Air pollution and breast cancer risk: a Mendelian randomization study.

Previous research yields inconsistent findings on the association between air pollution and breast cancer risk, with no definitive causal relationship established. To address this, we conducted a two-sample Mendelian randomization study on data from the IEU open GWAS databases and the Breast Cancer Association Consortium to explore the potential link between air pollution (including PM2.5, PM2.5 absorbance, PM2.5-10, PM10, NO2, and NOx) and breast cancer risk. We found that PM10 (odds ratio (OR) = 1.39, 95% CI: 1.07-1.80, p = 0.013) and NOx (OR = 1.67, 95% CI: 1.16-2.41, p = 0.006) were significantly associated with elevated breast cancer risk. Furthermore, PM2.5 (OR = 2.10, 95% CI: 1.09-4.03, p = 0.027) and NOx (OR = 3.08, 95% CI: 1.24-7.64, p = 0.015) were significantly associated with an elevated risk of luminal B/HER2-negative-like cancer. Results were stable in sensitivity analyses. This suggested that controlling air pollution could potentially reduce breast cancer risk.