Wildfire Smoke Is 10x More Toxic Than Traffic Pollution, Say Stanford Experts

As wildfires burn more frequently and intensely across the western U.S., researchers are warning: the smoke may be more dangerous than we realize.

According to Stanford scientists, wildfire smoke is about 10 times as toxic as air pollution from fossil fuels. Even at low levels, exposure has been linked to heart, lung, and neurological damage—and there’s no known “safe” threshold.

“Each new study should increase our concern,” said Dr. Lisa Patel, pediatrician and lead author of Climate Resilient Schools. Children, older adults, pregnant people, and those with asthma are especially vulnerable, but everyone is at risk when smoke lingers in the air.

What’s in wildfire smoke?

Wildfire smoke isn’t just soot. It’s a chemical stew of:

• Fine particulate matter (PM2.5) that enters deep into the lungs
• Volatile organic compounds and heavy metals
• Gases like carbon monoxide and benzene

These pollutants can damage the cardiovascular, respiratory, and nervous systems, and children’s lungs may be especially at risk due to ongoing development until age 21.

What can you do to stay safe?

Stanford experts recommend:

• Checking local air quality daily (use tools like AirView)
• Using a portable HEPA air cleaner indoors during wildfire events
• Wearing a well-fitting N95 mask outdoors when smoke is present
• Monitoring indoor air quality with a reliable air quality monitor like AirU
• And importantly: limit outdoor activity for kids, seniors, and people with chronic health conditions when smoke levels are high.

Why wildfire smoke is getting worse

Climate change is driving hotter, drier conditions, leading to more intense wildfires and longer smoke seasons. “Wildfire smoke has single-handedly reversed decades of clean air progress in the U.S.,” said Dr. Marshall Burke, an environmental economist at Stanford.

Public health messaging matters

Experts also stress the importance of accessible alerts and multilingual communication, especially in lower-income areas where protective resources may be limited.

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