Abstract: Objective To investigate the short-term acute exposure effects of fine particulate matter（PM_2.5） on population mortality in the ambient air of Huai'an City and evaluate average annual excess mortality risk in Huai’an. Methods Collected the daily mortality data in Huai'an City from 2017 to 2021,along with concurrent meteorological data and atmospheric PM_2.5 levels. Generalized additive models（GAM） were used to analyze the acute effects of PM_2.5 on resident mortality and the cumulative lag effects. Additionally,a health risk assessment model was employed to analyze the excess mortality risk attributable to PM_2.5. Results From 2017 to 2021,the annual average PM_2.5 level was 41.12 μg/m³ in Huai'an City,which exceeded the national air quality grade II limit. The GAM model revealed that the impact of PM_2.5 on mortality presented lag and cumulative lag effects. The acute effects of PM_2.5 on non-accidental,respiratory,and circulatory deaths peaked on the day of exposure（lag0 d）,with health risks increasing by 0.92%,1.29%,and 1.06%,respectively for every 10 μg/m³ increase in daily concentration. The cumulative effects of PM_2.5 on non-accidental,respiratory,and circulatory deaths reached their maxima at lag0：1 d,lag0：2 d,and lag0：1 d,respectively,with health risks increasing by 0.82%,1.47%,and 0.97%,respectively for each 10 μg/m³ increase in daily concentration. Using PM_2.5=35.0 μg/m³ as a reference mass concentration for assessing excess mortality risk,the annual average PM_2.5 concentration decreased from 44.42 μg/m³ in 2017 to 35.99 μg/m³ in 2021. Compared to 2017,the numbers of non-accidental,respiratory,and circulatory deaths in 2021 decreased by 32.55%,49.39% and 22.56%,respectively. Conclusion The ambient air PM_2.5 concentration in Huaian City is at a relatively high level,but effective control of PM_2.5 concentration can significantly reduce the risk of excess mortality among residents.

Key words: Fine particulate matter, Generalized additive model, Lag effect, Health risk assessment