Air Pollution and Suicide in 10 Cities in Northeast Asia: A Time-Stratified Case-Crossover Analysis

There is growing evidence suggesting an association between air pollution and suicide. However, previous findings varied depending on the type of air pollutant and study location.

We examined the association between air pollutants and suicide in 10 large cities in South Korea, Japan, and Taiwan.

We used a two-stage meta-analysis. First, we conducted a time-stratified case-crossover analysis to estimate the short-term association between nitrogen dioxide (NO₂), sulfur dioxide (SO₂), and particulate matter [aerodynamic diameter ≤10μm (PM₁₀), aerodynamic diameter ≤2.5μm (PM_2.5), and PM_10–2.5] and suicide, adjusted for weather factors, day-of-week, long-term time trends, and season. Then, we conducted a meta-analysis to combine the city-specific effect estimates for NO₂, SO₂, and PM₁₀ across 10 cities and for PM_2.5 and PM_10–2.5 across 3 cities. We first fitted single-pollutant models, followed by two-pollutant models to examine the robustness of the associations.

Higher risk of suicide was associated with higher levels of NO₂, SO₂, PM₁₀, and PM_10–2.5 over multiple days. The combined relative risks (RRs) were 1.019 for NO₂ (95% confidence interval [CI]: 0.999, 1.039), 1.020 for SO₂ (95% CI: 1.005, 1.036), 1.016 for PM₁₀ (95% CI: 1.004, 1.029), and 1.019 for PM_10–2.5 (95% CI: 1.005, 1.033) per interquartile range (IQR) increase in the 0-1 d average level of each pollutant. We found no evidence of an association for PM_2.5. Some of the associations, particularly for SO₂ and NO₂, were attenuated after adjusting for a second pollutant.

Our findings suggest that higher levels of air pollution may be associated with suicide, and further research is merited to understand the underlying mechanisms. https://doi.org/10.1289/EHP2223.