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How safe is firefighting foam?
With recent attention focused on firefighting foam contaminating groundwater, here's a closer look at the foam, the risks and the preventions
Firefighters use Aqueous Film Forming Foams to help extinguish difficult-to-fight fires, particularly fires that involve petroleum or other flammable liquids ‚ known as Class B fires. However, not all firefighting foams are classified as AFFF.
Some AFFF formulations contain a class of chemicals known as perfluorochemicals (PFCs) and this has raised concerns about the potential for contamination of groundwater sources from the use of AFFF agents that contain PFCs.
In May 2000, the 3M Company said it would no longer produce PFOS (perfluorooctanesulphonate)-based flurosurfactants using the electrochemical flouorination process. Prior to this, the most common PFCs used in firefighting foams were PFOS and its derivatives.
During the last few years, the firefighting foam industry has moved away from PFOS and its derivatives as a result of legislative pressure. Those manufacturers have developed and brought to market firefighting foams that do not use fluorochemicals, that is, that are fluorine-free.
Manufacturers of fluorine-free foams say these foams have less impact on the environment and meet international approvals for firefighting requirements and end-user expectations. Nonetheless, there continues to be environmental concerns about firefighting foams and research on the subject continues.
Concerns over AFFF use?
The concerns center around the potential negative impact on the environment from the discharge of foam solutions (the combination of water and foam concentrate). The primary issues are the toxicity, biodegradability, persistence, treatability in wastewater treatment plants and nutrient loading of soils. All of these are cause for concern when foam solutions reach natural or domestic water systems.
When PFC-containing AFFF are repeatedly used in one location over a long period of time, the PFCs can move from the foam into soil and then into groundwater. The amount of PFCs that enter the groundwater depends on the type and amount of AFFF used, where it was used, the type of soil and other factors.
If private or public wells are located nearby, they could potentially be affected by PFCs from the place where AFFF was used. Here's a look at what Minnesota's Department of Health published; it is one of several states testing for contamination.
"In 2008-2011, the Minnesota Pollution Control Agency (MPCA) tested the soil, surface water, groundwater, and sediments at and near 13 AFFF sites around the state. They detected high levels of PFCs at some of the sites, but in most cases the contamination did not affect a large area or pose a risk to humans or the environment. Three sites — Duluth Air National Guard Base, Bemidji Airport, and Western Area Fire Training Academy — were identified where PFCs had spread far enough that the Minnesota Department of Health and MPCA decided to test nearby residential wells.
"This is more likely to occur near places where PFC-containing AFFF has been used repeatedly, such as a fire training areas, airports, refineries, and chemical plants. It is less likely to occur from the one-time use of AFFF to fight a fire, unless large volumes of AFFF are used. Although some portable fire extinguishers may use PFC-containing AFFF, one time use of such a small amount would be unlikely to pose a hazard to groundwater."
A discharge of foam/water solution would most likely be the result of one or more of the following scenarios:
- Manual firefighting or fuel-blanketing operations;
- Training exercises where foam is being used in the scenarios;
- Foam equipment system and vehicle tests; or
- Fixed system releases.
Locations where one or more of these events would most likely occur include aircraft facilities and firefighter training facilities. Special hazard facilities, such as flammable/hazardous material warehouses, bulk flammable liquid storage facilities and hazardous waste storage facilities, also make the list.
It's highly desirable to collect foam solutions after its use for firefighting operations. Besides the foam component itself, the foam is very likely contaminated with the fuel or fuels involved in the fire. A regular hazardous materials event has now broken out.
Manual containment strategies used for spills involving a hazardous liquid should be employed when conditions and staffing permit. These include blocking storm drains to prevent the contaminated foam/water solution from entering the wastewater system or the environment unchecked.
Defensive tactics such as damming, diking and diverting should be employed to get the foam/water solution to an area suitable for containment until it can be removed by a hazardous materials cleanup contractor.
Training with foam
There are specially designed training foams available from most foam manufacturers that simulate AFFF during live training, but do not contain flourosurfactants like PFC. These training foams are normally biodegradable and have minimal environmental impact; they can also be safely sent to the local wastewater treatment plant for processing.
The absence of flourosurfactants in training foam means that those foams have a reduced burn-back resistance. For example, the training foam will provide an initial vapor barrier in a flammable liquids fire resulting in extinguishment, but that foam blanket will quickly break down.
That's a good thing from an instructor's point of view as it means you can conduct more training scenarios because you and your students are not waiting for the training simulator to become burn ready again.
Training exercises, particularly those using real finished foam, should include provisions for the collection of spent foam. At a minimum, fire training facilities should have the ability to collect the foam solution used in training scenarios for discharge to a wastewater treatment facility.
Prior to that discharge, the wastewater treatment facility should be notified and permission granted to the fire department for the agent to be released at a prescribed rate.
Surely the developments in induction systems for Class A foam (and perhaps the agent chemistry) will continue to advance as it has over the past decade. But as for Class B foam concentrates, agent chemistry development efforts seem to have been frozen in time with reliance on existing base technologies.
Only since the introduction of environmental regulations during the past decade or so on fluorine-based AFFFs have the firefighting foam manufacturers taken the development challenge seriously. Some of these fluorine-free products are first generation and others second or third generation.
They will continue to evolve in both agent chemistry and firefighting performance with the goal of achieving high performance on flammable and combustible liquids, improved burn-back resistance for firefighter safety and provide for many additional years of shelf life over foams derived from protein.