Spatiotemporal Trends in Mortality Burden from Suicide Associated with Short-Term Exposures to PM2.5 and Its Chemical Constituents in China: A Large Time-Stratified Case-Crossover Study

Abstract

Suicide is an important public health challenge globally, with ambient fine particulate matter with aerodynamic diameters ≤ 2.5 μm (PM_2.5) identified as a risk factor for suicide mortality. However, the spatiotemporal changes of the suicide mortality burden associated with short-term exposures to PM_2.5 chemical constituents in China remain unknown. In this study, we investigated the spatiotemporal trends of the mortality burden from suicide associated with short-term exposures to PM_2.5 chemical constituents at both national and provincial levels across China. A nationwide, time-stratified case-crossover design was conducted using the individual suicide mortality data from the Chinese National Mortality Surveillance System from January 1, 2014, to December 31, 2019. Conditional logistic regression models were applied to evaluate the nonlinear excess risks (ERs) of suicide mortality for short-term exposures (lag0–1 day) to PM_2.5 mass and chemical constituents, and the corresponding attributable fractions (AFs) associated with PM_2.5 and its constituents were also calculated. Temporal changes in AFs from 2014 to 2019 were analyzed using linear regression models at the national and provincial levels. This study included 372,164 suicide deaths from 2,758 counties/districts across China from 2014 to 2019. The annual average changes in the concentrations of PM_2.5 mass, black carbon (BC), organic matter (OM), ammonium (NH₄⁺), nitrate (NO₃^–), and sulfate (SO₄^2–) during 2014–2019 were −3.47, −0.17, −0.72, −0.55, −0.68, and −0.78 μg/m³/year, respectively. Correspondingly, the annual average change in AFs of suicide mortality in PM_2.5 mass was −0.38% (95% CI: −0.98%, 0.22%). Among the PM_2.5 chemical constituents, SO₄^2– (−0.56, 95% CI: −1.21, 0.09%) and NO₃^– (−0.45, 95% CI: −0.89, −0.02%) showed greater decreasing trends in annual average changes of AFs, followed by NH₄⁺ (−0.40, 95% CI: −0.75, −0.05%), BC (−0.40, 95% CI: −1.01, 0.22%), and OM (−0.23, 95% CI: −0.79, 0.34%). The temporal changes of AFs exhibited greater decreasing trends in violent suicides in the warm season, and people resided in Eastern and Western China. The top three provinces exhibiting the highest annual average reduction in PM_2.5 mass-related AFs were Qinghai, Xizang, and Fujian. The primary associated socio-economic indicators influencing the spatiotemporal trends in PM_2.5-related suicide mortality burden were identified as green space area, Gross Domestic Product per capita, and unemployment rate. Our findings robustly highlight the substantial health benefits of ambient PM_2.5 pollution control, especially SO₄^2– and NO₃^–, offering a valuable reference for other regions grappling with severe air pollution issues.