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Welcome to e-Bulletin #6

Welcome to the 6th edition of the Heat Stress e-Bulletin from Thermal Hyperformance, focusing on heatwaves. We aim to provide you with a monthly overview of what's happening in the heat stress space, without taking ourselves too seriously. We strive to maximise the health, safety and performance of workers exposed to hot conditions, and trust this information assists you in that endeavour.

What are Heatwaves?

Heatwaves have been a consistent feature of the 2016/17 summer for much of Eastern Australia, resulting in much media attention on the topic (see below for several headlines from January and February 2017). So what defines a heatwave? The Bureau of Meteorology applies the definition of 'three or more days of high maximum and minimum temperatures that are unusual for that location'. Unlike other jurisdictions  humidity is not considered by the Australian definition. These heat waves are classified as low intensity, severe or extreme based upon the deviation of temperature from the long term average.

Heatwaves are not a recent phenomena, with parts of NSW suffering through 24 days of continuous heat in January 1896. Like the recent heat events, the 1896 heatwave was well reported with several examples below. 


Heatwave Impact on Public Health

The 1896 heatwave placed a huge strain on public health services, with reports of hospitals overflowing with heat affected patients. A total of 437 deaths were attributed to the heatwave. The public health impact was so severe that the NSW government provided concessions and additional rail services for residents to 'head for the hills' to escape the heat.

A more recent heatwave in NSW occurred in late January/early February 2011 for a period of 8 days. The public health impact within metropolitan Sydney was studied and formed the basis of a paper published in Environmental Health by Schaffer et al. (2012). The 2011 Sydney heatwave resulted in a 13.6% increase (~4100) in emergency department visits across the 8 days, and ambulance callouts spiked by 20.3% (~1450) during this period. While it may be intuitive to expect many of these presentations and call outs to be directly heat related, only ~8% of both emergency department visits (340) and ambulance callouts (116) were attributed to heat related illnesses and/or dehydration. While the risk of hospital admission due to heat-related injuries and dehydration increase to a greater extent than other illnesses during heatwaves (Khalaj et al., 2010), they are coming off a 'low base'. It is diseases of the nervous, circulatory and respiratory systems, and individuals with underlying mental and behavioural disorders accounting for the majority of excess presentations and call outs during heat waves.  

In addition to chronic disease sufferers, the cohorts most susceptible to elevated ambient temperatures are persons with impaired capacity for thermoregulation, inclusive of infants and the elderly. Groups with high metabolic heat production should also be considered as 'at risk' during heat waves, extending the vulnerable groups classification to include athletes and workers in labour intensive industries. 


Khalaj B, Lloyd G, Sheppeard V, and Dear K. (2010). The health impacts of heat waves in five regions of New South Wales, Australia: a case-only analysis. International Archives of Occupational and Environmental Health 83(7):833-42.

Schaffer A, Muscatello D, Broome R, Corbett S, Smith W. Emergency department visits, ambulance calls, and mortality associated with an exceptional heat wave in Sydney, Australia, 2011: a time-series analysis. Environ Health. 2012;11(1):3.

Heatwave Impact on Workers

Research from the University of Adelaide has identified the impact of changes in ambient temperature on injuries to workers. Xiang et al., (2014) found that a 1 degree change in maximal temperature resulted in a 0.2% increase in daily injury (workers compensation) claims from Adelaide, SA (dry climate). To rephrase their findings, a 10 degree increase in maximal temperature from one day to the next is expected to result in a 2% increase in injury claims. Those most at risk are labourers, production and transport workers and tradespersons. While the industries at risk included agriculture, forestry and fishing, construction, and electricity, gas and water. 

Occupational heat illness was also positively associated with maximum temperature, with a 1 degree change in maximal temperature resulting in a 12.7% increase of occupational heat illness claims, especially above a threshold temperature of ~36 degrees (Xiang et al., 2015). Overall, during heatwave periods, the risk of occupational heat illness was ~4–7 times higher than that of non-heatwave periods, confirming that workers ought to considered as a vulnerable population during heat waves.

Much can be done to mitigate the risk of workers suffering heat illness during heatwaves, with a variety of practical solutions covering in previous e-Bulletins.


Xiang J, Bi P, Pisaniello D, and Hansen A. 2014. The impact of heatwaves on workers' health and safety in Adelaide, South Australia. Environmental Research 133:90-5.

Xiang J, Hansen A, Pisaniello D, and Bi P. 2015. Extreme heat and occupational heat illnesses in South Australia, 2001-2010. Occupational and Environmental Medicine 72(8):580-6.

Northern Australia Heat Stress Survey Update

A huge thank you to those who have assisted in gathering responses from workers exposed to the 2016 'build up' season (October to December) across Northern Australia thus far. We have decided to leave the survey open until the end of February to ensure that workers have had ample opportunity to complete the survey and so we hear from as many workers as possible. If you are interested in learning more about the survey, click the link to request additional information.

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