ACEME – A MULTIPATHWAY HEALTH RISK ASSESSMENT MODEL FOR MERCURY EMISSIONS

1. This presentation will probably involve audience discussion, which will create action items. Use PowerPoint to keep track of these action items during your presentation • In Slide Show, click on the right mouse button • Select “Meeting Minder” • Select the “Action Items” tab • Type in action items as they come up • Click OK to dismiss this box • This will automatically create an Action Item slide at the end of your presentation with your points entered. ACEME – A MULTIPATHWAY HEALTH RISK ASSESSMENT MODEL FOR MERCURY EMISSIONS 8th Electric Utilities Environmental Conference Tucson, AZ, January 2005 Khanh T. Tran AMI Environmental Henderson, NV 89015 www.amiace.com

2. Model Applicability • Site-specific Risk Assessment for Coal-fired Power Plants & Waste Combustors • US EPA Human Health Risk Assessment Protocol (HHRAP) • ACEME – Assessment of Chemical Exposure for Mercury Emissions • ACEME derived from other AMI’s models ACEHWCF & ACE2588

3. Health Risk Assessment • Identify Compounds of Concern (COPC) and Emissions • Calculate Concentrations and Deposition in Air and Other Media • Calculate Exposure Doses • Calculate Health Risks • Sensitivity & Uncertainty Analyses

4. COPC Identification • Stack Emission of Combustion By-Products (Hg, PCDD/PCDF, PAH, PCB, other organics and metals) • Over 200 Carcinogens & Noncancer Toxics • Health Effect Data File PCHEM.DAT (URF, Oral CSF, RfC, RfD, AIEC) • Mercury Speciation & Multipathway Chronic Exposure

5. Mercury Exposure Pathways

6. Mercury Emissions Partitioning 20 g Elemental Hg (v) 60 g HgCl2 (v) Assume 100 g Total Hg 20 g HgCl2 (p-b) Global Cycle 99% Loss Global Cycle 32% Loss Global Cycle 64% Loss 1% 68% 36% 40.8 g HgCl2 (v) Deposited 7.2 g HgCl2 (p-b) Deposited 0.2 g Elemental Hg (v) Deposited HWC Facility Only 48.2 g Total Hg Deposited Emission Rates Hg0 = 0.2% of Total Hg HgCl2 = 48% of Total Hg Vapor Phase Fractions, Fv Fv for Hg0 (0.2/0.2) = 1.0 Fv for HgCl2 (40.8/48.0) = 0.85

7. Mercury Transport & FateAfter Deposition Deposition to Soils & Water Body = (7.2g HgCl2)pb + (40.8g HgCl2 + 0.2 g Hg0)v Volatilization Ksv Runoff Load Lri + Lr Runoff Ksr Erosion Load Le Erosion Kse Leaching Ksl Cs 98% HgCl2 2% MeHg Cw 85% HgCl2 15% MeHg Prior to Soil Losses 47g HgCl2; 0.96g MeHg Prior to Loads from Soils 40.8g HgCl2; 7.2g MeHg Soil Losses Ks = Ksg + Kse + Ksr + Ksl + Ksv Total Load to Water Body Ltotal = Ldep + Ldiff + Lri + Lr + Le

8. Air Modeling • COPC Phases: Vapor, Particle and Particle-bound • Regulatory Dispersion Models: > local: ISCST3, ISC-PRIME, AERMOD > regional (>50 km): CALPUFF • 5-year Meteorological Data • Partial Contributions (X/Q, D/Q) for Single and Multiple Stacks

9. Other Media Modeling • Multipathway COPC with non-inhalation exposure • Other Media: soil, drinking water, produce, farm animals and fish • Chemical-specific and site-specific parameters (PSITE.DAT) • Options in Specifying Food Sources (homegrown or commercial), watershed areas and waterbodies

10. Exposure Doses • Daily Intakes & Lifetime Average Daily Doses from All Pathways • Receptor-specific Exposure Scenarios: Resident, Farmer, Fisher • Exposure: 6 years for child, 30 years for adult resident/fisher, 40 years for adult farmer • User-specified exposure pathways and scenarios

11. Noncancer Health Risk • Acute Hazard Quotient (HQ) for Hg0 and Hg2+ • Chronic HQ for Hg0, Hg2+ and MeHg • Multipathway Hg2+ and MeHg • Acute & Chronic HQ - total and individual target organs • Tables of Contributions by Sources and Pollutants

12. Sensitivity Analysis • Alternative Mercury Speciation (source-specific profiles) • Alternative Model (ISCST3 vs AERMOD, CALPUFF, ISC-PRIME) • Alternative Deposition Algorithms

13. Uncertainty Analysis • Conservative Point Estimate • Wide range in input parameters (transport and fate, exposure) • Monte Carlo probabilistic HRA • Realistic range of risk estimates

14. Model Validation • US EPA Region 6 - Mercury Exposure Scenario • HWCF Facility in Louisiana with 233 pollutants, over 5200 receptors, 5 years of met data • Output available from Website www.amiace.com

15. Sensitivity Analysis-Alternative Model • ISCST3 vs. ISCPRIME • New PRIME building downwash • Apply to HWCF in Louisiana • Predicted MEI-Farmer • Increase Cancer Risk by 31% • Increase Chronic HQ by 21%

16. Mercury Exposure from Fish • Methyl Mercury Chronic HQ – EPA R6 • HQ = ADD / RfD where ADD= Cfish CR EF ED / (365 *AT) Nominal EPA values: Cfish = 1.15952116 mg/ kg CR = 1.17E-3 kg/kg-day EF = 350 days/yr, ED = 30 years AT = 30 years RfD = 1.0E-4 mg/kg-day Chronic HQ = 13.009

17. Monte Carlo Uncertainty Analysis • Random variable CR • California OEHHA • Default CR = 0.48E-3 kg/kg-day • Chronic HQ = 5.34 • Lognormal with mean=0.48E-3 and • Standard deviation=0.71E-3 kg/kg-day • Monte Carlo with 10,000 iterations

18. MONTE CARLO ANALYSIS – FREQUENCY PLOT

19. MONTE CARLO ANALYSIS – CUMULATIVE FREQUENCY PLOT

20. Summary • ACEME implements the US EPA guidelines • Model provides realistic risk estimates with Monte Carlo • Model is validated against recent EPA modeling studies • Model is applicable to single or multiple facilities (cumulative)