Fine particulate matter (PM_2.5) and suicide in South Korea: an instrumental variable analysis using thermal inversion

Air pollution causes the deterioration of both physical and mental health and increases the risk of suicide. Existing studies on the association between air pollution and suicide rely on meta-analyses and simple correlation analyses, which cannot quantify how much the increase in air pollution levels increases suicide rates. This study thus examines the relationship between fine particulate matter (PM_2.5) pollution and suicide mortality in South Korea from 2015 to 2019 using thermal inversions as an instrumental variable to induce exogenous variations in PM_2.5 levels. The findings suggest that a 1 μg/m³ increase in PM_2.5 pollution is associated with a rise of 0.6628 suicide deaths per 1 million population (β = 0.6628, 95% CI: 0.1049-1.2208). The 2.94% increase in suicide mortality highlights the significant health impact of PM_2.5 exposure. Additionally, this study shows the differentiated effects of exposure to PM_2.5 on the suicide mortality rate. An increase in PM_2.5 was associated with higher suicide mortality (deaths per million) in males (7.873), older adults (21.18), individuals with lower education levels (4.091), and those living in non-metropolitan areas (5.434). These impacts are observed among several groups: older adults, males, adults without a college education, and people living in non-metropolitan areas. These results provide empirical evidence for the heterogeneous effect of PM_2.5 pollution on the suicide mortality rates across demographic groups.