New Source Review for Air Toxics

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New Source Review for Air Toxics

• November 2, 2005

Peter J. Moore Yorke Engineering 949-248-8490 x24
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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

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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

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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

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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

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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 TACs being added over time

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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 lt 1 x 10-5 (10 in one million) for new
  equipment
• lt1 x 10-6 to avoid public notice

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Health Risk Index - Chronic

• Chronic Hazard Index (HIC)
• Long term, non-cancer health effects
• Must be lt 1.0 for all target organs

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Health Risk Index - Acute

• Acute Hazard Index (HIA)
• Short term (1-hour average) health effects
• Must be lt 1.0 for all target organs

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What Are Target Organs?

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

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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
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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

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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

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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 Qtons x X/Q x AFann x 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 ((Qtons x X/Q x AFann x MET) x DBR
  x EVF x 10-6) x MP

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Chronic Index Equation
HIC Chronic hazard index (calculated for each
target organ) ?TAC Sum of the contribution for
each Toxic Air Contaminant (TAC) QyrTAC Emission
rate of each TAC (tons/year) X/Q Annual average
dispersion factor (?g/m3)/(ton/year) RELTAC Chroni
c Reference Exposure Level (?g/m3) for each
TAC MP Multi-pathway adjustment factor
(n.d.) MET Meteorological correction factor (n.d.)
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Acute Index Equation
HIA Acute hazard index (calculated for each
target organ) ?TAC Sum of the contribution for
each Toxic Air Contaminant (TAC) QhrTAC Emission
rate of each TAC (lb/hour) X/Qhr Hourly average
dispersion factor (?g/m3)/(lb/hour) RELTAC Acute
Reference Exposure Level (?g/m3) for each TAC
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Cancer Burden Calculation

• Only Needed if MICR gt10-6
• Estimate Area (km2) with Risk gt10-6
• Multiply Area by 4,000 - 7,000 persons/ km2
• Multiply Total Persons by MICR
• If Burden gt0.5
• More detailed calculations or modeling required

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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

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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

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TACs from Natural Gas

• Ventura County APCD did testing of internal
  external combustion equipment in 1995 for TACs
• Ventura Factors can be used for emission
  factors for external combustion only
• Use EPAs AP-42 emission factors for internal
  combustion

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TACs from External Combustion
As determined by Ventura APCD
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TACs from Internal CombustionEPA AP-42
Emission Factors, Table 3.2-3
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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 lt 1
• T-BACT Criteria Similar to Existing BACT

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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 gt1x10-6, and
• Reduction occurs within 100 m of new equipment
• Alternative Hazard Index lt10

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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

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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

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Risk is Dependent On

• Source and Receptor Location
• Emission Rate
• Emission Species
• Meteorology
• Stack Parameters
• Operating Schedule

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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