Carcinogenic air pollutants and breast cancer risk in the Arkansas rural community health study: A nested case-control study.

BACKGROUND

Previous epidemiological studies on the associations between hazardous air pollutants (HAPs) and breast cancer (BC) have largely neglected rural, medically underserved areas in the United States, which differ in exposures and disparities compared to urban areas.

OBJECTIVES

We aimed to examine the associations between carcinogenic HAPs and BC risk in a rural population.

METHODS

Using a nested case-control design, 574 cases and 2295 incidence density-sampled controls matched 1:4 on index age and race were included from the Arkansas Rural Community Health study. Twelve census-tract level HAPs from the 2005 National Air Toxics Assessment were geocoded to participants' baseline addresses and categorized into tertiles based on the control distributions. Multivariable conditional logistic regression analysis was used to estimate associations for BC and subgroups. Additionally, weighted quantile sum (WQS) regression was used to assess the effects of pollutant mixtures.

RESULTS

Adjusted models resulted in significantly increased risk of BC for moderate PAH (ORT2 = 1.32; 95% CI 1.03-1.69) and high chromium (ORT3 = 1.31; 95% CI 1.00-1.70, P trend = 0.04) exposure. The WQS index term, which is the regression coefficient of the combined pollutant mixture, was non-significantly positively associated with BC (OR = 1.21; 95% CI 0.96-1.53). Chromium (0.45), propylene dichloride (0.15), and polychlorinated biphenyls (0.09) were weighted the most, suggesting these pollutants had the greatest impact on the increased risk of BC. Joint effects models with first-degree family history of BC resulted in increased risk of BC for women with family history compared to women without family history and low PAH exposure.

CONCLUSION

This study highlights significant associations between specific HAPs, particularly PAHs and chromium, and increased BC risk in a rural population, emphasizing the need for targeted public health interventions and regulatory efforts to mitigate exposure in medically underserved areas.