As wildfire smoke plumes travel thousands of miles, sunlight and atmospheric chemistry bleach their color, strip away their campfire aroma and add them to the mix of urban smog.

Smoky skies plagued the East Coast and Midwest again in summer 2026, as wildfires hundreds of miles away forced people to cancel sports practices and run air conditioners around the clock.

Living in the western U.S., I am no stranger to this scene. Wildfires and the thick smoke they produce have become a fixture of summer life here. I also study wildfire smoke as an atmospheric chemist, in particular how the smoke evolves as it moves downwind from the flames to the communities where people breathe it.

To understand what’s in the smoke you might be breathing, you have to look at where it’s been.

When a forest burns, the wildfire emits large amounts of fine particulate matter, or PM2.5, along with nitrogen oxides and volatile organic compounds, or VOCs. The compounds and particles emitted by wildfires can harm human health, including the lungs, heart and organs, and include known carcinogens.

How this potent mix of pollutants transforms over time and distance is a complex puzzle. At the NOAA Chemical Sciences Laboratory, our team tracks this behavior, from studying controlled fuel burns in the lab to flying research aircraft through wildfire smoke plumes. Understanding how wildfire smoke ages is essential for predicting its impacts on human health.

It all starts at the flame

The story of smoke begins with how the wildfire burns. High........

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