Working in Heat: Risks and Duties


In last week’s feature we considered the risks arising from working in cold temperatures. This week we look at the risks of heat-related illnesses posed by working in high temperatures. Being exposed to high temperatures at work can give rise to a risk of overheating which can cause heat related injuries, such as heat stress. In this feature we discuss which occupations are most likely to be at risk of heat injuries, what these injuries consist of and legal obligations on employers to prevent them. 


Many people are exposed to heat in their jobs, not only outdoor workers but those that work indoors involving high air temperatures, radiant heat sources, high humidity, direct physical contact with hot objects or strenuous physical activities.

Workplaces with these conditions include, metal foundries, brick-firing and ceramic plants, glass and rubber products factories, electrical utilities (especially boiler rooms), bakeries, confectioneries, commercial kitchens, laundries, food canneries, chemical plants, mining sites, smelters and steam tunnels.[i] Some outdoor workers which face such exposure include, agricultural and construction workers and army personnel.


Climate change is said to be causing the surface of the earth to become warmer with expected increasing ambient temperatures and extreme climate events also predicted to increase in intensity, duration and frequency in the future[ii].  This could result in larger numbers of workers being exposed to more intense heat.  Since 1960 there has apparently been warming in the UK, with greater warming in the summer than winter[iii].  There has also been a decreasing trend in the frequency of cool nights and cool days and an increasing trend in the frequency of warm nights and warm days.  There has been a general increase in summer temperatures averaged over the country, making the occurrence of warm summer temperatures more frequent and cold summer temperatures less frequent.  In the heatwave of 2003, the UK recorded its highest temperature of 38.5 °C in Kent on the 10th of August.  Across the UK, temperatures exceeded 32 °C on three consecutive days and then again on 5 consecutive days (4-6 August and 8-12 August).  Similar conditions occurred in July 2006, resulting in the warmest month on record in the UK.  Detailed information about climate change is available from the Intergovernmental Panel on Climate Change (IPCC)[iv].

Although there is no official definition of a ‘heatwave’ in the UK, the term can be used to describe an extended period of hot weather relative to the expected conditions of the area at that time of year.  The Met Office triggers heatwave alerts when the probably of heatwaves reaches particular values.  A level 2 alert is issued when the Met Office forecasts that there is a 60 % chance and a level 3 alert is issued as soon as there is a 90 % chance of heatwave conditions, when temperatures are high enough over threshold levels to have a significant effect on health on at least two consecutive days.  The alert is usually issued 2 to 3 days before the heatwave is expected to occur.  The Met Office Heat-Health Watch Service is designed to help healthcare professionals manage through periods of extreme temperature[v].  The service acts as an early warning system forewarning of periods of high temperatures, which may affect the health of the UK public.  It operates in England from 1 June to 15 September each year, in association with Public Health England.  Public Health England publishes Heatwave Plans, which aim to prepare for, alert people to, and prevent, the major avoidable effects on health during periods of severe heat in England[vi].

The UK is projected to experience temperature increases of up to around 3 °C in the South and 2.5 °C further North[vii].


Acute exposure to extreme heat can cause heat stress.  Heat stress can result in heat stroke, heat exhaustion, heat cramps or heat rashes, and can increase the risk of injuries resulting from sweaty palms, fogged up glasses or dizziness.  Some particular groups are more at risk, including those aged over 65 and those who are obese. 

Heat stroke is where the body is no longer able to cool itself and a person’s body temperature becomes dangerously high. This is a medical emergency and can be fatal if not treated.   Symptoms of heat stroke include: confusion, altered mental state, slurred speech, loss of consciousness, coma, rapid, shallow breathing, hot, dry skin, profuse sweating, stopping sweating, seizures and very high body temperature.

Heat exhaustion is where you become very hot and start to lose water and salt, leading to symptoms of feeling sick, faint and sweating heavily.  If a person with heat exhaustion is taken quickly to a cool place, given water to drink and removes unnecessary, heavy clothing, they should begin to feel better within half an hour and have no long-term complications.  Without treatment, they could develop heatstroke. 

Rhabdomyolysis is a medical condition associated with heat stress and prolonged physical exertion, resulting in the rapid breakdown, rupture, and death of muscle.  When muscle tissue dies, electrolytes and large proteins are released into the bloodstream that can cause irregular heart rhythms and seizures, and damage the kidneys.  Symptoms include muscle cramps/pain, abnormally dark (tea or cola-coloured) urine, weakness and exercise intolerance[viii].  It is also associated with deliberate pesticide intoxication, and incidence increases with the amount of pesticide ingested[ix].

Heat syncope is a fainting episode or dizziness that may occur due to dehydration and lack of acclimatization.

In a heatwave, most deaths occur in the first 2 days[x].  The most common causes of heat-related death overall are cardiac and respiratory problems in those who are frail and chronically ill.

In the heatwave of summer 2003, over 21,000 deaths were related to the heat, of which 2,100 were in England and Wales[xi].  The worst affected were those over the age of 75; deaths in this age group increased by 59 % compared with 2002 in the London region.  Public Health England reports small increases in reports of heat-related illness in line with short periods of warmer weather[xii].  In July 2013, some reported increases were predominantly noted across the East of England, South West and South East Coast regions of England, and were reported across all age groups.  The impact of the moderate heatwave in 2013 on primary care and emergency department visits was investigated by Smith and colleagues[xiii].  Surveillance systems were used to monitor the health impact of heat/sun stroke symptoms (heat illness).  Both GP consultations and ED visits for heat illness increased during the heatwave period.  The highest rates were in school children and those aged 75 years or more.  Extrapolating to the whole population of the UK, the researchers estimated that the number of hourly GP consultations for heat illness during the whole summer (May to September) was 1166.  This was double the rate observed in non-heatwave years.

According to the London School of Hygiene and Tropical Medicine, the number of annual preventable deaths caused by hot weather in England and Wales is projected to increase from the current figure of around 2,000 to around 7,000 by the middle of the century[xiv].  Predicted population growth, longer lifespans and warmer summers with more intense, longer-lasting heatwaves will contribute to this increase.  The most direct way in which climate change is expected to affect public health relates to changes in mortality rates associated with exposure to ambient temperature[xv].

Workers exposed to hot indoor environments or hot and humid conditions outdoors are at risk of heat-related illness, especially those doing heavy work tasks or using bulky or non-breathable protective clothing and equipment. The table below illustrates factors that put workers at a heightened risk of these conditions we have mentioned:

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Some workers might be at greater risk than others if they have not built up a tolerance to hot conditions, or if they have certain health conditions.


Pre-existing Conditions

Certain heart medications, including beta blockers, ace receptor blockers, ace inhibitors, calcium channel blockers and diuretics can exacerbate the effects of heat on the body[xvi].  Those with coronary heart disease may start to experience angina, or find that their angina worsens during hot weather, because hot weather increases the workload on the heart and the demand for oxygen, especially during physical activity[xvii].  A 2014 study found that hot spells were associated with excess deaths from ischemic heart disease (IHD), and that chronic IHD was responsible for most of the excess, suggesting that those with chronic heart disease are at risk[xviii].  In general, tolerance to heat stress is impaired in patients with cardiovascular disease[xix].

Heat and agricultural workers

The United States, the National Institute for Occupational Safety and Health (NIOSH) lists farmers as a group of workers at risk of heat stress, along with firefighters, bakery workers, construction workers, miners, boiler room workers, factory workers, and others.  Workers at greater risk of heat stress are those who are 65 years of age or older, are overweight, have heart disease or high blood pressure, or take medications that may be affected by extreme heat[xx].

A 2010 paper from the United States found that between 1992 and 2006, 68 crop production workers died from heat related illness, which is 20 times higher than the average rate of civilian workers overall[xxi].  This is an average annual death rate of 0.39 per 100,000 workers.  The incidence and prevalence of non-fatal heat-related illness is essentially unknown, though it has been reported in the United States that between 2003 and 2008 there was an average of 2260 illnesses per year that resulted in one or more days away from work.  A 2016 article reported that among Latino farmworkers in Northern Carolina, 72 % had experienced at least one heat related illness symptom, and 27 % had 3 or more symptoms[xxii].  In agriculture, estimates of heat illness are likely to be undercounts because some surveys exclude workers on small farms (in the USA)[xxiii].

An Australian review, published in 2016, investigated heat stress risk within mining, construction, agriculture and emergency services[xxiv].  Despite workers being regularly exposed to high ambient temperatures (32-42 °C), often coupled with high humidity, physiological strain is generally low in terms of core temperature and dehydration.  Heat stress risk in higher in specific jobs in agriculture such as sheep shearing.

A report on deaths due to heat illness in the USA during 2012-2013 found 13 cases of a worker’s death and 7 cases in which two or more employees experienced symptoms of heat illness[xxv].  Most of the affected employees worked outdoors, and all performed heavy or moderate work.  Nine of the deaths occurred in the first 3 days of working on the job or after returning from time away from the job, and 4 were in long-term workers.  The researchers note that employers should be aware of the importance of acclimatisation.

The Farmers Weekly reported in November 2016 that a young farmer and his family are appealing for members of the farming community who have experienced rhabdomyolysis to make contact with them.[xxvi]  The young farmer became very ill the day after attending a farm show and was placed in the intensive care unit in hospital for two weeks.  According to FW, “although doctors were able to identify Mr Cook’s condition, it was hard for them to administer the correct treatment without knowing what had caused it”.  He told FW that two months later he was still unable to do any manual work and was attending physiotherapy twice a week to help to rebuild his muscles[xxvii].  Another local farmer also contracted a similar condition 2 years ago.  The young men affected are aged 22 and 33.  The articles do not mention heat exposure, but they note that the condition is normally the result of a severe muscle injury, or found in athletes who overwork themselves.

Chronic health effects

As well as the symptoms described above in relation to heat stress, there may also be chronic health effects associated with exposure to heat.  Severe heat-related illness may cause permanent damage to organs such as the heart, kidneys and liver, which could result in a chronic disorder.  Heat stroke may also lead to lung problems and blood clotting disorders[xxviii].  A study in which US military personnel hospitalised for heat illness or appendicitis found that the heat illness group had higher risk of all-cause mortality, and males were at greater risk of death from cardiovascular disease and ischemic heart disease than the appendicitis group[xxix].

Though there are case studies of individuals who have suffered exertional heat stroke leading to acute liver failure[xxx] [xxxi] [xxxii], we could not identify any studies that estimate the proportion of heat stroke or heat stress patients likely to develop such effects.

A large study found an association between self-reported occupational heat stress and doctor-diagnosed kidney disease in Thailand[xxxiii].  Among men exposed to prolonged heat stress, the odds of developing kidney disease was 2.22 times that of men without such exposure.  The incidence of kidney disease was even higher among men aged 35 years or older in a physical job, with a 5.3-times increase in risk.  Another study hypothesizes that occupational heat stress with dehydration is a major risk factor for chronic kidney disease in Central America, in response to anecdotal reports of high incidence of kidney disease among young male sugarcane workers[xxxiv].  A 2016 paper suggested that climate change may lead to worldwide increases in chronic kidney disease[xxxv] [xxxvi].

In some of those who survive heat stroke, the brain may not fully recover, leaving the patient with personality changes, clumsiness, or poor co-ordination.  Estimates of the proportion of heat stroke patients affected range from ‘very rare’[xxxvii] to 20 %[xxxviii].

Exposure to heat may also have effects on fertility.  Occupational heat exposure has been reported to have adverse effects on male fertility[xxxix], affecting sperm morphology and resulting in delayed conception[xl].  There is limited human data on the effects of heat exposure on pregnant women, but animal studies suggest the possibility of heat-related infertility and teratogenicity[xli].  Studies have reported that hyperthermia can cause adverse pregnancy effects such as birth defects, but some of the information stems from women with fevers, so it is difficult to determine whether effects are caused by the heat or other metabolic changes in the mother due to the infection[xlii].

In addition, changes to the core temperature of the body can alter the absorption, distribution, excretion and metabolism of agents such as pesticides.  Increases in breathing rate can lead to increased exposure to airborne agents, and sweat and increased blood flow to the skin can lead to more efficient absorption of agents through the skin[xliii].   In general, high temperatures exacerbate the effects of many toxicants[xliv].


Several factors can influence the heat load on the body. These include:[xlv]

  • Air temperature;
  • Radiant heat;
  • Humidity;
  • Air movement;
  • The level of physical work; and
  • The amount and type of clothing being worn

There are ways that the risk of heat stress may be reduced[xlvi].  Engineering control methods include increasing ventilation, bringing in cooler outside air, reducing the hot temperature of a radiant heat source, shielding the worker from a heat source, and using air conditioning.  Administrative control measures include limiting the exposure time and temperature (work/rest timing schedules, e.g. perform outdoor tasks early in the morning) and developing heat tolerance or acclimatising.  Additional preventative strategies include establishing a heat alert program and providing auxiliary body cooling and protective clothing (e.g. water-cooled garments, air-cooled garments, cooling vests, and wetted over garments).  Employee training should include identification of the early signs and symptoms of heat illness, proper hydration, use and care of protective clothing and equipment, effects of factors such as alcohol and obesity, importance of acclimatisation and first aid.

HSE offers information and guidance about working in the heat[xlvii], heat stress[xlviii], and about outdoor work in hot and cold temperatures[xlix].   Advice for hot environments is to:

  • Reschedule work to cooler times of day
  • Provide more frequent rest breaks and introduce shading to rest areas
  • Provide free access to cool drinking water
  • Introduce shading in areas where individuals are working
  • Encourage the removal of personal protective equipment when resting to help encourage heat loss
  • Educate workers about recognizing the early symptoms of heat stress.

Information is also available from the agencies such as the Canadian Centre for Occupational Health and Safety[l], the Occupational Safety and Health Administration in the USA[li], and Work Safe in Australian states[lii]  The United States Environmental Protection Agency (EPA) offers advice on preventing heat stress in agriculture, which includes[liii]:

  • Monitor temperature and humidity, and workers’ responses at least hourly in hot environments
  • Schedule heavy work and tasks requiring personal protective equipment (PPE) for the cooler hours of the day
  • Acclimatise workers gradually to hot temperatures
  • Shorten the length of work periods and increase the length of rest periods
  • Give workers shade or cooling during breaks
  • Halt work altogether under extreme conditions.

The United States Department of Labor, provides a useful guide for employers and workers which takes into account both temperature and humidity and outlines the recommended protective measures that should be taken.

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Much of the literature regarding outdoor work in the heat is from countries such as Australia and the United States, and literature specific to the effects of heat on agricultural workers tends to be from tropical or sub-tropical regions such as India and Central America[liv].  Though this data may not be directly applicable to the UK, it should be borne in mind that both ambient temperatures and the frequency and intensity of heatwaves are likely to increase in the UK in the future.


The Workplace (Health, Safety and Welfare) Regulations 1992 says that an employer must maintain a reasonable temperature in the workplace, but it does not specify a maximum temperature. Regulation 7 states that:

‘During working hours, the temperature in all workplaces inside buildings shall be reasonable.’

The application of the regulation depends on the nature of the workplace. However, employers have general duties to ensure health and safety under the Health and Safety at Work Act 1974 to assess and control risks from work under the Management of Health, Safety, and Welfare Regulations (MHSWR).  These legal requirements cover working outside in the heat.

The Approved Code of Practice (ACoP) states that the temperature should provide reasonable comfort without the need for special clothing and where this is not possible due to hot or cold processes or access to outside, all reasonable steps should be taken to achieve a temperature as close as possible to comfortable including, insulating hot plants or pipes, providing air-cooling plant, shading windows and siting workstations away from places subject to radiant heat. If a reasonably comfortable temperature cannot be achieved throughout a workroom, local heating or cooling (as appropriate) should be provided. In extremely hot weather, fans and increased ventilation may be used instead of local cooling. Thermometers should be available at suitable locations in every part of the workplace to allow people to measure temperatures, but do not need to be provided in each workroom. Thermometers should not be located directly in front of windows or near radiant heat sources.

In relation to the PPE worn by employees, the Personal Protective Equipment (PPE) at Work Regulations require employers to consider the work environment such as the weather, if the work is outside. So, adequate protective clothing should be provided where exposure to heat is unavoidable and a hazard. Specialised personal protective clothing is available which can incorporate personal cooling systems or breathable fabrics. The use of some protective clothing or respiratory protective equipment may increase the risk of heat stress.


As with cold injuries, many cases involving heat stress injuries have been reported in relation to army personnel. This was documented in the relatively recent case of the three SAS candidates that died from heat exhaustion during a training session in the Brecon Beacons during one of the hottest days of the year in 2013. The Army reservists were in the middle of a 16.4 mile timed hike on Pen y Fan, Brecon Beacons, Wales, in soaring 29.5C temperatures when they collapsed.[lv] Lance Corporal Roberts died from heat exhaustion on the Welsh mountainside shortly after collapsing, Lance Corporal Maher was discovered not breathing and rushed to hospital where he died the same day and Corporal Dunsby, also collapsed from heat exhaustion and passed away two weeks later. Both suffered multiple organ failures as a result of heat exhaustion.

Following an investigation of the Ministry of Defence by the HSE, it was found that there had been a failure to plan, assess, and manage risks associated with climatic illness during the training. The exercise, they said, should have been called off hours before when temperatures reached record highs. At the Coroner’s inquest it was held that all three soldiers would have survived if the MoD regulations on heat illness had been followed.

An investigation into these types of injuries was conducted by the Defence Select Committee and they warned that:

‘The vast majority of injuries suffered by military personnel do not occur in battle … They should properly be seen as accidents at work and the basic principles for avoiding injury are the same as those that apply to any employer who is using potentially dangerous equipment’.

Despite this, another soldier died on a training mission in March of 2016, just after finishing an eight-mile hike carrying a rifle and 25kg of kit, almost 4st. It was thought this was related to high temperatures and dehydration.[lvi]

Whilst an investigation was carried out by the HSE into the failings of the MoD they were unable to prosecute as the Ministry is a government body. Therefore, the highest sanction they were able to give was a Crown Censure. Whilst there is no financial penalty associated with Crown Censures, they are an official recording of a failing to meet the standards set out in law.

These cases show the importance of employers following the relevant guidance for working in heat and the risks posed if there is failure to do so.


Working in hot environments poses a risk of injury to several groups of employees, including those working outdoors, in construction, agriculture and the army and those working indoors in kitchens and bakeries. The type and severity of injury suffered will depend on how soon the injury is treated. It is possible for initial heat exhaustion to develop into more severe heat stroke if left untreated.

Whilst there is no legal limit ono how high temperatures are allowed to reach in the workplace, employers are under a duty to conduct risk assessments on workplaces in order to ensure that temperatures are ‘reasonable’.  Clearly, working in high temperatures is unavoidable in some occupations, but in these instances, employers should be aware of their obligations and provide the necessary PPE and other preventative measures, in line with their statutory duties.

Another fairly common effect of working outdoors, in heat, is UV radiation. We discussed this in editions 148 and 149 of BC Disease News and we will revisit developments on this topic in future editions.


[i] United States Department of Labor, ‘Occupational Heat Exposure’ (Occupational Safety and Health Administration) <> accessed 14 June 2017.


[iii] Climate: Observations, projections and impacts (Accessed 10 May 2017)

[iv] Intergovernmental panel on climate change (Accessed 11th May 2017)

[v] Met Office. Heat-Health Watch. Available at: (Accessed: 10th May 2017)

[vi] Public Health England, Heatwave Plan for England 2013 (Accessed 10 May 2017)

[vii] Ibid No 2

[viii] CDC - Heat Stress - Heat Related Illness - NIOSH Workplace Safety and Health Topic. Available at: (Accessed: 10th May 2017)

[ix] Park, J.-S. et al. Incidence, Etiology, and Outcomes of Rhabdomyolysis in a Single Tertiary Referral Center. J Korean Med Sci 28, 1194–1199 (2013). (Accessed 11 May 2017)

[x] Met Office. Level 2 heatwave alert issued - GOV.UK. Available at: (Accessed: 10th May 2017)

[xi] Ibid No 2

[xii] Public Health England, Small increases in heat related illness reported to PHE - GOV.UK. Available at: (Accessed: 10th May 2017)

[xiii] Smith, S. et al. Estimating the burden of heat illness in England during the 2013 summer heatwave using syndromic surveillance. J Epidemiol Community Health jech–2015–206079 (2016). doi:10.1136/jech-2015-206079

[xiv] Heat-related deaths projected to increase in the UK, February 2014 (Accessed 10 May 2017)

[xv] Hajat, S., Vardoulakis, S., Heaviside, C. & Eggen, B. Climate change effects on human health: projections of temperature-related mortality for the UK during the 2020s, 2050s and 2080s. J Epidemiol Community Health 68, 641–648 (2014).

[xvi] British Heart Foundation: Protect Your Heart in the Heat. Available at: (Accessed: 10th May 2017)

[xvii] Hot weather and your heart. Available at: (Accessed: 10th May 2017)

[xviii] Davídkovová, H., Plavcová, E., Kynčl, J. & Kyselý, J. Impacts of hot and cold spells differ for acute and chronic ischaemic heart diseases. BMC Public Health 14, 480 (2014).

[xix] Cui, J. & Sinoway, L. I. Cardiovascular responses to heat stress in chronic heart failure. Curr Heart Fail Rep 11, 139–145 (2014).

[xx] CDC - Heat Stress - NIOSH Workplace Safety and Health Topic. Available at: (Accessed: 10th May 2017)



[xxiii] Heat Illness and Death Among Workers — United States, 2012–2013. Available at: (Accessed: 10th May 2017)

[xxiv] Jay, O. & Brotherhood, J. R. Occupational heat stress in Australian workplaces. Temperature (Austin) 3, 394–411 (2016).

[xxv] Heat Illness and Death Among Workers — United States, 2012–2013. Available at: (Accessed: 10th May 2017)

[xxvi] On the search for rhabdomyolysis cases. FG Insight Available at: (Accessed: 10th May 2017)

[xxvii] Farmers suffering mysterious illness asked to come forward Farmers Weekly 22 November 2016 (Accessed 10th May 2017)

[xxviii] Exercise-Related Heat Exhaustion - Health Encyclopedia - University of Rochester Medical Center. Available at: (Accessed: 10th May 2017)

[xxix] Wallace, Robert F., David Kriebel, Laura Punnett, David H. Wegman, and Paul J. Amoroso. “Prior Heat Illness Hospitalization and Risk of Early Death.” Environmental Research 104, no. 2 (June 2007): 290–95. doi:10.1016/j.envres.2007.01.003.

[xxx] Carvalho, A. S., Rodeia, S. C., Silvestre, J. & Póvoa, P. Exertional heat stroke and acute liver failure: a late dysfunction. BMJ Case Reports 2016, bcr2016214434 (2016). (Accessed 11th May 2017)

[xxxi] Garcin, J., Bronstein, J., Cremades, S., Courbin, P. & Cointet, F. Acute liver failure is frequent during heat stroke. World J Gastroenterol 14, 158–159 (2008). (accessed 11th May 2017)

[xxxii] Salathé, C., Pellaton, C., Carron, P.-N., Coronado, M. & Liaudet, L. Acute liver failure complicating exertional heat stroke: possible role of hypophosphatemia. Curr Sports Med Rep 14, 49–50 (2015). (Accessed 11th May 2017)

[xxxiii] Tawatsupa, B., Lim, L. L.-Y., Kjellstrom, T., Seubsman, S. & Sleigh, A. Association Between Occupational Heat Stress and Kidney Disease Among 37 816 Workers in the Thai Cohort Study (TCS). J Epidemiol 22, 251–260 (2012). (Accessed 11th May 2017)

[xxxiv] Wesseling, C. et al. Heat stress: a cause of chronic kidney disease along the Mesoamerican west coast? Occup Environ Med 68, A66–A66 (2011).

[xxxv] Glaser, J. et al. Climate Change and the Emergent Epidemic of CKD from Heat Stress in Rural Communities: The Case for Heat Stress Nephropathy. CJASN CJN.13841215 (2016). doi:10.2215/CJN.13841215

[xxxvi] Truong, K. Climate change may be causing chronic kidney disease by triggering dehydration and heat stress. The George Institute for Global Health (2016). Available at: (Accessed: 11th May 2017)

[xxxvii] Royburt, M., Epstein, Y., Solomon, Z. & Shemer, J. Long-term psychological and physiological effects of heat stroke. Physiol. Behav. 54, 265–267 (1993). (Accessed 11th May 2017)

[xxxviii] Heatstroke - Injuries and Poisoning. Merck Manuals Consumer Version Available at: (Accessed: 10th May 2017)

[xxxix] Jensen, Tina Kold, Jens Peter Bonde, and Michael Joffe. “The Influence of Occupational Exposure on Male Reproductive Function.” Occupational Medicine 56, no. 8 (December 1, 2006): 544–53. doi:10.1093/occmed/kql116.

[xl] Thonneau, P., L. Bujan, L. Multigner, and R. Mieusset. “Occupational Heat Exposure and Male Fertility: A Review.” Human Reproduction 13, no. 8 (August 1, 1998): 2122–25. doi:10.1093/humrep/13.8.2122.

[xli] NIOSH 2016 as above

[xlii] Edwards, Marshall J. “Review: Hyperthermia and Fever during Pregnancy.” Birth Defects Research Part A: Clinical and Molecular Teratology 76, no. 7 (July 1, 2006): 507–16. doi:10.1002/bdra.20277.

[xliii] Leon, Lisa R. “Thermoregulatory Responses to Environmental Toxicants: The Interaction of Thermal Stress and Toxicant Exposure.” Toxicology and Applied Pharmacology, 2007 Toxicology and Risk Assessment Conference: Emerging Issues and Challenges in Risk Assessment2007 TRAC, 233, no. 1 (November 15, 2008): 146–61. doi:10.1016/j.taap.2008.01.012.

[xliv] Gordon, Christopher J. “Role of Environmental Stress in the Physiological Response to Chemical Toxicants.” Environmental Research, Contains papers from the 2001 APS Symposium on “Combined impact of exercise and temperature stress on the physiological response to toxic agents,” 92, no. 1 (May 2003): 1–7. doi:10.1016/S0013-9351(02)00008-7.

[xlv] Health and Safety Executive, ‘ Prevention of Heat Illness In Mines’ (HSE)<> accessed 14 June 2017.

[xlvi] NIOSH [2016]. NIOSH criteria for a recommended standard: occupational exposure to heat and hot environments. By Jacklitsch B, Williams WJ, Musolin K, Coca A, Kim J-H, Turner N. Cincinnati, OH: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication 2016-106

[xlvii] Temperature. Available at: (Accessed: 10th May 2017)

[xlviii] HSE – Heat stress in the workplace, A brief guide, 2013 (Accessed: 10th May 2017)

[xlix] HSE - Temperature: Outdoor working. Available at: (Accessed: 10th May 2017)

[l] Government of Canada, C. C. for O. H. and S. Maximum Temperature Limit for Working : OSH Answers. (2017). Available at: (Accessed: 10th May 2017)

[li] Government of Canada, C. C. for O. H. and S. Maximum Temperature Limit for Working : OSH Answers. (2017). Available at: (Accessed: 10th May 2017)

[lii] Guidance note, Working in heat.  Worksafe Victoria. (Accessed 10th May 2017)

[liii] US EPA, O. Preventing Heat Stress in Agriculture. Available at: (Accessed: 10th May 2017)

[liv] Xiang, Jianjun, Peng Bi, Dino Pisaniello, and Alana Hansen. “Health Impacts of Workplace Heat Exposure: An Epidemiological Review.” Industrial Health 52, no. 2 (2014): 91–101. doi:10.2486/indhealth.2012-0145.

[lv] David Barrett, ‘Ministry of Defence Escapes Prosecution Over SAS Heat Deaths’ (The Telegraph 2 March 2016)<> accessed 14 June 2017.

[lvi] David Connett, ‘MoD Negligence “Causes Injuries To Hundreds of Military Personnel A Year”’ (Independent 5 December 2015)<> accessed 14 June 2017.