Estimates of the current and future burden of lung cancer attributable to PM2.5 in Canada

The International Agency for Research on Cancer has classified PM2.5 (fine particulate matter, PM2.5) as a lung cancer carcinogen in humans. We estimated the proportion of lung cancer cases attributable to PM2.5 exposure in Canada in 2015, and future avoidable cancers over the period 2016-2042 under different future exposure scenarios. A meta-analysis was conducted to estimate the relative risk of lung cancer associated with PM2.5 that was generalizable to Canada. A population-weighted Canadian distribution of residential PM2.5 exposure was estimated annually using ecological-level, satellite-derived PM2.5 data for the period 1990 to 2009. Population attributable risks (PAR) were estimated for PM2.5 and applied to lung cancer incidence from the Canadian Cancer Registry. Potential impact fractions based on counterfactual scenarios for the year 2042 were estimated, along with cumulative preventable cases from 2016 to 2042. The relative risk of lung cancer associated with PM2.5 was 1.09 (95% CI: 1.06-1.12) per an increase of 10 mu g/m(3). The average population-weighted exposure to PM2.5 corresponding to a 20-year exposure window from 1990 to 2009 was 8.3 mu g/m(3). The PAR for PM2.5 was estimated at 6.9%, accounting for 1739 attributable lung cancer cases in 2015. If patterns of decline in PM2.5 continue, over 3000 lung cancer cases could be prevented between 2016 and 2042. Exposure to PM2.5 contributes to a considerable burden of lung cancer in Canada and policies aimed at sustaining outdoor PM2.5 declines are important for lung cancer prevention in Canada.