Climate Change and Workplace Heat Stress: Technical Report and Guidance

Abstract

Climate change implies that the health challenge associated with environmental heat stress will increase in intensity, and its direct as well as indirect negative effects will spread geographically. Adverse consequences of high environmental temperatures are currently experienced by approximately half the global population. They particularly affect health and quality of life for the most vulnerable citizens in developing countries, with children, older adults, and people living in poverty at highest risk of death and disease during extreme heat events. However, it is important to address the major negative health and productivity effects experienced by millions of manual workers exposed to workplace heat stress on a daily basis. These effects may affect not only individual livelihoods, but also family income and jeopardize the reduction of poverty—particularly in regions highly dependent on manual work, such as the agriculture, construction, and fishing sectors.

Executive Summary

Climate change implies that the health challenge associated with environmental heat stress will increase in intensity, and its direct as well as indirect negative effects will spread geographically.

Adverse consequences of high environmental temperatures are currently experienced by approximately half the global population.

They particularly affect health and quality of life for the most vulnerable citizens in developing countries, with children, older adults, and people living in poverty at highest risk of death and disease during extreme heat events. However, it is important to address the major negative health and productivity effects experienced by millions of manual workers exposed to workplace heat stress on a daily basis. These effects may affect not only individual livelihoods, but also family income and jeopardize the reduction of poverty—particularly in regions highly dependent on manual work, such as the agriculture, construction, and fishing sectors. ¹

Available Evidence

The present guidance provides an overview and update of relevant evidence generated since 1969, when the technical guidance health factors involved in working under conditions of heat stress was published by the World Health Organization.

The World Meteorological Organization has reported that 2024 was the warmest year on record, with the global temperature averaging 1.45 °C above preindustrial levels. The past 10 years (2015-2024) have been the warmest on record, underscoring the continuing long-term trend of rising global temperatures due to climate change. The rise in global temperatures and especially the increased frequency of extreme heat events during the five decades since the publication of that seminal guidance underscore the need to update stakeholders. This guidance describes increased exposure risks, new discoveries, and novel methodologies in the area of workplace heat stress, and evidence on solutions to prevent or minimize its negative consequences.

In the last decade, many studies have provided conclusive evidence that workplace heat stress directly threatens workers’ ability to live healthy and productive lives and leads subsequently to worsening poverty and socioeconomic inequality. The World Health Organization and the World Meteorological Organization recognize the undeniable increased exposure of workers to warmer conditions. In response, they have supported the development of this guidance as a frame of reference for managing workplace heat stress and mitigating its impacts on health and productivity. The guidance aims to summarize the latest scientific evidence and provide examples of effective interventions and practices for public health policymakers, employers, workers, and health service providers.

Conclusions and Recommendations

Exposure to heat has become a common problem for almost half the global population, as they live in areas where high environmental temperatures affect nearly all daily activities. In the context of climate change, exposure to workplace heat stress will further increase. Workers are at high risk of adverse consequences from global warming of 1.5 °C or more ² (311).

The present guidance provides practical information on both gaps and priorities in research, legislation, and practices. More importantly, it identifies the roles of the health, labor, and meteorological services in identifying risks and protecting workers.

To manage workplace heat stress and mitigate its impacts on health and productivity, public health policymakers should collaborate with scientists, meteorological services, health service providers, as well as organizations of employers and workers, while considering and acting on the following issues:

A combination of interventions for preventing exposure and health surveillance of workers can reduce workplace heat stress exposure, manage physiological heat strain, and prevent short- and long-term health effects.

Reducing the risks of physiological heat strain caused by workplace heat stress requires developing and implementing specific programs for workers and workplaces at risk.

To enhance the specificity of prospective guidelines related to workplace heat stress, heat-health advisories should be designed to address not only the weather conditions but also clothing, as well as the type, intensity, and duration of work. Another work-related factor of importance is whether the work is paid by piece or by the hour, as this determines workers’ motivation to continue working despite higher heat stress. Finally, heat-health advisories should also consider the adaptive strategies available to the workers. These factors should also help shape the direction of future research.

Certain population groups, such as middle-aged and older individuals, those who are physically unfit, and people with common chronic health conditions, are more vulnerable to the physiological strain caused by workplace heat stress. Relevant advisories and legislation must address the increased vulnerability of these populations.

Many mild and severe health outcomes are associated with workplace heat stress. While the treatment for most of these conditions is well known, they are often misdiagnosed, which can have serious negative effects on the patient's health. It is vital that the pathophysiology and treatment for these conditions receive greater emphasis in medical and health-related education.

The development of occupational heat-health recommendations and policies must involve key stakeholders, including managers and employers, workers, trade unions, representatives of self-employed persons, experts in environmental, physiological, ergonomic safety, health and safety representatives, occupational health experts, and representatives from local authorities. Engagement with the general public is also highly desirable.

The overall aim of occupational heat-health recommendations and policies should be to reduce workplace heat stress. However, it is also imperative to consider the practical feasibility, economic viability, and environmental sustainability of the recommended strategies. These should include elements related to workplace heat stress prevention policy, heat acclimatization, environmental and medical monitoring, training and education, and emergency response planning, as well as job-specific controls.

The use of technological solutions should be researched further to augment both workplace safety and productivity.

Future research should evaluate the efficacy of occupational heat-health advisories and relevant policies to ensure the highest level of protection for workers.

Policies and actions to reduce the extent of climate change will significantly contribute to protecting working populations from excessive heat in the future.