More people die of heatwave-related deaths in Melbourne than in Brisbane, Sydney, Perth or Adelaide, due to heat acclimatisation factors, according to a 2018 study in the journal, Climate Change.
Using data from the Bureau of Meteorology and Australian Bureau of Statistics (ABS), University of Technology Sydney (UTS) researcher, Dr Thomas Longden, found that 1,283 heatwave-related deaths were recorded in Melbourne between 2001-2015.
Meanwhile Sydney, Adelaide, Perth and Brisbane recorded 768, 549, 532 and 220 heatwave-related deaths respectively over the same period.
While residents of Australia’s northern east-coast endure sweltering summers, Longden – who is the senior researcher at UTS’s Centre for Health Economics Research and Evaluation – found that people in these cities were less likely to be caught out by sudden extreme heatwaves.
“While Sydney and Brisbane have hot summers, most of their summer days tend to be of a similar temperature and this assists people to acclimatise to the heat,” said Longden.
However, Melbourne, Adelaide and Perth were found to have had extreme heatwaves with “three-day average temperatures spiking up to 12°C above the 30-day average” much more frequently than Sydney and Brisbane.
This prevented people from acclimatising to and being prepared for extreme heatwaves.
Furthermore, Longden found that the most number of deaths occurred when the temperature reached more than 7°C above the 30-day average.
How does extreme heat cause death?
A human’s normal core body temperature is around 37°C, however a healthy person can cope well with fluctuations of up to 3.5°C.
In hot weather, the body maintains its core temperature by losing heat through the skin.
For example, blood vessels that supply blood to the skin dilate, allowing warm blood to flow near the skin’s surface where the air can cool it.
Sweat also functions to remove heat from the body through evaporative cooling, as long as there is sufficient airflow and low humidity.
Finally, people can reduce heat by resting, since around 80 per cent of the energy produced by working muscles is heat.
However, if the ambient temperature is greater than 35°C-37°C, or there is high-humidity, the body’s ability to cool itself via these mechanisms is greatly reduced.
If the body goes above safe core temperatures, it can start to show signs of distress – including dizziness, headache, nausea, vomiting, fainting, heatstroke, liver damage, and at worst, multi-organ failure.
How people can improve heat acclimatisation:
According to thermal physiologist, Matt Brearley, the key to heat acclimatisation is fitness and exercise. In fact, this is even more effective than living in hot environments.
“Exercise is critical. You can’t be heat acclimatised without exercise,” Brearley told THORZT in an earlier interview, adding that someone who lives in Darwin but works, lives and drives in air conditioning is not heat acclimatised.
“People really can’t be acclimatised without training. Training promotes all the heat loss mechanisms: sweating and the movement of blood to the skin for heat loss.”
Just like fitness, heat acclimatisation needs to be maintained and sedentary behaviour, poor diet and overuse of air conditioning inhibits the body’s ability to tolerate hot conditions.
According to Brearley, re-acclimatisation after a break can take around four days, or sometimes longer.
As a result, employers need to modify the work they give returning tradies to prevent heat-related illness or safety issues during the re-acclimatisation period.
Changes to contracts and policy needed:
Furthermore, president of the Climate and Health Alliance, Professor Liz Hanna said that Sydney is heading towards a 50°C day, while even Hobart’s 2016-17 summer was unusually hot and long.
“Australia needs to work out how it is going to keep functioning without risking the lives of our workers,” she said in a previous interview with THORZT.
Research conducted by Hanna and her colleagues from 2012-2015 found that “people uniformly overestimated their capacity to work in heat”.
She found that tradies working in hot environments were less productive due to heat and dehydration, adding that dehydration markedly increases heat stress risks.
While hydration monitoring and the correct work-rest ratios are critical, as is access to cooling vests and cool rooms, Hanna emphasised that policy and work contracts also need to change to prevent tradies from being forced to work in extreme heat.