Air Pollution and Breast Cancer Risk: An Umbrella Review

Breast cancer (BC) is a major global health challenge, responsible for one in four cancer diagnoses and one in six cancer-related deaths worldwide. It is the most frequently diagnosed cancer among women and the primary cause of cancer-related deaths in most countries. Recent studies have suggested a potential link between exposure to ambient air pollutants—such as nitrogen dioxide (NO2) and particulate matter (PM10 and PM2.5)—and an increased risk of breast cancer. However, the existing evidence remains inconclusive. This umbrella review, conducted according to PRISMA guidelines, aimed to evaluate the strength and reliability of epidemiological evidence concerning this association. All seven meta-analyses included in this review reported a relative risk greater than 1 for exposure to the three pollutants, though findings varied in terms of heterogeneity and publication bias. Notably, the overall analysis indicates that exposure to both NO2 and PM2.5 may be associated with an increased risk of breast cancer incidence, while the evidence linking PM2.5 exposure to breast cancer mortality appears to be weaker. The most vulnerable groups were identified as premenopausal European women exposed to NO2 and PM10, as well as individuals in developed countries exposed to PM2.5. Further research is necessary to examine PM composition and refine exposure assessment methodology. Given the widespread impact of breast cancer as the most common invasive malignancy, incorporating this outcome into environmental health research on air pollution is essential. A clearer understanding of these associations could support more targeted environmental interventions. Importantly, the available evidence suggests that breast cancer prevention can be addressed not only through personal lifestyle changes but also through broad public health policies focused on reducing NO2, PM10 and PM2.5 levels.