No nationwide studies have examined the associations between mortality risk and PM 1 (PM with an aerodynamic diameter of <1 μm) due to the scarcity of monitoring data of PM 1 . On the basis of newly released national scale PM 1 data, we performed a time series analysis to elucidate the cause-specific mortality risk caused by PM 1 exposure in China. During the period from January 2014 to December 2017, the PM 1 levels in 65 cities of China were on average 37 ± 32 μg/m 3 . Pooled results indicated a 10 μg/m 3 increase in the PM 1 level was associated with a 0.19% [95% confidence interval (CI) of 0.09−0.28%] increased risk in nonaccidental mortality, which was almost the same as that for PM 2.5 (0.18%, 95% CI of 0.08−0.27%) and PM 10 (0.17%, 95% CI of 0.01−0.24%). By comparison, the magnitude increased to 0.29% (0.12−0.47%) in cardiovascular disease for each 10 μg/m 3 uptick in PM 1 , which was significantly higher than that related to PM 2.5 and PM 10 exposure. This nationwide study supported the notion that PM 1 may be a higher risk factor for cardiovascular disease, which suggests rapid action is warranted to put more effort into mitigating the emissions of finer particulate matters.

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