Air Pollutants and Breast Cancer Risk: A Parallel Analysis of Five Large US Prospective Cohorts
Does breathing polluted outdoor air increase your chances of getting breast cancer?
College of Health researcher(s)
Abstract
Objectives
To determine whether outdoor air pollution exposure is associated with breast cancer incidence.
Methods
Residential-level concentrations of nitrogen dioxide (NO2, parts per billion [ppb]), fine particulate matter (PM2.5; ≤ 2.5 μ/m3) and ozone (ppb) in the United States were estimated for participants of the Nurses’ Health Studies, Women’s Health Initiative Clinical Trials and Observational Study Cohort, and Sister Study using high-resolution spatiotemporal models. Cox proportional hazards regression estimated cohort-specific hazard ratios (HRs) and 95% confidence intervals (CIs), and a random effects model determined summary HRs, overall and by estrogen receptor (ER)/progesterone receptor (PR) subtype and census region.
Results
NO2 was positively associated with overall breast cancer incidence (n = 28 811 cases; HR = 1.03; 95% CI = 1.00, 1.05), with little variation by subgroups. PM2.5 was associated with higher incidence of ER-/PR- tumors (n = 2367 cases; HR = 1.14; 95% CI = 1.04, 1.24; P-heterogeneity < .001) and with higher overall incidence in the Midwest (HR = 1.15; 95% CI = 1.01, 1.32; P-heterogeneity = .01). Ozone was not associated with overall incidence, but was associated with ER-/PR- tumors (n = 3406 cases; HR = 1.10; 95% CI = 1.00, 1.21; P-heterogeneity = .03).
Conclusions
In this largest US study to date, we confirmed an association between NO2 and breast cancer, and we present novel associations of PM2.5 and ozone with ER-/PR- tumors.