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 8 th Electric Utilities Environmental Conference Tucson, AZ, January 2005 Khanh T. Tran AMI Environmental Henderson, NV

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

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

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

Mercury Exposure Pathways

Mercury Emissions Partitioning Assume 100 g Total Hg Global Cycle 64% Loss 20 g Elemental Hg (v) 60 g HgCl 2 (v) Global Cycle 99% Loss 40.8 g HgCl 2 (v) Deposited Only 48.2 g Total Hg Deposited 20 g HgCl 2 (p-b) 7.2 g HgCl 2 (p-b) Deposited Global Cycle 32% Loss 1% 0.2 g Elemental Hg (v) Deposited HWC Facility 36% 68% Emission Rates Hg 0 = 0.2% of Total Hg HgCl 2 = 48% of Total Hg Vapor Phase Fractions, Fv Fv for Hg 0 (0.2/0.2) = 1.0 Fv for HgCl 2 (40.8/48.0) = 0.85

Mercury Transport & Fate After Deposition Volatilization Ksv Leaching Ksl Soil Losses Ks = Ksg + Kse + Ksr + Ksl + Ksv Runoff Load Lri + Lr Erosion Load Le Deposition to Soils & Water Body = (7.2g HgCl 2 )pb + (40.8g HgCl g Hg 0 )v Cs 98% HgCl 2 2% MeHg Cw 85% HgCl 2 15% MeHg Erosion Kse Runoff Ksr Total Load to Water Body Ltotal = Ldep + Ldiff + Lri + Lr + Le Prior to Soil Losses 47g HgCl 2 ; 0.96g MeHg Prior to Loads from Soils 40.8g HgCl 2 ; 7.2g MeHg

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

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

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

Noncancer Health Risk Acute Hazard Quotient (HQ) for Hg 0 and Hg 2+ Chronic HQ for Hg 0, Hg 2+ and MeHg Multipathway Hg 2+ and MeHg Acute & Chronic HQ - total and individual target organs Tables of Contributions by Sources and Pollutants

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

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

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

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%

Mercury Exposure from Fish Methyl Mercury Chronic HQ – EPA R6 HQ = ADD / RfD where ADD= C fish CR EF ED / (365 *AT) Nominal EPA values: C fish = 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 =

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

MONTE CARLO ANALYSIS – FREQUENCY PLOT

MONTE CARLO ANALYSIS – CUMULATIVE FREQUENCY PLOT

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)