Temperature modulation of the health effects of particulate matter in Beijing, China.

Particulate matter (PM) has been proven to cause health risks and may result in hospital emergency room visits (ERVs), which might be complicated by extreme temperature events. However, it remains unclear how temperature modulates the effect of different-sized particles on ERVs. This study used three separate time series analyses (2009-2011) to explore such temperature modulation effect in Beijing, China. The analytical approaches included a bivariate response surface model, a non-stratification parametric model, and a stratification parametric model. Results showed that the average daily concentrations of PM10 and PM2.5 in Beijing were 110.16 and 67.89 μg/m3, respectively, during the study period, which were higher than in most Western countries. Our findings indicated that the temperature modulation effects of PM2.5 were more evident than that of PM10. The effects of PM on morbidity depend on temperature. The effects were estimated for the increases in total, respiratory, and cardiovascular ERVs per 10 μg/m3 increase in PM2.5 and PM10 concentrations at high temperature level (> 28 °C). The estimated increases in the three types of ERVs for PM2.5 were 0.15, 0.35, and 0.34%, respectively. For PM10, the increases were 0.12, 0.08, and 0.14%, respectively. In addition, the results showed that the elderly (age ≥ 65) and women are more vulnerable to PM at high temperatures. These findings may have implications for the health impact associated with both air pollution and global climate change.