Emergency! Emergency! Evacuate now!
Published: 01 January, 2007
A recent session organised by the German Federal Environment Agency at the Annual Meeting of German State Public Health Institutes held in Berlin at the end of March 2006, was entitled “Fluorosurfactants - a Blessing for Consumers or an Unrecognised Risk?”.
The risks and benefits of using fluorosurfactants for the consumer were discussed, including their use in firefighting foams. Currently, fluorosurfactant (PFT or Perfluortenside in German) use had become a highly politicised issue in Germany as the result of degradation products such as PFOS, PFOA and PFHxA being found in human serum, drinking water and even breast milk.
A complete ban on fluorosurfactants?
Environmental politics is far more pro-active in Germany than in many other European countries, with the Green Party forming part of the coalition making up the Federal Government. Political pressure is growing for a complete ban on the use of fluorosurfactants.
Although ultimately a complete ban is unlikely for a number of reasons, both technical and commercial/legal, it does mean that the environmental impact of fluorosurfactants, as well as the conditions under which they are used, will be examined very closely in the coming months.
In the mere six to nine months since the meeting in Berlin, a number of important studies have been carried out and published by both academic institutes and State Health Authorities.
On the 25th October 2006 the European Parliament announced that it had adopted a resolution by 632 votes to 10, with 20 abstentions, accepting a proposed Directive aimed at eliminating, or at least substantially limiting, the use of PFOS-based surfactants.
Interestingly, the originally proposed derogation for firefighting foams has been dropped. Under the Directive all new foams must be PFOS-free. Foams containing PFOS that have already been placed on the market may be used until four-and-a-half years after the Directive comes into force, most likely early 2007.
PFOS is a ‘dead duck’
Two years after the Directive comes into force, i.e., sometime in 2009, Member States must provide an inventory of all existing stocks of PFOS-containing firefighting foams as well as listing the amounts used and released into the environment.
Thus in many senses, the issue of PFOS in firefighting foams is a ‘dead duck’! The only remaining issues are foam use during the transitional period and replacement of current stocks.
As a result of the Buncefield storage depot fire in December 2005, many of the same environmental issues are now topical in the UK. These include contamination of the water table by firewater run-off at major incidents, the measures that are necessary to contain the very large volumes of contaminated run-off produced, both operationally and at the planning stage, and what procedures are available for treating run-off so that it can be discharged safely to the aqueous environment.
All modern traditional AFFF Class B firefighting foam concentrates have used fluorosurfactants produced by the fluorotelomer manufacturing process, ever since the 3M company announced that it was ceasing production of PFOS-based surfactants by the electrochemical fluorination (ECF) process in 2000.
Considerable efforts have been made over the past five or six years by the fire engineering industry to produce fluorine-free foams, or at least foams with a much reduced fluorine content, while still retaining a Class B capability. Unfortunately, firefighting foams are often used under highly dispersive conditions under which containment may be all but impossible. Alternative technologies continue to be explored.
Two issues must be separated clearly. These are the short-term and long-term effects of releasing finished foam, which may be chemically contaminated, to the environment.
In the short-term, the damage done to ecosystems is primarily due to the detergent properties of the surfactants present, as well as due to additives such as glycols, bactericides, or metal ions, unless the run-off is contaminated with other highly toxic materials such as heavy metals or cyanides, for example.
Damage is usually immediate and short-lived, limited in time by the biodegradability of the individual chemical components making up the foam concentrate.
Unless the area is unusually sensitive, or an individual component highly toxic, ecosystems recover remarkably quickly. Testing for acute toxicity is carried out against a series of vertebrates and invertebrates, and is reported as the number of milligrams of test substance per litre of water needed to produce a 50% kill rate (the lethal concentration LC50) or 50% inhibition of a particular metabolic process (the effective concentration EC50).
Large values indicate less toxicity than small LC50 or EC50 values. Typical values for aquatic toxicity as given by the US Fish and Wildlife Service (USFWS) are as follows: <0.01 mg/l = super toxic; 0.01-0.1 mg/l = extremely toxic; 0.1-1.0 mg/l = highly toxic; 1-10 mg/l = moderately toxic; 10-100 mg/l = slightly toxic; 100-1000 mg/l = practically non-toxic; >1000 mg/l = relatively harmless. This scale is far too complex for normal use.
The OECD scale on the other hand is considerably more practical, having only three categories: <1.0 mg/l = highly toxic; 1.0-10.0 mg/l = toxic; 10.0-100.0 mg/l = harmful.
What about short term toxicity?
Claims are often made by the industry that Class A-type ‘wetting agents’ are much more toxic than Class B AFFF concentrates. It must be remembered first of all that all firefighting foams would be classified as wetting agents based on the NFPA criterion of reducing the surface tension of water to less than 30 Newtons/metre.
Secondly, it is the finished foam that is normally discharged to the environment not the concentrate. Class A additives are used at between 1/10 and 1/20 of the concentration of Class B concentrates. A Class B concentrate is inducted at either 3% or 6%, whereas Class A additives are used at between 0.1-1%.
When allowances are made for the dilution used in finished foams, the LC50 or EC50 for all foams whether Class A or Class B will be greater than ~200 mg/l, i.e., they would all be classified as ‘practically non-toxic’ under the USFWS criteria and not even harmful under the OECD rules.
Long-term toxicity problems
Long-term toxicity is more complex. This not only depends on the toxicity of individual components of the foam concentrate but also on that of the degradation products.
Moreover, certain chemicals may be taken up preferentially and concentrated by living organisms - processes known as bio-accumulation and bio-magnification.
Although most foams contain chemical substances which are biodegradable by soil or sewage bacteria, as well as liver enzymes, the perfluoro-tail of all fluorosurfactants, whether made by the obsolete PFOS method or the current fluorotelomer process, is chemically extremely stable and cannot be completely degraded biologically.
Such perfluoro residues are extremely persistent in the environment. Studies from Jennifer Field’s group at Oregon State University have shown that the half-lives in groundwater for PFOS (perfluoro-octanyl sulphonate) derived from the 3M series of LightWater(tm) or ATC(tm) foams, or H-PFOS (6:2FtS, fluorotelomer sulphonate) from fluorotelomer foams, are certainly of the order of a decade or more. PFOS and perfluoro-octanoic acid (PFOA) have been found in both humans and other animal species throughout the world.
These perfluoro degradation products are extremely persistent in the environment and widely dispersed throughout the biosphere. The environmental impact of a substance is characterised by its persistence, bio-accumulation, and toxicity (PBT) profile.
How serious is PFOS?
In the case of PFOS, it is classified as vPBT, meaning that it has been shown to be very persistent, to bio-accumulate in living organisms and to be toxic to living organisms.
H-PFOS (6:2FtS) is also very persistent but there is as yet insufficient evidence available to say for certain whether it too bio-accumulates to the same extent and is toxic to the same degree as its chemical analogue PFOS, although the index of suspicion remains high.
Because these perfluorinated degradation products are environmentally very persistent and of either known or suspected bio-accumulative and toxic potential, it is essential to take all practical steps to prevent them entering groundwater - the ‘precautionary principle’.
Once groundwater has become polluted with an environmentally-persistent contaminant, it is impossible to remove it. Perfluorinated residues have been shown to accumulate in sludges and sediments in waste-water treatment plants. These are then often spread on agricultural land, thus ultimately contaminating groundwater.
Discharging fluorosurfactants is forbidden
Contrary to popular belief and some recent statements in the technical press, discharge of PFOS-based fluorosurfactants as well as all other fluorosurfactants and their degradation products, including those of fluorotelomer origin, is, indeed, covered by legislation in the UK, i.e., the Groundwater Regulations 1998, which are based on the EU Groundwater Directive.
These Regulations prohibit the discharge of any List 1 substances to groundwater and this includes “...1(a) organohalogen compounds and substances which may form such compounds in the aquatic environment;...”.
A substance can only be downgraded by the national competent authority in writing if the following condition is fulfilled: A substance is not in list I if it has been determined by the [Environment] Agency (the UK Competent Authority) to be inappropriate to list I on the basis of a low risk of toxicity, persistence and bioaccumulation.
Limiting environmental impact
There are basically three ways of preventing or limiting fluorosurfactants or their degradation products entering the aquatic environment:
(i) Contain and treat all firewater run-off. Large petrochemical or chemical process plant installations, as well as tank farms, should be bunded so that the entire inventory, plus any foam needed, can be contained. Bunds must be isolated from drainage systems. Open areas like airport runways or areas used for training, unloading or handling hazardous materials should be constructed so that any contaminated run-off can be diverted to holding tanks. Containment is more difficult at old industrial sites or on motorways.
Attempts should be made, however, to prevent foam contaminated run-off entering drains, rivers and streams. Remember that firefighting foam is a detergent and will destroy the function of oil/petrol interceptors by flushing them out! Retained run-off should then be treated before discharge - see below;
(ii) Do not discharge portable extinguishers to the environment during maintenance procedures. Foam extinguishers are fully discharged and then refilled every five years as part of normal maintenance procedures. The discharged foam is normally disposed of either into toilets or down drains but also sometimes directly onto waste ground.
In the UK this amounts to some 2.6 million litres of finished foam a year, far exceeding the volume from portable extinguishers used in anger (two reports from trade associations, one from FETA and another from FIC, suggest about 0.5% of the total extinguisher foam is used for firefighting each year with 20% of the remaining 99.5% being discharged as part of maintenance). Thus maintenance represents a very substantial source of potential environmentalcontamination with fluoro-surfactants, which should therefore be collected and treated before disposal - see below - whereas the use of the extinguishers for firefighting does not; and
(iii) Use fluorine-free foams or those with a much reduced fluorine content. Considerable advances have been made in the last five years.
A number of companies provide true fluorine-free foam concentrates, such as Bio-Ex’s ECOPOL, Arctic Foam’s self-healing foams and 3M Australia’s RF6 series, with Class B performance to international test standards such as UL 162 and EN 1568. Other companies provide foam concentrates with a much reduced fluorine content.
Fixed CAFS systems also perform up to Class B standards using either Class A or Class B concentrates at reduced induction rates, as shown by work originally carried out by Crampton and Kim under the auspices of the National Research Council of Canada, and developed commercially as ICAF(r) Integrated Compressed Foam systems by FireFlex Systems Inc.
Treatment of run-off
Foam-contaminated firewater run-off can be treated in a number of ways in order to remove fluorosurfactants and their degradation products.
A recent FFFC Newsletter contains a report of the successful treatment by DuPont of 1.1 million gallons (5 million litres) of wastewater from an incident at a Missouri oil refinery in 15 days using 4.5 tonnes of granulated activated carbon (GAC) in a trailer-mounted system, based on a method first published by Martial Pabon and his colleagues (J. Fluorine Chem. 2002, 114, 149).
Catalytic-waterpurification represents another, potentially useful method for purifying large quantities of wastewater.
The Prosys (Bremen) system uses singlet oxygen generated photo-catalytically from a green dye to destroy contaminants. Methods specific for perfluorinated materials have been reported by Hori’s group in Japan (Environmental Science & Technology 2003-2006) based on high intensity ultraviolet (UV) irradiation of solutions containing catalysts such as persulphate or zero-valent iron in order to mineralise the fluorinated material giving fluoride ions which may then be converted to calcium fluoride, CaF2.
Recycling foams & powders
Bad commercial practices can ‘masquerade’ as environmental responsibility. The recycling of foam solution or powder from handheld extinguishers might appear, at first sight, to be an environmentally-responsible way of dealing with the disposal problem resulting from the requirement to discharge an extinguisher every five years as part of maintenance procedures.
Re-filling of extinguishers with used foam solution or powder, however, is thoroughly undesirable. At best it represents fraudulent practice as the end customer no longer has a guarantee of performance for the next five years or any idea of potential shelf-life.
At worst, it compromises the efficiency of the extinguisher in what is potentially a safety-critical application. There can be no guarantee on re-filling that the original foam solution, which would have had the manufacturer’s warranty, has been used thus invalidating the Kitemark.
Both powders and foam solutions degrade over time, as does the lining of the extinguisher body. Out-of-date powders aggregate and are unlikely to meet the requirement for >90% discharge as specified in EN3 and BS5306.
Actual rating and lifetime are unknown if an extinguisher has been refilled with used material. Inadvertent contamination of powders with those of a different type, either during refilling or during manufacture, can result in ammonia being released and the over-pressure disk rupturing.
The bottom line ...
Remember, there are no environmental shortcuts that do not result in a price being paid, either now or by future generations. Profit today may turn into considerable legal liabilities tomorrow, especially if the water table or aquatic environment become irreversibly contaminated!