Toxic Wildfire Smoke Is Not Just Outside — It’s Inside Our Homes Too
Toxic smoke from wildfires is not just an outdoor threat. It’s invading homes.
A major new study published in the “Science Advances Volume 11 | Issue 20 – May 2025” reveals that Between 2003 and 2022, over 1 billion people each year were exposed to at least one day of high indoor wildfire smoke. Most exposures happened in Africa, Asia, and South America. Africa had the highest levels, while South America had the largest share of indoor pollution from wildfires.
Scientists say climate change is fueling this danger. Hotter temperatures and longer droughts are increasing wildfires. This is making the smoke from wildfire a global health crisis.
Wildfire Smoke and Danger of PM2.5
Smoke from wildfires contains tiny particles called PM2.5. These are 30 times thinner than a human hair. They can travel thousands of miles and enter homes through the smallest cracks.
According to the United States Environmental Protection Agency, “PM stands for particulate matter (also called particle pollution): the term for a mixture of solid particles and liquid droplets found in the air.
Particle pollution includes:
- PM10 : inhalable particles, with diameters that are generally 10 micrometers and smaller; and
- PM2.5 : fine inhalable particles, with diameters that are generally 2.5 micrometers and smaller.”
PM2.5 is responsible for the most health issues linked to air pollution, both in the U.S. and around the world.
Inside the homes, the particulate matter may cause breathing problems, heart disease, early death, and even dementia.
Researchers found that indoor pollution during wildfires can be nearly three times higher than on normal days.
Global Hotspots of Indoor Exposure
People in South America, central Africa, and parts of Asia and Australia were hit hardest.
The study found that wildfires caused over half of the indoor pollution levels that exceeded World Health Organization (WHO) safety limits.
Talking about the ambient (outdoor) air pollution issue in the world, which is already in worse conditions, as in 2019, 99% of people worldwide lived in areas with air pollution above WHO’s safe limits.
Air Purifiers Work — But at a Price
Air purifiers with high-efficiency particulate air (HEPA) filters can reduce indoor wildfire smoke, but they are expensive.
The study estimated that keeping indoor air within WHO limits could cost over $4 trillion a year globally, with $69 billion spent just on wildfire smoke reduction.
The study says air purifiers reduce wildfire smoke indoors but are expensive, especially for low-income economies worldwide. Low-income regions like West Africa, Central Africa, and South Asia face the highest costs compared to their income.
Wildfires Are Only Getting Worse
Almost half of people in the U.S. breathe unhealthy air, says the American Lung Association’s 2025 report.
The American Lung Association reported 25 million more people in the U.S. breathed unsafe air last year due to wildfires, heat, and drought.
“Families across the U.S. are dealing with the health impacts of air pollution every day, and extreme heat and wildfires are making it worse. This year’s report shows the dramatic impact that air pollution has on a growing number of people,”
said Harold Wimmer, President and CEO of the American Lung Association in the press release citing the American Lung Association’s 2025 “State of the Air” report.
Scientists warn the problem is growing fast. People can no longer assume staying indoors will keep them safe from unhealthy air of the outdoor activities.
Also Read: Study Reveals the Climate Change Link to Canada’s 2023 Wildfire Crisis
The study recommends that as wildfires worsen with climate change, cutting indoor smoke exposure is urgent and needs policy action, not just personal steps. Research should measure health risks, improve real-world data, explore better building solutions, and understand public behavior.
Government support and policy measures in tackling the overall issue of air pollution are key to protect vulnerable groups and to reduce overall health costs.
