Humanity is suffering an "extreme heat epidemic," UN Secretary-General Antonio Guterres warned on Thursday, calling for action to limit the impacts of heat waves intensified by climate change.
"Billions of people are facing an extreme heat epidemic -- wilting under increasingly deadly heat waves, with temperatures topping 50 degrees Celsius around the world," he said. "That's 122 degrees Fahrenheit. And halfway to boiling."
Data from the United Nations' International Labour Organization shows that more than 70 percent of the global workforce was exposed to excessive heat during 2020 -- up nearly nine percent from year 2000.
In a fresh report breaking down the heat stress by region, ILO showed unexpectedly that Africa was hardest hit, with nearly 93 percent of workers suffering from excessive heat exposure on the job, followed by the Arab states at 83.6 percent and Asia and the Pacific at 74.7 percent.
But at a time when human-induced climate change is seen driving global temperatures ever higher, with last year by far the hottest ever recorded, the fastest changing working conditions were seen in regions not traditionally impacted by extreme heat.
Excessive heat exposure at work swelled the most in Europe and Central Asia, jumping 17.3 percent over the 20-year period to 29 percent, the ILO report found.
At the same time, the Americas, along with Europe and Central Asia, were found to have the most rapidly increasing proportion of heat-related occupational injuries, swelling 33.3 and 16.4 percent respectively over the two decades.
"Countries previously unaccustomed to extreme heat will face unfamiliar threats which they may be ill-equipped to deal with, while conditions in regions already contending with sustained high temperatures will only deteriorate," the report said.
At a global level, nearly 23 million occupational injuries attributed to excessive heat are reported each year, costing, on estimate, nearly 19,000 lives annually, the ILO said in a report published earlier this year.
At the time, it warned that climate change and excessive heat brought "a cocktail of hazards" for workers.
"Heat is an invisible force - a silent killer," Tuesday's report cautioned.
It said heat hazards both for indoor and outdoor work increases the "risk of health impacts such as heat exhaustion, heat stroke, cardiovascular and respiratory conditions, and death".
"As record-breaking temperatures continue across various regions, more workers than ever before are losing the fight against excessive heat."
The report highlighted the impact of heatwaves, which account for about 10 percent of overall excessive heat exposure globally, and which it said had cost 4,200 workers their lives in 2020.
In total, 231 million workers were exposed to heatwaves that year -- a 66-percent hike from 2000.
Europe, Central Asia and the Americas saw the fastest increase in exposure to excessive heat on the job during heatwaves, with around 78.5 percent of such exposure happening during heatwaves, the ILO report said.
"Excessive heat is creating unprecedented challenges for workers worldwide year-round, and not only during periods of intense heatwaves," Vera Paquete-Perdigao, head of ILO's governance department which produced the report, said in a statement.
Manal Azzi, head of ILO's occupational safety and health division, called for action.
"We need year-round heat action plans and legislation to protect workers, and stronger global collaboration among experts to harmonise heat stress assessments and interventions at work," she said.
According to the report, improved safety and health measures to prevent injuries from excessive heat in the workplace could save up to $361 billion globally in lost income and medical treatment expenses.