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 PM_2.5, PM_2.5 absorbance, PM_2.5–10, PM₁₀, NO₂, and NO_x) and breast cancer risk. We found that PM₁₀ (odds ratio (OR) = 1.39, 95% CI: 1.07–1.80, <i>p</i> = 0.013) and NO_x (OR = 1.67, 95% CI: 1.16–2.41, <i>p</i> = 0.006) were significantly associated with elevated breast cancer risk. Furthermore, PM_2.5 (OR = 2.10, 95% CI: 1.09–4.03, <i>p</i> = 0.027) and NO_x (OR = 3.08, 95% CI: 1.24–7.64, <i>p</i> = 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.