Abstract
BackgroundFrom 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.MethodsThis 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.ResultsThe 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.ConclusionThe 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.
Highlights
The health effects of particulate matter, fine particulate matter (PM2.5 that passes through a size-selective inlet with a 50% cut-off level of 2.5 μm in aerodynamic diameter), are an international concern,[1] and epidemiologic evidence increases year by year
Evidence of the effects of PM2.5 exposure on health in Japan is extremely limited because the routine measurement of PM2.5 in Japanese air pollution monitoring stations only began after the Air Quality Standard for PM2.5 was established in 2009.5 Previously, we reported that short-term exposure to PM2.5 was positively associated with all-cause mortality in those aged 65 years or older in 20 regions between 2002 and 20046; PM2.5 concentration measurement equivalence was not ensured among the 20 automated measuring devices in the study
With regard to exposure to coarse particulate matter, for which there is still limited health effects evidence globally, we explored the association with mortality using an exposure surrogate for coarse PM, estimated as the difference between the concentrations of suspended particulate matter (SPM that passes through a size-selective inlet with a 100% cut-off level of 10 μm in aerodynamic diameter) and PM2.5
Summary
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
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