Risk of death from bladder cancer in relation to long-term exposure to fine particulate air pollution in Taiwan

The International Agency for Research on Cancer (IARC) has classified fine particulate matter (PM_2.5) from outdoor air pollution as carcinogenic to humans. However, few studies have examined the association between residential ambient PM_2.5 exposure with the occurrence of bladder cancer (BC). It is noteworthy that available findings remain inconclusive. Several Taiwanese investigators reported a significant positive association between long-term exposure to PM_2.5 and various non-lung cancers. Building upon this evidence, the aim of the present study was to examine the relationship between long-term exposure to ambient PM_2.5 and BC-attributed mortality across 66 municipal areas in Taiwan. Annual PM_2.5 concentrations were compared with age-standardized BC mortality rates among male and female residents from 2012 to 2023. Municipal annual PM_2.5 levels were categorized into tertiles, and adjusted risk ratio (RRs) were estimated using multiple-regression models controlling for the following factors: municipal lung cancer mortality, urbanization level, annual household income, and physician density. Among men, adjusted RRs for municipalities in the intermediate (19.34-25.11 ug/m³) and the highest PM_2.5 tertiles (25.12-30.82 ug/m³) were 1.07 (95% CI = 0.98-1.18) and 1.31 (95% CI = 1.19-1.44), respectively, compared with those in the lowest tertile. Among women, corresponding adjusted RRs were 1.05 (95% CI = 0.91-1.21) and 1.29 (95% CI = 1.12-1.48). These findings indicate that long-term exposure to elevated ambient PM_2.5 concentrations may increase the risk of mortality attributed to BC among both men and women in Taiwan.