Associations between sulfur dioxide exposure and mortality, with a focus on cardiovascular disease: a multi-county time series analysis in central China.

BACKGROUND: Despite growing evidence on health effects associated with atmospheric pollutants, limited research has investigated the effect of ambient sulfur dioxide (SO2) on disease-specific mortality, particularly cardiovascular disease (CVD). METHODS: We evaluated the effect of SO2 on CVD mortality in 122 counties, Hunan Province, Central China, during the period 2018-2022. Daily mortality records and ambient air pollution concentrations were collected, and time-series regression models combined with multilevel meta-analyses were utilized for data analysis. RESULTS: A total of 2.21 million all-cause deaths were recorded, with CVD accounting for 1.15 million cases. The annual average SO2 concentration exhibited a significant decline, decreasing from 11.30 µg/m3 in 2018 to 8.08 µg/m3 in 2022, with an overall mean concentration of 9.39 µg/m3. The relative risk (RR) for per 10 µg/m3 increase in SO2 at lag03 were 1.0258 (95% CI: 1.0033, 1.0488) for CVD and 1.0346 (95% CI: 1.0092, 1.0607) for ischaemic heart disease, respectively. Ambient exposure to SO2 was linked to an excess mortality fraction of 2.52% (95% CI: 2.17%, 2.84%) for CVD, with a decline from 3.11% (95% CI: 2.66%, 3.49%) in 2018 to 2.17% (95% CI: 1.86%, 2.44%) in 2022. For ischaemic heart disease, the excess mortality fraction was 3.13% (95% CI: 2.87%, 3.37%). After adjustment for co-pollutants such as PM10, PM2.5 or NO2, the effect of SO2 on CVD mortality remained significant and was even enhanced. CONCLUSIONS: The results highlight the importance of continued air quality improvements and targeted public health interventions to mitigate the burden of CVD mortality associated with SO2.