The impacts of long-term exposure to PM2.5 on cancer hospitalizations in Brazil

Background: Long-term exposure to PM2.5 has been linked to cancer incidence and mortality. However, it was unknown whether there was an association with cancer hospitalizations. Methods: Data on cancer hospitalizations and annual PM2.5 concentrations were collected from 1,814 Brazilian cities during 2002-2015. A difference-in-difference approach with quasi-Poisson regression was applied to examine State-specific associations. The State-specific associations were pooled at a national level using randomeffect meta-analyses. PM2.5 attributable burden were estimated for cancer hospitalization admissions, inpatient days and costs. Results: We included 5,102,358 cancer hospitalizations (53.8% female). The mean annual concentration of PM2.5 was 7.0 mu g/m3 (standard deviation: 4.0 mu g/m3). With each 1 mu g/m3 increase in two-year-average (current year and previous one year) concentrations of PM2.5, the relative risks (RR) of hospitalization were 1.04 (95% confidence interval [CI]: 1.02 to 1.07) for all-site cancers from 2002 to 2015 without sex and age differences. We estimated that 33.82% (95%CI: 14.97% to 47.84%) of total cancer hospitalizations could be attributed to PM2.5 exposure in Brazil during the study time. For every 100,000 population, 1,190 (95%CI: 527 to 1,836) cancer hospitalizations, 8,191 (95%CI: 3,627 to 11,587) inpatient days and US$788,775 (95%CI: $349,272 to $1,115,825) cost were attributable to PM2.5 exposure. Conclusions: Long-term exposure to ambient PM2.5 was positively associated with hospitalization for many cancer types in Brazil. Inpatient days and cost would be saved if the annual PM2.5 exposure was reduced.