Metals in Wildfire Suppressants.

Area of Science:

• Environmental Chemistry
• Ecotoxicology
• Wildfire Management

Background:

• Wildfires are increasing in frequency and severity, leading to greater use of fire suppression products.
• Elevated metal concentrations in post-wildfire environments are often attributed to ash or urban sources.
• Formulations of U.S. Forest Service-approved fire suppressants include trade secrets.

Purpose of the Study:

• To quantify metal concentrations in fire suppression products.
• To evaluate the contribution of these products to environmental metal contamination.
• To assess potential risks to aquatic ecosystems.

Main Methods:

• Quantification of metal concentrations (V, Cr, Mn, Cu, As, Cd, Sb, Ba, Tl, Pb) in fire retardants, water enhancers, and Class A foams.
• Comparison of measured metal levels against drinking water regulations and aquatic toxicity thresholds.
• Estimation of total toxic metal release into the environment from fire retardant applications.

Main Results:

• Long-term fire retardants exhibited toxic metal concentrations 4–2,880 times higher than regulatory limits for drinking water.
• Some fire retardants may exceed aquatic toxicity thresholds upon environmental release.
• Water enhancers and Class A foams contained lower metal concentrations compared to retardants.
• An estimated 380,000 kg of toxic metals were released via fire retardant application in the U.S. (2009-2021).

Conclusions:

• Fire suppression products, particularly long-term retardants, are a significant source of toxic metals in post-wildfire environments.
• The widespread application of fire retardants poses a potential risk to soil and water quality.
• Further research is needed to understand the long-term ecological impacts of these metal contaminants.