Objectives To summarize and explore the risk of acute cardiovascular premature death (CVD) caused by exposure to ambient air PM_2.5 and analyze the effect of environmental factors on CVD death risk caused by PM_2.5.

Methods Based on the PRISMA principle, literatures published in 1990-2017 on time-series studies or case-crossover studies of CVD death risk and ambient air PM_2.5 exposure in China were retrieved from database for systematic review and meta-analysis. Relative risk (RR) or extra death rate (ER) was extracted from these studies to estimate the summarized CVD death risk caused by PM_2.5. Software R 3.5.1 was used to perform meta-analysis. The modification of environmental factors on the CVD death risk caused by PM_2.5 was tested by meta-regression.

Results According to the inclusion and exclusion criteria applied in this study, 20 published studies were included. Results of meta-analysis showed that the estimated acute CVD death risk caused by PM_2.5 was 0.50% (RR=1.005 0, 95%CI:1.003 6~1.006 3) for every increase of 10 μg/m³PM_2.5. Ambient air temperature, relative humidity and ambient air ozone concentration were used as numeric modulators separately in the model. Meta-regressions showed that the CVD death risk caused by PM_2.5 might be significantly increased by 13.20% (RR=1.132 0, 95% CI:1.028 4~1.246 1) for every increase of 10% relative humidity; the CVD death risk caused by PM_2.5 might bemodified by ambient air temperature (marginally significant, P=0.060 2) and ambient air ozone concentration had no significant confounding effects (P=0.534 7).

Conclusions Hot and wet weather might significantly increase the risk of acute premature death of cardiovascular diseases caused by exposure to PM_2.5.