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Seeing Red

Controversy smolders over federal use of aerially applied fire retardants

by Cheryl Hogue
August 29, 2011 | A version of this story appeared in Volume 89, Issue 35

Credit: Roger Archibald
A plane drops fire retardant over a forest as ground crews battle flames nearby.
Credit: Roger Archibald
A plane drops fire retardant over a forest as ground crews battle flames nearby.

Dramatic images of planes releasing red fire retardant flashed in news reports about the enormous blaze that ripped through more than a half-million acres in Arizona and New Mexico this summer. The red-tinted chemicals applied on unburned vegetation by hired aircraft were employed by the U.S. Forest Service to help slow the progress of the fire. All told, air and ground crews battled flames for weeks before finally extinguishing them.

The red fire retardant dropped from planes may have aided in ending this and other wildfires, but it has sparked controversy. For years, opponents have decried the Forest Service’s use of these aerially applied chemicals, citing the negative impacts to the environment of the product’s main firefighting chemicals: ammonium phosphates.

These environmental concerns led to lawsuits against the Forest Service that forced the agency to prepare a detailed environmental impact statement on the fire retardants. Currently in draft form, this policy document could have a broad impact on how fire is controlled on federal lands. This is because the Forest Service, which is part of the Department of Agriculture, sets policy for use of fire retardants for all federal wildland fire management agencies, including the Bureau of Land Management and the National Park Service within the Department of the Interior.

Ammonium phosphates have been deployed from the air to fight forest fires for nearly 50 years. But the idea of using these compounds to control fire is far older. Joseph Louis Gay-Lussac, the French chemist and physicist who formulated a gas law that bears his name, first proposed the use of ammonium phosphates as flame retardants in 1821 (Ann. Chim. 1821,18, 211).

Unlike some of the brominated and chlorinated flame retardants in consumer goods from computer housings to upholstery foam, the chemicals sprayed on forests and scrubland aren’t considered persistent and bioaccumulative. In fact, the Forest Service’s draft analysis concludes, “No risks to line firefighters, airtanker base personnel, or the public were predicted for routine exposures” to aerially applied fire retardants.

Instead, the controversy over the Forest Service’s use of fire retardant focuses on environmental effects.

The group that is suing the Forest Service says the chemicals do little to combat fires and pose hazards to fish and some rare plants. The organization, Forest Service Employees for Environmental Ethics (FSEEE), a group promoting reforms in the Forest Service, wants the government to stop spraying retardant on federal lands.

FSEEE isn’t against just the U.S. government’s use of fire retardants. The organization says its goal is “to protect fish, wildlife, and rare plants from the Forest Service’s fruitless, self-defeating, extremely expensive, and environmentally destructive war against natural forest fires.” FSEEE views fire as a natural part of the ecosystems of most forests and believes the Forest Service pours too many resources into fighting fire. The group says fire requires thoughtful management that respects nature and ensures both healthy forests and the safety of homes and communities near federal wildlands.

Credit: Roger Archibald
The Forest Service hires private planes and helicopters to apply the fire retardant it purchases.
Credit: Roger Archibald
The Forest Service hires private planes and helicopters to apply the fire retardant it purchases.

The organization filed suit in 2004 against the Forest Service over the use of fire retardants. In 2005, a federal trial court in Montana found that the Forest Service had failed to conduct an environmental analysis of aerially applied fire retardants on federal lands. This, the court said, violated the National Environmental Policy Act, a law that requires the U.S. government to formally consider ecological issues when making decisions. The court also determined that the Forest Service violated the Endangered Species Act by failing to consult with other federal agencies on the use of fire retardants.

In response, the Forest Service in 2007 issued an environmental assessment and a finding of no significant impact from the use of retardants. The agency amended the assessment a year later to include “reasonable and prudent alternatives” for use of fire retardants that were recommended by the Interior Department’s Fish & Wildlife Service and the Commerce Department’s National Oceanic & Atmospheric Administration (NOAA).

In 2008, FSEEE filed a second suit, challenging the adequacy of the Forest Service’s environmental assessment and the advice from the Fish & Wildlife Service and NOAA. The federal court in Montana last year ordered the Forest Service to prepare a more detailed document, called an environmental impact statement (EIS), and to make a final decision about retardant usage by Dec. 31, 2011. If the Forest Service fails to act by that deadline, the agency could face an injunction against using aerially applied fire retardants, Judge Donald W. Molloy warned in the July 2010 order.

In accordance with the court’s instructions, the Forest Service drafted an EIS and released the document in May. The draft proposes to continue aerial application of fire retardants.

“The use of fire retardant, in concert with firefighters on the ground, allows the Forest Service to safely protect landscapes, resources and, most importantly, people’s lives,” Forest Service Chief Thomas Tidwell said when the agency released the draft EIS. “Research and experience demonstrate that aerially applied fire retardant, used in an appropriate manner, reduces wildfire intensity and the rate of spread, which increases the effectiveness of our fire suppression efforts on the ground.”

But FSEEE questions whether using the retardants actually saves firefighters’ lives or leads to fewer acres burned or fewer homes destroyed. “The Forest Service uses retardants because they can, not because it is helpful,” says Andy Stahl, executive director of the group. For instance, aerially released retardants can’t be used effectively against windblown fires as winds not only make flying dangerous, but they also make effective application nearly impossible because the chemicals dissipate.

Retardant is generally used in areas ground-based firefighters can’t easily get to. The Forest Service’s draft document says: “In some instances, high fire intensities and rates of spread greatly reduce the ability of ground-based firefighters to safely fight wildland fires. In addition, remote locations and rugged topography can delay the deployment of ground forces for suppression.”

When it opts to drop retardant, the Forest Service hires pilots and planes or helicopters to apply it. The privately owned craft are mainly prop-driven planes that can fly slowly and low to the ground, allowing crews to apply retardant accurately.

The chemicals dropped from the air are not used directly on flaming vegetation. Instead, they are applied to areas before the fire reaches them. According to the Forest Service, most aerially applied retardant gets released on ridgetops or adjacent to roads, rock outcrops, and meadows which serve as firebreaks. These areas, where there is little fuel to burn, can slow the spread of a fire and help firefighters gain the upper hand against flames. Because retardant gets spread before the fire reaches an area, it helps widen a firebreak, the Forest Service says.

Nearly all retardant the Forest Service buys to fight wildfires is used in the western U.S. Virtually none is used to combat fires east of the Mississippi River, Stahl says. Conflagrations regularly occur in national forests in the Appalachian Mountains, he says, albeit not as frequently as in the huge swaths of federal land in the arid West. For example, a federal spokesman tells C&EN that firefighters are not using retardant against the ongoing fire in the Great Dismal Swamp area in eastern Virginia and North Carolina.

In fact, according to the Forest Service, most wildfires on federal lands are managed without the use of fire retardants. Some 90 million gal of fire retardant was dropped from aircraft on national forest lands from 2000 to 2010, according to the draft EIC. The agency estimates that fire retardant is applied to between 2,358 and 4,715 acres of this land each year. This is about 0.002% of Forest Service acreage, according to the draft.

The Forest Service budget for wildland fire management was $2 billion each in fiscal 2009 and 2010, though Congress also appropriated $413 million in a reserve fund for firefighting in 2010. Much of the service’s budget went to hire firefighters, aircraft, and pilots. But the agency spent $17 million in fiscal 2009 and $10 million in 2010 to procure fire retardants for aerial application, an agency spokeswoman tells C&EN.

A single company supplies these retardants to the U.S. government: ICL Performance Products LP (ICL-PPLP), the St. Louis-based subsidiary of Israel Chemicals Ltd. (ICL).

ICL-PPLP’s Phos-Chek products currently are the only aerially applied retardants that meet Forest Service requirements, according to the agency and the company. Those specifications include that the products undergo health and safety testing and are studied for their efficacy in slowing fires, and that retardant concentrates are stable for at least 52 weeks and meet standards for color and viscosity.

ICL-PPLP also is the sole supplier of aerially applied retardant to Canada’s provincial fire management agencies. The company manufactures Phos-Chek at two U.S. facilities—in Ontario, Calif., and Moreland, Idaho—and two in Canada—in Kamloops, British Columbia, and Fort Saskatchewan, Alberta.

The first aerially applied Phos-Chek product was introduced in 1962 by Monsanto, says Edward Goldberg, ICL-PPLP business director for fire safety. That business passed to Solutia in 1997 and to Astaris in 2000. ICL purchased Astaris in 2005 and a Canadian competitor, Fire-Trol, in 2007. All ICL-PPLP’s aerially applied fire retardant is now sold under the Phos-Chek brand.

Retardants Drive Wood Decomposition To Dehydration, Hinder Ignition

Trees and brush don’t just ignite from a stray spark. Wood itself, composed of cellulose, a natural polymer, doesn’t burn.

For wood to catch fire, heat—such as that generated by an approaching wildfire—must first thermally degrade cellulose. Decomposition, however, happens via two processes, one of which results in fire and the other imparts a protective carbon coating to wood.

The predominate decomposition process is depolymerization, which breaks the molecular bonds of cellulose. This initially produces a tarry mixture of which levoglucosan is a major constituent. Further heating turns this goo into volatile compounds that include alcohols, aldehydes, hydrocarbons, and ketones. The gases escape from the tree and can react—ignite—with atmospheric oxygen in the exothermic, light-emitting process called fire.

A smaller amount of decomposition takes place through dehydration. In this process, cellulose breaks down to water vapor and a solid that becomes slow-burning or smoldering char, a carbon-based solid that can eventually turn to ash. Char also forms an insulating barrier on wood that can slow further thermal degradation of cellulose.

Treating vegetation with ammonium phosphate-based fire retardants alters the balance of decomposition processes, leading to more dehydration and less depolymerization, explains Edward Goldberg, ICL Performance Products LP business director for fire safety.

The firm produces the aerially applied fire retardant used by the U.S. Forest Service. This happens because at the high temperatures generated by forest fires, the phosphates in fire retardants decompose to phosphoric acid and then to water and phosphorus pentoxide, Goldberg says.

P2O5 causes dehydration of cellulose and thus promotes formation of char instead of flammable tars. The water vapor released in dehydration both helps cool the fire and reacts with P2O5 at lower temperatures to regenerate phosphoric acid, he says.

Because the phosphoric acid is regenerated repeatedly, Goldberg says, “a small amount of retardant will treat a large amount of fuel.”

These products are mixed with water to make a slurry before they are loaded onto aircraft that will deliver the retardant. The mixture is about 85% water. The rest is retardant and additives including corrosion inhibitors, thickeners, and suspension agents. According to the Phos-Chek website, “The water contained in the fire retardant solution functions only as a carrier for the fire retardant, evaporating before arrival of the fire and, consequently, contributing little in terms of fire retardancy.”

Phos-Chek products applied from the air are long-term fire retardants—meaning they are effective for days to months, depending on rainfall. Once sprayed on vegetation, “retardant will be effective until it is physically removed by one-fourth to one-half inch of rain,” Goldberg says.

The slurry dropped from aircraft is colored a dramatic red to help air crews in applying it. “Pilots must be able to see retardant on the ground so they can tie drops together to form a continuous line,” Goldberg explains.

The vivid red Phos-Chek dropped from planes gets its color in one of two ways. One line of these products contains iron oxide pigments that fade slowly with time. A second contains a food-grade dye that disappears after a few days with exposure to sunlight, Goldberg explains. Both types of products work the same against fires; persistence of the color is up to the customer. Managers of some public lands prefer to have the nonstaining color, Goldberg says.

The Forest Service’s draft EIS notes that use of retardants can have “a temporary impact on scenic resources on National Forest System lands.” It adds, “Most commonly, the effect on the scenic resource is short-lived and of minimal consequence.”

But the colorant isn’t the ingredient that is the focus of the controversy over the use of fire retardants. The ammonium phosphates are.

Credit: Roger Archibald
Retardant sticks to a tank on a plane after an airdrop.
Credit: Roger Archibald
Retardant sticks to a tank on a plane after an airdrop.

If sprayed on mountain streams, the retardant dissolves and releases ammonia, which is toxic to fish. Ammonia, the Forest Service says, is the most toxic ingredient in long-term fire retardants. A release of hundreds or thousands of gallons of fire retardant can wipe out fish life for miles along a stream, says Stahl of FSEEE.

Fish aren’t the only concern. When areas that are treated with fire retardants get rain, the chemicals wash off and into the soil. This provides nitrogen and phosphates that are plant fertilizers, says a company information sheet about Phos-Chek.

This fertilizing effect can pose a risk to threatened or endangered plants, many of which have evolved to live on soils that are low in nutrients, Stahl says. The extra nutrients often encourage the growth of invasive, noxious weeds that outcompete native plants, he explains.

The Forest Service now requires pilots to avoid the aerial application of retardant in areas with endangered, threatened, or sensitive species and within 300 feet on either side of streams and other waterways. According to the agency, only one of every 5,000 retardant drops in the past decade has impacted waterways in lands managed by an agency, the Interior Department, or states. Meanwhile, Goldberg says Phos-Chek retardants have been rigorously tested and meet the Forest Service’s stringent standards for safety, health, and environment, including mammalian and fish toxicity.


This summer, the Forest Service held a series of public “listening sessions” about its draft EIS. It will consider comments from the public as it finalizes its policy on the use of fire retardants.

What will happen after the agency issues a final version of the impact statement is uncertain. It’s possible that the controversy will continue in federal court. ◾


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