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 (O-3) 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 O-3 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 O-3 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) O-3 levels on cool days and a 12% elevation on warm days was associated with increase in mental health hospitalizations. In our two-pollutant models, O-3 remained significantly associated with elevated number of hospitalizations after adding any one of possible air pollutants, PM10, PM2.5, SO2, NO2, and CO, to our model on cool and warm days. Data suggested that temperature may affect the association between outdoor ambient air O-3 exposure and enhanced risk of hospitalization for substance abuse. Further study is needed to better understand these findings.