Workers are feeling the heat – so, what are we doing to help?

While the media rages with reports of the devastation caused by wildfires, storms, droughts and crop failures, IOSH’s Dr Karen Michell considers the impact of extreme weather events and excessive heat on workers – and what employers and OSH professionals can do to help protect them.

Dramatic headlines and film footage of the climate crisis shout at us on almost a daily basis. Yet the impact all this is having on the world’s workers, many of whom are continuously exposed to extreme heat simply to make a living, is expressed in not much more than a whisper.

Consequently, the dangers of heat exposure, though increasingly significant, remain an underappreciated occupational risk, despite it causing worryingly adverse health outcomes. It’s a risk intensified by climate change. Global analysis estimates heat extremes could be responsible for almost half a million excess deaths each year. In particular, at temperatures above 27oC, the daily mortality rate increases more rapidly with each one-degree rise compared with when the temperature drops, thereby emphasising the impact of high temperatures.

While anyone can be affected by heat-related illness, some population cohorts are more vulnerable. Heat exposure leads to an elevated risk of both morbidity (illness or disease) and mortality (death) for women, older workers (over 65yrs), those with underlying medical conditions, those in low-middle income countries and urban populations. A vulnerable cohort includes workers who are exposed to extreme heat by virtue of their occupational activities.

Medical conditions

Occupational health and safety professionals are familiar with medical conditions directly associated with extreme heat, such as heat rash, heat syncope (fainting), heat cramps, heat exhaustion and life-threatening heatstroke. Other lesser-known morbidities associated with heat exposure include chronic respiratory disease exacerbations, cardiovascular disease, kidney disease, preterm labours, food-and water-borne infectious diseases and increased mental ill health, including suicide and suicidal behaviour.

A meta-analysis from 40 counties, covering 447 million workers in all occupations, found that 15 per cent of workers who typically or frequently worked in heat stress conditions had kidney disease or acute kidney injury; 35 per cent of workers who worked a single shift had occupational heat strain; and 30 per cent had losses in productivity which increased by 2.6 per cent for every one degree increase beyond 24oc Wet Bulb Globe Temperature (WBGT – a measure of heat stress in direct sunlight).

There is a dearth of evidence-based literature on prevention measures that effectively lower the total heat-related burden on disease and death. The available evidence focuses on high income areas where the least vulnerable populations are located. The following are, however, interventions that have been deemed effective at local level, while acknowledging the challenges experienced in implementing them.

Regulation and legislation

The risk of heat-related illness is increased by the lack of regulations or enforcement of regulations to protect exposed workers. Recommendations to prevent adverse health effects are manifold (ie providing rest, shade and water; training; acclimatisation) but these are often poorly enforced. For example, regulation to limit work hours in summer peak times (eg stopping work between 11H30 and 15H00) has been shown to be poorly enforced in the construction sector. The disparate geographical patterns of temperature-related mortality and morbidity burden are important considerations when developing policies and strategies for worker health protection.

Work activity

Work activities can be adjusted to reduce exposure to daily heat peaks or seasonal heat concerns (eg early starts to avoid the hottest hours of the day). The application of basic occupational health principles, such as supplying drinking water, work-rest regimes and the training of workers and supervisors, is essential. In addition, providing shade; acclimatisation programmes; developing a system to monitor for signs of heat related injury; rescheduling non-essential work; closely monitoring workers’ vital signs; and strictly enforcing work/rest cycles are effective in reducing physiological workload/strain and hence heat related injury.

Quantitative occupational exposure assessments, such as physiological workload via continuous heart rate monitoring, are essential to identify exposure risk for workers as well as the efficacy of workplace interventions. Employers need to develop and implement health surveillance programmes that can detect early physiological responses to heat related injury among vulnerable workers. Mechanisation can be introduced to labour-intensive activities to reduce the level of physical activity required by workers.

Personal protection

All existing heat indices assume an average or standard person who is heat acclimatised, adequately hydrated, unmedicated, fit and healthy. While thresholds for a standard person help identify safe boundaries for a heat stress management system, individual differences blur the boundaries and make it necessary to adapt systems to enable individual coping and protection of vulnerable workers. Recent technological advancements have led to the development of personal cooling systems, such as personal cooling vests that can provide a convenient and flexible method to reduce heat stress and improve thermal comfort among working populations.

Organisational culture

Discretionary differences that result in low and middle management prioritising production over health protection appear to account for a fair share of the implementation challenges. They indicate that more efforts are needed to align operational requirements, production and health goals. The piecework pay system, such as that used in the agricultural sector and construction, is a factor undermining efforts devoted to heat-related safety interventions. Piecework places workers in a situation where they prioritise their immediate income against longer-term health, often neglecting safety regulations.

Knowledge, attitudes and practice

What do our workers know and understand about heat symptoms? Research has shown that if workers know the symptoms of both heat exhaustion and heat stroke it will increase the likelihood of workers reporting these symptoms. The concern, however, lies in the fact that many workers do not understand the symptoms associated with heat stress and will therefore not report them, not act when they are experienced and may well fall victim to the adverse health outcomes. Workers have to know about the adverse effects of heat exposure and need to be equipped with the necessary tools to respond appropriately.

Based on the actions, or lack of action, coming from the political arena, the extremes of heat exposure aren’t going to be resolved any time soon. As OSH professionals, it’s our ethical and moral responsibility to ensure that not only are we developing the correct health management strategies on paper, but that they are implemented effectively for the benefit of our workers.

Dr Karen Michell,
IOSH Research Programme Lead – Occupational Health

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Jeremy Waterfield
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