LATEBREAKER
Cancer
Carcinogenic Air Pollutants and Breast Cancer Risk in the Arkansas Rural Community Health Study: A Nested Case-Control Study Edgar Ellis* Edgar Ellis Sean Young Rachel Carroll Shelbie Stahr Gail Runnells Elizabeth Grasmuck L. Joseph Su Yong-Moon Mark Park Ping-Ching Hsu
Purpose: Previous epidemiological studies on the associations between outdoor air pollutants and breast cancer (BC) have not focused on rural areas in the United States, which differ in disparities and exposures compared to urban areas. We aimed to examine carcinogenic hazardous air pollutants (HAPs) and BC risk in a rural population.
Methods: Using a nested case-control design, 602 cases and 2,407 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. HAPs were categorized into tertiles based on the control distributions. Multivariable conditional logistic regression analyses were used to estimate associations between HAPs and overall BC, and within cancer subgroups. Weighted quantile sum (WQS) regression was used to assess HAP mixtures.
Results: Adjusted models resulted in significantly decreased risk of overall BC for cadmium (ORT3 = 0.76; 95% CI 0.57-0.96), and increased risk for polycyclic aromatic hydrocarbons (PAH) (ORT2 = 1.28; 95% CI 1.03-1.59) and chromium (ORT3 = 1.26; 95% CI 1.01-1.58). Interaction analysis revealed having family history of BC positively modulated the association (Pinteraction PPD x family history = 0.14). Subgroup analyses resulted in higher risk for trichloroethylene (ORT2 = 1.68; 95% CI 1.01-2.80) among early-onset cases (≤50 years), and PAH (ORT2 = 1.31; 95% CI 1.03-1.68) and chromium (ORT3 = 1.28; 95% CI 1.00-1.65) among later-onset cases (>50 years). The WQS term was not significantly associated with BC, but chromium was weighted the most.
Conclusion: Future research is needed to obtain individual exposures and information on genetic susceptibility in this cohort to address gene-environment interactions that may be contributing to BC in rural populations.