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Geneva, Switzerland – A new comprehensive report from the World Health Organization (WHO) and the World Meteorological Organization (WMO) issues a stark warning about the escalating health and economic impacts of workplace heat stress, a global challenge intensified by climate change. Billions of workers are already at risk, facing a spectrum of illnesses, injuries, and significant productivity losses that jeopardize individual livelihoods and national economies.
The report, titled “Climate change and workplace heat stress: technical report and guidance,” highlights that occupational heat stress is no longer confined to equatorial regions but has become a worldwide concern, with its consequences expected to worsen significantly with continued global warming.
Devastating Health Repercussions for Workers
Workplace heat stress leads to physiological heat strain, which can manifest in exhaustion, pathological conditions, and even death. Over one-third of individuals who frequently work in hot conditions experience these symptoms. The health impacts range from mild to life-threatening:
- Mild Health Outcomes: These commonly include heat fatigue, where physical effort feels more strenuous due to blood diversion for cooling; miliaria (heat rash); heat syncope (dizziness/fainting) caused by insufficient blood flow to the brain; heat cramps (painful muscle spasms); and heat oedema (swelling of peripheral blood vessels). While often resolving with rest and rehydration, they signal underlying strain.
- Severe Health Illnesses (Serious Heat Illness): These demand immediate medical attention due to the risk of tissue and organ damage.
- Heat exhaustion is characterized by cardiovascular dysfunction and/or dehydration, often with hyperthermia (core body temperature ≥39°C), increasing the likelihood of damage to organs like kidneys and liver.
- Heat stroke is a life-threatening condition defined by profound central nervous system dysfunction (e.g., severe disorientation, seizures, coma), severe hyperthermia (usually ≥40°C), organ/tissue damage, and often coagulopathy and systemic inflammatory response syndrome. It can be fatal.
- Fluid and electrolyte imbalances such as hypohydration, dehydration, hypernatraemia, and hyponatraemia frequently accompany heat stress, impairing work capacity and nervous system function, and increasing morbidity and mortality risk.
- Other severe effects can include dermatoses, acute/chronic kidney injury, kidney stones (urolithiasis), and heat-induced dyslipidaemia. In 2020 alone, an estimated 26.2 million people lived with chronic kidney disease attributable to workplace heat stress.
- Chronic Health Consequences: After severe heat illnesses, victims face significant long-term morbidity and mortality. Heat exhaustion can cause damage persisting for weeks, while heat stroke often leads to skeletal muscle, organ (liver, kidney, cardiac, central nervous system), and systemic pathologies that may take months or longer to resolve, leaving residual damage. Heat stroke victims are at a greater risk of death from ischaemic heart disease (rate ratio: ~2.2) and other cardiovascular diseases (rate ratio: ~1.7) within 30 years, and a higher incidence of major cardiovascular events (hazard ratio: ~3.9), ischaemic stroke (hazard ratio: ~5.5), and atrial fibrillation (hazard ratio: ~15) over a 14-year follow-up period.
- Mental Health Impacts: Working in hot environments can significantly increase fatigue, irritability, and lethargy, and impair judgment, concentration, vigilance, dexterity, and coordination. Workplace heat stress is associated with increased psychological distress (adjusted odds ratio: 1.84), and can undermine human information processing and psychomotor capacities by about 10%.
- Occupational Injuries and Fatalities: The sheer scale of exposure is alarming, with more than 2.4 billion workers exposed to workplace heat stress globally, leading to over 22.85 million occupational injuries and 18,970 fatalities worldwide annually. Cognitive impairments induced by heat stress are a major contributing factor to unsafe behaviors and accidents. The International Labour Organization (ILO) estimates that 2.09 million disability-adjusted life years (DALYs) are directly linked to excessive heat at work each year.
Crippling Economic Losses
Beyond the human toll, workplace heat stress inflicts substantial economic damage, primarily through significant loss of labour productivity. This negatively impacts individual livelihoods, family incomes, and national economies.
- A systematic review found that 30% of workers frequently exposed to heat stress report labor productivity losses.
- Worker productivity decreases by 2–3% for every degree increase beyond 20°C in wet-bulb globe temperature (WBGT). More recent data suggest an average 2.4% decline for every degree increase beyond 15°C WBGT.
- For occupations involving moderate-intensity work in the worst-affected countries, annual work hour losses currently range from 2% to 4%, with projections indicating an increase to between 8% and 11% by the end of the century under current climate change policies (RCP6.0). These losses account for necessary breaks and reduced work pace to prevent acute health effects.
- The economic impacts are most pronounced in countries, industries, and for individuals directly reliant on manual labor, such as those in the agriculture, construction, and fishing sectors, thereby jeopardizing poverty reduction efforts.
- Furthermore, there are indirect and broader geographical and economic impacts on distal sectors, such as those that rely on stable food prices and value chains affected by primary sector productivity.
The report underscores the urgent need for greater mobilization across government sectors, civil society, employers, and workers to implement effective prevention and mitigation strategies. As temperatures continue to rise, proactive measures and robust occupational heat action plans are crucial to protect workers’ health and ensure productive lives for all.
Disclaimer: The information in this article is drawn from the specified technical report and guidance. It is intended for general informational purposes and does not constitute medical or professional advice. Readers should consult with qualified professionals for specific health concerns or workplace safety guidance.
Reference: World Health Organization and World Meteorological Organization. Climate change and workplace heat stress: technical report and guidance. Geneva: World Health Organization and World Meteorological Organization; 2025.
https://www.who.int/publications/i/item/9789240099814
