ACEME A MULTIPATHWAY HEALTH RISK ASSESSMENT MODEL FOR MERCURY EMISSIONS

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ACEME A MULTIPATHWAY HEALTH RISK ASSESSMENT
MODEL FOR MERCURY EMISSIONS

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• 8th Electric Utilities Environmental Conference
• Tucson, AZ, January 2005
• Khanh T. Tran
• AMI Environmental
• Henderson, NV 89015
• www.amiace.com

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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 AMIs models ACEHWCF
  ACE2588

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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

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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

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Mercury Exposure Pathways
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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
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68
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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
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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
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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

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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

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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

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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

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Sensitivity Analysis

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

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Uncertainty Analysis

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

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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

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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

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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

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Monte Carlo Uncertainty Analysis

• Random variable CR
• California OEHHA
• Default CR 0.48E-3 kg/kg-day
• Chronic HQ 5.34
• Lognormal with mean0.48E-3 and
• Standard deviation0.71E-3 kg/kg-day
• Monte Carlo with 10,000 iterations

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MONTE CARLO ANALYSIS FREQUENCY PLOT
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MONTE CARLO ANALYSIS CUMULATIVE FREQUENCY PLOT
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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)