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Hourly association between ambient PM2.5 and emergency ambulance dispatches in 11 cities in Japan
- Phung, Vera Ling Hui, Ueda, Kayo, Seposo, Xerxes, Takami, Akinori, Sugata, Seiji, Yoshino, Ayako, Michikawa, Takehiro, Yamazaki, Shin, Honda, Akiko, Takano, Hirohisa
- Environmental research 2020 v.185 pp. 109448
- acute exposure, children, cities, elderly, epidemiological studies, morbidity, mortality, particulates, regression analysis, relative risk, Japan
- Numerous epidemiological studies have demonstrated that short-term exposure to ambient PM₂.₅ increases mortality and morbidity. Investigating the association using hourly ambient PM₂.₅ exposure may provide important insights, as current evidence is limited mostly to daily lag term. This study aimed to investigate the hourly association between ambient PM₂.₅ concentrations and all-cause emergency ambulance dispatches (EAD) in 11 cities in Japan. We used a time-stratified case-crossover design and examined the hourly lags of ambient PM₂.₅ up to 24 h (unconditional distributed lags and moving average lags) using a conditional Poisson regression model. A significant increase in all-cause EAD was observed at lag 0 h [relative risk (RR): 1.0037 (95% CI: 1.0000, 1.0074)] and all moving average lags. The highest RR was observed within the first 6 h (at lag 0–5 h) [RR: 1.0091 (95% CI: 1.0068, 1.0114)], with a slight ascending pattern. This was followed by a descending pattern at lags 0–11, 0–17, and 0–23 h, but significant positive RR was observed even at lag 0–23 h, when the lowest RR was observed [RR: 1.0072 (95% CI: 1.0044, 1.0100)]. Though similar pattern was observed among the elderly, a different pattern was observed among the children (gradually ascending pattern). We conclude that all-cause EAD could be triggered by ambient PM₂.₅ exposure with very short lags.