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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

November 2, 2005

Peter J. Moore

Yorke Engineering

949-248-8490 x24


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 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

  • 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)

  • 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?

  • 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

  • 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

  • Chronic Hazard Index (HIC)

  • Long term, non-cancer health effects

  • Must be < 1.0 for all target organs


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?

  • Specific systems in the human body that are affected by TACs


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

  • 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

  • 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

  • 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

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/QAnnual average dispersion factor (g/m3)/(ton/year)

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

MPMulti-pathway adjustment factor (n.d.)

METMeteorological correction factor (n.d.)


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

  • 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

  • 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

  • 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

  • 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

*As determined by Ventura APCD


TAC’s from Internal CombustionEPA: AP-42 Emission Factors, Table 3.2-3


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

  • 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

  • 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)

  • 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:

  • Source and Receptor Location

  • Emission Rate

  • Emission Species

  • Meteorology

  • Stack Parameters

  • Operating Schedule


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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