Association between long-term exposure to air pollutants and cardiopulmonary mortality rates in South Korea

BACKGROUND: The association between long-term exposure to air pollutants, including nitrogen dioxide (NO(2)), carbon monoxide (CO), sulfur dioxide (SO(2)), ozone (O(3)), and particulate matter 10 μm or less in diameter (PM(10)), and mortality by ischemic heart disease (IHD), cerebrovascular disease (CVD), pneumonia (PN), and chronic lower respiratory disease (CLRD) is unclear. We investigated whether living in an administrative district with heavy air pollution is associated with an increased risk of mortality by the diseases through an ecological study using South Korean administrative data over 19 years. METHODS: A total of 249 Si-Gun-Gus, unit of administrative districts in South Korea were studied. In each district, the daily concentrations of CO, SO(2), NO(2), O(3), and PM(10) were averaged over 19 years (2001–2018). Age-adjusted mortality rates by IHD, CVD, PN and CLRD for each district were averaged for the same study period. Multivariate beta-regression analysis was performed to estimate the associations between air pollutant concentrations and mortality rates, after adjusting for confounding factors including altitude, population density, higher education rate, smoking rate, obesity rate, and gross regional domestic product per capita. Associations were also estimated for two subgrouping schema: Capital and non-Capital areas (77:172 districts) and urban and rural areas (168:81 districts). RESULTS: For IHD, higher SO(2) concentrations were significantly associated with a higher mortality rate, whereas other air pollutants had null associations. For CVD, SO(2) and PM(10) concentrations were significantly associated with a higher mortality rate. For PN, O(3) concentrations had significant positive associations with a higher mortality rate, while SO(2), NO(2), and PM(10) concentrations had significant negative associations. For CLRD, O(3) concentrations were associated with an increased mortality rate, while CO, NO(2), and PM(10) concentrations had negative associations. In the subgroup analysis, positive associations between SO(2) concentrations and IHD mortality were consistently observed in all subgroups, while other pollutant-disease pairs showed null, or mixed associations. CONCLUSION: Long-term exposure to high SO(2) concentration was significantly and consistently associated with a high mortality rate nationwide and in Capital and non-Capital areas, and in urban and rural areas. Associations between other air pollutants and disease-related mortalities need to be investigated in further studies.