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 associationbetween short-term exposure to PM2.5components and morbidity. The presentcase-crossover study explored the association between exposure to total PM2.5andits components and emergency ambulance dispatches, which is one of theindicators of morbidity, in the 23 Tokyo wards. Between 2016 and 2018 (meanmass concentrations of total PM2.513.5 mu g/m3), we obtained data, from the TokyoFire Department, on the daily cases of ambulance dispatches. Fine particles werecollected at afixed monitoring site and were analyzed to estimate the daily meanconcentrations of carbons and ions. We analyzed 1038301 cases of health-basedall-cause ambulance dispatches by using a conditional logistic regression model.The average concentrations of total PM2.5over one and the previous day werepositively associated with the number of ambulance dispatches. In terms of PM2.5components, the percentage increase per interquartile range (IQR) increase was0.8% for elemental carbon (IQR = 0.8 mu g/m3; 95% CI = 0.3-1.3%), 0.9% forsulfate (2.1 mu g/m3; 0.5-1.4%), and 1.1% for ammonium (1.3 mu g/m3; 0.4-1.8%) in the PM2.5-adjusted models. This is thefirst studytofind an association between some specific components in PM2.5and ambulance dispatches.