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New Source Review for Air Toxics. November 2, 2005. Peter J. Moore Yorke Engineering 949-248-8490 x24. What is Toxics New Source Review (NSR)?. Evaluation of the health risk impacts to nearby exposed individuals (receptors) Calculate health risk indices

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new source review for air toxics

New Source Review for Air Toxics

November 2, 2005

Peter J. Moore

Yorke Engineering

949-248-8490 x24

what is toxics new source review nsr
What is ToxicsNew Source Review (NSR)?
  • Evaluation of the health risk impacts to nearby exposed individuals (receptors)
  • Calculate health risk indices
  • Health risk indices cannot exceed thresholds
when is toxics nsr applied
When is Toxics NSR Applied?
  • When a new or modified source causes an increase in Toxic Air Contaminants (TAC), Toxics NSR is required
  • SCAQMD Rule 1401 – New Source Review of Toxic Air Contaminants
  • Also Rule 219 permit-exempt equipment if health risk may exceed thresholds
implications of toxics nsr
Implications of Toxics NSR
  • Permit denied if calculated health risk is too high
  • Public notice required if cancer risk increase exceeds 1 in one million
  • CEQA is triggered if combined project cancer risk increase exceeds 10 in one million
    • May require Environmental Impact Report
implications continued
Implications (continued)
  • May set permit conditions
    • Example: Natural Gas Engine
    • Toxic Air Contaminants from internal combustion must be evaluated for Toxics NSR
    • If health risk calculations show that a limit on operation is necessary to stay below health risk thresholds, a daily or monthly limit on natural gas use may become a permit condition
  • Carefully consider all possible toxic emissions for any new source
what toxics are considered
What Toxics are Considered?
  • Toxic Air Contaminants (TAC) are listed in Rules 1401 and 1402
    • Carcinogenic: 153 compounds
    • Acute: 58 chemicals
    • Chronic: 125 chemicals
  • Risk factors are assigned by the California EPA Office of Environmental Health Hazard Assessment (OEHHA)
  • New TAC’s being added over time
health risk index micr
Health Risk Index - MICR
  • Maximum Individual Cancer Risk (MICR)
  • Long term impact
  • Probability that an individual will contract cancer over 70 years (resident receptor) or 40 years (commercial receptor)
  • Must be < 1 x 10-5 (10 in one million) for new equipment
    • <1 x 10-6 to avoid public notice
health risk index chronic
Health Risk Index - Chronic
  • Chronic Hazard Index (HIC)
  • Long term, non-cancer health effects
  • Must be < 1.0 for all target organs
health risk index acute
Health Risk Index - Acute
  • Acute Hazard Index (HIA)
  • Short term (1-hour average) health effects
  • Must be < 1.0 for all target organs
what are target organs
What Are Target Organs?
  • Specific systems in the human body that are affected by TACs
risk assessment tiers
Risk Assessment Tiers
  • Tier 1: Screening Emission Levels
    • Use Table 1A to check if emission rates are below thresholds
  • Tier 2: Screening Risk Assessment
    • Use Tables 2-10 to determine dispersion factors, etc.
  • Tier 3: Screening Dispersion Modeling
    • Use SCREEN3 to determine dispersion factors
  • Tier 4: Detailed Risk Assessment
    • Use HARP for highest fidelity model, full meteorology

Less Conservative

tier i screening evaluation
Tier I Screening Evaluation
  • Max Annual Controlled Emissions (tons/year)
  • Max Hourly Controlled (lbs/hr)
  • Look up tables in: “Risk Assessment Procedures for Rules 1401 and 212”
    • Check for most recent version!
  • If emissions are lower than screening levels, Rule 1401 is satisfied. If not, proceed to Tier II
tier ii health risk assessment
Tier II Health Risk Assessment
  • Max Annual Controlled Emissions (tons/year)
  • Max Hourly Controlled (lbs/hr)
  • Look up tables in: “Risk Assessment Procedures for Rules 1401 and 212”
  • If health risk indices lower than thresholds, Rule 1401 is satisfied. If not, proceed to Tier III
tier ii risk assessment for micr
Tier II Risk Assessment for MICR
  • MICR = CP x DI x MP
    • CP: cancer potency factor (mg/kg-day)-1
    • DI = Dose inhalation (mg/kg-day)
    • DI = Cair x DBR x EVF x 10-6
      • Cair = concentration in air (µg/m3)
      • DBR = daily breathing rate (L/kg-day)
      • EVR = Exposure value factor (unitless)
      • 1 x10-6 = convert µg to mg(10-3 mg/µg), liters to cubic meters (10-3 m3/l)
    • Cair = Qtonsx X/Q x AFannx MET
      • Qtons = Emission rate (tons/year)
      • X/Q = Dispersion Factor ((µg/m3)/(ton/yr)
      • AFann = Annual Averaging factor
      • MET = meteorological correction factor (unitless)
    • MP: multipathway factor (unitless)
  • MICR = CP x ((Qtonsx X/Q x AFannx MET) x DBR x EVF x 10-6) x MP
chronic index equation
Chronic Index Equation

HIC Chronic hazard index (calculated for each target organ)

TACSum of the contribution for each Toxic Air Contaminant (TAC)

QyrTACEmission rate of each TAC (tons/year)

X/Q Annual average dispersion factor (g/m3)/(ton/year)

RELTACChronic Reference Exposure Level (g/m3) for each TAC

MP Multi-pathway adjustment factor (n.d.)

MET Meteorological correction factor (n.d.)

acute index equation
Acute Index Equation

HIA Acute hazard index (calculated for each target organ)

TACSum of the contribution for each Toxic Air Contaminant (TAC)

QhrTACEmission rate of each TAC (lb/hour)

X/QhrHourly average dispersion factor (g/m3)/(lb/hour)

RELTACAcute Reference Exposure Level (g/m3) for each TAC

cancer burden calculation
Cancer Burden Calculation
  • Only Needed if MICR >10-6
  • Estimate Area (km2) with Risk >10-6
  • Multiply Area by 4,000 - 7,000 persons/ km2
  • Multiply Total Persons by MICR
  • If Burden >0.5
    • More detailed calculations or modeling required
tier iii health risk assessment
Tier III Health Risk Assessment
  • Similar to Tier II
  • Use SCREEN3 to determine dispersion factors (X/Q) instead of from tables
  • Exhaust temperature and velocity are included
  • Simple building downwash effects
  • Single source
  • Equation is the same
  • If health risk indices lower than thresholds, Rule 1401 is satisfied. If not, proceed to Tier IV
tier iv health risk assessment
Tier IV Health Risk Assessment
  • Most detailed health risk assessment
  • Requires details of building dimensions, local topography, and local meteorology
  • Use Hot Spots Analysis and Reporting Program (HARP) to calculate dispersion factors and health risk indices
    • Free download from CARB website www.arb.ca.gov/toxics/harp/harp.htm
  • Multiple sources in different locations
tac s from natural gas
TAC’s from Natural Gas
  • Ventura County APCD did testing of internal & external combustion equipment in 1995 for TAC’s
  • “Ventura Factors” can be used for emission factors for external combustion only
  • Use EPA’s AP-42 emission factors for internal combustion
tac s from external combustion
TAC’s from External Combustion

*As determined by Ventura APCD

rule 1401 limitations
Rule 1401 Limitations
  • MICR of 1 X 10-6 Without T-BACT *
  • MICR of 1 X 10-5 With T-BACT
  • Cancer Burden, excess cancer cases in the population subject to a risk greater than (1 x 10-6), of 0.5
  • Acute and Chronic Hazard Index of < 1

* T-BACT Criteria Similar to Existing BACT

rule 1401 exemptions
Rule 1401 Exemptions
  • Emergency Internal Combustion Engines
  • Modifications with no increase in toxic emissions
  • Functionally identical replacement
  • Contemporaneous Risk Reductions
    • No MICR increase at any location >1x10-6, and
    • Reduction occurs within 100 m of new equipment
  • Alternative Hazard Index <10
example
Example
  • Facility adding three large, natural-gas fueled, cogeneration engines
  • Four existing emergency diesels
  • Nearby residents
  • Each engine passed Rule 1401 with MICR of 9 in one million
  • CEQA triggered due to combined MICR of 27 in one million
example continued
Example (continued)
  • We calculated that cogeneration engines resulted in less usage of diesel backup engines
  • Diesel health risk is high
  • Contemporaneous health risk reduction allowed project to proceed without requiring an Environmental Impact Report
risk is dependent on
Risk is Dependent On:
  • Source and Receptor Location
  • Emission Rate
  • Emission Species
  • Meteorology
  • Stack Parameters
  • Operating Schedule
strategies
Strategies
  • Locate equipment away from adjacent residents or workers
  • Raise stack height
  • Perform detailed modeling to determine risk impacts to specific receptors
  • Source test for actual toxic emissions
    • Tests showed high destruction of PAH across catalyst
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