Risk Assessment 101 Scott D. Dwyer, PhD, DABT Practice Leader Risk Analysis and Toxicology Kleinfelder 14710 NE 87 th Street, Suite 100 Redmond WA 98074 425-636-7910 [email protected]The Risk Assessment/Risk Management Process What is risk assessment? The process of evaluating environmental information about a site to estimate the likelihood that adverse health effects will occur in humans or animals. Goal - to develop the information necessary to make sound and reasonable decisions about how to manage risks associated with a contaminated site.
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The Risk Assessment/Risk Management Process...Risk Assessment 101 Scott D. Dwyer, PhD, DABT Practice Leader Risk Analysis and Toxicology Kleinfelder 14710 NE 87th Street, Suite 100
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Risk Assessment 101
Scott D. Dwyer, PhD, DABTPractice LeaderRisk Analysis and ToxicologyKleinfelder14710 NE 87th Street, Suite 100Redmond WA [email protected]
The Risk Assessment/Risk Management Process
What is risk assessment?The process of evaluating environmental information about a site to estimate the likelihood that adverse health effects will occur in humans or animals.Goal - to develop the information necessary to make sound and reasonable decisions about how to manage risks associated with a contaminated site.
Value of Risk Assessment
Sound scientific basis for deciding whether remediation is necessarySound scientific basis for deciding how much remediation is necessary
Where:C = exposure point concentrationIR = intake rate (soil or water ingestion, etc.)EF = exposure frequency (days per year)ED = exposure duration (years)BW = estimated body weightAT = averaging time
Sources – IRIS, PPRTVs, HEAST, ATSDRDescribe toxicology of chemicals of concern
Risk Characterization
Quantifying Risk and Hazard
Exposure Assessment:estimate of intake
Toxicity Assessment:slope factor or RfD
Risk Characterization:cancer risk or noncancer hazard
Risk Characterization
Integrate exposure and toxicity assessmentsQuantify risk and hazard from individual chemicalsSum risk and hazard from multiple chemicalsSum risk and hazard across exposure pathwaysDiscuss uncertainty
Quantifying Risk and Hazard (Carcinogens)
1. From Exposure Assessment - Estimate Intake (dose)
Intake = (C x IR x EF x ED)/(BW x AT)
Intake = (100 mg/kg x 100 mg/d x 350 d/yr x 30 y)/(70 kg x 25,550 d)
Intake = 0.0000587 mg/kg-day
2. From Toxicity Assessment - Find Cancer Slope FactorExample: Benzene, 0.029 (mg/kg-day)-1
3. Risk Characterization (Calculate Cancer Risk)
Cancer Risk = Intake x SF = 0.0000587 x 0.029 = 2 x 10-6
If cancer risk < 1 x 10-6, no further actionIf cancer risk > 1 x 10-6, further investigation or risk management
If hazard quotient < 1.0, no further actionIf hazard quotient > 1.0, further investigation or risk management
Risk Management
Risk Management Options
No Further ActionSource ControlDeed Restrictions, Institutional ControlsRemediation
Calculating Remediation GoalsProvides a screening level for evaluation of a site during the investigationEstablishes a soil or water concentration for a given hazard or risk levelProvides a target for remediation
Calculating Remediation Goals
Information Needed:
Target hazard or risk level (e.g., hazard quotient = 1 or cancer risk = 1 x 10-6)RfD for noncancer hazard, or SF for cancer riskExposure assumptions
Calculating Remediation Goals (Noncancer)
C = (THQ x BW x AT x RfD)/(EF x ED x IR)
C = remediation goal in soil (mg/kg) or water (mg/L)THQ = target hazard quotientBW = body weight (kg)AT = averaging time (days)RfD = reference dose (mg/kg-day)EF = exposure frequency (days/year)ED = exposure duration (years)IR = intake rate (mg/day, soil; L/day, water)
Calculating Remediation Goals (Cancer)
C = (TR x BW x AT)/(EF x ED x IR x SF)
C = remediation goal in soil (mg/kg) or water (mg/L)TR = target cancer riskBW = body weight (kg)AT = averaging time (years)EF = exposure frequency (days/year)ED = exposure duration (years)IR = intake rate (mg/day, soil; L/day, water)SF = slope factor (1/mg/kg-day)