Transcript Air Quality Training for Gas Company Account Executives

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)?
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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?
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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
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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
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May require Environmental Impact Report
Implications (continued)
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May set permit conditions
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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?
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Toxic Air Contaminants (TAC) are listed
in Rules 1401 and 1402
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Carcinogenic:
Acute:
Chronic:
153 compounds
58 chemicals
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
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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
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<1 x 10-6 to avoid public notice
Health Risk Index - Chronic
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Chronic Hazard Index (HIC)
Long term, non-cancer health effects
Must be < 1.0 for all target organs
Health Risk Index - Acute
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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
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Symbol
Description
Chronic
Acute
X
AL
Alimentary system (liver)
X
BN
Bones and teeth
X
CV
Cardiovascular system
X
X
DEV
Developmental
X
X
END
Endocrine system
X
EYE
Eye
X
X
HEM
Hematopoietic system (blood)
X
X
IMM
Immune system
X
X
KID
Kidney
X
NS
Nervous system
X
X
REP
Reproductive system
X
X
RESP
Respiratory system
X
X
SKIN
Skin
X
X
Risk Assessment Tiers
Less Conservative
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Tier 1: Screening Emission Levels
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Tier 2: Screening Risk Assessment
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Use Tables 2-10 to determine dispersion factors, etc.
Tier 3: Screening Dispersion Modeling
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Use Table 1A to check if emission rates are below thresholds
Use SCREEN3 to determine dispersion factors
Tier 4: Detailed Risk Assessment
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Use HARP for highest fidelity model, full meteorology
Tier I Screening Evaluation
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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
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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
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MICR = CP x DI x MP
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CP: cancer potency factor (mg/kg-day)-1
DI = Dose inhalation (mg/kg-day)
DI = Cair x DBR x EVF x 10-6
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Cair = Qtons
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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)
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
Chronic Index Equation
T otalHICtarget organ
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 Q yrTAC  X/Q  MET  MP 
 

Chronic
REL
TAC
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target organ
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 Chronic Reference Exposure Level (g/m3) for each TAC
MP
Multi-pathway adjustment factor (n.d.)
MET Meteorological correction factor (n.d.)
Acute Index Equation
T otalHIAtarget organ
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 Q hrTAC  X/Qhr 
 

Acute
REL
TAC  target organ
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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
Cancer Burden Calculation
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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
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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
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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
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Free download from CARB website
www.arb.ca.gov/toxics/harp/harp.htm
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Multiple sources in different locations
TAC’s from Natural Gas
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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
Toxic Air Contaminant*
Benzene
Formaldehyde
Polycyclic Aromatic
Hydrocarbons (PAH's)
Naphthalene
Acetaldehyde
Acrolein
Propylene
Toluene
Xylenes
Ethylbenzene
Hexane
MICR
X
X
X
HIC
X
X
X
X
X
X
X
X
X
X
X
X
*As determined by Ventura APCD
HIA
X
X
X
X
X
TAC’s from
Internal
Combustion
EPA: AP-42 Emission Factors, Table 3.2-3
Toxic Air Contaminant
MICR
HIC
1,1,2,2-Tetrachloroethane
X
1,1,2-Trichloroethane
X
1,1-Dichloroethane
X
1,3-Butadiene
X
X
Acetaldehyde
X
X
Acrolein
HIA
X
X
Benzene
X
X
X
Carbon Tetrachloride
X
X
X
Chlorobenzene
Chloroform
X
X
Ethylbenzene
X
X
X
Ethylene Dibromide
X
X
Ethylene dichloride (1,2-dichloroethane)
X
X
Formaldehyde
X
X
X
X
X
X
X
Methanol
Methylene Chloride
X
n-Hexane
X
Naphthalene
X
PAHs (w/o naphthalene)
X
X
Phenol
X
X
Styrene
X
X
Toluene
X
X
Vinyl Chloride
Xylene
X
X
X
X
Rule 1401 Limitations
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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
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Emergency Internal Combustion Engines
Modifications with no increase in toxic emissions
Functionally identical replacement
Contemporaneous Risk Reductions
-6, and
 No MICR increase at any location >1x10
 Reduction occurs within 100 m of new
equipment
Alternative Hazard Index <10
Example
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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)
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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
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Strategies
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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
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Tests showed high destruction of PAH
across catalyst