Mark Harris, PhD Principal Health Scientist ChemRisk Inc. Houston Air Toxics Workshop II

1. Houston Air Quality: Modeling, Monitoring and Risk Associated with Hazardous Air Pollutants (HAPs) Mark Harris, PhD Principal Health Scientist ChemRisk Inc. Houston Air Toxics Workshop II June 12, 2007

2. Houston Air Quality: Outline • Recent Events • Mayor’s Task Force Report • data utilized • risk characterization • Conclusions

3. Current Situation • Houston complies with Clean Air Act (CAA) criteria pollutant standards except for ozone • Coming into compliance with the CAA ozone standard is important: • Human health (asthma) • Federal funding • Remain competitive with other metropolitan areas

4. Current Situation Table from “The State of Health” Report for Houston and Harris County (2007)

5. Houston Air Quality: HAPs Recent Events • 2005 – “In Harm’s Way” series by Dina Cappiello • Four neighborhoods near industrial facilities • Compared results to ESLs and to more stringent values used by the federal government and other states • Compared results to NATA background • Assessed TCEQ monitoring data/some in home sampling as well • Summer 2006: Mayor’s Task Force report • Survey of 179 air pollutants, 10 county area • Used modeled annual average air concentrations from EPA’s 1999 National Air Toxics Assessment (NATA) and some monitoring data • Ranked pollutants based on theoreticalcancer risk

6. Houston Air Quality: HAPs Recent Events • September 2006: The Control of Air Toxics Report • Rice University, UH Law Center, Baylor College of Medicine, Texas Southern University, and UTMB • 4 HAPs: benzene, 1,3-butadiene, formaldehyde, diesel particulates • Follow up to Mayor’s Task Force Report • Based on TCEQ monitoring data and compared concentrations to other cities

7. Houston Air Quality: HAPs Recent Events • 2007: UT School of Public Health Preliminary Report • Retrieved Texas Cancer Registry Data • TCEQ & NATA data for benzene and 1,3-butadiene • Estimated rate ratios based on distance from HSC and air concentrations • 2007: Mayor’s benzene reduction plan • Focused on ship channel facilities • Suggested modifications for facilities • Houston City Council authorized litigation • Novel in that most facilities targeted are not in Houston

8. Houston Air Quality: HAPs Recent Events • Reports have limitations • Selection of modeling data • Modeled values reflect upper bound of monitoring data • Use of worst-case toxicity values • Risks not placed into perspective • Transparency • Statistical procedures unclear • Lack of cost benefit analyses • Errors in reported information • Failure to consider met data in some cases • Reports comprise parts of a risk assessment but we are missing key pieces

9. Risk Assessment - HAPs Cost/Benefit Analyses Hazard Identification 1 Risk Management Risk Characterization 4 Dose-Response Assessment 2 Exposure Assessment 3

10. Focus on Mayor’s Task Force Report

11. Mayor’s Task Force Report • Utilized ASPEN data as opposed HAPEM • Some use of monitoring data • Higher of CAL EPA or EPA toxicity criteria for a chemical • Calculated cancer risk on a census tract basis using ASPEN data • Ranked chemicals using risk estimates • Forms basis for other reports and recent actions by Mayor’s office

12. Houston Air Quality: Mayor’s Report • 12 chemicals flagged as “definite” risks: • “Those substances for which there was compelling and convincing evidence of significant risk to the general population or vulnerable subgroups at current ambient concentrations..”

13. Ozone Fine Particulate Matter 1,3-Butadiene Chromium VI Benzene Ethylene dibromide Acrylonitrile Formaldehyde Acrolein Chlorine Hexamethylene Diisocyanate Diesel Particulate Matter Definite Health Risks per the Mayor’s Task Force Report

14. Our Evaluation • Comparison of NATA modeled air concentrations for certain HAPs to monitoring results • Risk Characterization • Sprinkles, a thunderstorm or hurricane?

15. NATA Air Modeling • As part of NATA, air concentrations were modeled by EPA using ASPEN and HAPEM for 895 census tracts in our 10 county area • Air concentrations used by EPA to predict risk • 1999 vintage information • We pulled the modeled air concentrations into ArcGIS, and plotted with TCEQ air monitoring locations

16. Houston Air Quality: Air Modeling Benzene 1,3 Butadiene

17. Houston Air Quality: Monitoring Data • Obtained air monitoring data from TCEQ for several HAPs • 24 hour canisters taken every 6th day • 15 sites available, east Harris County • 13 sites 2003-2006, 2 sites 2005-2006 • Hourly auto GC data • 8 sites available, east Harris County • 6 sites 2003-2006, 1 site 2005-2006, 1 site 2004-2006

18. Houston Air Quality: 24 hour canister data • Period of Record: 1/2003 to 1/2006 • 160 measurements, 24 hour canisters collected every 6 days

19. Houston Air Quality: Auto GC data • Period of Record: 1/2003 to 8/2006 • N Benzene = 1131 N 1,3 Butadiene = 902 • Auto GC data used to determine daily averages

20. Houston Air Quality: Modeled vs. Monitored Air Concentration • Results for Channelview monitor typical • Results for Auto GC daily averages matches well with 24 hour cans taken every 6 days • Modeled benzene concentration typically at or greater than the 90th percentile of monitoring data • Modeled 1,3-butadiene concentration typically at or greater than 70th percentile, often over 80th percentile

21. Mayor’s Task Force Report • Our attempt to place the risks into perspective

22. Risk Characterization • Total excess cancers for census tract over a lifetime = CR x pop • where, • CR = cancer risk in a census tract for an airborne pollutant • pop = population of census tract • Example • population of a census tract = 4,000 people • theoretical excess cancer risk for a chemical = 1 x 10-5 • Total excess cancers for census tract = 4,000 x 1 x 10-5 • Total excess cancers for census tract = 0.04

23. Total Excess Cancers for the 895 Census Tracts in the 10 County Area

24. Risk Characterization • In the population of the study area (4,715,407), approximately 1 in 3 (or 1,556,085) will develop cancer in their lifetime • 33% background rate • Using EPA Toxicity Criteria - these HAPs add an additional 0.003% to the background rate over a lifetime • Using CAL EPA Toxicity Criteria - these HAPS add an additional 0.016% to the background rate over a lifetime • Excess cancers associated with these chemicals would be very difficult if not impossible to detect • Risk characterization does not support the conclusion that there is “compelling and convincing evidence of significant risk” associated with these HAPs

25. Risk Characterization Table from “The State of Health” Report for Houston and Harris County (2007)

26. Risk Characterization Table from “The State of Health” Report for Houston and Harris County (2007)

27. Conclusions • Mayor’s Report missing perspective • Modeling data is conservative relative to measured air concentrations in the Houston area • Risk Characterization indicates a level of increased risk that would be very difficult to detect • More important to focus meeting ozone criteria

28. Co-Authors • Dr. Laurie Haws • Mr. Andrew Tachovsky • Dr. Spencer Williams • Ms. Ly Nguyen • Ms. Laura Scott

29. Are there any questions? For further information: Mark Harris, Ph.D. Principal Health Scientist ChemRisk, Inc. 10375 Richmond Ave, Suite 350 Houston, TX 77042 phone: 713-974-6200 ext. 1001 fax: 713-974-6111 email: mharris@chemrisk.com Thank you!