1. Kentucky Division for Air Quality Taimur Shaikh Ph.D.
Air Toxics & Modeling
Kentucky Division for Air Quality
Taimur Shaikh Ph.D.

2. Introduction Air Toxics Implementation Air Toxics Modeling
Ambient Sampling
Modeling
Risk Assessment
Air Toxics Modeling
Scope
Sample Projects
Various Toxics Modeled Facilities
Pb NAAQS Modeled Facility

3. Air Toxics Implementation

4. 401 KAR 63:020
Potentially hazardous matter or toxic substances regulation
“No owner or operator shall allow any affected
facility to emit potentially hazardous matter or
toxic substances in such quantities or duration as
to be harmful to the health and welfare of
humans, animals and plants.”

5. Ambient Sampling VOC’s SVOC’s Metals/Metalloids (Future)
EPA Method TO-15
Analyze for volatile organics
Both grab and 24-hour composite samples
SVOC’s
EPA Method TO-13A
Analyze for Poly-Aromatic Hydrocarbons
24-hour composites samples
Metals/Metalloids (Future)
PM10 including metals speciation
24-hour (or greater) composite samples

6. Air Toxics Modeling Consists of multiple tiers Usually performed:
1st tier – Screening via Screen3, conducted by permit reviewers
2nd tier – AERMOD modeling using pertinent meteorological data and LULC data
3rd tier – Same as 2nd tier but can require validated stack test emission rates, mass balances, and other data
Usually performed:
For new facilities/major modifications
In addition to sampled data
As a follow-up to citizen complaints

7. ATRA Reference Library
As part of the interpretation of 401 KAR 63:020, the Division
uses EPA’s Air Toxics Risk Assessment (ATRA) Reference
Library Volumes I, II, and III as the procedural direction for
conducting risk evaluations.

8. Risk Assessment Air Toxics Reference Library (ATRA)
“Tiered” Risk Assessment
Three distinct tiers
The higher tiered assessments involve more complexity and have more rigorous data requirements
1st tier – Risk is based on Screen3 output
2nd tier – Risk is based on annual average from AERMOD (chronic assessment)
3rd tier – Risk is based on ambient sampling data in addition to modeled values, at impacted individual, includes a more complex exposure and toxicity assessment
Based on EPA guidance documents
Most often, the data requirements limits the scope of the assessment

9. The Tiered Risk Assessment
Complete study-specific data, no assumptions - higher cost, lower uncertainty
Add quantitative uncertainty / variability analysis
More refined exposure assessment
More refined dispersion & exposure modeling
Simple dispersion model
Lookup Table
MORE REFINED
Tiers 2 & 3
SCREENING
Tier 1
No data, all assumptions - lower cost, high uncertainty

10. The Tiered Risk Assessment
Lookup tables
Exposure = maximum offsite levels
Simple dispersion modeling (MEI)
No data – all assumptions
Lower cost – high uncertainty
Conservative results – consistently over-estimates risk
Tier 1
(Screening Level)
Exposure = residential air levels
More refined dispersion & exposure modeling (MIR)
Moderate cost
Tier 2
(Moderate Complexity)
Exposure = exposure assessment
Detailed site-specific modeling (MIR)
Complete study-specific data
No assumptions
Higher cost – lower uncertainty
Tier 3
(High Complexity)
A key component of future efforts to reduce air toxics is the Integrated Urban Air Toxics Strategy released by EPA in July The Strategy presents a framework to address air toxics in urban areas and builds on the substantial emission reductions already achieved from cars, trucks, fuels, and industries such as chemical plants and oil refineries.

11. Air Toxics Domain All higher-level (tiers 2 & 3) risk assessments
As directed by DAQ Management, risk assessments involving:
Unlisted pollutants
Acute health effects
Bioaccumulation
Cumulative risk
Carcinogenic risk
Target organ specific hazard index
Emissions from multiple sources
Environmental damage

12. Air Dispersion Modeling

13. Sample Projects Examples of incorporating modeling into Air Toxics:
Toxics analysis – Dioxins & Furans
Toxics analysis – Hydrazine
Toxics analysis – HF modeling under
401 KAR 53:010
Modeling that belongs to Air Toxics by managerial default:
NSR/PSD review
Site evaluation of monitors for the Pb NAAQS.

14. Toxics Analysis – Dioxins & Furans
Secondary Aluminum Smelter
Emissions of Dioxin and Furans covered under Subpart RRR – NESHAP for Secondary Aluminum Production
Facility could not demonstrate capture efficiency due to deviations from RRR
Modeled annual average (4.3*10-7 g/m3) exceeds 1*10-6 carcinogenic risk (6.4*10-8 g/m3)
The facility is operational at the moment but has taken a production limit

15. Secondary Al Smelter (Dioxin 1 Hour Average)
Please note that the scale is adjusted by two orders of magnitude.

16. Secondary Al Smelter (Dioxin Annual Average)

17. Toxics Analysis – Hydrazine
A specialty chemical facility manufacturing organic and organometallic compounds
The facility was permitted to emit Ni, Cd, Pb, and hydrazine
After initial modeling with AERMOD, modeled ambient concentrations exceeded 1:1,000,000 carcinogenic risk with cadmium driving the risk at 1:1,000
After our investigation, the facility choose to remove Cd, and Ni and reduce Pb and hydrazine emissions

18. Specialty Chemical Facility (Hydrazine Annual Average, Pre-reduction)

19. Specialty Chemical Facility (Hydrazine Annual Average, Post-reduction)
Stack 17 is not emitting hydrazine at this point. They have gone to a closed system.

20. Ambient Air Quality Standards
Toxics Analysis - HF
401 KAR 53:010 is the Kentucky Ambient Air Quality Standards which include standards for HF
These are not to be exceeded more than once per year
A ceramic and tile manufacturing facility was modeled to show compliance
401 KAR 53:010
Ambient Air Quality Standards
Averaging Period
Concentration (μg/m3)
12 hour
3.68
24 hour
2.86
1 week
1.64
1 month
0.82

21. Ceramic Manufacturer (HF 12 Hour Average)

22. Ceramic Manufacturer (HF 24 Hour Average)

23. Pb NAAQS
The modeling was used in site selection criteria for a Pb monitor in conjunction with the new Pb National Ambient Air Quality Standard (10/15/2008)
Primary Standard
Secondary Standard
Concentration
Averaging Time
Lead
0.15 mg/m3
Rolling 3-Month Average
Same as Primary
1.5 mg/m3
Quarterly Average
10/15/2008 – Only rolling 3 month average
Used 1 month and annual to get an idea for siting location

24. Pb From a Coal Fired Power Plant
Used air dispersion modeling of a coal fired power plant to site a monitor for the Pb NAAQS
The NAAQS is based on a 3-month rolling and quarterly average
Compared the one month and annual averages to choose the site for the monitor

25. Coal Fired Power Plant (Pb Month Average)

26. Coal Fired Power Plant (Pb Annual Average)

27. Conclusions Air dispersion modeling:
Features prominently in the KY Air Toxics strategy
Is applied in situations where monitoring is not feasible due to cost or time involved
Can be binding from a regulatory standpoint
Yields useful information for risk assessment

28. Questions? Dr. Taimur Shaikh - Taimur.Shaikh@KY.gov
Kentucky Division for Air Quality – (502) ext. 4480