Dan Westervelt explains how invisible wildfire smoke particles can impact public health even when the sky appears clear.
Dan Westervelt, an atmospheric scientist at Columbia University, notes that wildfire smoke can be hazardous even when it is not clearly visible to the human eye. While many people associate smoke with orange or brown hues caused by "brown carbon," these pollutants can undergo oxidation, becoming clearer while remaining toxic. The air quality is often dictated by particulate matter 2.5 (PM 2.5), which are tiny particles small enough to penetrate deep into the lungs and heart. These particles can travel hundreds of miles and remain airborne for weeks. Additionally, wildfire smoke produces invisible gases like ground-level ozone and formaldehyde, which can irritate the respiratory system and increase cancer risks over time. Westervelt emphasizes that visibility depends on the smoke's altitude; high-altitude plumes may filter light without significantly affecting ground-level air quality. Because smoke can lose its color without losing its chemistry, experts recommend relying on government air quality monitors rather than visual cues alone to determine when to use filters or masks.