Heat waves, cooling methods and the research from the Thermal Ergonomics Laboratory

By TdDie Image via Shutterstock. Stock photo ID: 592000556

It often comes as a surprise to many that over the past 20 years heatwaves, both in Australia and overseas, have caused more deaths than all other natural disasters (e.g. earthquakes, floods, hurricanes) combined. The elderly, poor, and especially people with pre-existing cardiovascular diseases are the most vulnerable, with cardiac arrest among the leading causes of death.

By far the most effective cooling strategy for mitigating the physiological strain that develops when exposed to high temperatures and humidity during a heatwave is air conditioning use. Yet, >25% of Australians do not have AC, and rising electricity prices as well as the greater likelihood of blackouts associated Australia’s imminent energy crisis makes the reliance on widespread AC use in heatwaves even more tenuous. The sustained annual increase in CO2 emissions associated with AC use in Australia also cements our status as one of the top polluters per capita in the world.

Given the undeniable increase in frequency, intensity, and duration of heatwaves in Australia and worldwide associated with anthropogenic climate change, identifying simple, cost-effective, and sustainable ways of cooling has never been more important. Electric fan use is an obvious cooling strategy with up to 50-times lower electricity requirement and cost than AC. However, most major public health agencies such as the World Health Organization (WHO) have stated for at least the last 15-20 years that fans should be turned off above air temperatures of ~35°C as they paradoxically “speed the onset” of heat exhaustion and exacerbate dehydration. In stark contrast, a systematic assessment of the scientific literature in 2012 concluded that no physiological evidence exists supporting or refuting the effectiveness of fan use for cooling in a heat wave.

Over the past 3 years our research team in the Thermal Ergonomics Laboratory in the Faculty of Health Sciences at the University of Sydney, along with international partners in the United States, has conducted a series of research studies trying to identify the most effective low-cost cooling strategies (including fan use) that people, particularly those who are at the greatest risk, can use to reduce heat-related physiological strain in different types of heat waves. Our state-of-the-art climatic chamber enables us to simulate a range of different heat waves, from very hot-dry events such as the 2009 heatwave in Adelaide to cooler but much more humid events such as the Chicago (1995) or European (2003) heatwaves, and measure how people physiologically respond (e.g. how hot they get, and how much work their heart must do) when using different cooling interventions.

So far, we have found that best cooling methods are dependent on the type of heatwave and a person’s ability to sweat. For example, contrary to the existing public health guidance on fan use in heatwaves, we have shown that fans can be very effective cooling devices at air temperatures up to at least 42°C with 50% relative humidity for young healthy people, but less so in older adults (>65 y) because of age-related reductions in the ability to sweat. However in very hot (46°C), but dry (<15%RH) heat waves all sweat evaporates anyway and more heat is just added to the body with fan use resulting in accelerated body heating even in young healthy people. These limitations can likely be offset though by wetting the skin with a sponge and/or placing the feet in a bucket of cold water.

This work is ongoing and in the next year, we plan to extend our studies to focus on developing an understanding (which is desperately lacking) of how different prescription medications and health disorders (e.g. coronary artery disease) affect the ability to keep cool in a heat wave. Ultimately, the goal of this work is to develop and disseminate through changes to national and international public policy the world’s first evidence-based guidance for sustainable cooling strategies for the most vulnerable in all types of heatwaves. This work will also demonstrate the utility of various cooling interventions that can be used to mitigate the unsustainable energy demands and destructive environmental impact of mass air conditioning use.

The opportunity to incorporate our work into a theatric performance opens up a brand new way to communicate our research findings. Given the importance of reaching as many people as possible with our message, such novel knowledge translation collaborations are absolutely essential to maximise the impact of our research. After all, if we couldn’t reach the people that that our research intends to help, our work would be wasted!

Ollie Jay is a Collaborator for ‘Anastasia: Communicating heat & climate vulnerability through performance’. The project is funded by the Pop-up Research Lab scheme awarded by the Sydney Social Sciences and Humanities Advanced Research Centre (SSSHARC). The project is exploring the real life impacts of heatwaves as well as the theoretical problems which come from communicating academic research of shock climate events to non-academic audiences such as policymakers, community organisations, and the general population, through the medium of theatre. For more information on the project here.

SEI’s Deputy Director Michelle St Anne at the heat lab with Ollie Jay

Ollie Jay is the Director of the Thermal Ergonomics Laboratory, in the Faculty of Health Sciences at the University of Sydney, and Lead Researcher of the Charles Perkins Centre (CPC) Research Node on Climate Adaptation and Health. Prior to moving to Australia in January 2014, he was a tenured Associate Professor at the University of Ottawa in Canada (2008-2013). Originally from Wales (UK), he obtained his PhD in Thermal Physiology from Loughborough University in 2002, which was then followed 4½ years of international postdoctoral research experience at Simon Fraser University (2003-05) and the University of Ottawa (2005-08). His research activities primarily focus on developing a better understanding of the physiological and physical factors that determine human heat strain and the associated risk of heat-related health problems during work and/or physical activity, as well as among the general population during heat waves.