Heat, air pollution and solar ultraviolet radiation: mass gathering-specific considerations and research gaps

The annually averaged global mean near-surface temperature in 2024 was 1.55 °C ± 0.13 °C above the 1850–1900 average. This made it the warmest year in the 175-year observational record, beating the previous record set only the year before. The problem of extreme heat, however, does not exist in isolation. As temperatures rise, air pollution levels can also increase and deplete the ozone layer, allowing more dangerous solar ultraviolet (UV) radiation. Workers and attendees at sports events and mass gatherings are especially vulnerable to extreme heat, air pollution and solar UV exposure.

The document aims to synthesize existing WHO and other United Nations (UN) guidance on heat, air pollution and solar UV radiation in mass gathering settings, identify knowledge gaps and help draft a research agenda for future evidence review and subsequent development of guidance and tools for mass gathering events.

The target audience includes hosting governments or organizations, other programmes and agencies involved in mass gatherings, such as decision-makers at international, national, regional and municipal levels; government officials; higher-level policymakers; key actors such as staff at subnational and municipal levels; community health workers and nongovernmental organizations planning or managing mass gatherings.