Ambient ozone exposure and hospitalization for substance abuse: A time-stratified case-crossover study in Taipei

A number of studies investigating the possibility that air pollutant exposures increases the risk of adverse effects on mental health including frequency of suicide and depression, is a major growing public health concern. Human data demonstrated that exposure to various ambient air contaminants including ozone (O₃) adversely affected nervous system functions. It is also well-established that substance abuse produces central nervous system dysfunctions with resultant increase in suicide rates. However, the role of substance abuse in combination with O₃ exposure on mental health remained to be determined. The aim of this investigation was to conduct a time-stratified case-crossover study to examine the possible correlation between short-term ambient O₃ exposure and daily hospital admissions for substance abuse, including alcohol dependence syndrome and non-dependent abuse of drugs, in Taipei from 2009 to 2013. In our single pollutant model, a 35% rise in interquartile (IQR) O₃ levels on cool days and a 12% elevation on warm days was associated with increase in mental health hospitalizations. In our two-pollutant models, O₃ remained significantly associated with elevated number of hospitalizations after adding any one of possible air pollutants, PM₁₀, PM_2.5, SO₂, NO₂, and CO, to our model on cool and warm days. Data suggested that temperature may affect the association between outdoor ambient air O₃ exposure and enhanced risk of hospitalization for substance abuse. Further study is needed to better understand these findings.