Associations of acute exposure to fine and coarse particulate matter and mortality among older people in Tokyo, Japan

•Evaluated associations between short-term exposure to PM and mortality•We observed adverse effects of PM on mortality.•PM2.5 and coarse particles were independently associated with increased risk.•Observed adverse health effects even below Japanese air quality guidelines

ABSTRACTRecent studies have reported adverse health effects of short-term exposure to coarse particles independent of particulate matter less than 2.5 μm in diameter (PM2.5), but evidence in Asian countries is limited. We therefore evaluated associations between short-term exposure to particulate matter (PM) and mortality among older people in Tokyo, Japan. We used a time-stratified, case-crossover design. Study participants included 664,509 older people (≥ 65 years old) in the 23 urbanized wards of the Tokyo Metropolitan Government, who died between January 2002 and December 2013. We obtained PM2.5 and suspended particulate matter (SPM; PM < 7 μm in diameter) from one general monitoring station. We calculated PM7-2.5 by subtracting PM2.5 from SPM to account for coarse particles. We then used conditional logistic regression to estimate odds ratios (ORs) and 95 confidence intervals (CIs). Same-day PM2.5 and PM7-2.5 were independently associated with all-cause and cause-specific mortality related to cardiovascular and respiratory diseases; for example, both pollutants were positively associated with increased risk of all-cause mortality even after simultaneous adjustment for each pollutant: OR of 1.006 (95% CI: 1.003, 1.009) for PM2.5 and 1.016 (95% CI: 1.011, 1.022) for PM7-2.5. Even below concentrations stipulated by the Japanese air quality guidelines for PM2.5 and SPM (PM7), we observed adverse health effects. This study provides further evidence that acute exposure to PM2.5 and coarse particles is associated with increased risk of mortality among older people. Rigorous evaluation of air quality guidelines for daily average PM2.5 and larger particles should be continued.

Graphical abstractAdjusted odds ratios and 95% confidence intervals following a 10 μg/m3 increase in PM2.5 and PM7-2.5 on the event day for mortality among elderly people in Tokyo's 23 wards, Japan, 2002-2013 (multi-pollutant model)Download high-res image (66KB)Download full-size image