Associations between long-term exposure to PM and site-specific cancer mortality: A nationwide study in Brazil between 2010 and 2018.

Long-term exposure to PM has been linked to lung cancer incidence and mortality, but limited evidence existed for other cancers. This study aimed to assess the association between PM on cancer specific mortality. An ecological study based on the cancer mortality data collected from 5,565 Brazilian cities during 2010-2018 using a difference-in-differences approach with quasi-Poisson regression, was applied to examine PM-cancer mortality associations. Globally gridded annual average surface PM concentration was extracted and linked with the residential municipality of participants in this study. Sex, age stratified and exposure-response estimations were also conducted. Totalling 1,768,668 adult cancer deaths records of about 208 million population living across 5,565 municipalities were included in this study. The average PM concentration was 7.63 μg/m (standard deviation 3.32) with range from 2.95 μg/m to 28.5 μg/m. With each 10 μg/m increase in three-year-average (current year and previous two years) concentrations of PM, the relative risks (RR) of cancer mortality were 1.16 (95% confidence interval [CI]: 1.11-1.20) for all-site cancers. The PM exposure was significantly associated with several cancer-specific mortalities including oral, nasopharynx, oesophagus, and stomach, colon rectum, liver, gallbladder, larynx, lung, bone, skin, female breast, cervix, prostate, brain and leukaemia. No safe level of PM exposure was observed in the exposure-response curve for all types of cancer. In conclusion, with nationwide cancer death records in Brazil, we found that long-term exposure to ambient PM increased risks of mortality for many cancer types. Even low level PM concentrations had significant impacts on cancer mortality.