CA Resliency Alliance
Wildfire Knowledge Tidbit
Smoke from WUI Fires: Chemical Composition
Smoke pollution depends on what burns. Unlike wildland fires, which mainly consume vegetation, wildland-urban interface (WUI) fires involve homes, vehicles, businesses, and infrastructure. This mix of fuels produces a distinct chemical profile with important health implications. Studies show that all fires release elements such as magnesium, aluminum, and calcium. But WUI fires generate higher levels of toxic trace metals—including copper, lead, and zinc—linked to the burning of structures and manmade materials. For example, during the 2018 Camp Fire, average lead concentrations measured 200 km away were more than 40 times higher on smoke-impacted days. These elevated metals raise concerns for both public health and ecosystems. Many can cause acute, chronic, or delayed health effects through inhalation, skin contact, or ingestion, putting downwind communities at particular risk.
Source: Wildland Fire Research: What’s in Smoke?, EPA, July 22, 2025 and The Chemistry of Fires at the Wildland-Urban Interface, National Academies of Sciences, Engineering, and Medicine, 2022