The impact of fire department operations on the environment
Published: 01 January, 2009
Fire fighting operations almost always represent a balance between extinguishing fire, saving of human life or property, or otherwise resolving the incident – for example dealing with a hazardous materials spill – and the impact of these operations on the environment.
Two different aspects of operational procedures need to be assessed both strategically and tactically for the risk these pose of damaging the environment. First, what effects, potential or immediate, do normal fire fighting procedures and extinguishing agents have on the environment. Secondly, at incidents involving hazardous materials (Hazmat), what procedures can be used to mitigate damage caused by release of toxic materials either directly or as part of fire-water run-off.
Halons are probably the best example of extinguishing agents with a serious and unacceptable environmental impact. Identification of the damage to the atmospheric ozone layer caused by free radical breakdown of halons, especially over the poles, resulted in the 1974 Rowland-Molina hypothesis and in 1995 the Nobel Prize in Chemistry for Crutzen, Molina and Rowland. This work led to the banning of certain halons through the 1987 Montreal Protocol which came into force on 1st January 1989 and to the development of more environmentally friendly alternatives. Recent data suggest that the upper atmosphere is now recovering with ozone depletion halted by 1994 (2002, World Meteorological Organization, Global Ozone Research and Monitoring Project Report No. 47, WMO, Geneva, 2003), indicating that concerted international effort can remedy or even reverse environmental damage, leading Kofi Annan to call it ‘perhaps the single most successful international agreement to date’.
Replacement of halons highlights a problem which is highly topical in the current discussion of AFFF fluorosurfactant-containing fire fighting foams versus fluorine-free alternatives. Whereas there are still legitimate concerns about the efficiency of halon substitutes, similar critical concerns about fluorine-free foams expressed by manufacturers of traditional AFFF seem now unfounded and based on hearsay and commercial self-interest. Currently there are available on the market Class B foam concentrates that are completely fluorosurfactant-free, have the relevant approvals such as EN 1568 and ICAO, satisfy the petrochemical industry standard LASTFIRE for both freshwater and seawater, and can be used efficiently on both non-polar and polar fuels (AR-type foams). Indeed under certain rigorously and independently controlled test circumstances one of these fluorine-free products has even been found to outperform traditional AFFF!
An argument often put forward in the industry against fluorine-free Class B foam concentrates and indeed Class A foams or additives (also known as wetting agents), is that these are more acutely toxic to the aquatic environment than fluorosurfactant-containing AFFF foams because they use hydrocarbon surfactants. All foams contain surfactants which are detergents that cause lowering of the surface tension of water from its normal value of 72 dynes/cm to between 20 and 30 dynes/cm. This lowering of the surface tension of water is inimical to most organisms. Acute toxicity is, by definition, short term and most ecosystems recover rapidly, except under arid or desert conditions. But what is important to remember is that the acute toxicity of different foams must be compared at their final working concentration as finished foam not as the concentrate. When this is done there is often little to choose between the various formulations.
What are the environmental issues involved in using fluorosurfactant fire fighting foams operationally?
All fluorosurfactants, whether manufactured by the PFOS-based Simons ECF method or the modern fluorotelomer process, when they are broken down chemically or biologically produce highly stable, environmentally persistent fluorinated degradation products. These can be toxic and bio-accumulative to varying degrees. The combination of persistence, bio-accumulative potential and toxicity is known as the substance’s PBT profile.
In the case of the legacy PFOS-based products the end-product of breakdown is PFOS itself. PFOS has been found to be dispersed worldwide in a large variety of animal species including man, as well as in animals whose habitats are far removed from any obvious source of contamination such as the polar regions. PFOS is known to be toxic, affecting hormonal metabolism and reproduction in test species, and is bio-accumulative showing bio-magnification in the food chain. The lithium salt of PFOS is classified in the USA as an insecticide for use against wasps and hornets. PFOS is so chemically stable that it will withstand hot nitric or sulphuric acid for twenty four hours without decomposition!
A seminal paper in 1999 from Jennifer Field’s group at Oregon State University (Environmental Science & Technology 1999, 33, 2800; with a review EST 2000, 34, 200) demonstrated that high levels of PFOS persisted in groundwater at former US military firefighting foam-training sites a decade or more after the sites were last used. In some instances the groundwater was still foaming! This sort of data suggests that perfluorinated materials like PFOS are extremely persistent in the environment with half-lifes of the order of at least decades. The half-life is the time taken for 50 per cent to disappear, so that seven half-lives are required to reduce a concentration to ~1 per cent (actually (1/2)7 = 0.78 per cent) of the starting value. Many perfluorinated materials are exceedingly persistent in the environment: for example, fluoromethane CF4 is estimated as having an atmospheric half-life of between 10,000 and 20,000 years; trifluoroacetic acid CF3COOH, the simplest perfluorocarboxylic acid extensively used as a catalyst by industry, has no known degradation pathway in the aqueous environment.
In a later study published in 2004 Jennifer Field (Environ. Sci. Technol. 2004, 38, 1828) demonstrated that the degradation product from fluorotelomer foams, the fluorotelomer sulphonate 6:2 FtS or H-PFOS, also accumulated at very high concentrations in groundwater, persisting for at least decades. Moreover, 6:2 FtS concentrations were generally higher than PFOS at those sites that had seen both ECF (PFOS-based) and fluorotelomer foams used. One site showed only PFOS as a contaminant and no 6:2 FtS indicating that no fluorotelomer foams had been used. Another site exhibited incredibly high levels of 6:2 FtS, up to 14,600 micro g per litre (14.6 mg/l!), a decade or more after the site was last used. Interestingly the fluorotelomer sulphonate (6:2 FtS) is very persistent and clearly chemically highly stable in groundwater, although based on the scientific literature one would have expected to see bacterial breakdown giving perfluorohexanoic acid (C5F11COOH, PFHxA) as the final degradation product by a process of partial dehydrofluorination involving the -CH2-CH2- moiety. There is currently little information in the peer-reviewed scientific literature regarding the toxicity or bio-accumulative potential of the 6:2 fluorotelomer sulphonate. Reports at meetings have suggested that toxicity and bio-accumulation in limited test species are somewhat less than for PFOS, as might be expected based on the chemical structure. The chemical debris produced when fluorosurfactants breakdown may also include toxic materials such as PFOA, classified as a “likely carcinogen” by the US Environmental Protection Agency, used in their manufacture. There is now a voluntary EPA industry Stewardship Program aimed at a complete phasing out PFOA by 2015. Atmospheric breakdown of volatile fluorotelomer precursors has been implicated as the source of perfluorocarboxylic acids found dispersed worldwide.
The bottom line
The bottom line is that all fluorosurfactants, whether PFOS-based or fluorotelomer-based, produce very persistent long-lived fluorinated degradation products which are widely dispersed throughout the environment. Recent studies have identified such products throughout continental Europe, for example, in air samples, in rivers, lakes, soil and groundwater, in potatoes and in human breast milk, raising the toxicological spectre of maternal-foetal transmission. Stored human serum samples from before WWII when perfluorinated chemicals were not manufactured, were always negative for organic fluorine compounds which do not occur naturally. This is no longer true even for the general population not occupationally exposed to these chemicals.
Unfortunately because these fluorinated materials are so environmentally persistent, continued release into groundwater, whether direct or indirect, will result in increasing concentrations as time passes resulting ultimately in the no observable effect level (NOEL) being exceeded. This will occur whether or not the fluorinated material is toxic or relatively non-toxic; it will just take a longer or shorter time even for the relatively non-toxic compounds depending on the mass flow into groundwater. It is only a matter of time!
There are certain incidents at which foam must be used to protect human life or health even if this potentially puts the environment at risk. A decision has to be taken based on a comparative assessment of risk combined with a cost-benefit analysis given all the circumstances. This decision, which at the time has to be an operational one, must be grounded on well established strategic guidelines which have established politically and socially acceptable limitations and constraints to human risk and environmental impact. In European Member States local implementations of the EU Groundwater Directive forbid the discharge of organohalogens (this includes fluorosurfactants and their degradation products) to groundwater.
A foam concentrate with the correct specifications for the job in hand must be used. The current trend towards using a fluorosurfactant foam originally formulated for Class B hydrocarbon fires at a lower induction rate as a “one stop” solution for Class A carbonaceous fires, should be strongly discouraged. Class B fluorosurfactant foams do not penetrate carbonaceous fuels nearly as efficiently as properly formulated Class A products, so calling into question their “fitness for purpose” with all its legal implications. Moreover, because most Class B foams contain fluorosurfactant and most Class A fires, for example, wildland or bush fires, require highly dispersive application of foam directly onto vegetation and soil with no possibility of containing run-off, there is a very serious risk of contaminating surface and groundwater with highly persistent fluorinated degradation products. This is environmentally highly irresponsible, given that normal Class A concentrates do not contain fluorochemicals. The arguments given for a “one stop” philosophy range from procurement issues to a form of institutional laziness “. . . we can’t expect firefighters to distinguish between different types of foam concentrate on the incident ground. . . ”. Why not? That is what training is for!
If a fluorosurfactant foam must be used, and there are situations especially at fixed installations in the petrochemical and chemical process industries where this is still considered essential, then containment and subsequent treatment of fire-water run-off can be used to limit the environmental impact. Good bunding of storage areas, with bund volumes calculated to take all the stored volume of fuel plus the foam used to control the fire, together with drainage systems that can be isolated provide one solution. Allowing very large volumes of contaminated run-off to go to the local water treatment works may not be feasible. Old industrial chemical sites represent a huge environmental problem. They are generally inadequately bunded, near to watercourses and often surrounded by later office and residential development. At the Allied Colloids fire in the UK in 1992 the local water undertaking had to open the storm valves to protect its water treatment beds, needed for the sewage outflow from a very large conurbation, thus contaminating the Aire and Calder river systems and producing a 40-50 km “river kill”.
Where possible run-off should be contained for subsequent treatment and disposal by bunding and sealing access to the drainage system. If petroleum spirit interceptors have been fitted, eg, on motorways, airport runways or training areas, it should be remembered that the detergent action of foam is very effective at thoroughly cleaning them by destroying their function and carrying through hydrocarbon deposits! For incidents requiring Class B foam at which containment is all but impossible, for example, motorway incidents, aircraft crashes, petrol station fires, fires involving shipping or harbour facilities, one should consider alternative solutions in addition to using a fluorine-free product.
Alternative extinction technologies may be more appropriate than classical foam systems in specific instances. For example, water mist or fog, compressed air foam systems (CAFS), hydrophilic gels, or free-radical chain breaking powders. Combined branches using both powder and foam may have a place also, especially in the petrochemical industry.
Hazmat incidents – or even a CBNR incident which is nothing more than a Hazmat incident writ large associated with logistical, political and societal problems – embody all the problems mentioned above: contamination of groundwater, acute and chronic toxicity, stable degradation products, and the need for containment of run-off. What distinguishes a Hazmat is often, unfortunately, the amount of toxic material released. Absolute amounts are misleading. More useful is the idea of how many “toxic units” have been released and this can be estimated from the value for the biological toxicity. If, for example, the material has an aqueous LD50 toxicity of 1 mgm/l and 1 tonne has been allowed to run off into a water course, then potentially you have at least 1 million litres or 1,000 m3 of water contaminated at the LD50 level, or 106 toxic units released.
In all fire fighting operations that involve potential environmental contamination, whether operationally as in the use of foam, during a Hazmat or CBNR incident, or even when a decision is made to let a fire burn itself out, a suitable and sufficient assessment of risk and a cost-benefit analysis must be carried out. This assessment and analysis should be done strategically as part of emergency planning as well as tactically as part of operational incident management.
A decision to let a fire burn out may be the best solution environmentally. Highly toxic material, whether chemical or biological, may be destroyed or rendered harmless thus preventing dispersion of the hazard. An interesting example is an LNG (liquefied methane) fire which produces heat, carbon dioxide and water. If it is extinguished then the liquefied methane will vaporise. In terms of environmental impact caused by the global warming potential (GWP) of the gases, it is far better to let the fire burn. The carbon dioxide produced has a GWP = 1, whereas the 20-year GWP for methane is 72! There are, however, reasons for not letting a fire burn out; these may be political – large black smoke clouds are unpopular – or due to the possibility of radiant heat damage. Each incident must be assessed on its own merits.
Finally do not forget that although acute toxicity is short lived and systems generally recover, the same cannot be said for chronic effects. Especially if this involves discharging a highly persistent contaminant to atmosphere or into groundwater, an increasingly rare and valuable resource in many parts of the world. Continuing discharge of highly stable contaminants such as fluorocarbon sulphonates or any other perfluorinated material to groundwater will lead to increasing levels over time with unknown and unpredictable results given what little we know of their long-term toxicity and bio-accumulative potential. The precautionary principle dictates that we should avoid such “opened ended” contamination scenarios if at all possible. Remember protect your groundwater, protect your livelihood!
