The whole climate is changing … Temperature is just a bit of it.
John Holdren
Humans are warm-blooded species - they maintain a temperature higher than that of their environment. Human core body temperature is usually 37-degrees Celsius, with some variation (Youssef et. al., 2023). Human core body temperature is kept within tight ranges because consistent body temperature supports the function of organs, tissues, and cellular processes which maintain homeostasis - the state of normal function in the human body (National Institute of Health (NIH), n.d.). Where human core body temperature rises or falls, the effects can be adverse and in some cases can be life-threatening. Human core body temperature can rise naturally as a consequence of physical effort or of illness that causes fever which itself causes a temperature rise in the body. Human core body temperature can decrease naturally as well, such as during the sleep cycle. Human core body temperature is kept consistent by biological, chemical, and physical processes, because changes in temperature can be lethal if dramatic or sustained, and can cause injury even if they are not lethal.
In Australia, heatwaves are the deadliest natural events experienced by the population (Australian Broadcasting Corporation (ABC), 2024). Australia as a continent is largely a desert, but even within the urban centers, heat-related injuries are prevalent. The Australian Institute of Health and Welfare (AIHW) notes that within the past ten years, heatwave related deaths were larger in number than those deaths resulting from all other natural disasters combined (AIHW, 2024). Most of these injuries occur during and between November and March of the following year. The intensity of these weather events can be driven by climactic changes such as the El Niño and La Niña Pacific cycles, but even within these variations, injury hospitalisations owing to extreme heat are significant (AIHW, 2024). Hospitalisations due to extreme heat occurred at an incidence of almost ten times those injuries due to extreme cold, being 7,104 for the former and 773 for the latter (AIHW, 2024). The incidence of these injuries may increase into the future, as the effects of climate change and global warming increase temperatures across the planet as well as make weather patterns more unpredictable, and extreme weather events more common (Climate Council, 2016; National Museum of Australia, 2024). Where humans are exposed to higher-than comfortable temperatures, they have ways of cooling themselves including sweating, adjusting ventilation, increased heart rate, and increased rate of respiration. These responses arise from and rely on internal human physiology, and can be exhausted. Excess sweating causes dehydration. Sustained increased heart rate and respiration can cause heat fatigue and heat exhaustion. If a person is exposed to sustained high temperature, they may experience heat stroke or collapse, and in extreme cases may die. When someone is exposed to cold temperature, the body attempts to offset the temperature loss by increasing temperature through raised metabolism, and physical responses such as shivering. Hypothermia follows when the body’s ability to raise its temperature is insufficient to address the temperature loss from the environment. Freezing and non-freezing injuries of the extremities may consequently result.
Work requires physical effort. Even sitting at a desk and typing on a keyboard requires the engagement of postural muscles, of the upper limbs, and of the hands. More vigorous jobs require more physical effort - pick-packing, hospitality work, trade work, and labouring use larger muscle groups against greater resistance for increased amounts of time, and so generate more heat, cause workers to sweat more, and may exhaust them faster. The speed at which workers become exhausted may increase if the environment is warm (Nielsen et. al., 1993), or if the worker is unacclimatised to heat (Lundgren et. al., 2013), of below-average fitness (Rhampal-Naley, 2012), or otherwise unwell (Kjellstrom et. al., 2009). Heat is generated from within a person’s body by the simple metabolic action of their body (Beker et. al., 2018), which transforms chemical substrates consumed in food into usable energy. In addition to this, the action of muscles and body segments engaged in work generates heat, as has been noted. Workers are also exposed to heat from their environment - workers are exposed to heat from solids and fluids with which the worker may be in direct contact through conduction (Varghese et. al., 2018), such as in the case of a hospitality worker who needs to transfer warm plates, or a printer moving hot vinyl from a press. Workers are also exposed to heat through convection from the movement of gas and air which may be of higher temperature than the worker’s body (De Dear, 1997), such as hot exhaust, boiled vapours from pickling vats, or rising hot air. Where work is done close to heat sources, such as in furnaces, over open flames such as gas hobs, or near hot substrates with high thermal mass, a worker can be exposed to heat through the radiation of heat from those objects, in the same way as holding a hand near red-hot metal will let someone feel the heat (Xiang et. al., 2014). The accumulation and interaction of these heat sources serves to increase the thermal stress to which a worker is exposed over the course of their working period. The rate of this accumulation can be affected by environmental and operational factors. Workers in confined spaces are more vulnerable to heat accumulation as there are smaller distances of exposure, smaller volumes of gas that can be heated, and less distance between heat sources and the worker (Mufaidah & Dwiyanti, 2022; Arifin et. al., 2023). Workers in outdoor environments do not need to worry about accumulative heat, but may be at increased risk of UV exposure. Workers wearing protective gear in addition to longsleeve attire may experience increased thermal stress owing to the inability to exchange heat over their garments.
The worker’s only natural means of decreasing their core body temperature is through heat loss by the evaporation of sweat, and even that may be complicated by the humidity of the environment in which they are working, and the clothing which they are wearing. Sweating is a physiological response wherein water and salts are secreted from the body (Snellen, 1966). This liquid is then evaporated from the skin where the partial pressure of water in the environmental air allows that liquid to reach its vapour pressure. Where liquid sweat changes phase from liquid to gas, heat is lost. Where there is a greater water vapour pressure in the air, such as when there is high relative humidity, the water will drip from the individual and the efficiency of heat exchange is decreased. The lower the relative humidity, the drier the air, and the higher the evaporation rate. The more humid the air, the closer the air is to saturation, and less evaporation can occur (Di Corleto & Britton, 2019). This is important because sweat can only evaporate into the air around it, and if that air is stagnant, in an enclosed room, or in continuous protection, sweat may begin to drip and the efficiency of temperature regulation can be affected. The efficiency of evaporation of sweat can be improved by improving the speed of air moving over the skin or other evaporation surface by improving convective heat loss. Core temperature may be protected with over-body cooling equipment like ice vests, but the effect of these are short-lived, as well as diminished by their bulkiness and their inability to be quickly changed.
Safe Work Australia reports that in the 2022-2023 period, 1700 serious injuries owing to heat, electricity or other environmental factors (SWA, 2024). In 2009-2010 to 2018-2019 period, 1774 claims for injury resulting from working in heat were accepted (SWA, 2020a). That infographic notes that the majority of those claims were for skin-cancer and related conditions, with outdoor work representing more than 400 of those claims, and indoor work representing 95 of those claims. Considering the proportion of claims that were related to skin cancer, it is worth noting that where workers are obliged to work in areas of high UV-exposure, reasonable care such as UV mitigation and worker protection should be undertaken even if the ambient temperature is not uncomfortable, as the UV dose a worker experiences may be high even if the measured temperature is not (Cancer Council, n.d.). However, these statistics only discuss those injuries which were reported and whose severity was sufficient enough to warrant further and due consideration. Even if excessive heat does not cause injury, exposure to heat can cause exhaustion that can impact performance in the short-term (Xiang et. al., 2014), increasing error rate (Beheshti et. al., 2015), impacting attention (Golbabei et. al., 2020), and increasing the risk of adverse outcomes. The incidence of heat-stress related injuries has been noted to be highest among piece-work occupations and among new workers (Varghese et. al, 2020) and may be worsened by the protective equipment that workers are obliged to wear. Heavier, double-layer or enclosed workwear limits the evaporation of sweat owing to the thickness of fabric. Additionally, where workers are working in high-humidity, stagnant, or wet environments, saturation of clothing may further exacerbate the effect of sustained high heat as it’s hard to sweat through something wet (Nagata, 1978; Zhao et. al., 2025).
Currently, the published guidance recommends adjustment of working duties and modification to the environment as the primary means of managing risks to workers that arise from heat (SWA, 2020b; SWA, 2021). Adjusting work to different times of the day to mitigate the effect of environmental heat and to compensate for temperature changes is appropriate for those jobs where this adjustment is practical. However, in industries such as hospitality, laundries, indoor and some labour work, adjustment of working time to compensate for the day may not sufficiently address the risk. In these cases, modifications to the working environment that support ventilation and dehumidification can make up for the inability to adjust working time (Mazzei et al., 2005). While these adjustments may be appropriate, they may not be practicable owing to scale and implementation factors like building codes, or simply because of budgets. It is not always practical to design and implement a HVAC solution to control air quality in small commercial kitchens or small-scale business operations where the price of installation may be inhibitive. Lower-impact solutions such as shade oases are a handy stop-gap but are best implemented within a wider ecosystem of measures including work adjustment, selection of appropriate workers, and adequate support through hydration as well as the occasional icy pole, as a little treat. Worker acclimation to high-heat environments has been found to protect against heat related injury (Jackson & Rosenburg, 2010), but this acclimation may be less appropriate or practical for workers who are older, pregnant, or who experience heart or lung disease (Safe Work New South Wales, n.d.). Pregnant workers themselves should avoid high-heat environments as high heat is suspect in foetal malformation. As the Australian working population becomes older and the prevalence of diseases of age increases, the necessity of generalisable heat protection practice also increases. Humidity can be mitigated by decreasing the moisture content of the airwhere that air is in an enclosed environment, but that too requires conditioning of the air using power and external interventions. Workers themselves benefit from interventions to improve their safety in hot environments, where worker training incorporating education, acclimation, and monitoring has been found to decrease liability in non-insignificant amounts (McCarthy et. al., 2019) given some populations’ identified variances in knowledge regarding safety in hot working environments (Stoecklin-Marois et. al., 2013). While hydration is an effective stopgap, simply giving workers water in hot environments fails to engage with the broader ecosystem of risk produced by environmental, organisational, occupational, and individual risk factors.
Where the worker is working in colder environments, such as those workers working in high-elevation locales or in enclosed temperature controlled environments like coolrooms and cellars, the challenge is the opposite. Many environments are kept at low temperature owing to the perishability of their contents, but then workers must navigate and labour in these places. In these cases, workers need to maintain their body heat through physical activity that balances exertional strain against the body’s ability to generate energy and heat through metabolism. Just as in high-heat environments, operational and organisational considerations are used to reduce worker exposure to cold environments either by shift timing or by work allocation. Engineered controls such as heat oases are useful as well (Anttonen et. al., 2009), and where workers are trained, acclimated, and prepared with the right equipment for the work they are doing, with appropriate monitoring and measurement (Holmér, 2009), fewer injuries are reported (Risikko et. al., 2003). It would appear that those same principles of protecting against high heat are applicable to low-heat environments, though they require their own specific consideration owing to their ubiquity among certain industries and increased representation in different parts of the global economy.
Both high-heat and low-heat environments are conditions that mankind has made artificially. While climactic and geographic variation gives rise to deserts, mesas, tundras and ice shelves, human industrial expansion and activity has created surroundings and environments whose characteristics are far more dramatic than those that can be achieved naturally through nature. Workers across the globe are at increased risk of heat stress owing to the proceeding effects of climate change, whose impacts will be felt most acutely among those poorer populations globally and those more physical populations occupationally. Regardless of whether a worker is office based or outdoors, in hot or cold environments, increased extremity in climactic events and temperatures is a challenge that needs to be addressed proactively and comprehensively. All workers are going to do their jobs in environments whose systems of risk mitigation and control will better or more poorly prepare those people for the challenges of their jobs, and which may positively or negatively impact their health. The environment is an inescapable reality of human existence - we can ensconce ourselves in increasingly isolated cocoons supported by increasingly elaborate and energy-hungry technological buttresses, or we can engage with the global challenge of controlling and maintaining working environments in an environmentally and occupationally sustainable manner.
Regardless of the heat, we’re all in this kitchen.
None of this information constitutes medical, legal, occupational health and safety, best guidance, standard, or other guidance, instruction, or prescription.
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