The synergies of heat stress and air pollution and their health impacts

This technical brief summarizes priority actions for the short, medium and long term to protect public health from heat stress and air pollution, and provides success stories of addressing these issues jointly. It forms part of the World Health Organization's (WHO) Air Quality, Energy, and Health Science and Policy Summaries (SPS). These summaries provide concise overviews of current knowledge and evidence on air quality, energy access, climate change, and health. They aim to support decision-makers by presenting key insights from scientific research.

The key messages include that projections indicate climate change will result in more frequent and intense extreme weather events in the coming decades. This will include an increase in the frequency, duration, intensity, and magnitude of heatwaves. Heat impacts health directly and acutely. Increases in mortality associated with high temperatures, particularly heatwaves, have been documented around the world. In particular, outdoor and manual workers and civil protection personnel are exposed to excessive heat, making them vulnerable to exertional heat stress. Lastly, heat increases the levels of some air pollutants, such as ozone. In addition, recent studies indicate that high levels of fine particulate matter and ozone augment the health impacts of heat. Thus, there are many joint effects of the air pollution and heat stress interaction.

The priority actions for short-term health benefits include adaptation measures and protection of the vulnerable; and for long-term health benefits, they include reducing ambient air pollution and mitigating the occurrence of extreme heat.