Fire Retardant and Burn Morels – Research & Recommendations

Everyone has witnessed in person, or seen news coverage of, huge planes swooping across the landscape and dropping red clouds across

Yeah, I made this silly image with AI but wrote the whole article with my human brain

swaths of a forest in the path of a forest fire. What is this red stuff? Is it dangerous? Is it poisonous? Are we somehow digesting it when we pick and eat fire morels? Are burn morels safe to consume?

This post offers an attempt to get beyond the rhetorical questions and find an answer. If you don’t want to read further, the answer to the final question above is “probably!”  The Forest Service study referenced below specifically states that berries and mushrooms in the regrown forest are safe to pick and eat. However, I could find no direct science on morels and fire retardant. 

Read on if you are the inquisitive type and want to learn more about fire retardant and burn morels. I have tried to provide ample links to resources where you can read more.

What is Fire Retardant?

The primary aerial retardant used in western wildfires is called Phos-Chek. Originally developed by Monsanto 60 years ago Phos-Chek is now manufactured by an outfit called Perimeter Solutions. Phos-Chek contains about 80% water and 10% ammonium phosphate fertilizer solution that sticks to plants and inhibits combustion. (link)

Generally speaking, fire retardants may contain the following fire retardant ingredients (link).

  • Water
  • Ammonium sulfate: a fertilizer used to reduce the fuel for fires.
  • Potassium silicate: a mineral salt that reduces the combustibility of fuels
  • Borates: they serve as a wetting agent
  • Lignosulfonates: a byproduct of wood pulp production that act as an additional wetting agent.
  • Gelling agents: help to adhere the fire retardant onto the fuel, allowing it to stick longer.
  • Other additives may also be included depending on the fire, such as an anti-foaming agent to prevent it from developing suds on the surface and an organic dye for easy tracking of its deployment.

An airtanker can carry up to 8,000 gallons of retardant and it looks like the Forest Services drops 10 – 20 million gallons annually. In 2021, 22.8M gallons were dropped. In 2022, 12.7M gallons in 4,736 tanker trips were dropped.  


In terms of what they drop, the USFS maintains a list of qualified retardants that their firefighters can use and information on specs, testing & data sheets.

Is Fire Retardent Dangerous?

Fire retardant has been studied by the forest service.  In December 2011 the Forest Service released the Nationwide Aerial Application of Fire Retardant on National Forest System Lands, Here are few notable quotes:  

On Application:

Most aerial fire retardant is applied to ridgetops and adjacent to existing fire breaks such as roads, meadows, old fire scars, and rock outcrops to increase the size of the firebreak. Fire retardant is used to address specific firefighting objectives and can be used in any situation, especially when firefighters, public safety, or structures are threatened.

Note: fire retardant is applied tactically and the discerning picker can completely avoid these areas.

On Wildlife:

Aerial retardant drops are not allowed in mapped avoidance areas for threatened, endangered, proposed, candidate or sensitive (TEPCS) species or in waterways. This national direction is mandatory and would be implemented except in cases where human life or public safety is threatened and retardant use within avoidance areas could be reasonably expected to alleviate that threat.

Note: fire retardant is bad for wildlife and not allowed in specific areas, notably waterways

On Public Health: 

The human health effects… are likely to be minimal: primarily temporary skin irritations…There is some potential for fire retardant to drop on private property or gardens and for pets to make contact with fire retardant… the Forest Service does not advise consuming garden produce coated with fire retardant even after removing the fire retardant from the produce.

Note: Don’t eat food with retardant on it, silly.

In January 2024, the USFS released a new Decision which regulated the usage more carefully, but did not add any information relating to mushrooms.  The “Avoidance Areas” are visible in the USFS Aerial Fire Retardant Avoidance Map if you want to investigate.

What about the Wildlife?

The Forest service does acknowledge the danger to animals, especially amphibians, rodents, insects and other species that cannot escape the geographic area, like, say, a bear can. The study concluded that fire retardants adversely affect water quality, especially in small ponds and pools with no flowing water, where it might linger for two years. Specifically, the fertilizer element leads to algal blooms that impact oxygen levels.

It must be noted that many different fire retardants have been used over the years in the US and also internationally. Studies based on retardants we don’t use in the USA anymore may help explain where we are today, but they shouldn’t be used to evaluate our foraging decisions in 2024 because the underlying chemicals are different.   

Regardless, fire retardants in general are pretty dangerous for wildlife and even the newer retardants have serious problems.

The main concern for aquatic life is the ammonia in the fertilizer component of retardants, which damages organs and gills and can hinder reproductive success. Clearly dangerous for  fish, the ammonia/nitrogen has proven to have a big impact on salmon and steelhead. It is not supposed to be sprayed in or around rivers, but of course as we know, every inch of mountain land drains somewhere! link to a map of wildlife studied

But, can I eat it?

In 2021, another study on Human Heath Risk Assesment of Wildland Fire-Fighting Chemicals was released. They studied skin exposure, inhalation and ingestion. Of note, in section 3.5.2  “Potential public exposures that were addressed qualitatively in the risk discussion include … individuals harvesting mushrooms or berries from wildlands after vegetative regrowth has occurred. 

4.3.3 Harvesting Wild Vegetation Individuals may harvest mushrooms and berries from wildlands after vegetative regrowth has occurred, in areas that were treated with retardants. The dermal exposure from harvesting these edibles is expected to generally present negligible risk and would be similar to the exposure of rehabilitation team members, hunters, ecologists, or others who re-enter treated areas.

YES – you can eat mushrooms or berries that have grown after the area was sprayed.

4.3.4 Ingesting Vegetables or Wild Vegetation Individuals are advised against consuming vegetables from home gardens to which retardant may have been applied, or from areas in wildlands where residues are apparent. In addition to avoiding consuming food items with visible residues, the ammonium-based fertilizer component of some retardants may lead to temporary increases in the nitrate content of soils in areas of application. Some vegetables are known to concentrate nitrates, particularly cauliflower, beets, spinach, broccoli, collard greens, carrots, turnips, and other root vegetables. Elevated levels of ingested nitrate could pose a risk upon conversion to nitrite, especially to infants who are more susceptible to methemoglobinemia.

Avoid foods with Visible Residues! Mushrooms grow the following spring, so, will not have been sprayed.

Could the Mushroom Uptake any harmful chemicals?

If you consider the biology of the matter, mushrooms are decomposers. They use enzymes and such to break down complex chemicals in the soils around them into simpler substances, and then digest them. Mycoremediation experts use them to break down harmful chemicals and absorb metals. Mushrooms cannot break down heavy metals and will uptake them, sometimes quite voraciously. Elements like arsenic or lead and cadmium can all be hyper-accumulated.  

Certainly, if a mushroom is found in a public park or on a golf-course, it could have been sprayed by any number of non-food safe herbicides, pesticides and fertilizers. In this case the harmful spray is direct to the fruiting body of the mushroom, making them likely unsafe to consume.


There is no evidence to show that burn morels are dangerous, or safe, per se. Clearly fire retardant is toxic to wildlife (some more than others) and potentially toxic to the people that work around it, and are exposed more than casually.

I recommend these five strategies:

  1. Watch for any visible fire retardant sign and don’t pick mushrooms there.
  2. Avoid picking. near strategic firebreaks like roads, meadows, rock outcrops. 
  3. Avoid structures and other assets that firefighters may have been protecting.
  4. Focus your harvest on the interior of fire perimeters
  5. Study the “avoidance zone” map above if you want to find areas where no retardant should have been applied.

I am inspired to leave you with a haiku, enjoy!

red spray fell last fall
sclerotium fruited this spring
they decompose red


Relevant Environmental Impact and Record of Decision docs:

2024 Aerial Fire Retardant Final Record of Decision, (PDF) (740 KB)

2023 Aerial Fire Retardant Final SEIS, (5 MB), (PDF)

2023 Notice of Availability of Final SEIS, (182 KB), (PDF)

2022 Aerial Fire Retardant Draft SEIS

Notice of Availability of Draft SEIS

2011 Record of Decision

2011 Final Environmental Impact Statement (FEIS)


If you are a mycologist or an expert or have any additional facts to shed, please comment below and add any resources. Likewise, if you think I missed something or am flat out wrong about something, please comment below (and share links to new fact!)

I will update this article if I am able to make it more accurate or more up-to-date or even just better!

Showing 10 comments
  • Patti Adams

    Very interesting. Thanks for looking in to this as best you could. I hope you will touch on this down in Brookings at our WRMC meeting. We had a pretty good dump of retardant on our local fire last summer.

    • Trent Blizzard

      Yes, I will make sure to discuss… there is not an easy answer. The USFS says don’t eat food with the retardant ON it. And it is OK to pick and eat berries and mushrooms the next season after regrowth. But somehow, that doesn’t address the concerns that people have. Obviously it is bad for wildlife, but that is primarily because of the algae blooms the nitrogen causes, and other fertilizer-related issues. Ultimately, it comes down to each persons’s comfort level since there is not proof of the “negative” that “this doesn’t hurt you”. I don’t want to try to “convince” people of anything! After doing this research, I personally would probably prefer to eat a mushroom picked the year following a fire retardant spray to a vegetable in the grocery store that has been directly exposed to pesticides and herbicides.

      • Dave Helmrick

        A note: wildlife such as elk LIKE the retardant. If I’d been faster would have gotten photo of cow elk licking metal fence post covered in retardant. Each morning would pick up elk moving off the retardant that hit some scree. They would not go after it on ground where it soaked into soil.

  • Kevin Sharman

    Thanks for this in depth look! And great AI image of glowing morels. Reminded me of the ski movie “The Burn” where they have special effects showing the burned trees glowing.

    • Trent Blizzard

      Thanks Kevin! I totally resist doing anything in AI – our blog is 100% human created and I have noted how much AI created content is flooding the webs with mushroom stuff…I feel like it easy to spot because their is no human touch to it or connection to it by the author. That will probably change.

      I want to really write our blog in a way that shows it was written by two mushroom loving human beings!

      but, in this case I just couldn’t resist using AI to make cool images for this post!


    I love it, wild organic Hand Written and picked.

  • Joseph

    I think a very significant point is over looked herein and that is why is American Industry so poisonous to begin with. don’t they have enough imagination and humanity to use products that are good for the environment and all of the living or life? Must we always look forward to one step forward and one step backward always ending up at zero?

    • Elizabeth (Beth)

      Thank you so much for a great article Trent! An age old question we have all asked year after year …when picking in the burns it seems. I think based on the article I might be more comfortable on a 2 year pass if fire retardant was involved.. but that’s just me. Thank you again and I will be spreading the shroom wealth of info to my buds!!

      • Trent Blizzard

        Elizabeth, I hear you! At the end of the day, there really isn’t an “answer” – I am trying to help people make informed decisions about eating burn morels, and the fire retardant risks, based on facts. FYI, I am allergic to morels… I pick them like crazy but never eat them because they make me sick. I just give them away :). But, I would eat them if I could.

  • Kathleen

    Great post, Trent! I learned a lot and appreciate the education…😊

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