Smoke and ash contain chemicals that can harm wildland firefighters, and not just when they breathe it in. White River National Forest/BLM via Flickr Wildland firefighters are exposed to a mix of harmful chemicals in the smoke they breathe and the ash and soot that gets on their clothing. Over long assignments fighting fires that can last for days to weeks, those chemicals can be absorbed by their skin. Some of those chemicals are carcinogens. A 2025 study found that firefighters in general had