title: Comparative assessment of air pollution-related health risks in Houston.
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.
  
  
  OBJECTIVE
  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.
authors.affiliation: The University of Texas School of Public Health, Brownsville, Texas 78520-4956, USA. ken.sexton@utb.edu
authors.forename: Ken
authors.initials: K
authors.lastname: Sexton
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Linder
authors.forename: Dritana
authors.initials: D
authors.lastname: Marko
authors.forename: Heidi
authors.initials: H
authors.lastname: Bethel
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Lupo
mesh_terms: D000393:Air Pollutants / Q000009:adverse effects* / Q000032:analysis; D002947:Cities; D004781:Environmental Exposure / Q000009:adverse effects*; D004782:Environmental Health; D005104:Expert Testimony; D006291:Health Policy; D006801:Humans; D019570:Inhalation Exposure; D011050:Policy Making; D011634:Public Health; D018570:Risk Assessment; D013781:Texas; D014505:Urban Population
chemical_list: D000393:Air Pollutants