Assessing Associations Between Cancer Risk Estimates Attributable to Air Toxics and Sociodemographic Factors

BACKGROUND:  Studies suggest that the burden of exposure to air toxics falls on minorities and others in disadvantaged communities.  However, these studies have not always controlled for urbanicity, which could confound the analysis.  This analysis is an attempt to better understand the variation in cancer risk estimates associated with air toxics by sociodemographic variables in New York State, within and between levels of urbanicity.

METHODS:  The Environmental Protection Agency’s 2005 National Air Toxics Assessment dataset was used to identify census tract level estimates of total cancer risk attributable to outdoor air toxics per million population.  The US Census American Community Survey was used to calculate census tract level estimates of median household income and percent minority population. US Census data were used to create an indicator for urbanicity.  Data were summarized graphically to better understand the distribution of the variables of interest.  Non-parametric statistical tests were used to better understand how cancer risk estimates are distributed across New York State and how they vary by race and socioeconomic status.  Multivariate regression analyses were used to assess associations with control for potential confounding variables.

RESULTS:  Consistent with previous studies, census tracts in the lowest quartile of median household income tended to have higher cancer risks than wealthier census tracts, and census tracts with the highest quartile of percent minority population tended to have higher cancer risks than census tracts with lower minority population in New York State.  Urban areas had higher estimates of cancer risk than non-urban areas.  Urban-New York City (NYC) census tracts had the highest risks, followed by urban-non-NYC areas and then non-urban areas of New York State.  Initial analyses within levels of urbanicity suggest that trends in risk estimates by census tract measures of median household income and percent minority population are more difficult to interpret.

CONCLUSIONS:  These results are consistent with previous research that suggests that levels of air toxics are higher in urban areas, and that reducing the levels of air toxics in cities would have the most positive effect on reducing cancer risks related to the pollutants.  However, within levels of urbanicity, cancer risk estimates across different census tract-level measures of socioeconomic status and minority population is less clear.