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Welcome to the inaugural edition of the Heat Stress e-Bulletin from Thermal Hyperformance. We aim to provide you with an overview of what's happening in the heat stress space, from the latest research to interesting media articles, all without taking ourselves too seriously. We strive to maximise the health, safety and performance of workers exposed to hot conditions, we trust this information assists you in that endeavour. 

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Climate Forecast, September - November

Workers based in Northern Australia have already endured a preview of what this build up season has in store, with a sharp increase in overnight temperatures and humidity during early September. So what can we expect over the coming months? The Bureau of Meteorology predict that Northern Australia and Tasmania will experience higher than average minimum and maximum temperatures, while the Red Centre, South Australia and Victoria are also likely to see warmer than normal temperatures. Regions encompassing the Eastern state capitals are expected to experience average conditions. We eagerly await the December to February forecast, look out for the projections in our next newsletter.  

September to November
Chance of above median minimum temperature
September to November
Chance of above median maximum temperature

Heat Stress Symptoms

Much of our time is invested into understanding how working in hot and humid conditions impacts workers. While a variety of scientific methods are available to monitor these 'industrial athletes', for a subjective viewpoint who better to ask then the workers? So in collaboration with a large organisation, we conducted an anonymous electronic survey following the harsh 2015/16 wet season, with the high response rate resulting in some great insights. In the short term, heat stress education sessions can be tailored based on the feedback, and in the longer term the issues workers perceive as contributing to harm can be addressed. We seek to publish this research in 2017 and will provide more information in future bulletins.

Knowledge of the heat stress symptoms suffered by workers and the impact on health, productivity and social factors is valuable information. But what if we could identify the individual factors that precipitated such symptoms? To this end Charles Darwin University honours student Sarah Guajardo is investigating worker heat stress symptoms and physiological markers. Sarah has been busy piloting this work in the law enforcement field and recently completed her proposal seminar. We look forward to supervising Sarah through a busy wet season of data collection.

Long Term Climate Projections

In September 2008, Professor Ross Garnaut released a Commonwealth, State and Territory Government commissioned report on impacts of climate change on the Australian economy. Below are the projected number of days per year over 35C for capital cities from the review. The most alarming projection was for the capital of the Northern Territory, Darwin. The exponential increase can be attributed to the number of 33C and 34C days they currently experience. Few workers would have nominated Hobart as having a similar climate to Brisbane, but as the table demonstrates, basing climate solely on ambient temperature excludes the impact of environmental moisture/humidity, a major contributor to worker heat stress. Factoring in humidity and the projected number of days over 35C, the challenge of physically demanding work in Darwin becomes more extreme. 

As part of recent work for a client (based on Bureau of Meteorology data), we reported on the number of 35C plus days for three major population centres of the Northern Territory in recent years, with Katherine the clear winner. While each centre has a unique climate, the table below demonstrates that workers in these locations are exposed to seasonally hot conditions now. Hence the need for strategies to mitigate heat stress now and into the future. 

Commonwealth Scientific and Industrial Research Organisation 2008, ‘projections of days over 35C to 2100 for all capital cities under a no-mitigation case’, data prepared for the Garnaut Climate Change Review, CSIRO, Aspendale, Victoria. 

Choosing the optimal work rate in the heat can be difficult, even for Olympians.

For those who suffered sleep deprivation during the Rio Olympics, Day 14 was a tough one. On face value, the 50km walk seemed like an opportunity to catch up on some sleep as despite featuring an Aussie medal chance in Jared Tallent, this race does not rank against higher profile sports for excitement. However, the Rio 50km walk was an enthralling event, something too great to sleep through.  

Tallent was towards the front of the race throughout but bided his time, not willing to match the blistering pace of sole leader and world record holder, Yohann Diniz. Diniz set a cracking pace in the hot and humid conditions, establishing a 28s lead by the 5km mark. He increased his lead to 53s by 15km and 1m 40s by half way. His effort was made more remarkable by the fact that he was suffering gastrointestinal issues. At the 32km mark, his effort began to unravel, pausing on course, giving up his sizable lead and shortly after recommencing racing he collapsed. He managed to continue racing after being doused with ice cold water. Ultimately, Diniz would finish a gutsy 8th while Aussie Jared Tallent saved his effort for the final 10km and looked the winner close to home, claiming the silver medal.

Post race, Diniz was critical of the race organisers for scheduling the grueling race to start at 0800 (finish approx. 1200), exposing the athletes to some of the harshest daily conditions. While the weather was not favourable, it should have been factored into Diniz’ selection of pace. Since Rio was awarded the games in 2009, heat and humidity were widely acknowledged as potential issues for athletes. In 2015, a comprehensive Olympic weather report was prepared by Brazil's National Institute of Meteorology (INMET), available here.

So the conditions should not have been a surprise. It's likely that Diniz selected an unsustainable pace based upon his physiological state and the prevailing weather. A similar dilemma faces workers exposed to hot and humid conditions, how hard do I work to get the job done without compromising my health and safety? It's apparent that experience plays a key role in selecting the correct work rate, but selection of pace is not a constant, requiring adjustments in accordance to recovery from previous shift(s), heat acclimatisation (eg. FIFO first shift back), illness (infection, gastro), physical fitness, nutrition, hydration etc.

As we noted in our 2015 paper, 'By understanding the tasks required, number of staff available, time frame for completion, anticipated climatic conditions and factoring in their personal experience, physical fitness, and acute physiological status, workers can initiate behavioral and work load adjustments, thereby selecting an appropriate pace to complete the task and prevent excessive body heat storage. Hence, selecting the optimal pace requires sharing of information with workers and the freedom to work to how they feel. As Diniz demonstrated, ignoring the climate and personal well being may not end well. 

Brearley M, Harrington P, Lee D, Taylor R. Working in hot conditions – a study of electrical utility crews in the Northern Territory of Australia. Journal of Occupational and Environmental Hygiene 12(3):156-62, 2015

Cool Clothing

Stanford University engineers have developed a porous plastic based textile that permits more heat loss than conventional fabric. Essentially, the textile is similar to the common household cling wrap that permits infrared radiation (heat) to pass from the body to the environment. The research article can be found here. While use of the textile as a substitute for regular clothing may appear unlikely, it's an interesting development. Many workers report that their personal protective clothing/equipment (PPC/PPE) increases their heat stress due to the trapping of body heat, essentially limiting infrared radiation. Achieving a balance between protection from workplace hazards and heat stress can be difficult, so we are involved in the development of alternative options to commercially available PPC/PPE for industrial settings. We hope to provide more information on these developments in future bulletins should they become commercially viable. 

Upcoming Events

Science of Sport, Exercise and Physical Activity in the Tropics Conference, September 7-9, Townsville. Invited presentation on the evidence of a heat hangover in occupational settings. 

Tour de Timor, September 12-19, Timor Leste. We are managing rider heat stress following each stage and monitoring the Australian Medical Assistance Team (AusMAT) during their deployment.

Physiological Monitoring, September 26 - October 1, Darwin. Fitness testing and monitoring staff during construction of AusMAT field medical facility for World Health Organisation verification.

Dili Marathon, October 8-10, Timor Leste. Managing runner heat stress.

Heat Stress Research Partnership Meetings, October 19-21, Darwin. Hosted by the Northern Institute, Charles Darwin University. Attendees include James Cook University, Menzies School of Health Research and RMIT.


For more information on what we are up to, check

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