Breast cancer risk in relation to ambient concentrations of nitrogen dioxide and particulate matter: results of a population-based case-control study corrected for potential selection bias (the CECILE study).

Abstract

BACKGROUND\nThere is only scant evidence that air pollution increases the risk of breast cancer.\n\n\nOBJECTIVES\nWe investigated this relationship for three air pollutants: nitrogen dioxide (NO2) and particulate matter with an aerodynamical diameter below 10\xa0µm (PM10) and 2.5\xa0µm (PM2.5).\n\n\nMETHODS\nWe conducted a population-based case-control study on breast cancer in two French départements, including 1,229 women diagnosed with breast cancer in 2005-2007 and 1,316 control women frequency-matched on age. Concentrations of NO2, PM10 and PM2.5 at participants addresses occupied during the last 10\xa0years were assessed using a chemistry transport model. Odds ratios (OR) and 95% confidence intervals (95% CI) were estimated using multivariable logistic regression models where each woman was assigned a weight depending on her probability of selection into the study.\n\n\nRESULTS\nThe OR for breast cancer per 10-µg/m3 increase in NO2 was 1.11 (95% CI, 0.98, 1.26), and 1.41 (95% CI 1.07, 1.86) in the highest exposure quintile (Q5), compared to the first. The ORs per 10-µg/m3 NO2 did not markedly differ between pre- (OR 1.09, 95% CI 0.89, 1.35)) and post-menopausal women (OR 1.14, 95% CI 0.97, 1.33)), but the OR was substantially higher for hormone-receptor positive (ER+/PR+) breast tumor subtypes (OR 1.15, 95% CI 1.00, 1.31) than for ER-/PR- tumors (OR 0.95, 95% CI 0.72, 1.26). Breast cancer risk was not associated with either PM10 (OR per 1\xa0µg/m3 1.01, 95% CI, 0.96, 1.06) or PM2.5 (OR per 1\xa0µg/m3 1.02, 95% CI 0.95, 1.08), regardless of the menopausal status or of the breast tumor subtype.\n\n\nDISCUSSION\nOur study provides evidence that NO2 exposure, a marker of traffic-related air pollutants, may be associated with an increased risk of breast cancer, particularly ER+/PR+\xa0tumors.