Planning for Survival: Protecting Public Health at Mass Gatherings in a Changing Climate

The WHO report warns that climate change is making mass gatherings increasingly dangerous, with extreme heat, air pollution and solar UV radiation posing serious health risks to crowds, workers and visitors, especially those from cooler climates. It calls for proactive planning, better communication and integrated health systems so major events are designed around environmental safety, not just logistics.

Produced by the World Health Organization with contributions from the World Meteorological Organization, the International Labour Organization, the International Olympic Committee, UN agencies, national public health institutes and universities across Europe, Asia, Australia and the Americas, the 2025 report examines how climate change is transforming the health risks of mass gatherings. With 2024 confirmed as the hottest year on record, the document argues that events such as sports tournaments, religious pilgrimages, music festivals and political rallies now take place in an era of routine environmental stress. These gatherings concentrate large numbers of people, often outdoors, often during hot seasons, and often far from familiar health systems, making them especially vulnerable to extreme heat, air pollution and solar ultraviolet radiation.

Heat: the most urgent and visible danger

Extreme heat is identified as the most immediate threat at mass gatherings. High temperatures can cause illness and death within hours or days, leaving little time to react once a crisis begins. Risk is shaped by age, chronic illness, medication use, disability and social isolation, but mass gatherings create new vulnerable groups. Visitors from cooler climates, pilgrims, volunteers and temporary workers may experience heat stress at lower temperatures than local residents. Long queues, crowd density, lack of shade, limited water access and physical exertion increase danger even for otherwise healthy people. The report stresses that standard heat–health warning systems are not enough for planned events. Instead, heat risk must be managed proactively through event design, including shaded spaces, cooling areas, water stations, adjusted schedules and clear, multilingual communication.

Air pollution: an invisible but deadly companion

Air pollution is described as both a chronic global killer and an acute event-level risk. Polluted air worsens heart and lung disease and can trigger sudden spikes in hospital admissions, especially during hot weather when ozone and fine particles increase. Mass gatherings can intensify pollution through traffic surges, construction, generators and fireworks, while encouraging heavy physical activity that increases breathing rates. Although WHO air quality guidelines exist, the report notes that air quality information is often confusing or poorly communicated to the public. Air Quality Indices may not clearly explain health risks. Authorities are encouraged to plan events in cleaner locations or seasons where possible, integrate air quality monitoring with heat alerts, and provide simple, actionable advice, especially for children, older adults and people with chronic illness, while being mindful of equity and the limits of personal protective measures.

Solar UV radiation: a neglected outdoor risk

Solar ultraviolet radiation receives less attention than heat or pollution but remains a serious health hazard at outdoor events. UV exposure can cause sunburn, eye damage, skin ageing and cancer, with risks rising near the equator, at high altitude and around reflective surfaces such as water or sand. Visitors from low-UV countries are particularly vulnerable. The report finds that many mass gatherings lack adequate shade, visible UV risk information or access to sunscreen and protective clothing. It highlights the Global Solar UV Index as a useful but underused tool and calls for sun protection to be built into event planning through shaded areas, schedule adjustments, clear signage and free or affordable protective items.

Planning, communication and the road ahead

Beyond individual hazards, the report emphasizes that environmental health risks at mass gatherings are governance challenges. Effective protection requires coordination between health authorities, meteorological services, emergency responders, event organizers, transport agencies and media. Communication must be simple, multilingual and delivered through event-specific channels such as tickets, mobile apps, venue screens, signage and trained staff, rather than relying only on traditional media. Surveillance systems must also adapt to track health problems among visitors and temporary workers who are not part of local registries. The report concludes by highlighting major research gaps, including low-cost cooling solutions, better crowd heat management, improved risk communication tools and stronger evidence on air pollution interventions. Overall, it argues that mass gatherings should now be planned as climate-sensitive public health systems, not just logistical events, in a warming and more polluted world.