Association of air pollution and breast cancer incidence in the Multiethnic Cohort Study

Recent studies suggested that fine particulate matter (PM_2.5) exposure increases the risk of breast cancer, but evidence among racially and ethnically diverse populations is sparse. Analysis among participants of the Multiethnic Cohort Study (58,358 women in California; 70% African American and Latinas; 3,524 breast cancer cases during average 19.3 years follow-up) examined associations of satellite-based time-varying PM_2.5 exposure with invasive breast cancer risk. Per 10 μg/m³ increase of PM_2.5 exposure the breast cancer HR was 1.28 (95% CI 1.08-1.51). There was no evidence of heterogeneity in associations by race and ethnicity and hormone receptor status. In a meta-analysis of the Multiethnic Cohort Study and 10 other prospective cohorts, breast cancer increased in association with exposure to PM_2.5 (HR per 10 μg/m³ increase 1.05; 95% CI 1.00-1,64). The authors conclude that breast cancer prevention should include not only individual-level behavior-centered approaches but also population-wide policies and regulations to curb PM_2.5 exposure.