Does ambient ozone air pollution trigger suicide attempts? A case cross-over analysis in Taipei

Epidemiologic studies indicated that exposure to ambient air pollutants was associated with increased mortality rates attributed to suicide. The objective of this study was to investigate the potential relationship between ambient ozone (O-3) levels and daily number of hospital admissions for suicide attempts in Taipei for the period 2008-2012 using a time-stratified case-crossover analysis. In the single-pollutant model (without adjustment for other pollutants), the risk of committing a suicide attempt increased by 9% on warm days and 27% on cool days for each interquartile range (IQR) rise in O-3 levels, respectively. The concentration of O-3 was thus significantly associated with daily number of suicide attempts both on warm and cool days. In the two-pollutant models, O-3 levels remained significant after the inclusion of other air pollutants (particulate matter (PM10), PM2.5, sulfur dioxide (SO2), nitrogen dioxide (NO2), and carbon monoxide (CO)) on cool days. However, on warm days, no significant correlation was found between O-3 levels and reported daily number of suicide attempts. The relationship between O-3 and suicide attempts appeared to be dependent upon temperature; however, the basis for these observations requires further investigation.