| Comparative Assessment of Air Pollution–Related Health Risks in Houston Ken Sexton,1 Stephen H. Linder,2 Dritana Marko,2 Heidi Bethel,3 and Philip J. Lupo4 1The University of Texas School of Public Health, Brownsville, Texas, USA; 2The University of Texas School of Public Health, Institute for Health Policy, Houston, Texas, USA; 3U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology, Health and Ecological Criteria Division, Washington, DC, USA; 4The University of Texas School of Public Health, Division of Epidemiology, Houston, Texas, USA Abstract
Background: Airborne emissions from numerous point, area, and mobile sources, along with stagnant meteorologic conditions, contribute to frequent episodes of elevated air pollution in Houston, Texas. To address this problem, decision makers must set priorities among thousands of individual air pollutants as they formulate effective and efficient mitigation strategies. Objectives: Our aim was to compare and rank relative health risks of 179 air pollutants in Houston using an evidence-based approach supplemented by the expert judgment of a panel of academic scientists. Methods: Annual-average ambient concentrations by census tract were estimated from the U.S. Environmental Protection Agency's National-scale Air Toxics Assessment and augmented with measured levels from the Houston monitoring network. Each substance was assigned to one of five risk categories (definite, probable, possible, unlikely, uncertain) based on how measured or monitored concentrations translated into comparative risk estimates. We used established unit risk estimates for carcinogens and/or chronic reference values for noncarcinogens to set thresholds for each category. Assignment to an initial risk category was adjusted, as necessary, based on expert judgment about the quality and quantity of information available. Results: Of the 179 substances examined, 12 (6.7%) were deemed definite risks, 9 (5.0%) probable risks, 24 (13.4%) possible risks, 16 (8.9%) unlikely risks, and 118 (65.9%) uncertain risks. Conclusions: Risk-based priority setting is an important step in the development of cost-effective solutions to Houston's air pollution problem. Key words: air pollution, air toxics, comparative risk, diesel particles, hazardous pollutants, particulate matter, risk assessment. Environ Health Perspect 115:1388–1393 (2007) . doi:10.1289/ehp.10043 available via http://dx.doi.org/ [Online 5 July 2007]
Address correspondence to K. Sexton, The University of Texas School of Public Health, 80 Fort Brown, RAHC Building, Brownsville, TX 78520-4956 USA. Telephone: (956) 882-5168. Fax: (956) 882-5152. E-mail: ken.sexton@utb.edu Supplemental Material is available online at http://www.ehponline.org/docs/2007/10043/suppl.pdf We especially thank E. Marks, A. Blanco, D. Hoyt, K. Pepple, L. Raun, and W.-Y. Wang from the City of Houston, and our colleagues from the U.S. Environmental Protection Agency (EPA) , California EPA, Texas Commission on Environmental Quality, Houston Advanced Research Center, and Greater Houston Partnership for their help. A special thanks to other members of the Mayor's Task Force: S. Abramson (Baylor College of Medicine) ; M. Bondy (M.D. Anderson Cancer Center) ; G. Delclos (University of Texas School of Public Health) ; M. Fraser (Rice University) ; T. Stock (University of Texas School of Public Health) ; and J. Ward (University of Texas Medical Branch) . Support was provided by the City of Houston, the Institute for Health Policy at the University of Texas School of Public Health and M. Zilkha. The opinions expressed in this paper are those of the authors and do not represent the opinions of, or any obligations upon, the organizations with which they are employed. The authors declare they have no competing financial interests. Received 2 January 2007 ; accepted 5 July 2007.
Correction Table 4, published online in the original manuscript, has been deleted here. The relevant information now appears in "Results."
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