A Case-Crossover Analysis of the Association between Exposure to Total PM 2.5 and Its Chemical Components and Emergency Ambulance Dispatches in Tokyo.

A limited number of studies have investigated the association between short-term exposure to PM 2.5 components and morbidity. The present case-crossover study explored the association between exposure to total PM 2.5 and its components and emergency ambulance dispatches, which is one of the indicators of morbidity, in the 23 Tokyo wards. Between 2016 and 2018 (mean mass concentrations of total PM 2.5 13.5 μg/m 3 ), we obtained data, from the Tokyo Fire Department, on the daily cases of ambulance dispatches. Fine particles were collected at a fixed monitoring site and were analyzed to estimate the daily mean concentrations of carbons and ions. We analyzed 1038301 cases of health-based all-cause ambulance dispatches by using a conditional logistic regression model. The average concentrations of total PM 2.5 over one and the previous day were positively associated with the number of ambulance dispatches. In terms of PM 2.5 components, the percentage increase per interquartile range (IQR) increase was 0.8% for elemental carbon (IQR = 0.8 μg/m 3 ; 95% CI = 0.3-1.3%), 0.9% for sulfate (2.1 μg/m 3 ; 0.5-1.4%), and 1.1% for ammonium (1.3 μg/m 3 ; 0.4-1.8%) in the PM 2.5 -adjusted models. This is the first study to find an association between some specific components in PM 2.5 and ambulance dispatches.