# Short-term exposure to ambient air pollution and onset of severe mental disorders: a case-crossover study in Northwestern China

## TL;DR

Short-term exposure to air pollution is linked to a higher risk of severe mental disorders in China, with some groups being more vulnerable.

## Contribution

This study identifies specific air pollutants associated with severe mental disorders and highlights vulnerable subpopulations in China.

## Key findings

- PM2.5, CO, NO2, PM10, and SO2 exposure increases the odds of severe mental disorders onset.
- Females, elderly individuals, and those with higher socioeconomic status are more vulnerable.
- Associations remain robust after adjusting for multiple pollutants and other factors.

## Abstract

The associations between short-term exposure to air pollution and severe mental disorders (SMDs) remain poorly understood, particularly in China and among potentially vulnerable subpopulations.

We conducted a time-stratified case-crossover study of 49,707 individuals diagnosed with SMDs in Gansu Province, China, from 2013 to 2020. Individual-level exposures to particulate matter ≤ 2.5 μm in aerodynamic diameter (PM2.5), particulate matter ≤ 10 μm in aerodynamic diameter (PM10), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon monoxide (CO), and ozone (O3) were estimated using high-resolution spatiotemporal data from the China High Air Pollutants dataset. We employed conditional logistic regression models to estimate associations between pollutant exposures and SMDs onset, controlling for temperature and humidity. Stratified analyses were performed to identify potentially vulnerable subpopulations.

Each interquartile range increase in exposure to PM2.5 (23.1 μg/m3), CO (0.51 mg/m3), NO2 (11.9 μg/m3), PM10 (57.5 μg/m3), and SO2 (19.1 μg/m3) was associated with increased odds of SMDs onset: 3.61% (95% CI: 1.53%-5.74%), 16.54% (95% CI: 12.26%-20.99%), 9.61% (95% CI: 6.34%-13.00%), 2.15% (95% CI: 0.90%-3.40%), and 28.04% (95% CI: 22.16%-34.20%), respectively. Exposure–response relationships displayed positive trends for all significant pollutants. Effect estimates were generally stronger among females, elderly individuals (≥ 65 years), those with higher socioeconomic status, and during warm seasons (May–October). Associations remained robust in two-pollutant models and various sensitivity analyses.

Short-term exposure to multiple air pollutants is positively associated with SMDs onset, with differential vulnerability across population subgroups. These results suggest that air pollution may represent an important modifiable environmental risk factor for SMDs, particularly in regions with elevated pollution levels.

The online version contains supplementary material available at 10.1186/s12889-025-25906-z.