What’s in Wildfire Smoke?

A toxicologist explains the health risks and which masks can help

Wildfire smoke changes as it hangs in the air, its chemical properties changing due to the effects of the sun and chemicals in the air. Evgeny Dubinchuk/Shutterstock

Fire and health officials began issuing warnings about wildfire smoke several weeks earlier than normal this year. With almost the entire U.S. West in drought, signs already pointed to a long, dangerous fire season ahead.

Smoke is now turning the sky hazy across a large swath of the country as dozens of large fires burn, and a lot of people are wondering what’s in the air they’re breathing.