Screening Level Health Risk Assessment of PCCD/PCDF Contamination Da Nang Airbase Case Study

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1 Regional Capacity Building Program for Health Risk Management of Persistent Organic Pollutants (POPs) in South East Asia Program 7/15/2009 SLIDE 1 Screening Level Health Risk Assessment of PCCD/PCDF Contamination Da Nang Airbase Case Study Final Regional Workshop Da Nang, Viet Nam, July 22-24, 2009 Mike Rankin, Vancouver, BC SLIDE 2

2 Integrated Risk Management Framework For Contaminated Sites INVESTIGATION INVESTIGATION REMEDIATION REMEDIATION Site Discovery RISK RISK MANAGEMENT MANAGEMENT Public Interests RISK RISK ASSESSMENT ASSESSMENT FRAMEWORK FRAMEWORK Problem Formulation Site Characterization Site Remediation Compliance Monitoring Regulatory Policy Goal Setting Options Analysis Exposure and Toxicity Analysis Risk Characterization Decision Making COMMUNICATION SLIDE 3 Environmental Risk Assessment Framework SLIDE 4

3 Health Risk Components e.g., POPs e.g., PCDDs e.g., PCDFs e.g., fish/humans e.g., ingestion SLIDE 5 2,3,7,8-TCDD: Reference Molecule for TEFs and International Toxicity Equivalents (I-TEQ) I-TEQ = [Conc n] x TEF PCB SLIDE 6

4 Problem Formulation for Da Nang Air Base Dan Nang Airbase and surrounding areas constitute a complex site Various historic sources/areas of Agent Orange usage Various environmental compartments Persistent contaminants in the form of PCDDs/PCDFs, and other substances Various types of receptors (i.e., people and animals) Various types of pathways and activities that could cause exposure What data is needed to approach the risk assessment and risk management questions? SLIDE 7 Dioxin Risk Exposure Model, Da Nang People living on or outside airbase Base Perimeter Drainage ditch to Phu Loc River dust Sen Lake C Sen Lake B Sen Lake A Xuan Lake Aquatic Fish Plants Aquatic Plants Fish Aquatic Plants Fish Aquatic Plants Fish March 29 Lake Aquatic Fish Plants Sediment Sediment Sediment Sediment Sediment primary ditch secondary ditch Base soils Storage Area Drainage ditch Loading/ Washdown Area potential direct A.O. exposure SLIDE 8

5 Human Exposure Pathways SLIDE 9 Screening Level Conceptual Exposure Model for Humans On-Site Da Nang Airbase Scenario SLIDE 10

6 Screening Level Conceptual Exposure Model for Ecological Receptors On-Site Da Nang Airbase SLIDE 11 Environmental Risk Assessment Framework SLIDE 12

7 Soils Mixing/Loading Area and Storage Area Hot Spots SLIDE 13 On-site Soil Data for PCCDs/PCDFs SLIDE 14

8 Perimeter-site Soil Data for PCDDs/PCDFs SLIDE 15 Perimeter-site Soil Data for PCCDs/PCDFs SLIDE 16

9 Soil/Sediment in Da Nang City SLIDE 17 Off-site Da Nang City Soil Data for PCCDs/PCDFs SLIDE 18

10 Fish Tissue and Vegetation Data PCDD/PCDFs SLIDE 19 SLIDE 20

11 SLIDE 21 SLIDE 22

12 SLIDE 23 Data Input Table Exposure Modeling Data Grouped for Model Input - Da Nang Airbase Site, Viet Nam On-Site Receptor Scenario Perimeter Site Receptor Scenario City Receptor Scenario On-site Worker Local Resident Local Resident Local Resident Location Adult Adult Child Location Adult Child Location Adult Child Accidental Soil Ingestion Accidental Soil Ingestion Accidental Soil Ingestion C S (mg/kg) C S (mg/kg) C S (mg/kg) IRS kg/day IRS kg/day IRS kg/day AF GIT (no units) AF GIT (no units) 1 1 AF GIT (no units) 1 1 Dhours (hours/day) Dhours (hours/day) Dhours (hours/day) D day s (days/w eek) D day s (days/w eek) 7 7 D day s (days/w eek) 7 7 Dweeks (w eeks/year) Dweeks (w eeks/year) Dweeks (w eeks/year) Dy ears (years) Dy ears3 (years) Dy ears3 (years) BW (kg) BW (kg) BW (kg) LE (years) LE3 (years) LE3 (years) Food Ingestion Food Ingestion Food Ingestion 1 Cf ood (mg/kg) 1 Cf ood (mg/kg) 1 Cf ood (mg/kg) Food Food Food IR (kg/day) IR (kg/day) IR (kg/day) AFGIT (no units) AFGIT (no units) 1 1 AFGIT (no units) 1 1 Contaminant Characterization Receptor Characterization D day s (days/year) D day s (days/year) D day s (days/year) Dy ears (years) Dy ears3 (years) Dy ears3 (years) BW (kg) BW (kg) BW (kg) LE 3 (years) LE 3 (years) LE 3 (years) Inhalation of Contaminated Particles Inhalation of Contaminated Particles Inhalation of Contaminated Particles C S (mg/kg) C S (mg/kg) C S (mg/kg) PAIR IR A PAIR PAIR (µg/m3) (µg/m3) (µg/m3) (m 3/h) IR A (m 3/h) IR A (m3/h) AFInh (no units) AFInh (no units) 1 1 AFInh (no units) 1 1 D hours (hours/day) D hours (hours/day) D hours (hours/day) Dday s (days/w eek) Dday s (days/w eek) 7 7 Dday s (days/w eek) 7 7 D weeks (w eeks/year) D weeks (w eeks/year) D weeks (w eeks/year) Dy ears (years) Dy ears3 (years) Dy ears3 (years) BW (kg) BW (kg) BW (kg) LE 3 (years) LE 3 (years) LE 3 (years) Dermal Contact with Contaminated Soil Dermal Contact with Contaminated Soil Dermal Contact with Contaminated Soil C S (mg/kg) C S (mg/kg) C S (mg/kg) SAH SL H SAH SAH (cm2) (cm2) (cm2) (kg/cm 2-event) SL H (kg/cm 2-event) SL H (kg/cm2-event) AFSkin (no units) AFSkin2 (no units) AFSkin2 (no units) EF (events/day) EF (events/day) 1 1 EF (events/day) 1 1 Dday s (days/w eek) Dday s (days/w eek) 7 7 Dday s (days/w eek) 7 7 Dweeks (w eeks/year) Dweeks (w eeks/year) Dweeks (w eeks/year) Dy ears 3 (years) Dy ears 3 (years) Dy ears 3 (years) BW (kg) BW (kg) BW (kg) LE 3 (years) LE 3 (years) LE 3 (years) Food scenario based on w eighted mean of composited tilapia fish samples of fat (10%) and muscle (90%), from Sen Lake. 2. Estimated value. 3. Additional variables required for running carcinogen (non-threshold) model (show n as Bold). SLIDE 24

13 Environmental Risk Assessment Framework SLIDE 25 2,3,7,8-TCDD: Reference Molecule for TEFs and International Toxicity Equivalents (I-TEQ) I-TEQ = [Conc n] x TEF PCB SLIDE 26

14 Toxicity Reference Values for PCDD/PCDF For Non-Cancer Endpoints Health Canada Tolerable Daily Intake (TDI) defines the daily intake below which no adverse effects are expected as a result of lifetime exposure (i.e., considered safe ) Predicated on concept that effects occur only when threshold exposure is exceeded (TDI is set below threshold for safety) For PCDD/PCDF, the TDI is 2E-9 mg TEQs/kg-day as defined by Health Canada SLIDE 27 Toxicity Reference Values for PCDD/PCDF For Cancer Endpoints USEPA Cancer Slope Factor (SF) is the upper bound of the slope relating the proportion of individuals with cancer (tumours) to the lifetime-averaged daily intake rate of the contaminant. Predicated on concept that any exposure level presents some risk of cancer The larger the slope factor, the greater the carcinogenic potency of the chemical For PCDD/PCDF, the cancer SF is 1.3E5 kg-day/mg TEQs as defined by the USEPA. SLIDE 28

15 Environmental Risk Assessment Framework SLIDE 29 Risk Estimation and Risk Characterization Risk Estimates Hazard Quotient (HQ) = Exposure Ratio HQ = Dose Rate/Reference Dose (e.g., TDI) Hazard Index = ΣHQ for all pathways and similar toxic effects Incremental Lifetime Cancer Risk (ILCR) ILCR = (Cancer Slope Factor) x (Dose Rate) Risk Characterization the process of describing and interpreting risk estimates A HQ of <0.2 is often considered acceptable Other jurisdictions may use HQ = 1.0 as acceptable ILCR < 1 x 10-5 (i.e., <1E-5) often considered acceptable Evaluation of Uncertainty in risk estimates SLIDE 30

risk estimates (HQ) based on input data and assumptions 1a On-site Worker Hazard

16 Figure 5.1a On-site Worker Hazard Quotient (non-cancer risk) SLIDE 31 Dose and Non-Cancer risk estimates (HQ) based on input data and assumptions Figure 5.1a On-site Worker Hazard Quotient (non-cancer risk) Figure 5.1b On-site Local Resident Adult (non-cancer risk) Figure 5.1c On-site Local Resident Child (non-cancer risk) SLIDE 32

17 Figure 5.2a. On-site Worker ILCR SLIDE 33 Dose and Cancer risk estimates (ILCR) based on input data and assumptions Figure 5.2a. On-site Worker ILCR Figure 5.2b. On-site local resident adult ILCR Figure 5.2c. On-site local resident child ILCR SLIDE 34

18 Exposure and Risk Estimation Exercise and Discussion Audience will split into 4 assigned groups as instructed and conduct two exercises as described in Da Nang Case Study Report (Box II and Box III): Box II Exercise: Examine data for soil and compute the arithmetic and geometric mean concentration of total TEQs based on Table 4.1. Then compare these to the maximum value to determine the ratio (max/mean) and consider how this could affect risk estimation. Box III Exercise: Using the data input table (Table 4.5) according to your assigned group, enter the data into the POPs website risk calculation tool to compute exposure and risk. SLIDE 35 Closure on Risk Estimation Observations on variability in exposure concentration and other sources of variability; Comments on multiple exposure pathways and effect of errors or missing exposure routes on final interpretation Ideas on Quality Assurance of Risk Calculations Connecting the risk assessment results to the risk managers needs to facilitate decisions on risk mitigation Practice and question assumptions detailed risk assessment require various transport and exposure models, and expertise. Always start with screening level and a clear vision of Problem Formulation SLIDE 36

19 Thank you for your kind attention. Questions? 7/15/2009 SLIDE 37

5.0 HAZARD ASSESSMENT AND RISK CHARACTERIZATION

5.0 HAZARD ASSESSMENT AND RISK CHARACTERIZATION 5.1 SELECTING A TOXICITY REFERENCE VALUE (TRV) Appropriate Toxicity Reference Values (TRVs) are required to characterize the potency of the contaminants