Japanese Nationwide Study on the Association between Short-term Exposure to Particulate Matter and Mortality

Abstract

Background: From around 2012, the use of automated equipment for fine particulate matter (PM₂.₅) measurement with equivalence to a reference method has become popular nationwide in Japan. This enabled us to perform a national health effect assessment employing PM₂.₅ concentrations based on the standardized measurement method. We evaluated the association between non-accidental mortality and short-term exposure to PM₂.₅ and coarse particulate matter (PM), with the latter estimated as the difference between suspended particulate matter and PM₂.₅, for the fiscal years 2012–2014. Methods: This was a time-stratified case-crossover study in 100 highly-populated Japanese cities. Mortality data was obtained from the Ministry of Health, Labour and Welfare. City-specific estimates of PM-mortality association were calculated by applying a conditional logistic regression analysis, and combined with a random-effects meta-analysis. Results: The respective averages of daily mean concentration were 14.6 µg/m³ for PM₂.₅ and 6.4 µg/m³ for coarse PM. A 10 µg/m³ increase in PM₂.₅ concentrations for the average of the day of death and the previous day was associated with an increase of 1.3% (95% confidence interval (CI), 0.9–1.6%) in total non-accidental mortality. For cause-specific mortality, PM₂.₅ was positively associated with cardiovascular and respiratory mortality. After adjustment for PM₂.₅, we observed a 1.4% (95% CI, 0.2–2.6%) increase in total mortality with a 10 µg/m³ increase in coarse PM. Conclusion: The study revealed that short-term exposure to PM₂.₅ had adverse effects on total non-accidental, cardiovascular, and respiratory mortality in Japan. Coarse PM exposure also increased the risk of total mortality.