How Does Pink Fire Retardant Affect the Environment?

Mitigating the impacts of fire retardants used in wildfires to ecosystems and drinking water through risk assessments

To combat the Los Angeles wildfires, aircraft dropped pink fire retardant on vegetation and hillsides to slow the rate of burn, coating surfaces in a blanket of ammonium phosphate and iron oxide. This use of flame retardant has spurred concerns over the environmental and ecological safety of aerially applied fire retardants, especially to stream ecosystems and water supplies. 

The unease regarding fire retardant safety is not limited to the Golden State. With global climate change and increasing extreme weather-related conditions, states throughout the U.S. are struggling to sustainably manage wildfires.

Because baseline conditions — impacts from urbanization, agriculture, and, potentially, mining and logging — may exacerbate the effects of both wildfires and wildfire control efforts, proactive and reactive assessments are essential to evaluating their impacts. 

Assessing the ecological and water quality impacts of wildfire runoff and wildfire control methods, like fire retardants, requires a thorough investigation that utilizes a comprehensive understanding of baseline conditions, wildfire severity, retardant use, and subsequent environmental conditions. 

Wildfire control methods vs. wildfire runoff 

The most common method of controlling wildfires is using fire retardants, which primarily consist of ammonia- and phosphorous-based compounds, similar to chemical fertilizers, amended with additives to aid in precise application and persistence during firefighting efforts. They are applied to terrestrial habitat at rates of 1 to 8 gallons per 100 square feet. While this prevents the spread of wildfire, both plants and wildlife may be exposed to fire retardant compounds coating the landscape, and these compounds may also enter aquatic systems.

Guidance from the U.S. Forest Service specifies that fire retardants should not be applied aerially within 300 ft of water bodies and that the toxicity of ammonium-phosphate-based fire retardants to aquatic species is low. Yet there is concern that drift or accidental application to streams and movement of terrestrially applied retardants into aquatic systems during rain events could cause harm.

Given this concern, any potential environmental risk associated with the use of fire retardants must be weighed against the risks and effects of burn damage from wildfires themselves and the aftermath, making a holistic risk assessment necessary.

Benefits of risk assessments 

The impacts of wildfires and wildfire control efforts on aquatic ecosystems, such as vegetation, invertebrates, fish, and wildlife, are highly complex; and preventing wildfires can help sustain these valuable natural resources. Because baseline conditions — impacts from urbanization, agriculture, and, potentially, mining and logging — may exacerbate the effects of both wildfires and wildfire control efforts, proactive and reactive assessments are essential to evaluating their impacts on drinking water systems; human health; and terrestrial, wildlife, and aquatic systems. Some key factors for consideration include:

• Drinking water systems 
  • Evaluating water quality impacts to drinking water sources and optimizing water treatment when fire-impacted waters must be used for drinking water production
  • Assessing the feasibility of securing alternative water sources
  • Assessing the infrastructure surrounding wild-fire impacted areas to isolate damaged infrastructure from compromising the rest of the drinking water distribution systems
  • Developing priorities to aid in the reconstruction of drinking water infrastructure
• Terrestrial, wildlife, and aquatic systems
• Examining complex baseline conditions in control areas
• Modeling the fate and transport of various chemicals, including fire retardant compounds
• Characterizing the bioavailability of chemicals in the environment 
• Appropriately considering the risk associated with not using flame retardants and with allowing fire spread to vegetation and structures and consequential impacts such as erosion