BACKGROUND AND AIM: Nitrogen dioxide (NO2) is one of an important air pollutant due to its adverse effects on human health, however whether it is consistently associated with the risk of breast cancer (BC) is limited. In this study, we investigated the association between long term exposure to NO2 and risk of BC. METHODS: A total of 5,222 BC cases identified over the follow up period and 5,222 matched controls of a nested case-control study within a French E3N cohort study were examined. Mean exposure estimates to NO2 were estimated by CHIMERE and land use regression (LUR) models and assigned to the geocoded residential postal codes of participants for each year from recruitment 1990 through 2011. Multivariable conditional logistic regression models were used to compute odds ratios (ORs) and 95% confidence intervals (CIs). RESULTS: Overall, in all women, for each 1 interquartile range (IQR) increase in NO2 levels (CHIMERE: 11.1 ug/m3, LUR: 17.8 ug/m3), the ORs of the model adjusted for confounders were 1.16(95% CI: 1.06-1.26) and 1.09(95% CI: 1.01-1.18) according to CHIMERE and LUR measures, respectively. The corresponding ORs in the fully model additionally adjusted for established BC risk factors = 1.13(95% CI: 1.03-1.24) for CHIMERE and 1.07(95% CI: 0.99-1.16) for LUR measures. Comparable results were found for postmenopausal women. Substantial heterogeneity in the ORs was observed by hormone receptor status, using NO2 measured by CHIMERE the ORs of the model 3 was 1.17 (95% CI: 1.04-1.31) for ER. With LUR NO2, the OR of ER+BC in the fully model = 1.08 (95% CI: 0.98-1.19). CONCLUSIONS: We provide an evidence of an increase BC risk in association with long term exposure to NO2 air pollution according to CHIMERE and LUR measures, with risks being higher for CHIMERE model. Subgroup analyses suggested stronger effects especially in postmenopausal women and for hormone dependent BC.< Leer menos