Remains of a house and car after the Carr Fire passed through the western edge of Redding, California, in 2018. Credit: Cecilio Ricardo/ USDA Forest Service
Key Points:
- Increased wildfire frequency raises the prospect of fires burning into urban areas, mobilizing pollutants few have researched.
- A new study found that some post-fire chemicals, such as nitrate, some metals, benzene and disinfection by-products exceeded regulatory levels in treated drinking water.
- The duration of effects was less than 5 years for most pollutants on average following fire, although effects did extend 15 years or more in some individual cases.
Thanks in part to climate change, wildfires have picked up throughout the U.S. in both intensity and frequency. In a new study, researchers say much more research is needed on the release of toxic materials post-wildfire into watersheds.
The paper, published in Water Resources Research, looks at the trends in water after wildfires as documented across 184 scientific papers since 1980. The researchers found that stream flow often increases for a few years following a wildfire, as do sediments and water temperature. Nutrients also often increased, along with toxic metals and some organic chemicals, which sometimes reach 10 to 100 times higher concentrations than pre-fire levels.
The study found that some post-fire chemicals in the water, such as arsenic, can exceed regulatory limits, even in processed drinking water. Elevated levels of the carcinogen benzene in tap water following the burning of houses and vehicles in the town of Paradise, California, are among the reports cited in the review. Researchers also found higher concentrations of metals in the ash from these fires, which could potentially affect runoff.
The review found that little research has been done on the kinds of pollutants that come from urban wildfires. This leaves water managers and planners at a disadvantage when recovering from a fire.
“We point this out as a major gap in the scientific understanding of fire effects,” said study author Stephen LeDuc of the U.S. Environmental Protection Agency's Center for Public Health and Environmental Assessment. “We anticipate this review will help water quality managers and decision makers better understand the likely impacts of fire, and ultimately inform the design of mitigation and recovery strategies and policies. For researchers, the review highlights the state of current knowledge, while identifying key knowledge gaps for future work.”
Information provided by American Geophysical Union.