2 Risk Assessment Topics What is Risk?Risk, Hazard and ExposureHow is Risk Expressed?Risk CategoriesWhat is Risk Assessment?Risk Assessment Applications
3 What is Risk?Risk is the probability or likelihood of an adverse effect due to some hazardous situationSafety is the complement of risk, or the probability that an adverse effect will not occurRisk = f ( Hazard, Exposure)Magnitude or severity of risk are a function of the type of harm i.e. Hazard and the extent or likelihood of Exposure
4 Risk and Hazard Determination Chemical A Pipe 1Chemical A Pipe 2Chemical A Pipe 3Leaking Pipe
5 Risk = Hazard * Exposure Chemical A Pipe 1Chemical Pipe 2Chemical A Pipe 3Leaking PipeRisk = Hazard * Exposure
6 Hazard : Potential for creating undesired adverse consequences. In this case it remains same as chemical flowing through pipe is same.Chemical A Pipe 1Chemical A Pipe 2Chemical A Pipe 3Leaking Pipe
7 Exposure : Vulnerability to hazard Pipe 2 poses greatest risk of exposure due to leakage.Chemical APipe 2Chemical A Pipe 3Chemical APipe 1Leaking Pipe
8 How is risk expressed?Probability of adverse effects associated with a particular activityUnitlessFrom 0-1E.g. 1x One in 101x One in 100
9 Factors in Risk Acceptability VoluntarySmokingBungee JumpingDietNonvoluntaryRisk resulting from uncontrollable actions of others (Occupational exposure, pesticide residues)Natural disastersDegree of controlMagnitude of the outcomeAwarenessCatastrophic PotentialGroup involvementCost of alternatives
10 Risk Values Activity Annual Risk Smoking 10 cigarettes/day 1 x 10-3 Motor vehicle accidents x 10-4Manufacturing work accident x 10-5Pedestrian hit by automobiles x 10-5Drinking two beers/day x 10-5Person in a room with a smoker x 10-5Peanut butter (4 teaspoons/d) x 10-6Drinking water withEPA limit of Trichloroethene x 10-9
11 What is Risk Assessment? Analytical tool for studying situations that could result in adverse consequencesQualitative and quantitative assessment of environmental statusProcess to identify and quantify the risk and select necessary action
12 Risk Assessment Applications Identification of any ecological risk Identification of the need for additional data collectionSite remediation alternative selectionEstablishment of cleanup standards
16 In place containment, groundwater pumping and retreatment alternative No ActionIn place containment, groundwater pumping and retreatment alternativeExcavation, Incineration/re-landfilling
17 Groundwater contamination is definite No ActionNo capital costGroundwater contamination is definite
18 In place containment, groundwater pumping and retreatment alternative Volatilization and Particulate migrationCreating a barrier to prevent or extend the groundwater contamination around the siteConstruction of containment facilityAir StrippingVolatilization
19 Excavation Incineration/ Re-Landfilling Particulate migration / VolatilizationVehicular transport to incineratorRe- LandfillingStockpiling at incineratorIncineratorFlue Gas Emissions
21 Risk Assessment Process Hazard IdentificationDose ResponseExposure AssessmentRisk characterization
22 Hazard Identification Toxicity assessment determines whether exposure to a chemical, physical, or biological agent can cause an increase in the incidence of an adverse effect.Necessary condition for a health or safety riskPhysical, metabolic, and chemical properties of the agent;Potential routes of exposure; toxicological effects; results of animal studies (dose-response); and site characteristics
23 Hazard Identification – Toxicity Score Ranking of chemicals from contaminated sites depending upon their toxicity scoresHelp in identifying contaminants with a significant impact at the siteNeed data from the contaminated site
27 Hazard Identification – Toxicity Score ChemicalsRfD( mg/kg-day)Soil (mg/kg)MeanCmaxChlorobenzene2.00E-021.39E+006.40E+00Chloroform1.00E-021.12E+004.10E+001,2-DichloroethaneNANDBEHP1.03E+022.30E+02ND – Not Detected; NA-Not ApplicableRank the non-carcinogenic chemicals for soil
28 Hazard Identification – Toxicity Score ChemicalsRfD( mg/kg-day)Soil (mg/kg)TS = Cmax/RfDRankMeanCmaxChlorobenzene2.00E-021.39E+006.40E+003203Chloroform1.00E-021.12E+004.10E+0041021,2-DichloroethaneNANDBEHP1.03E+022.30E+0211,5001ND – Not Detected; NA-Not ApplicableBEHP poses the greatest risk for the given site followed by chloroform and Chlorobenzene.
29 Hazard Identification – Toxicity Score Selection of chemicals by TS method is followed by further evaluation which deals with other properties of that contaminant like mobility, persistence in environment, treatability etc. depending on the purpose of assessment.
30 Hazard Identification – Toxicity Score Now try the same problems for carcinogens.Also find RfD for the same contaminants in groundwater and air, on web and perform TS calculations
31 Risk Assessment Process Hazard IdentificationDose ResponseExposure AssessmentRisk Characterization
32 Risk Assessment Process Dose ResponseHow large a dose causes what magnitude of effect?
33 Dose-Response Assessment Dose-response assessment is the process of characterizing the relation between the dose of target contaminant administered or received, and the incidence of an adverse health effect in exposed populations, and estimating the incidence of the effect as a function of human exposure to the agent.
34 Dose-Response CurveRepresents variations in response of receptor at different contaminant levelsGenerally, increasing the dose of contaminant will result in a proportional increase in both the incidence of an adverse effect as well as the severity of the effect.Quantitative relationship between exposure and toxic effectsEnables risk assessor to estimate a safe doseActual dose is compared with safe dose in risk assessment process
35 Dose-Response Curve No-Observed-Adverse-Effect-Level (NOAL) Dose: mg chemical/kg of body weightResponse: % population affected by dose.Curvature of dose response curve illustrates varying sensitivity of exposed population.No-Observed-Adverse-Effect-Level (NOAL)the greatest test dose level at which no adverse effect is notedLowest-Observed-Adverse-Effect-Level (LOAEL)Lowest level at which an adverse effect is detected
36 Cancer Response-Dose Curve Dose: mg chemical/kg of body weightResponse: % population cancerExtrapolate to low dose/risk
37 Reference DoseRfD: An estimate of daily exposure to the human population that is likely to be without appreciable risk of deleterious effects during a lifetimeExpressed as mg pollutant / kg body weight/dayAlso expressed as Reference Concentration (RfC), mg/m337
38 Reference Dose RfD = NOAEL /(FAFHFSFLFD) Where: NOAEL: No-Observed-Adverse-Effect-LevelFA: An adjustment factor to extrapolate from animal to human populationFH: Adjustment factor for differences in human susceptibilityFL: An adjustment factor applied when LOAEL is used instead of NOAELFS: An adjustment factor applied when data set is dubious or incomplete
39 Reference Dose - Problem In a three month subchronic study in mice, the NOAEL for tris-(1,3-dichloro-2-propyl) phosphate was 15.3 mg/kg body weight per day; the LOAEL was 62 mg/kg at which dose abnormal liver effects were noted. If each of the adjustment factor is equal to 10, calculate the reference dose for chemical.
40 Reference Dose - Problem Given: NOAEL = 15.3 mg/kg body weight per day LOAEL = 62 mg/kg (no need here as NOAEL is given) Calculate RfD using NOAEL and LOAEL RfD = NOAEL / (FA FH FS FLFD) Adjustment factors applicable for this problem are: FA, FH, Fs RfD = 15.3/(10*10*10) = mg/kg-day
41 Reference Dose - Problem Using LOAEL : RfD = LOAEL/(FA FH FS FLFD) Adjustment factors applicable are : FA, FH, Fs and FL RfD = 62/(10*10*10*10) = mg/kg-day
42 Reference Dose - Problem RfD = mg/kg-day (Using NOAEL)RfD = mg/kg-day (using LOAEL)The lowest of two values will be the reference dose for tris-phosphate i.e mg/kg-day
43 Reference Dose - Problem Repeat the RfD calculations for tris-phosphate for which NOAEL was determined to be 22mg/kg-day and the LOAEL was found to be 44 mg/kg-day for increased weight of liver and kidneys in rat.
44 Risk Assessment Process Hazard IdentificationDose ResponseExposure AssessmentRisk characterization
45 Deals with various exposure pathways for released contaminant Exposure AssessmentExposure AssessmentDeals with various exposure pathways for released contaminant
53 Calculation ( C x CR x EF x ED) I = -------------------------- (BW x AT)I = Intake (mg/kg of body weight per day)C = Concentration at exposure point (e.g. mg/L in water or mg/m3 in air)CR = Contact Rate ( e.g L/day or m3/day)EF = Frequency (day/year)ED = Exposure Duration (yr)BW = Body weight (kg)AT = Averaging Time (days)
54 Standard Parameters for Calculating Exposure and Intake AdultsChild Age (6-12)Child Age ( 2-6)Average Body Weight (kg)702916Skin surface are (cm2)18,150104706980Water Ingested (L/day)21Air breathed (m3/hour)0.830.460.25Retention rate (inhaled air)100%Absorption rate (inhaled air)Soil ingested (mg/day)100200Bathing duration (minutes)30Exposure frequency (days)365Exposure duration (years)64
55 Intake Rate Calculation Determine the chronic daily inhalation intake, by adults, of a non-carcinogenic chemical as a function of concentration in fugitive dust at a landfill ABC.
56 Intake Rate Calculation ( C x CR x EF x Ed x RR x ABS)I = (BW x AT)Air breathing rate for adults = 0.83 m3/hrCR = 0.83 x 24 = m3/dayEF = 365 daysED = 30 years ( For chronic exposure, non-carcinogen)RR = 1, ABS = 1 ( Assumption in the absence of any data)AT = 365 days x 30 years
57 Intake Rate Calculation I = (C x x (365 x 30) x 1x1)/ (70 x (365x60))I = m3/kg-day x CC = Exposure point concentration (mg/m3)
58 Risk Assessment Process Hazard IdentificationDose ResponseExposure AssessmentRisk characterization
59 Risk Characterization Final step of risk assessment processIntegration of hazard identification, dose response assessment and exposure assessment.
62 Risk Characterization - Carcinogenic Calculate the average carcinogenic risk from chloroform due to dermal contact of soil by workers at the landfill ABC. From TS calculation table: C = 1.12 mg/kg From carcinogenic dose intake calculations I = 2.9 x 10-9 x C = 3.26 x 10-9 mg/kg-day SF for Chloroform = 6.1 x 10-3 Risk = 6.1 x 10-3 x 3.26 x 10-9 mg/kg-day Risk= 1.99 x 10-11
63 Risk Characterization: Non-carcinogenic Normally characterized in terms of hazard index (HI)HI = (CDI/RfD) whereCDI = Chronic daily intake (mg/kg-day)RfD = Reference dose (mg/kg-day)HI = Hazard Index (Unitless)HI < 1.0 is acceptable
64 Risk Characterization: Non -carcinogenic Calculate the hazard index for chlorobenzene, based on intake calculated for landfill ABC.Solution:HI = CDI/RfDRfD = 2 x 10-2 ; CDI = 2.82 x 10-7HI = 1.41 x 10-5 < 1 OK
66 UncertaintyThe risk assessment process is extremely conservative in nature and utilizes measurements which are uncertain.Insufficient data or information gaps often exist in characterizing the potential risk of an agent, necessitating the need for assumptions or educated guesses.
67 UncertaintyUse computational tools from the field of decision analysis to account for the uncertainties in the processThese tools allow risk to be expressed as a probability distribution rather than a single number which can then be used to make a more informed decision during risk management
68 Return to Home Page Return to Home Page Last updated October 2008 by Dr. Reinhart