LAUSR

Fine particulate matter (PM_2.5) has been manifested to be one of the major health-threatening airborne pollutants in the urban environment, as it is composed of inhalable particles, which may have considerable adverse health effects on the human respiratory system. However, there is limited evidence on the difference in these effects among various population groups in China. This paper aimed to perform a comparative analysis on the health effect of PM_2.5 on hospital admissions of acute respiratory infections (ARI) for both children and adults. Total 396 04 hospital admission records were collected from 98 hospitals and then matched with air pollution data from 19 monitoring stations from January 1 to December 31 in 2014. A spatial correlation test was used to estimate the spatial dependency and a time series analysis designed with a distributed lag non-linear model was further involved to evaluate the associations between PM_2.5 pollution and ARI admissions. Significant effect distinctions were detected between children and adults, mainly revealing in acute lower respiratory infections (ALRI). For ALRI, the spatial correlation coefficient between population exposure and hospital admissions was 0.69 for children and 0.34 for adults. Meanwhile, for children, significant associations between PM_2.5 and ALRI admissions were found at quite low concentrations (slightly above zero) and lasted for six days, with each 10- $\mu \text{g}/\text{m}^{3}$ increase in PM_2.5 corresponded to a 4.3% (95%CI: 1.2%, 7.2%) increase in the number of admissions. While for adults, no significant association emerged until the concentration of PM_2.5 exceeded a threshold value ( $100~\mu \text{g}/\text{m}^{3}$ for the lag of two days) and lasted no more than three days. Our results suggested that short-term exposures to PM_2.5 were associated with increased risk of ALRI admissions for children and adults in various ways, and emphasized the needs for specific preventive measures for different age groups.