Introduction: As the frequency and intensity of heatwaves increases, emergency health service utilisation, including ambulance callouts, have correspondingly increased across the world. The impact of air pollution on health adds to the complexity of the effects. This research work is the first known study to analyse the joint effect of heatwaves and air pollution on the ambulance service in Western Australia (WA).
Methods: A time series design was used. Daily data on ambulance callouts, temperature and air pollutants (PM10, PM2.5, O3, NO2, SO2 and CO) were collected for the Perth metropolitan area, WA for 2006-2015. Poisson regression modelling was used to assess the association between heatwaves, air pollution, and ambulance callouts. Risk assessments on age, socio-economic status (SES), and joint effect between air pollution and heatwaves on ambulance callouts were conducted.
Results: The ambulance callout rate was higher during heatwave days (14.20/100,000/day) compared to non-heatwave days (13.95/100,000/day) with rate ratio 1.017 (95% confidence interval 1.012-1.023). The ambulance callout rate was higher in people aged 60 years and above, people with low SES, and those who lived in inland areas. Significant joint effects were observed between heatwaves and PM10, O3 & CO on ambulance callouts after adjusting for the other risk factors.
Conclusions: Ambulance service callouts are an important indicator to evaluate heatwave related emergency morbidity in WA. As the concentration of all air pollutants were lower than the Australian National Standards, the interactive effect of heatwave and air pollutants need to be further examined, especially when it exceeds the standards.