Risk Assessment Risk Assessment Topics What is Risk

Risk Assessment

Risk Assessment Topics Ø Ø Ø What is Risk? Risk, Hazard and Exposure How is Risk Expressed? Risk Categories What is Risk Assessment? Risk Assessment Applications

What is Risk? Ø Risk is the probability or likelihood of an adverse effect due to some hazardous situation Ø Safety is the complement of risk, or the probability that an adverse effect will not occur Risk = f ( Hazard, Exposure) Ø Magnitude or severity of risk are a function of the type of harm i. e. Hazard and the extent or likelihood of Exposure

Risk and Hazard Determination Chemical A Pipe 1 Chemical A Pipe 2 Leaking Pipe Chemical A Pipe 3

Chemical A Pipe 1 Chemical Pipe 2 Chemical A Pipe 3 Risk. Leaking = Hazard * Exposure Pipe

Hazard : Potential for creating undesired adverse consequences. In this case it remains same as chemical flowing through pipe is same. Chemical A Pipe 1 Chemical A Pipe 2 Leaking Pipe Chemical A Pipe 3

Exposure : Vulnerability to hazard Pipe 2 poses greatest risk of exposure due to leakage. Chemical A Pipe 1 Chemical A Pipe 2 Leaking Pipe Chemical A Pipe 3

How is risk expressed? ØProbability of adverse effects associated with a particular activity ØUnitless ØFrom 0 -1 ØE. g. 1 x 10 -1 - One in 10 Ø 1 x 10 -2 - One in 100

Factors in Risk Acceptability Ø Ø Voluntary – Smoking – Bungee Jumping – Diet Nonvoluntary – Ø Ø Ø Risk resulting from uncontrollable actions of others (Occupational exposure, pesticide residues) – Natural disasters Degree of control Magnitude of the outcome Awareness Catastrophic Potential Group involvement Cost of alternatives

Risk Values Activity Annual Risk Smoking 10 cigarettes/day 1 x 10 -3 Motor vehicle accidents 2 x 10 -4 Manufacturing work accident 8 x 10 -5 Pedestrian hit by automobiles 4 x 10 -5 Drinking two beers/day 4 x 10 -5 Person in a room with a smoker 1 x 10 -5 Peanut butter (4 teaspoons/d) 8 x 10 -6 Drinking water with EPA limit of Trichloroethene 2 x 10 -9

What is Risk Assessment? ØAnalytical tool for studying situations that could result in adverse consequences ØQualitative and quantitative assessment of environmental status ØProcess to identify and quantify the risk and select necessary action

Risk Assessment Applications Identification of any ecological risk Establishment of cleanup standards Site remediation alternative selection Identification of the need for additional data collection

Groundwater Compartmentalized Hazardous Waste Leaching of waste Migrating contaminant Plume Increasing migration distance with time

Remediation Options?

No Action In place containment, groundwater pumping and retreatment alternative Excavation, Incineration/relandfilling

No Action Ø No capital cost Ø Groundwater contamination is definite

In place containment, groundwater pumping and retreatment alternative Creating a barrier to prevent or extend the groundwater contamination around the site Volatilization and Particulate migration Construction of containment facility Air Stripping Volatilization

Excavation Incineration/ Re-Landfilling Vehicular transport to incinerator Particulate migration / Volatilization Stockpiling at incinerator Re- Landfilling Incinerator Flue Gas Emissions

Process

Risk Assessment Process Hazard Identification Dose Response Exposure Assessment Risk characterization

Hazard Identification Ø Toxicity assessment determines whether exposure to a chemical, physical, or biological agent can cause an increase in the incidence of an adverse effect. Ø Necessary condition for a health or safety risk Ø Physical, metabolic, and chemical properties of the agent; Ø Potential routes of exposure; toxicological effects; results of animal studies (dose-response); and site characteristics

Hazard Identification – Toxicity Score Ø Ranking of chemicals from contaminated sites depending upon their toxicity scores Ø Help in identifying contaminants with a significant impact at the site Ø Need data from the contaminated site

Hazard Identification – Toxicity Score – Non=carcinogens Toxicity score (TS) = Cmax / Rf. D Cmax = Maximum Concentration Rf. D = Chronic Reference Dose i. e. acceptable daily intake TS = Toxicity score

Hazard Identification – Toxicity Score - Carcinogens Toxicity score (TS) = Cmax * CSF Cmax = Maximum Concentration CSF = Cancer Slope factor TS = Toxicity score

Hazard Identification – Toxicity Score – Example Landfill ABC Chemicals Air (mg/m 3) Mean Max Chlorobenzene (NC) 4. 09 E-08 8. 09 E-08 Chloroform (C, NC) 1. 12 E-12 1, 2 Dichloroethane (NC) BEHP (C, NC) Groundwater (mg/L) Mean Max 2. 5 E-04 1. 10 E-02 1. 39 E+00 6. 40 E+00 3. 12 E-12 3. 3 E-04 7. 60 E-03 1. 12 E+00 4. 10 E+00 1. 12 E-08 2. 40 E-08 2. 1 E-04 2. 00 E-03 ND ND 3. 29 E-07 8. 29 E-07 1. 03 E+02 2. 30 E+02 ND Max Soil (mg/kg) ND ND – Not Detected; C= Carcinogenic, NC = Non-carcinogenic

Hazard Identification – Toxicity Score Chemicals Rf D ( mg/kg-day) Soil (mg/kg) Mean Cmax Chlorobenzene 2. 00 E-02 1. 39 E+00 6. 40 E+00 Chloroform 1. 00 E-02 1. 12 E+00 4. 10 E+00 1, 2 -Dichloroethane NA ND ND BEHP 2. 00 E-02 1. 03 E+02 2. 30 E+02 ND – Not Detected; NA-Not Applicable Rank the non-carcinogenic chemicals for soil

Hazard Identification – Toxicity Score Rf D ( mg/kgday) Mean Cmax Chlorobenzene 2. 00 E-02 1. 39 E+00 Chloroform 1. 00 E-02 1, 2 Dichloroethane BEHP Chemicals Soil (mg/kg) TS = Cmax/Rf. D Rank 6. 40 E+00 320 3 1. 12 E+00 4. 10 E+00 410 2 NA ND ND 2. 00 E-02 1. 03 E+02 2. 30 E+02 NA 11, 500 ND – Not Detected; NA-Not Applicable BEHP poses the greatest risk for the given site followed by chloroform and Chlorobenzene. 1

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.

Hazard Identification – Toxicity Score Now try the same problems for carcinogens. Also find Rf. D for the same contaminants in groundwater and air, on web and perform TS calculations

Risk Assessment Process Hazard Identification Dose Response Exposure Assessment Risk Characterization

Risk Assessment Process Dose Response How large a dose causes what magnitude of effect?

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.

Dose-Response Curve Ø Represents variations in response of receptor at different contaminant levels Ø Generally, 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. Ø Quantitative relationship between exposure and toxic effects Ø Enables risk assessor to estimate a safe dose Ø Actual dose is compared with safe dose in risk assessment process

Dose-Response Curve Ø Dose: mg chemical/kg of body weight Ø Response: % population affected by dose. Ø Curvature of dose response curve illustrates varying sensitivity of exposed population. No-Observed-Adverse-Effect-Level (NOAL) – the greatest dose level at which no adverse effect is noted Ø Lowest-Observed-Adverse. Effect-Level (LOAEL) – Lowest level at which an adverse effect is detected

Cancer Response-Dose Curve Ø Dose: mg chemical/kg of body weight Ø Response: % population cancer Ø Extrapolate to low dose/risk

Reference Dose Ø Rf. D: An estimate of daily exposure to the human population that is likely to be without appreciable risk of deleterious effects during a lifetime Ø Expressed as mg pollutant / kg body weight/day Ø Also expressed as Reference Concentration (Rf. C), mg/m 3

Reference Dose Rf. D = NOAEL /(FAFHFSFLFD) Where: NOAEL: No-Observed-Adverse-Effect-Level FA: An adjustment factor to extrapolate from animal to human population FH: Adjustment factor for differences in human susceptibility FL: An adjustment factor applied when LOAEL is used instead of NOAEL FS: An adjustment factor applied when data set is dubious or incomplete

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.

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 Rf. D using NOAEL and LOAEL Rf. D = NOAEL / (FA FH FS FLFD) Adjustment factors applicable for this problem are: F A , F H, F s Rf. D = 15. 3/(10*10*10) = 0. 015 mg/kg-day

Reference Dose - Problem Using LOAEL : Rf. D = LOAEL/(FA FH FS FLFD) Adjustment factors applicable are : F , FH, Fs and F Rf. D = 62/(10*10*10*10) = 0. 0062 mg/kg-day A L

Reference Dose - Problem Ø Rf. D = 0. 015 mg/kg-day (Using NOAEL) Ø Rf. D = 0. 0062 mg/kg-day (using LOAEL) The lowest of two values will be the reference dose for tris-phosphate i. e. 0. 0062 mg/kg-day

Reference Dose - Problem Repeat the Rf. D calculations for trisphosphate for which NOAEL was determined to be 22 mg/kg-day and the LOAEL was found to be 44 mg/kg-day for increased weight of liver and kidneys in rat.

Risk Assessment Process Hazard Identification Dose Response Exposure Assessment Risk characterization

Exposure Assessment Deals with various exposure pathways for released contaminant

Exposure Assessment - Pathways Ø Source (e. g. landfill, lagoon) Ø Chemical release mechanism (e. g. leaching) Ø Transport mechanism (e. g. groundwater) Ø Transfer mechanism (e. g. sorption) Ø Transformation mechanism (e. g. biodegradation) Ø Exposure point (e. g. residential well) Ø Receptor Ø Exposure route ( e. g ingestion, inhale)

Exposure Assessment Means of Exposure Occupational Exposure, i. e. exposure at workplace Community Exposure, i. e. exposure at workplace

Exposure Assessment Routes of Exposure Dermal Exposure (Skin) Lungs Exposure (Inhalation) Ingestion

Exposure Assessment Process Work Surface Air Skin Inhalation Ingestion Dermal Absorption

Inhalation/Ingestion Exposure Framework Exposure Duration (Time) Severity (mass/time) Env. concentration (mass/volume) Breathing/ Ingestion Rate (volume/time) Frequency (no. exposures) Period (time/exposure)

Dermal Exposure Framework Exposure (mass) Severity (mass/time) Surface (area skin exposed) Frequency (no. incidents) Absorption (mass/area/incident)

NSP: Nanoscale particles

Calculation I= I C ( C x CR x EF x ED) -------------(BW x AT) = Intake (mg/kg of body weight per day) = Concentration at exposure point (e. g. mg/L in water or mg/m 3 in air) CR = Contact Rate ( e. g L/day or m 3/day) EF = Frequency (day/year) ED = Exposure Duration (yr) BW = Body weight (kg) AT = Averaging Time (days)

Standard Parameters for Calculating Exposure and Intake Parameter Adults Child Age (6 -12) Child Age ( 2 -6) Average Body Weight (kg) 70 29 16 Skin surface are (cm 2) 18, 150 10470 6980 Water Ingested (L/day) 2 2 1 Air breathed (m 3/hour) 0. 83 0. 46 0. 25 Retention rate (inhaled air) 100% Absorption rate (inhaled air) 100% Soil ingested (mg/day) 100 200 Bathing duration (minutes) 30 30 30 Exposure frequency (days) 365 365 Exposure duration (years) 30 6 4

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.

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 m 3/hr CR = 0. 83 x 24 = 19. 92 m 3/day EF = 365 days ED = 30 years ( For chronic exposure, non-carcinogen) RR = 1, ABS = 1 ( Assumption in the absence of any data) AT = 365 days x 30 years

Intake Rate Calculation I = (C x 19. 92 x (365 x 30) x 1 x 1)/ (70 x (365 x 60)) I = 0. 285 m 3/kg-day x C C = Exposure point concentration (mg/m 3)

Risk Assessment Process Hazard Identification Dose Response Exposure Assessment Risk characterization

Risk Characterization ØFinal step of risk assessment process ØIntegration of hazard identification, dose response assessment and exposure assessment.

Risk Characterization Carcinogenic Risk Non-carcinogenic Risk

Risk Characterization Carcinogens Risk = CDI x SF Where: CDI = Chronic daily intake (mg/kg-day) hazard assessment SF = carcinogenic slope factor (kgday/mg)

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

Risk Characterization: Noncarcinogenic ØNormally characterized in terms of hazard index (HI) ØHI = (CDI/Rf. D) where • CDI = Chronic daily intake (mg/kg-day) • Rf. D = Reference dose (mg/kg-day) • HI = Hazard Index (Unitless) ØHI < 1. 0 is acceptable

Risk Characterization: Non carcinogenic Calculate the hazard index for chlorobenzene, based on intake calculated for landfill ABC. Solution: HI = CDI/Rf. D = 2 x 10 -2 ; CDI = 2. 82 x 10 -7 HI = 1. 41 x 10 -5 < 1 OK

Risk Management Ø Regulatory action Ø Decision to mitigate risk Ø Action level

Uncertainty Ø The risk assessment process is extremely conservative in nature and utilizes measurements which are uncertain. Ø Insufficient data or information gaps often exist in characterizing the potential risk of an agent, necessitating the need for assumptions or educated guesses.

Uncertainty Ø Use computational tools from the field of decision analysis to account for the uncertainties in the process Ø These 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

Return to Home Page Last updated October 2008 by Dr. Reinhart