BackgroundWe investigated the association of several air pollution measures with postmenopausal breast cancer (BCa) risk.MethodsThis study included 155,235 postmenopausal women (of which 6146 with BCa) from UK Biobank. Cancer diagnoses were ascertained through the linkage to the UK National Health Service Central Registers. Annual exposure averages were available from 2005, 2006, 2007, and 2010 for NO2, from 2007 and 2010 for PM10, and from 2010 for PM2.5, NOX, PM2.5–10and PM2.5absorbance. Information on BCa risk factors was collected at baseline. Cox proportional hazards regression was used to evaluate the associations of year-specific and cumulative average exposures with BCa risk, overall and with 2-year exposure lag, while adjusting for BCa risk factors.ResultsPM10in 2007 and cumulative average PM10were positively associated with BCa risk (2007 PM10: Hazard ratio [HR] per 10 µg/m3= 1.18, 95% CI 1.08, 1.29; cumulative average PM10: HR per 10 µg/m3= 1.99, 95% CI 1.75, 2.27). Compared to women with low exposure, women with higher 2007 PM10and cumulative average PM10had greater BCa risk (4th vs. 1st quartile HR = 1.15, 95% CI 1.07, 1.24, p-trend = 0.001 and HR = 1.35, 95% CI 1.25, 1.44, p-trend < 0.0001, respectively). No significant associations were found for any other exposure measures. In the analysis with 2-year exposure lag, both 2007 PM 10 and cumulative average PM10 were positively associated with BCa risk (4th vs. 1st quartile HR = 1.19, 95% CI 1.10, 1.28 and HR = 1.29, 95% CI 1.19, 1.39, respectively).ConclusionOur findings suggest a positive association of 2007 PM10and cumulative average PM10with postmenopausal BCa risk.Supplementary InformationThe online version contains supplementary material available at 10.1186/s13058-023-01681-w.