1. icfi.com April 30, 2009 icfi.com © 2006 ICF International. All rights reserved. AIR TOXICS IN MOBILE COUNTY, ALABAMA: A MONITORING AND MODELING STUDY WEBINAR: USEPA Office of Air Quality Planning and Standards Arlene Rosenbaum, Ed Carr, Yi Hua Wei, Jonathan Cohen ICF International

2. icfi.com Mobile County Air Quality Study Sponsored by local consortium –South Alabama Regional Planning Council –Mobile AL Chamber of Commerce –Mobile Bay Watch –Local industrial group –Alabama Department of Environmental Management –US EPA Region 4

3. icfi.com Mobile County Air Quality Study Air toxics monitoring Modeling –Air quality –Population exposure –Health risk Community-based expectations process

4. icfi.com Air Toxics Monitoring 5 monitoring sites 45 HAPs –Fine and coarse fractions for 11 metals Meteorological data

5. icfi.com Air Toxics Monitoring Locations –Industrial area 1 –High population area –High traffic area –Industrial area 2 –Rural background area

6. icfi.com Modeling Tools Air dispersion: Assessment System for Population Exposure Nationwide (ASPEN) Exposure: Hazardous Air Pollutant Exposure Model (HAPEM6a) Health Risk: IRIS, ATSDR, OEHHA

7. icfi.com ASPEN Modeling: Refinements from NATA Spatial resolution –783 populated grid squares (2 km x 2 km) –NATA:114 Census tracts Temporal resolution –3 seasons, according to local weather patterns –NATA: annual

8. icfi.com Emissions 130 HAPs From NEI, with some corrections by local experts 113 individual point sources Non-point sources : –manufacturing –non-manufacturing Non-road mobile: –aircraft –railroad –marine vehicles –other Onroad vehicles: –gasoline –diesel

9. icfi.com Onroad Vehicle Emissions: Refinements from NATA NEI county totals Spatial allocation to grid squares: Local TDM link activity –primary highway with limited access –primary highway without limited access –secondary and connecting roads

10. icfi.com Meteorological Inputs: Refinements from NATA Stability Array (STAR) sets: joint frequency distributions of wind speed, wind direction, stability class Measurements from 11 surface stations CALMET used to create STAR sets, by season, for each grid square –Capture variations in patterns at land-sea boundary

11. icfi.com Background Concentration: Refinements from NATA Background = [Measured – modeled] at rural site Benzene: -1.7 ug/m 3 to 0.4 ug/m 3 Annual average = -0.60 ug/m 3 Rural site concentrations also overestimated for –Xylene –Toluene –Ethylbenzene –Hexane NATA: 0.35 ug/m 3 (small urban) 1,3–Butadiene: 0.04 ug/m 3 to 0.06 ug/m 3 Annual average = 0.05 ug/m 3 1.5 per million cancer risk NATA: 0.03 ug/m 3 (small urban)

12. icfi.com Comparison of MCAQS and NATA Similarities –Annual emission totals from NEI –ASPEN air dispersion model for onroad emissions –HAPEM6 population exposure model –Health risk factors from IRIS, ATSDR, OEHHA MCAQS Refinements –Finer spatial resolution –Seasonal temporal resolution –Spatial allocation of onroad emissions from TDM –Finely resolved local meteorology –Background concentrations from local measurements

13. icfi.com Benzene Model to Monitor Comparison

14. icfi.com Benzene Population-Weighted Average Exposure Concentration Contributions by Source Type

15. icfi.com Benzene Carcinogenic Risk Distribution: Comparison to NATA 2002

16. icfi.com Benzene Carcinogenic Risk Spatial Distribution

17. icfi.com 1,3-Butadiene Model to Monitor Comparison

18. icfi.com 1,3-Butadiene Population-Weighted Average Exposure Concentration Contributions by Source Type

19. icfi.com 1,3-Butadiene Carcinogenic Risk Distribution: Comparison to NATA 2002

20. icfi.com 1,3-Butadiene Carcinogenic Risk Spatial Distribution

21. icfi.com Acrolein Population-Weighted Average Exposure Concentration Contributions by Source Type

22. icfi.com Acrolein Hazard Quotient Distribution: Comparison to NATA 2002

23. icfi.com Acrolein Hazard Quotient Spatial Distribution

24. icfi.com Diesel Particulate Matter: Exposure Concentration Distribution 0 10 20 30 40 50 60 70 80 90 100 1.E-011.E+001.E+011.E+02 Exposure Concentration (ug/m3) Percentile MCAQS NATA 2002

25. icfi.com Diesel Particulate Matter: Population-Weighted Average Exposure Concentration Contributions by Source Type

26. icfi.com Cancer Risk Summary

27. icfi.com Non-Cancer Risk Summary

28. icfi.com Conclusions MCAQS: an approach to refining NATA methodology for regional modeling domains Relatively easy to apply using NATA modeling tools and data bases Refined model predictions show increased risk variability Model to monitor comparisons suggest that onroad mobile emissions for Mobile County are overestimated in the NEI