Mental health emergencies and mortality following public fine particulate matter alerts: A Nationwide case-crossover study in South Korea.

Abstract

Little is known about whether issuing particulate matter ≤2.5 μm (PM_2.5) alerts influences emergency department presentations for mental health or mortality. We evaluated the impact of PM_2.5 alerts on mental disorder-related emergency visit and mortality. We conducted a time-stratified case-crossover analysis comparing PM_2.5 alert versus non-alert days between 1 January 2015 and 31 December 2021 using multiple South Korean databases. Alert days were 1:1 matched to non-alert days on the basis of daily mean municipal-level of PM_2.5. We applied conditional Poisson regression models, stratified by region, to estimate relative risks of mental disorder, related emergency department visits and mortality for PM_2.5 alert. A 20 μg/m³ increase in PM_2.5 was associated with elevated risks of mental disorder-related emergency department visits and mortality. On PM_2.5 alert days, the risk of mental disorder-related emergency visits was lower compared with matched non-alert days (RR = 0.94, 95 % confidence intervals [CI]: 0.92, 0.97). This association was observed for both organic and non-organic mental disorders. All-cause, cardiovascular, and respiratory mortality showed small, non-significant increases on alert days. Issuance of PM_2.5 alerts in South Korea was associated with a modest reduction in emergency visits for mental disorders but did not correspond with lower mortality.