Beyond Particulate Matter Mass: Heightened Levels of Lead and Other Pollutants Associated with Destructive Fire Events in California
Abstract: As the climate warms, wildfires are increasing in size and intensity, posing a risk to human health and sensitive ecosystems. Studies have reported on particulate matter (PM) in wildfire smoke; however, the chemicals associated with PM, including toxic metals, have received surprisingly little attention. Here, we analyzed 13 years (2006-2018) of PM2.5 chemical composition data from Air Quality System monitors in California on smoke-impacted days (identified using the National Oceanic and Atmospheric Administration’s Hazard Mapping System). Levels of some chemicals (e.g. aluminum, potassium, and sulfate) were statistically elevated on smoke-impacted days for more than half of the years studied. In contrast, other chemicals, mostly trace metals toxic to ecosystems and human health (e.g., lead, copper, chromium, and arsenic), were elevated during select fires only. For example, lead was ~4,100% higher on average on smoke days at the Point Reyes station in 2018 due to the Camp Fire, burning over 200 kilometers away. There was an association between these metals and the combustion of anthropogenic material in the wildland-urban interface (e.g., houses and vehicles). Overall, these destructive fires are not only threatening human life and property, but also mobilizing toxic chemicals in smoke far downwind, at levels generally unseen except in the most polluted areas of the country. Although still currently rare, these fires are likely becoming more common with urbanization and climate change. We hope a greater understanding of the chemicals mobilized by these fires will assist in the communication and reduction of public health risks.