If you can’t stand the heat…Cooling Vest

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James Russell, Managing Director of climate control apparel specialist TechNiche Europe, explains why heat stress poses a growing problem for industries around the world and discusses the steps you can take to keep your employees safe.

The world is getting hotter. Over the last century the global average surface temperature has increased by around 0.74°C and the rate of increase is rising too[1]. Heatwaves around the world are predicted to become more frequent and intense, increasing occupational heat exposure and presenting a growing challenge to health and safety professionals around the world[2][3] as they try to manage heat stress

Understanding heat stress

Heat stress occurs when the body’s ability to control its internal temperature fails. It isn’t usually a problem because under normal circumstances the human body is quite effective at regulating its internal temperature – balancing heat transferred into and generated within the body itself with heat coming out of the body. When exposed to heat, the body immediately reacts to cool itself down by increasing blood flow to the skin’s surface and producing sweat. As sweat evaporates from the skin and heat carried to the body’s surface is able to escape, the body cools down.

However, if the body’s efforts to create balance are hampered in some way, this can lead to heat stress. For example, in a workplace with an ambient temperature over 35°C, the small difference between skin temperature and that of the surroundings means that sweating becomes the only real way to reduce body temperature[4]. In addition, at ambient temperatures above 37°C the skin itself can actually become a source of heat gain[5]. Under these conditions, and particularly if the person is performing physical activity that is creating more heat internally, the body may not be able to reduce its temperature. If this happens in a work environment where exposure to heat is unavoidable or protective equipment stops sweat from evaporating, the body’s core temperature will begin to rise.

The body reacts to elevated core temperature by sweating more, potentially leading to dehydration. A higher core body temperature can also result in an increase in heart rate, putting yet more strain

[1] Nilsson M and Kjellstrom T. November 2010. Climate change impacts on working people: how to develop prevention policies. Global Health Action. 2010; 3: 10.3402/gha.v3i0.5774. Published online 2010 November 29. doi: 10.3402/gha.v3i0.5774.

[2] Nilsson M and Kjellstrom T. November 2010. Climate change impacts on working people: how to develop prevention policies. Global Health Action. 2010; 3: 10.3402/gha.v3i0.5774. Published online 2010 November 29. doi: 10.3402/gha.v3i0.5774.

[3] Xiang J, Bi P, Pisaniello D and Hansen A. March 2014. Health Impacts of Workplace Heat Exposure: An Epidemiological Review. Industrial Health. 52(2): 91-101. Published online 2013 December 21. doi: 10.2486/indhealth.2012-0145

[4] Miller BS and Bates GP. 2007. The Thermal Work Limit Is a Simple Reliable Heat Index for the Protection of Workers in Thermally Stressful Environments. The Annals of Occupational Hygiene. Vol. 51, No. 6, pp. 553–561.

[5] Hyatt OM, Lemke B and Kjellstrom T. December 2010. Regional maps of occupational heat exposure: past, present and potential future. Global Health Action. 2010; 3: 10.3402/gha.v3i0.5715. Published online 2010 December 13. doi: 10.3402/gha.v3i0.5715

on the body. If the situation continues and the body continues to gain more heat than it can lose through its usual coping mechanisms, body temperature will continue rising and the body’s ability to control its internal temperature may fail.

The ideal ambient working temperature is actually between 20°C and 22°C, with working capacity falling as temperature rises above that[1]. Above 26°C, concentration becomes difficult and fatigue sets in[2]. Other symptoms of heat stress include muscle cramps and heat rashes, as well as severe thirst[3]. Heat exhaustion, a more serious condition, may follow, with symptoms such as fatigue, dizziness, nausea, headaches, heavy sweating and clammy skin[4][5]. The most severe heat disorder is heat stroke. Characterised by hot dry skin, confusion, convulsions and eventually loss of consciousness, heat stroke can result in death if not detected early[6].

Recognising the risk

Heat stress affects people in different ways and vulnerability can be exacerbated by a number of factors. For example, people who are overweight, pregnant or over the age of 65 are at increased risk, as are those who have heart disease, are on certain medications, abuse alcohol, aren’t physically fit or are simply not acclimatised[7][8].

Risk levels vary from industry to industry too. Typically manual workers exposed to extreme heat or working in hot environments in low or middle-income countries in tropical regions are most at risk[9], but workers in certain industries can be at risk wherever in the world they are. In fact, in the U.S.A., two out of every 1,000 workers are at risk for heat stress[10], while in the 28 member countries of the EU, temperature is a risk factor in 36% of workplaces[11].

Industries most at risk include those where the work process causes heat, such as bakeries, kitchens, laundries, brick-firing facilities, ceramics plants, foundries and smelting operations[12], as well as situations such as mines where work done in a confined space results in a hot environment. Outdoor work environments, such as those in construction and agriculture, where heat exposure varies according to the weather and the work being done are also at greater risk[13].

[1] European Agency for Safety and Health at Work. January 2008. Hot environments in HORECA. http://bit.ly/1jSzJ4U.

[2] European Agency for Safety and Health at Work. January 2008. Hot environments in HORECA. http://bit.ly/1jSzJ4U.

[3] Health and Safety Executive. June 2013. Heath stress in the workplace: A brief guide. http://bit.ly/1G1RLf1.

[4] Health and Safety Executive. June 2013. Heath stress in the workplace: A brief guide. http://bit.ly/1G1RLf1.

[5] Walter L. May 2012. The Heat Is On: Protecting Workers from Heat Stress. EHS Today. Cleveland, USA. http://bit.ly/1Zk10h3.

[6] Health and Safety Executive. June 2013. Heath stress in the workplace: A brief guide. http://bit.ly/1G1RLf1.

[7] Walter L. May 2012. The Heat Is On: Protecting Workers from Heat Stress. EHS Today. Cleveland, USA. http://bit.ly/1Zk10h3.

[8] Government of Western Australia. Working safely in hot conditions – heat stress. http://bit.ly/1Zk19kG.

[9] Xiang J, Bi P, Pisaniello D and Hansen A. March 2014. Health Impacts of Workplace Heat Exposure: An Epidemiological Review. Industrial Health. 52(2): 91-101. Published online 2013 December 21. doi: 10.2486/indhealth.2012-0145

[10] National Institute for Occupational Safety and Health. May 2013. Workplace Solutions: Preventing Heat-related Illness or Death of Outdoor Workers. DHHS (NIOSH) Publication No. 2013−143.

[11] European Agency for Safety and Health at Work. 18 March 2015. Second European Survey of Enterprises on New and Emerging Risks (ESENER-2). Bilbao, Spain: Prevention and Research Unit.

[12] Health and Safety Executive. June 2013. Heath stress in the workplace: A brief guide. http://bit.ly/1G1RLf1.

[13] Xiang J, Bi P, Pisaniello D and Hansen A. March 2014. Health Impacts of Workplace Heat Exposure: An Epidemiological Review. Industrial Health. 52(2): 91-101. Published online 2013 December 21. doi: 10.2486/indhealth.2012-0145

The risk of heat stress should be a serious consideration for all employers, most importantly from the point of view of worker welfare, but also in terms of the impact that it may have on safety compliance and workforce productivity.

Chronic workplace heat exposure can have adverse long-term health effects such as cardiovascular illnesses, mental health problems and chronic kidney illnesses, but it can also increase the risk of workplace injuries and accidents through fatigue, impaired judgement, decreased coordination and poor concentration[1]. For example, people working in the heat may struggle to grip equipment or tools with sweaty hands, while people who become dizzy might fall[2]. Additionally, where protective clothing or equipment is worn, employees may fail to wear it correctly in hot conditions, further increasing the risk of injury.

Prevention and management

Heat stress is already a well-recognised health hazard in some regions and industries, although some are more advanced than others in as far as heat stress management programmes are concerned. Government bodies in the U.S.A., Canada, Australia and the U.K. all provide information about working safely in the heat, the factors that can lead to heat stress and how employers can reduce the risk of heat stress, as does the European Agency for Health and Safety at Work.

So how hot is too hot? In adults, the human body maintains its temperature around 37°C and deviation – up or down – of a degree or more can have serious consequences. Once core temperature exceeds 38°C the risk of heat stress occurring increases, at 39°C heat exhaustion can set in and above 40°C heat stroke may occur[3][4]. To ensure worker safety, it is important to maintain a safe core body temperature (<38.2°C) and sweat rate (<1.2kg per hour) during work in any set of environmental conditions[5].

In order to assess the potential heat strain of employees, establish the maximum safe work rate for the given conditions and develop an appropriate prevention strategy, there are a number of risk assessments that employers can undertake with the help of an occupational hygienist. Doing so will make it easier to implement a heat stress prevention programme.

Some of the steps that employers can take to protect employees from heat stress include:

Installing additional ventilation or air conditioning to reduce heat exposure if possible Providing workers with cooling or protective clothing to mitigate the effects of heat exposure Allowing workers to gradually acclimatise to conditions if the conditions have changed or workers are new to them Provide cool drinking water that is easy to drink and encourage them to drink small amounts of water frequently before and during their shifts to stay hydrated Provide cool and/or shaded areas for breaks and build time for these into shifts Schedule heavier or more physically demanding work for the cooler hours of the day Be aware of any health conditions or medications that could have an effect on workers’ heat tolerance Ensure that first aid workers are trained to recognise and treat heat stress disorders Put a plan in place to address the problem immediately if a worker begins to show symptoms However, what is most important in any programme aimed at helping workers keep cool, hydrated and safe is maintaining communication with them and ensuring that they are trained and knowledgeable of heat stress symptoms[1]. While setting guidelines on safe maximum sustainable work rates for the conditions is vital, it is also important to empower employees to have a say in their own safety by encouraging them to speak up when they feel conditions are too hot.

Heat stress may be a growing challenge for many industries, but with the right approach you can help your workforce stay cool, safe and productive.

[1] Walter L. May 2012. The Heat Is On: Protecting Workers from Heat Stress. EHS Today. Cleveland, USA. http://bit.ly/1Zk10h3.

[1] Xiang J, Bi P, Pisaniello D and Hansen A. March 2014. Health Impacts of Workplace Heat Exposure: An Epidemiological Review. Industrial Health. 52(2): 91-101. Published online 2013 December 21. doi: 10.2486/indhealth.2012-0145

[2] Walter L. May 2012. The Heat Is On: Protecting Workers from Heat Stress. EHS Today. Cleveland, USA. http://bit.ly/1Zk10h3.

[3] Bethea D and Parsons K. 2002. The development of a practical heat stress assessment methodology for use in UK industry. Sudbury, UK: HSE Books.

[4] Government of Western Australia. Working safely in hot conditions – heat stress. http://bit.ly/1Zk19kG.

[5] Brake DJ and Bates GP. 2002. Limiting Metabolic Rate (Thermal Work Limit) as an Index of Thermal Stress. Applied Occupational and Environmental Hygiene. 17(3) pp. 176-186