Substitution of PFOS for use in nondecorative hard chrome plating

4.3.1.6 Risk assessment
The U.K. Committee on Toxicity (2006) has recommended a provisionally
Tolerable Daily Intake (TDI) for PFOS of 0.3 g/kg bw/d, using an
uncertainty factor of 100. They conclude that for some small children the
TDI may already be exceeded.
This assessment was based on results from animal experiments, which may be
very arbitrary and unreliable, because of the large differences in blood halflives
between rodent (days) and humans (years). The renal clearances of
PFOS are almost insignificant in humans, contrary to a large active excretion
in experimental animals.
This means that PFOS in humans leave the blood mainly by redistribution to
internal organs and not by elimination from the body as in rodents. This may
increase the internal exposure time in critical human organs considerable.
4.3.1.7 Conclusion
PFOS is found widespread in nature and in animals and humans because it is
a very persistent chemical and non-degradable in nature. Furthermore, PFOS
and its precursors do have a tendency to bioaccumulate and biomagnify in
food chains.
PFOS causes various adverse effects in humans, and for children a very
conservative Tolerable Daily Intake of PFOS may already be exceeded.
4.3.2 1H,1H,2H,2H-perfluorooctane sulfonic acid (CAS No. 27619-97-2)
The basic structure of 1H,1H,2H,2H-perfluorooctane sulfonic acid is very
similar to PFOS. Both contain a fluorinated C 8 alkyl chain, however, the
alternative is not perfluorinated but has two non-fluorinated carbon atoms
making it a polyfluorinated compound (fluorotelomer). Fluorotelomers are
DuPont’s alternatives to PFOS.
Figure 4-2 Alternative to PFOS as mist suppressant - 1H,1H,2H,2H-perfluorooctane
sulfonic acid (CAS 27619-97-2)
F
F
F
F F
F
F
F F
F
F H
H
F F
H
H
O
S
OH
O
As for PFOS the perfluorinated part of 1H,1H,2H,2H-perfluorooctane
sulfonic acid is not degradable. However, the non-fluorinated part of the alkyl
chain can be degraded. 1H,1H,2H,2H-perfluorooctanesulfonic acid is,
therefore, expected to be degraded in nature to the further non-degradable
perfluorohexanoic acid (PFHxA) and perfluoroheptanoic acid (PFHpA) or
their salts. The toxicity of PFHxA with a C 6 chain is 100 to 1000 times lower
than for PFOA with a C 8 -chain (Richard Holt, DuPont, 2010).
Chinese QSAR model results exist for persistence (half-lives) of Fumetrol ® 21
in water, sediment, soil, and air, bioconcentration factors and toxicity to fish
(BCFs) (see Table 4-1). This data shows that Fumetrol ®
21 seems to be less
persistent, less bioaccumulative, and less toxic compared to PFOS.
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