:where: ELCR = Excess Lifetime Cancer Risk, the risk of ELCR = Excess Lifetime Cancer Risk, the risk of developing cancer due to site-related exposuredeveloping cancer due to site-related exposure

EPC = Exposure Point Concentration, the EPC = Exposure Point Concentration, the concentration of asbestos fibers in air (f/cc)concentration of asbestos fibers in air (f/cc)

IUR = Inhalation Unit Risk (f/cc)-1IUR = Inhalation Unit Risk (f/cc)-1

TWF = Time Weighting Factor, to account for TWF = Time Weighting Factor, to account for less-than-continuous exposure during a one-less-than-continuous exposure during a one-

year year exposure, where:exposure, where:

TTWF = [Exposure time (hours exposed/day ) / 24] x WF = [Exposure time (hours exposed/day ) / 24] x [Exposure [Exposure frequency (days/year ) / frequency (days/year ) / 365]365]

Example TWFsExample TWFs

TWFs for Example Exposure ScenariosTWFs for Example Exposure Scenarios

Exposure ScenarioExposure Scenario Hrs/DayHrs/Day Days/YearDays/Year TWFTWFContinuousContinuous 2424 365365 11

Baseline residentialBaseline residential 2424 350350 0.960.96

GardeningGardening 1010 5050 0.0570.057

RecreationalRecreational 11 156156 0.0180.018

Child playing in soilChild playing in soil 22 350350 0.0800.080

TTWF = [Exposure time (hours exposed/day ) / 24] x [Exposure frequency (days/year ) / WF = [Exposure time (hours exposed/day ) / 24] x [Exposure frequency (days/year ) / 365]365]

Asbestos IURs Asbestos IURs

Cancer risk estimates depend not only on Cancer risk estimates depend not only on EF and ED, but also on age at first EF and ED, but also on age at first exposureexposure

Refer to handout (Table 2 and Table 3 Refer to handout (Table 2 and Table 3 from EPA Asbestos Framework) for IURsfrom EPA Asbestos Framework) for IURs

Estimation of Potential Estimation of Potential Cumulative Risk from Asbestos Cumulative Risk from Asbestos

ELCRc = ELCRc = Σ Σ EPCi • TWFi • IURLTLiEPCi • TWFi • IURLTLi

where:where: ELCRc = the cumulative excess cancer risk ELCRc = the cumulative excess cancer risk to an individual from exposure to multiple to an individual from exposure to multiple environments or multiple scenariosenvironments or multiple scenarios

Example Risk Calculation for Example Risk Calculation for AsbestosAsbestos

Refer to handout (Example 3 from EPA Refer to handout (Example 3 from EPA Asbestos Framework)Asbestos Framework)