Ambient air pollution and subtype-specific breast cancer risk by race and rurality: findings from a population-based study

Abstract

Air pollution is the leading environmental risk factor in the U.S. for premature morbidity and mortality and disproportionately impacts marginalized populations. Although the causal link between air pollution and lung cancer is well established, its impact on breast cancer is less understood. Therefore, in this study, we examined the association between traffic-related air pollution (NO 2 ) and particulate matter (PM 2.5 ) with the development of breast cancer-specific subtypes among non-Hispanic Black (NHB) and non-Hispanic White (NHW) women in Georgia. Using the Georgia Cancer Registry, we identified women with a first primary breast cancer diagnosis 2010–2017 and geocoded their address at diagnosis to the census tract level. Daily PM 2.5 and NO 2 concentrations modeled on a 1-km grid (SEDAC) were aggregated to census tracts and averaged to annual means; women were assigned the annual mean concentration lagged 5 years prior to diagnosis based on tract of residence at diagnosis. We used logistic regression to compute case-only odds ratios (ORs) and 95% confidence intervals (CIs) associating air pollutant concentrations to a diagnosis of triple negative breast cancer (TNBC) compared with other breast cancer subtypes, overall and in strata of race/ethnicity and rurality. We identified 13,634 NHB and 29,508 NHW women diagnosed with first primary breast cancer between 2010 and 2017 in Georgia. After adjustment for age at diagnosis, race, rurality, and neighborhood poverty, a 5 µg/m 3 increase in PM 2.5 was associated an increase in the odds of TNBC (OR = 1.11, 95%CI 1.02, 1.21) among all breast cancer patients, with no evidence of effect modification by race or rurality. In the fully adjusted model, a 5-ppb increase in NO 2 was associated with a decrease in the odds of ER-negative breast cancer (OR = 0.98, 95%CI 0.96, 0.99) and these effect estimates were consistent within racial groups and by rurality. Our results indicate etiologic heterogeneity by breast cancer subtype, with PM 2.5 associated with higher odds of TNBC and NO 2 weakly associated with ER-positive disease; however, these associations were consistent across race and rurality, with no evidence of effect modification.