There is a gap in research relating to acute cardiac events that occur during extremely high air pollution episodes. The severity and extended duration of the 2006–2007 bushfires in Victoria, Australia, have provided unique data to better investigate associations between particulate air pollution and cardiac arrests.
We collected data for the study period (01 November, 2006–31 March, 2007) on out-of-hospital cardiac arrests (OHCAs) from the Victorian Ambulance Cardiac Arrest Registry, which captures all OHCAs attended by the Ambulance service. We restricted the analysis to those who were at least 35 years old and living in Melbourne (N = 807). Air pollution concentrations (PM10, PM2.5, NO2, CO, O3, SO2) and meteorological data were measured during the study period. Case-crossover methodology was used to investigate the relationship between bushfire-related high air pollutant concentrations and OHCA. This design controls for confounding by day of week and monthly trends.
During the study period, after adjusting for temperature and humidity, an interquartile range (IQR) increase of 6.0 μg/m3 in PM2.5 was significantly associated with an increased risk of an OHCA of 4.52% (95% CI: 0.48, 8.70), and an IQR increase in PM10 (11.7 μg/m3) resulted in an increased OHCA risk of 6.57% (0.42, 13.11). For NO2, SO2, O3, and CO, the associations between OHCA risk per IQR increase were nonsignificant: −0.11% (−11.12, 12.26), −11.87% (−22.85, 0.68), 16.05% (−0.72, 35.66), and 8.14% (−2.61, 20.07), respectively.
An increased risk of OHCA was associated with an increase in particulate matter during the 2006/2007 bushfire season in Melbourne, Australia.