Extreme heat arrangements in South Australia: an assessment of trigger temperatures

The high mortality and morbidity associated with the 2009 heat wave across South Eastern Australia highlighted the need for effective heat-related health promotion and preventive strategies. The adverse health effects of extreme heat are largely preventable, and heat-related health promotion can advise the public about the dangers of hot weather and how to reduce health risks. The South Australian State Emergency Service has outlined a co-ordinated response system in their Extreme Heat Arrangements for South Australia. This paper evaluates the health impacts at the temperature trigger levels incorporated in this plan.

Heat events in Adelaide between 1994 and 2009 were compared in terms of heat duration, heat intensity and their impact on mortality and ambulance call-outs.The health impacts for events meeting specific temperature triggers were estimated.

Individual heat events varied in terms of estimated excess mortality and ambulance call-outs. Increased mortality was associated with heat events of 3 or more consecutive days with maximum temperature (T(max)) > or = 43 degrees C or average daily temperature (ADT) > or = 34 degrees C, while ambulance call-outs increased significantly at lower T(max) levels.The two events reaching the temperature triggers for an extreme heat warning were associated with a 44% (95% CI 26-63%) increase in mortality.

The results support the temperature trigger for an extreme heat warning within the Extreme Heat Arrangements for Adelaide, and indicate a limited health impact at lower temperature triggers.