2023 was the hottest year on record; 2024 is set to be even hotter. The rise in climate change-driven occupational heat stress is putting the health and livelihoods of workers at grave risk.1 2 The number of workers suffering the consequences of excessive heat is alarming. An International Labor Organization (ILO) report in 2024 has shown that at least 71% of the global working population are exposed to excessive heat leading to almost 23 million injuries and 19 000 deaths every year.3 Another 2024 ILO report has shown that workers in Africa (92.9%), the Middle East (83.6%) and Asia and the Pacific (74.7%) were the most exposed to excessive heat.4 Meanwhile, the Americas and Europe have experienced the steepest increases in heat-related workplace injuries since 2000 with a rise of 33.3% and 16.4%, respectively.4 Recent reports of regulatory violations5 and media stories6 7 have highlighted the preventable loss of life due to hazardous heat exposure while at work across various regions previously unaccustomed to this level of heat.
In response to this escalating global crisis, the US occupational health regulatory agency, the Occupational Health and Safety Administration (OSHA), has taken the lead by issuing a newly proposed comprehensive rule addressing heat-related occupational hazards in the USA (https://www.osha.gov/heat-exposure/rulemakin g ). Under this new rule, OSHA would apply two heat index thresholds nationally factoring in temperature and humidity. At 80°F (26.7°C), employers would be required to provide drinking water and break areas. More protections would kick in at 90°F (32.2°C) including monitoring for signs of heat illness and mandatory 15-min rest breaks every 2 hours. The rule offers an option for employers to use thresholds previously developed by the US federal occupational health research arm, the National Institute for Occupational Safety and Health (NIOSH). This option would use the wet bulb globe temperature (WBGT) and the metabolic work rate of the job. This optional approach aligns WBGT thresholds with the work intensity of physical labour to establish appropriate work–rest schedules.8