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Environmental health impacts from fire retardants and future mitigation strategies
Madison Talent
MPH Candidate, 2024
OHSU-PSU School of Public Health
Photo by: Rob Kerr, The Bulletin, The Oregonian/OregonLive
In our attempt to extinguish wildfires, are we actually causing more harm?
In our attempt to extinguish wildfires, are we actually causing more harm?
As our planet has warmed, we have seen a drastic increase in wildfires, particularly in the Western States. In 2021, over seven million acres burned from wildfires across the United States (National Interagency Fire Center, 2021), and over 52 million gallons of fire-retardant chemicals were dispersed (US Department of Agriculture, 2021). Fire retardants help firefighters contain wildfires, protecting people and natural resources, but scientific research sheds light on the toxicity of fire retardants on terrestrial and aquatic life.
Fire-Retardant Chemicals: An Overview
Fire-Retardant Chemicals: An Overview
Photo by: Alida Saxon, Pixabay
What are fire retardants?
What are fire retardants?
Fire retardants are chemicals that reduce the flammability of combustibles. These chemicals are applied to products, including furniture, electronics, toys, and building materials, and are also used to prevent and suppress wildfires. Many fire-retardant chemicals have been identified as endocrine disruptors, meaning they interfere with hormone production and are associated with increased cancer risk and developmental and reproductive harm (National Institute of Health, 2021).
Why should we worry about fire retardants?
Most fire-retardant chemicals used in consumer products:
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Bioaccumulate
Bioaccumulate
Build up in the bodies of humans & animals.
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Toxic
Toxic
Associated with cancer, reproductive & neurological health issues.
Photo source: Clipart Library:
Persist
Persist
Do not break down in the environment.
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Travel
Travel
Can travel large distances in the environment via air and water.
What types of fire retardants are used to prevent and control of wildfires?
What types of fire retardants are used to prevent and control of wildfires?
There are hundreds of different fire retardants. This page focuses on the three types of fire-retardant chemicals used by the U.S. Forest Service to fight wildfires, which exhibit a unique set of environmental concerns to those used in consumer products.
Photo by: USDA Forest Service
Long-Term Retardants
Long-Term Retardants
Photo by: KUAC
Foam Suppressants
Foam Suppressants
Photo by: Iván Tamás, Pixabay
Water Enhancers
Water Enhancers
Long-term retardants create a perimeter around a fire rather than being applied directly to the flames...
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The active ingredient in long-term fire retardant is ammonium phosphate fertilizer which reduces flame intensity and remains effective on fuels (trees, ground, structures, etc.). Iron oxide or die is added to make these chemicals identifiable by wildfire personnel. Phosphate fertilizers do not evaporate, making them effective at containing fires but persistent in the environment. Phos-Chek is the primary long-term retardant used in wildlands (Yu et al. 2019).
Foam suppressants work by slowing the evaporation of water and helping water penetrate fuels...
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These surfactant-based foams are highly effective at suppressing actively burning fires. Studies have shown class A suppressants to be high-risk environmental contaminants because of their long-term environmental persistence, potential for bioaccumulation, and toxicity (Yu et al. 2019). Foams are rarely applied aerially, but rather they are dispersed from ground equipment (pumps and engines). Foams are not compatible with long-term retardant (USFS, 2020).
Water enhancers increase the firefighting capabilities of water and are applied directly to the fire...
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They contain ingredients, usually polymers or thickeners, that alter the properties of water to make it adhere to surfaces or prevent drifting during aerial drop (USFS, 2020). Water enhancers are gel substances added to water at a specific mixing ratio. Water enhancers' effectiveness depends on the water's quality (ph, softness/hardness). Water enhancers stop working as soon as the water evaporates (Yu et al. 2019).
Explore resources by the U.S. Forest Service
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Explore resources by the U.S. Forest Service
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Explore resources by the U.S. Forest Service
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Over 50 million gallons of fire retardant was used to fight wildfires in 2021 (USDA, 2021).
Photo by: Linda Rogers, KQED
The U.S. Forest Service spent nearly $200 million dollars on fire retardant in 2020-2021 (LA Times, 2022).
Photo by: Mamta Popat, Arizona Daily Star
Photo by: Kent Porter, The Associated Press
The U.S. Forest Service sets guidelines for where fire retardants can be applied to protect water sources and endangered species from chemical contamination. However, it's challenging to control the specificity of aerial drops given wind conditions and the height of the drop. As a result, long-term retardant often ends up in places where it wasn't intended. Explore the U.S. Forest Service retardant avoidance map to learn more.
Fire-Retardants & Environmental Health
Fire-Retardants & Environmental Health
"We assume that we're masters of our environment, rather than being a part of it."
"We assume that we're masters of our environment, rather than being a part of it."
Tyrone Hayes, Scientist & Professor of Biology at UC Berkeley
Human health, animal health, and ecosystem health are interdependent; humans impact the environment, and in turn the environment impacts human health. The ecological perspective provides a framework for analyzing how different environmental factors (built, social, natural environment) affect health, health behaviors, and health determinants at both the population and individual levels. The environment is a core determinant of human health. In the case of a polluted environment, humans and animals are likely to come into contact with contaminants, toxins, or diseases.
What happens when fire retardants disrupt environments?
Photo by: Anilga, Pixabay
Contamination of Aquatic Areas
Contamination of Aquatic Areas
Long-term fire retardants should only be applied terrestrially. The U.S. Forest Service prohibits fire retardants within 300 feet of rivers, lakes, streams, or any water source. However, accidental spills and misapplications have resulted in the chemical ending up in aquatic habitats. Numerous studies have identified direct toxicity of long-term retardants to aquatic species that encounter the chemical. A study examining the toxicity of forest fire retardant chemicals on chinook salmon found that two types of retardant (Phos-Chek 259F and LC-95A) resulted in a 50% mortality rate of salmon exposed concentrations to that could occur from accidental drops to aquatic areas (140.5 and 339.8mg/L of retardants, respectively) (Dietrich et al., 2012).
Fire retardants are inorganic and highly soluble in water (Carrat et al., 2017). One of the main concerns of fire retardant in aquatic areas is that it increases the ammonia concentration in water. Ammonia causes acute and longer-term lethal and sublethal toxicity to freshwater fish and other aquatic species (USFS, 2021). In 2002, an accidental drop of more than 1000 gallons of long-term fire retardant over Central Oregon's Fall River resulted in the death of 22,000 trout (Chu, 2007).
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Danger to Native Plants and Biomes
Danger to Native Plants and Biomes
According to the U.S. Forest Service's 2021 Ecological Assessment of long-term retardants, "the ecological effects that may be caused by retardants are those associated with (1) direct toxicity to terrestrial wildlife and aquatic species that encounter the chemical, (2) phytotoxicity, and (3) effects on vegetation diversity" (USFS, 2021). Phytotoxicity is direct toxicity to plants, and the ecological assessment above also cited inhibited plant growth, survival, and reproduction of endangered and sensitive species (USFS, 2021). Additionally, long-term retardants reduced plant species diversity, likely caused by the disruption of the soil nutrient balance. Long-term fire retardant is essentially a fertilizer. The deposit of phosphate and other components found in Phos-Chek (the primary long-term retardant used in wildlands) encourages the growth of invasive plants that crowd out native species (Mayfield et al., 2021).
The U.S. Forest Service asserts that "persistent exposures through terrestrial environmental pathways are not expected" (USFS, 2021). However, the degradation of fire-retardants is reliant on rainwater, a scarce resource in drought-ridden and fire-prone climates like the chaparral biome that encompasses millions of acres from Southern Oregon to Baja California. Most optimistically, it is estimated that fire retardants linger in the environment for weeks or months (Carratt et al., 2017). However, more research is needed to understand chemical persistence in actual conditions.
Photo by: Craig, Flickr
Toxic Algae
Toxic Algae
The main components of long-term fire retardants are ammonium-based compounds containing phosphate or sulfate, which has been linked to increasing the amount of nitrogen and phosphorus in water runoff (Waskom et al., 2014). When fire retardant ends up in bodies of water through aerial drops or downstream run-off, it creates optimal conditions for toxic algae blooms. The increased concentrations of nutrients like phosphorus offer a food source for the cyanobacteria (EPA, 2022), commonly known as blue-green algae. Not only do these algae blooms reduce light and oxygen, killing many fish and aquatic plants, but the cyanobacteria is toxic to humans and animals if ingested. Cyanobacteria algal blooms impact marine and freshwater ecosystems, and the bacteria can contaminate water reservoirs. Drinking water contaminated with cyanobacteria has high toxicity to humans (Otero & Silva, 2022). Wildfire ash transported by surface runoff is also responsible for increased nutrients (phosphorus, nitrogen, carbon) that feed algal blooms (Bladon et al., 2014).
Fire Retardants & Human Health
Fire Retardants & Human Health
Routes of Exposure
Routes of Exposure
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Dermal:
Wildfire personnel who mix the fire-retardant concentrates and ground crews who apply long-term retardants and foam suppressants to fuel are at the most significant risk of dermal exposure (through skin contact). The maximum exposure scenario would likely occur through an accidental "drench" of fire retardants (Carrat et al., 2017), which has happened.
Individuals foraging for mushrooms or picking wildland berries; forest rehabilitation crews; hikers, researchers, hunters, and children playing in an area where retardant has been applied are all at risk of dermal exposure. (USFS, 2021).
Inhalation:
Individuals, mainly firefighters, have the potential to inhale aerosol particles or vapors from fire retardants. The greatest exposures occur in air tanker base personnel who mix the powdered concentrate of long-term retardant with water before it is loaded onto the plane (USFS, 2021). Mixers wear dust masks to prevent exposure.
During a wildfire, fire retardants are dropped into the air from planes and helicopters amid smoke-polluted air where they mix with wildfire smoke. These chemicals and their combustion products are then volatilized when flames contact the fire-retardant. From here, there is potential for humans to inhale this potentially toxic mixture of fumes. A literature review by researchers investigating wildfire suppression chemicals and California wildfires concluded that there is little existing research looking into this topic and that "Future epidemiological studies that characterize the health impacts of wildfire smoke in California should consider the interaction between retardant use and smoke generation," particularly in small urban wildfires, where fire retardants are likely to be a more significant component of the smoke (Carrat et al., 2017).
Oral:
Oral exposure to fire-retardant chemicals is low, and the manufacturer of Phos-Chek cautions against ingesting the chemical. The most probable way individuals are exposed to fire retardant orally is via food or water. There needs to be more information on the effects of oral consumption of fire retardants. Still, the U.S. Forest Service advises that any food or crops contaminated with chemical retardants be disposed of (USFS, 2021).
Photo By: Rii Butov, Pixabay
Photo by: Semevent, Pixabay
Health Effects
Health Effects
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Phos-Chek, the main chemical fire retardant used for wildland fire management by the U.S. Forest Service, is listed as generally "safe" at the estimated espourses of wildfire personal and the general public, but it is known to cause the following side effects:
Irritation to the respiratory tract, including difficulty breathing
Skin irritation, including dryness and cracking
Eye irritation, including redness and itching
View the entire safety data sheet on Phos-Chek LC95A here.
Clean-up Protocol
Clean-up Protocol
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The Oregon Department of Environmental Quality advises the following precautionary measures when cleaning up fire-retardants in residential areas:
Retardants must be wetted to control any hazardous dust before it is swept up.
Retardants should not be hosed off into storm drains due to potential impacts to local streams.
Do not use a leaf blower to clean up retardant, it will create more airborne particles.
Foams should be removed by thoroughly rinsing an area with water.
View the entire fire retardant clean-up protocol here.
Photo by: US Department of Health and Human Services
View infogram; source US Forest Service
Fire Retardant Mitigation Strategies
Fire Retardant Mitigation Strategies
Proactive Fire Management Strategies
Proactive Fire Management Strategies
Focused on Restoration and Adaptation
Focused on Restoration and Adaptation
As hotter, drier global conditions become more conductive to wildfires, and as urban and wildland areas converge, it is evident that we must change our approach to managing forests and wildfire. Proactive fire management strategies offer solutions for reducing the use of fire-retardant chemicals and mitigating the environmental impacts they cause.
Ecological forest management: Recognizing the value of all elements in a forest and creating policies and practices that make forest ecosystems more resilient by moving them back to completeness (Johnson et al, 2018). Strategies of ecological forest management include using site adapted species, improving soil productivity and enhancing habitat and biodiversity (Gersonde, 2017). Sustainable solutions for forest management will need to be versatile, catering to a changing world by incorporating cross-boundary collaboration and community adaptation.
Fuels reduction: Prescribed fires and forest thinning are tools that forest managers can use to help mitigate opportunistic fire ignitions.
Suppressing fewer fires: The default response has historically been to extinguish every fire that ignites. Low to moderately severe fire can benefit forest resiliency and support high species diversity (Richter et al, 2019). Prioritizing when it is and is not appropriate to extinguish a fire is essential for future wildfire management.
Getting more firefighters on the ground: Fire retardants don't extinguish fires, rather, they act as a tool to help firefighters control the blaze and buy time to deploy ground crews who are able to extinguish the flames. Investing in and deploying more ground crews to manage the fire, rather than dousing the entire forest in chemicals could help limit the need for fire retardant chemicals and preserve the health of the forest ecosystem.
Fire Resistant Vegetation: Many plants are naturally fire resistant, examples include coyote brush which contains fire retardant leaves to prevent the spread of wildfires. Most of the plants in the chaparral biome are not only tolerant of fire, but some of the species, such as laurel sumac, rely on fire for their persistence or rejuvenation (Keeley et al 2006). Many old-growth large-trees, like oak, eucalyptus, sequoia, and cork oak, which has thick bark that protects the tree from catching fire and shields its cambium, are naturally fire resistant (Tributsch & Fiechter, 2008). The green fire barrier approach is a centuries old technique that utilize low-flammability vegetation, planted in strategic areas to contain wildland fires (Wang et al, 2021).
Video source: Forest Service, 2019
Additional Considerations
Additional Considerations
Other sources of exposure to fire-retardant chemicals:
Other sources of exposure to fire-retardant chemicals:
While this page focused on the fire retardants used to control wildfires, we encounter numerous other flame retardants that are used in commercial and consumer products everyday; many of which are far more toxic than those used in wildland management. Explore the resources below to learn more:
Photo by: Arek Socha, Pixabay
Toxic Flame Retardants
Toxic Flame Retardants
Learn more about the dangers of these chemicals including brominated flame retardants and organophosphates by reading more from the National Institute of Health.
Photo by: Adina Voicu, Pixabay
Protective Legislation
Protective Legislation
Check out current legislation to protect consumers from these toxic substances through SafterStates bill tracker and learn about the Stockholm Convention on persistent organic pollutants.
Want to Learn More?
Want to Learn More?
Continue learning about the impact of wildfires on human and environmental health by following the links below
Continue learning about the impact of wildfires on human and environmental health by following the links below
References
References
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Calfee, R. D., & Little, E. E. (2003). Effects of a fire-retardant chemical to fathead minnows in experimental streams. Environmental science and pollution research international, 10(5), 296–300. https://doi.org/10.1065/espr2003.03.148
Carratt, SA, Flayer, CH, Kossack, ME, & Last, JA. (2017). Pesticides, wildfire suppression chemicals, and California wildfires: A human health perspective. Current Topics in Toxicology, 13, 1-12. https://escholarship.org/uc/item/7rh1s9z8
Chu, K. (2007, August 26). A mistake that killed 22,000 fish. The Bulletin. https://www.bendbulletin.com/localstate/a-mistake-that-killed-22-000-fish/article_e007d374-46fa-5ac7-a3b7-839231438449.html
Department of Environmental Quality . (n.d.). After the Fire: Cleaning Up Fire Retardant and Fire Suppressants. DEQ Wildfire Response. https://www.oregon.gov/deq/wildfires/Documents/FireChemlCUpWQ.pdf
Dietrich, J. P., Myers, M. S., Strickland, S. A., Van Gaest, A., & Arkoosh, M. R. (2012). Toxicity of forest fire retardant chemicals to stream-type Chinook salmon undergoing Parr-Smolt Transformation. Environmental Toxicology and Chemistry, 32(1), 236–247. https://doi.org/10.1002/etc.2052
Environmental Protection Agency. (2022, June 16). Indicators: Phosphorus. EPA. https://www.epa.gov/national-aquatic-resource-surveys/indicators-phosphorus#:~:text=Too%20much%20phosphorus%20can%20cause,to%20human%20and%20animal%20health
Gersonde, R. (2016, June 11). Ecological Forest Management. https://www.nnrg.org/wp-content/uploads/2016/04/Ecological-Forestry-Gersonde.pdf
Giménez, A., Pastor, E., Zárate, L., Planas, E., & Arnaldos, J. (2004). Long-term forest fire retardants: A review of quality, effectiveness, application and environmental considerations. International Journal of Wildland Fire, 13(1). https://doi.org/10.1071/wf03001
Keeley, J. E. (2006). Fire severity and plant age in postfire resprouting of woody plants in safe scrub and chaparral. Madroño, 53(4), 373–379. http://www.jstor.org/stable/41425666
Meyer, S.E., Callaham, M.A., Stewart, J.E., Warren, S.D. (2021). Invasive Species Response to Natural and Anthropogenic Disturbance. In: Poland, T.M., Patel-Weynand, T., Finch, D.M., Miniat, C.F., Hayes, D.C., Lopez, V.M. (eds) Invasive Species in Forests and Rangelands of the United States. Springer, Cham. https://doi.org/10.1007/978-3-030-45367-1_5
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Nexreg Compliance Inc. (2020, August 4). PHOS-CHEK LC95A / PHOS-CHEK LC95A-MV Safety Data Sheet. Wildland Fire Chemical Systems, National Technology and Development Program. https://www.fs.usda.gov/rm/fire/wfcs/products/
Otero, P., & Silva, M. (2022). The role of toxins: Impact on human health and Aquatic Environments. The Pharmacological Potential of Cyanobacteria, 173–199. https://doi.org/10.1016/b978-0-12-821491-6.00007-7
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Rehmann, C. R., Jackson, P. R., & Puglis, H. J. (2021). Predicting the spatiotemporal exposure of aquatic species to intrusions of fire retardant in streams with limited data. Science of The Total Environment, 782, 146879. https://doi.org/10.1016/j.scitotenv.2021.146879
Richter, C., Rejmánek, M., Miller, J. E., Welch, K. R., Weeks, J. M., & Safford, H. (2019). The species diversity × fire severity relationship is hump‐shaped in semiarid yellow pine and mixed conifer forests. Ecosphere, 10(10). https://doi.org/10.1002/ecs2.2882
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