NEW DELHI: Heat stress induced by climate change decreases work productivity, a report brought out by the UN health and climate agencies says, adding that the productivity of workers in extreme heat drops by two to three per cent for every degree above an ambient temperature of 20°C.
According to the report from the World Health Organization (WHO) and the World Meteorological Organization (WMO), approximately half of the global population suffers adverse effects due to high temperatures. The report, titled ‘Climate Change and Workplace Heat Stress,’ emphasises that the frequency and intensity of extreme heat events have risen sharply, posing increased risks to both outdoor and indoor workers, particularly in developing countries like India.
It notes that daily fluctuations in weather and seasonal changes create a double burden for workers -- they earn less due to reduced capacity while also facing higher expenses for health-related issues. “Heat stress is already harming the health and livelihoods of billions of workers, especially in the most vulnerable communities,” said Dr Jeremy Farrar, WHO Assistant Director-General for Health Promotion, Disease Prevention, and Care.
The analysis reveals that each hourly increase in Wet Bulb Globe Temperature (WBGT)—an indicator used to measure the effects of heat stress on the human body—during the daytime causes a reduction in work capacity for those in heat-exposed jobs. The report indicates that productivity decreases by 2–3% for every degree above 20°C.
In the case of India, the report shows that early-day temperature rises drastically reduce working capacity for indoor and outdoor jobs. Work capacity tends to decline until midday and then gradually increases as temperatures decrease.
Under normal conditions, a healthy individual can maintain core body temperature between 36.5°C and 37.5°C. However, rising temperatures due to climate change disrupt this balance, particularly during exposure to hot environments or physical exertion.
Increased temperatures elevate health risks, including heatstroke, dehydration, kidney dysfunction, and neurological disorders, all of which threaten long-term health and economic security.
The report calls for the implementation of occupational heat action plans tailored to specific industries and regions, developed in collaboration with employers, workers, unions, and public health experts to address this challenge.
“Occupational heat stress has become a global societal challenge, which is no longer confined to countries located close to equator – as highlighted by the recent heatwave in Europe,” said WMO Deputy Secretary-General Ko Barrett. “Protection of workers from extreme heat is not just a health imperative but an economic necessity.”.