Coarse particulate matter and emergency ambulance dispatches in Fukuoka, Japan: a time-stratified case-crossover study.

Objectives: There is no conclusive evidence of adverse health effects caused by short-term exposure to coarse particulate matter, so in this case-crossover study we looked for an association between exposure and emergency ambulance dispatches (as a proxy of acute health outcomes).
Methods: We used data on emergency ambulance dispatches in Fukuoka City, Japan between 2005 and 2010. After excluding ambulance dispatches related to external injuries and pregnancy/childbirth, we analyzed data on 176,123 dispatches. Citywide daily mean concentrations of suspended particulate matter (SPM) and fine particulate matter (PM2.5) were calculated from ambient monitoring data, and the differences between concentrations of SPM and PM2.5 were used as an exposure surrogate of coarse particulate matter. Using a conditional logistic regression model, we estimated the ambient temperature and relative humidity adjusted odds ratios (ORs) per 10 μg/m(3) increase in coarse particulate matter.
Results: The average daily concentration of coarse particulate matter over the study period was 9.9 μg/m(3), representing 33% of the total concentration of SPM. Elevated concentrations of coarse particulate matter were associated with an increase in respiratory disease-related emergency ambulance dispatches for adults aged 65 years or older (9,716 dispatches, OR for lag0-1 = 1.065, 95% confidence interval = 1.023-1.109). After additional adjustment for exposure to PM2.5, we observed a statistically non-significant increased risk (OR = 1.035, 0.986-1.086).
Conclusions: We found weak evidence of adverse effects of short-term exposure to coarse particulate matter on human health.