to the fluorinated surfactants (fluorosurfactants)
that are a key ingredient in aqueous film-forming
foams (AFFF). Fluorosurfactants provide AFFF
agents with the required low surface tension and
positive spreading coefficient that enables film
formation on top of lighter fuels. It is this film
formation capability that gives AFFF its name and
its effectiveness against flammable liquid fires.
3M used a unique process to manufacture the
fluorinated components of the fluorosurfactants
contained in its AFFF formulations. The process is
called electrochemical fluorination (ECF), and
fluorosurfactants produced by this process both
contain and degrade into a chemical known as
PFOS (perfluorooctyl sulfonate). Other competitive
manufacturers use a process called telomerization
to produce the chemical components of the
fluorosurfactants contained in AFFF agents. Chem-
icals produced by this process are generally
referred to as fluorotelomers.
Over the past several years there has been a
substantial shift from PFOS-based AFFF agents to
equally or more effective AFFF agents containing
fluorotelomer-based fluorosurfactants (see Figure
1). With the withdrawal of the PFOS-based prod-
ucts due to their persistence, bioaccumulative and
toxic properties (beginning in May 2000) and their
subsequent regulation by various national govern-
ments, makers of fluorotelomer-based products
began more intensive study of the toxicology and
environmental fate of their products.
Environmental impacts of
fluorosurfactants
A primary debate about fluorotelomer-based prod-
ucts centers on the perceived similarity to PFOS,
the presence and/or generation of perfluoro-
carboxylic acids (PFCAs) such as perfluorooctanoic
acid (PFOA), and the ultimate breakdown products
of these surfactants.
First and foremost, fluorotelomer-based AFFF
agents do not contain or degrade to PFOS, and
contain 30-60% less fluorine than PFOS-based
AFFF. They are not made with PFOA or PFCAs.
The predominant breakdown product from the
six-perfluorinated carbon (C6) based fluorotelomer
surfactants is commonly referred to as the 6:2
fluorotelomer sulfonate (6:2 FtS)2. They may also
contain trace levels of PFOA and the C6
acid, perfluorohexanoic acid
(PFHxA). The highlighted red
box on the left side of Figure
1 calls out the 6:2 FtS struc-
ture (where n = 6). Although
there have been numerous
articles and conference pre-
sentations that purport
the 6:2 FtS to be a PFOS
analog (sometimes incorrectly
referred to as H-PFOS), the
scientific data do not sup-
port this allegation. The
physical, chemical, biopersis-
tence and toxicological
properties of 6:2 FtS are not
similar to PFOS.
Toxicology
A second part of the debate
seems to focus on the
potential hazards of PFHxA
and the 6:2 FtS. These two compounds can be
both contaminants in the final products as well as
potential degradants once the AFFF agents are
used. Extensive data on PFHxA were presented at
a US Environmental Protection Agency (EPA) PFOA
Information Forum in June 2006 that gave a very
favorable initial toxicology (hazard) profile3. Addi-
tional information was presented in September
2007 at a major foam conference in the UK
(Reebok) that further supported the favorable toxi-
cology profile of PFHxA4. Preliminary data were
shared on four major toxicology end points: sub-
chronic toxicity in rats, reproductive toxicity in rats,
developmental toxicity in rats, and genetic toxicity.
It was noted at this conference that PFHxA was
neither a selective reproductive nor a selective
developmental toxicant. In addition it was clearly
shown to be neither genotoxic nor mutagenic.
Combining these data with those presented in
June 2006 provides significant evidence that this
particular end product has a low hazard profile
based on current data.
Based on recent groundwater studies, the 6:2
FtS has been shown to be the likely ultimate
degradation product of the C6 fluorotelomer-
based surfactants used in today's AFFF agents. The
screening study cited above (Figure 2) indicated
that the 6:2 FtS had a low relative biopersistence
potential. The 6:2 FtS had a high NOEC (no
observed effect concentration, the higher the
NOEC the lower the concern for toxicity) in the
90-day early life stage trout study. Results presented
at the Reebok foam conference provided prelimi-
nary new results on environmental effects as well
as bioconcentration (BCF) and bioaccumulation
(BAF) in rainbow trout. Although the data were
preliminary in nature, the results were clear and
compelling. Moreover both the BCF and the BAF
values suggest low concern for bioaccumulation
from water or diet. The data strongly suggested
that 6:2 FtS is not bioaccumulative according to
published regulatory criteria and affirmed that it
does not behave like PFOS.
Biopersistence
The results of a 6:2 FtS biopersistence screening
study were also presented at the Reebok foam
conference. The data presented are shown in
Figure 2 (publication in preparation). This screen-
30 INTERNATIONAL FIRE PROTECTION
Figure 1. Fluorotelomer-
based and PFOS-based
Chemistry
AFFF INDUSTRY IN POSITION TO EXCEED ENVIRONMENTAL GOALS
FIRE FIGHTING FOAM COALITION

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