How do wildfires affect health and what can be done about it?

For people living in the northern hemisphere, this summer has been beset by deadly wildfires across parts of Europe, the U.S. and Canada. In the U.K., more than 21,000 hectares (52,000 acres) had already burned by late July 2026 across 66 fires larger than 30 hectares (74 acres), while England and Wales recorded their driest July in nearly two centuries and many areas moved into official drought.

Across Europe, Greece, Spain, France and the Netherlands are simultaneously fighting major fires, with Spain reporting more than 186,000 hectares (460,000 acres) burned since January.

Dr. Kamal Jyoti Maji, research fellow at the London School of Hygiene & Tropical Medicine, explains why wildfires are so toxic and dangerous and how to reduce harm.

How do wildfires affect health?

Wildfires affect health in a range of ways, and the immediate danger of flames is only one of them. The most direct harms are injury and death, destruction of homes and infrastructure, and the disruption evacuation causes to ongoing health care, particularly for people who rely on regular treatment.

For the wider population, however, the main public health impact comes from smoke inhalation. Fine particulate matter, or PM_2.5 (particles 30 times smaller than the width of a human hair), and other combustion pollutants can travel far beyond the fire itself. These particles have been linked to increased respiratory and cardiovascular illness, hospital admissions and premature death. A global analysis estimated that landscape-fire-related PM_2.5 is associated with substantial excess mortality worldwide each year.

Wildfires also typically coincide with heat wave and drought conditions that are themselves dangerous. When heat, drought and fire smoke combine, as they are across Europe this summer, the cumulative health burden is greater than that of any single hazard alone.

There is also growing evidence on the psychological toll of wildfires, such as anxiety, trauma and a sense of loss due to repeated damage to familiar landscapes. This matters for people living through recurrent fire seasons even where physical exposure to smoke is limited.

What makes wildfire smoke particularly toxic?

Wildfire smoke is a complex mixture dominated by fine particulate matter (PM_2.5), alongside carbon monoxide, nitrogen oxides, volatile organic compounds and polycyclic aromatic hydrocarbons. The particles penetrate deep into the lungs and pass into the bloodstream, causing respiratory and cardiovascular harm.

When fire spreads into urban areas, the smoke can become even more toxic. As fire burns through buildings, vehicles, plastics or electrical equipment, the burning materials release additional contaminants not typically present in vegetation fires, including heavy metals and other synthetic products.

As a smoke plume from a wildfire drifts, it mixes and reacts with existing urban air pollution. Sunlight-driven chemical reactions between the smoke components and urban emissions can generate secondary pollutants, including ground-level ozone and secondary organic aerosols. This can extend both the geographic reach and toxicity of the plume as it moves over towns and cities downwind of the fire.

How far can wildfire smoke travel, and how long can its effects on air quality and health persist?

The toxic particles caused by wildfire smoke can remain suspended in the atmosphere for days to weeks and be carried thousands of kilometers from their source. Southern and Western Europe’s fires this summer are producing plumes that can, depending on wind direction, affect air quality well beyond the countries where the fires are burning, including in the U.K.

A 2025 study traced the global footprint of the record-breaking 2023 Canadian wildfires, finding that smoke from these fires raised PM_2.5 levels in Europe to dangerous levels (above WHO guidelines) for around two weeks. It estimated that 22,400 premature deaths in Europe were caused by long-range exposure to the smoke. This is a striking demonstration that a wildfire burning on another continent can leave a measurable population-level impact thousands of kilometers downwind.

How long effects persist depends heavily on weather: Without rain or a change in wind, smoke-laden air can sit over a region for several days, keeping pollution levels high even after the plume has technically passed. Because wildfire seasons increasingly bring repeated smoke episodes rather than a single event, cumulative exposure across a season—rather than any one bad-air day—is what matters most for population health.

Who is most affected by wildfire smoke?

Some groups are more vulnerable than others. Children breathe more air relative to their body weight and have lungs that are still developing. Older adults and people with preexisting asthma, chronic obstructive pulmonary disease or cardiovascular disease are at greater risk of harmful effects or hospitalization from smoke. Particular caution is also warranted during pregnancy, given evidence linking air pollution exposure with adverse birth outcomes such as low birth weight.

Other groups may also be disproportionately affected, including outdoor workers and firefighters, people experiencing homelessness, nursing home residents, and lower-income households that may live in poorer-quality housing or don’t have access to air conditioning or affordable air filtration.

Are wildfires more likely in Europe and the UK in the future, and how prepared are we for this growing risk?

Climate projections suggest that weather conditions favorable for extreme wildfire will become more frequent in many parts of Europe during this century, including regions that historically experienced relatively few large fires.

Rising temperatures, prolonged drought, lower fuel moisture (i.e., drier vegetation), earlier snowmelt, more frequent heat waves and changing precipitation patterns are extending wildfire seasons and increasing fire intensity. At the same time, changes in vegetation and land use are increasing available fuels and exposing more people and infrastructure to fire.

Although Mediterranean countries remain at greatest risk, recent fires in the U.K. demonstrate that northern Europe is not immune. The U.K. has experienced increasing numbers of large heathland, peatland and grassland fires during exceptionally warm and dry periods.

Preparedness has improved through satellite monitoring, free databases such as Copernicus emergency services, and national wildfire response systems, but significant challenges remain. Compared with countries such as Australia or parts of North America, many European nations have historically invested less in wildfire risk management because fire was considered a relatively infrequent hazard.

What solutions should governments and public health authorities be considering now?

Research suggests that strategic, well-managed prescribed (controlled) burning can reduce the population’s overall exposure to wildfire smoke over time. This involves deliberately burning vegetation under carefully chosen conditions to reduce the amount of fuel available for more severe wildfires. But the evidence comes with important caveats.

Research modeling forest management in the Central Sierra, California found that the health benefits of prescribed burning for reducing smoke-related asthma impacts level off once burning goes beyond a moderate amount because the fire’s own emissions start to erode the net benefit.

A survey of a medically vulnerable population in a Californian wildland-urban interface community (where homes and buildings meet or mix with wild plants, trees and open land) found many residents lacked confidence in their ability to protect themselves from smoke, whether from wildfire or prescribed burns. This is a reminder that technical solutions must be paired with genuine public trust and clear communication.

Taken together, the evidence points to six priorities for governments and agencies to consider:

1. Expand strategic, well-timed prescribed burning and fuel management, planned jointly with air quality forecasting so that burns are scheduled to minimize smoke exposure to nearby communities.
2. Invest in monitoring and modeling that can separate wildfire-specific PM_2.5 from background pollution in near-real time, as current air quality standards do not distinguish between pollution sources.
3. Build heat-health-alert-style early warning systems that link fire weather forecasts, air quality forecasts and health services so at-risk groups and clinicians receive advance notice.
4. Issue clear guidance on restricting high-exposure activities such as outdoor events during high-risk days, with particular attention to vulnerable groups.
5. Invest in clear, trusted public health messaging that is developed and tested with the communities most affected, given documented gaps in public confidence about how to protect their health during smoke events.
6. Target ignition prevention directly, given that the large majority of wildfires are human-caused rather than naturally ignited. This could include sustained public awareness campaigns on disposable grills, discarded cigarettes, campfires and glass; temporary local restrictions or bylaws on high-risk activities during red-flag fire-danger days.

What practical steps can I take to reduce harm from smoke?

• Check local air quality index readings and air pollution alerts before planning outdoor activity.
• Keep windows and doors closed and, where possible, run an air purifier when there is smoke.
• Avoid strenuous outdoor exercise on high-pollution days.
• Keep asthma or other rescue medication accessible.
• If it is genuinely necessary to be outside in heavy smoke, use a properly fitted FFP2/FFP3 or N95-standard respirator rather than a cloth or surgical mask, which does not filter fine particles effectively.
• Seek medical advice promptly if chest pain, breathlessness or a persistent cough develops, and check on older or unwell relatives and neighbors during smoke episodes, since they may be less able to act on air quality warnings themselves.

Who’s behind this story?

Lisa Lock

BA art history, MA material culture. Former museum editor, paramedic, and transplant coordinator. Editing for Science X since 2021.

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Alexander Pol

PhD nano-engineering from Delft University. Published researcher and journal reviewer. Brings scientific insight to content standards.

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