Air toxics are of particular concern in Greater Houston, home to one of the world’s largest petrochemical complexes and a quarter of the nation’s refining capacity. Much of this complex lies along a navigable ship channel that flows 50 miles from east of the central business district through Galveston Bay and into the Gulf of Mexico. Numerous communities, including both poor and affluent neighborhoods, are located in close proximity to the 200 facilities along this channel. Our aim is to examine the spatial distribution of cumulative, air-pollution-related cancer risks in Houston and Harris County, with particular emphasis on identifying ethnic, economic, and social disparities. We employ exposure estimates from NATA-1999 and census data to assess whether the cumulative cancer risks from air toxics in Houston (and Harris County) fall disproportionately on certain ethnicities and on the socially and economically disadvantaged. The cancer risk burden across Harris County census tracts increases with the proportion of residents who are Hispanic and with key indicators of relative social disadvantage. Aggregate disadvantage grows at each higher level of cancer risk. The highest cancer risk in Harris County is concentrated along a corridor flanking the ship channel. These high-risk neighborhoods, however, vary markedly in relative disadvantage, as well as in emission source mix. Much of the risk they face appears to be driven by only a few hazardous air pollutants. Results provide evidence of risk disparities from hazardous air pollution based on ethnicity and social disadvantage. At the highest levels of risk the pattern is more complex, arguing for a neighborhood level of analysis, especially when proximity to high-emissions industries is a substantial contributor to cumulative cancer risk.

BackgroundAirborne 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.ObjectivesOur 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.MethodsAnnual-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.ResultsOf 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.ConclusionsRisk-based priority setting is an important step in the development of cost-effective solutions to Houston’s air pollution problem.

Interventions to reduce ambient air pollution may help alleviate the diabetes burden in the US.

The effectiveness of 'triple first' and 'quadruple first' strategies is similar, although the latter seems slightly more cost-effective.