January 14, 2025 • Air quality in the Los Angeles region has plummeted due to smoke from the ongoing wildfires. With all that smoke comes possible risks to human health. So what actually is smoke and why is it so harmful? Jessica Gilman, an atmospheric chemist with the National Oceanic and Atmospheric Administration, explains what smoke is made of, how it behaves in the atmosphere and smoke's role in climate change. Plus, tips for how to lessen your exposure.