The impact of air pollutants on emergency ambulance dispatches due to mental and behavioral disorders in Shenzhen, China.

Abstract

Background: The relationships between air pollutants and mental and behavioral disorders (MBDs) remain unclear. We aimed to identify the primary pollutants affecting mental health and evaluate the short-term effects on emergency ambulance dispatches (EADs) due to MBDs.

Methods: Time-stratified case-crossover study and conditional logistic regression model were adopted to explore the impact of air pollutants on EADs due to MBDs from 2013 to 2020 in Shenzhen, China. In order to clarify the influence of gender and age on association, subgroup analysis was carried out. We also applied binary response surface model and distributed lag interaction model to examine the interaction effects between pollutants and meteorological factors on EADs due to MBDs.

Results: Nitrogen dioxide (NO₂) was the primary pollutant in Shenzhen that affects the EADs due to mental and behavioral disorders, exhibiting significant immediate exposure effects and cumulative lag effects. As NO₂ concentration increased, the risk of EADs due to mental and behavioral disorders showed a linear upward trend without a threshold. For each interquartile range (IQR) increase of NO₂, the odds ratio (OR) associated with MBDs was highest at lag 2 in the single-day lag pattern (OR = 1.035, 95% CI: 1.012-1.060) and the effect of NO₂ reached its maximum at lag 0-6 with OR of 1.078 (95% CI: 1.037-1.122). We did not observe significant associations between PM_2.5, PM₁₀, SO₂, O₃ and CO exposures and EADs due to MBDs. In addition, there was an interaction effect between NO₂ and Humidity index (Humidex). Both high and low Humidex would aggravate the influence of pollutants on mental health.

Conclusions: Short exposure to NO₂ was positively associated with acute onset of MBDs in Shenzhen, China. Health departments should take effective measures to raise public awareness of NO₂ and Humidex, as well as their interaction effects.