161
Trifuoroacetic Acid from CFC Replacements
(Cahill et al., 2001). The NOEC was determined for a series of terrestrial plants
with crop species being the most common test organisms. The NOEC for the
root uptake mechanism ranged from approximately 1 to 32 mg/L (Table 9.2).
The average NOEC over several species was 7.2 mg/L although this is an
underestimate since a large number of the toxicology data are reported as
lower limits. This is considerably lower than the estimated NOEC for aquatic
plants at 520 mg/L since the aquatic plants lacked evaporative bioconcentration. Given the affnity of TFA for water, it is expected that aquatic plants are
more likely be exposed to elevated TFA concentrations. However, terrestrial
plants associated with water systems, and terminal water systems in particular, may suffer from both elevated concentrations and bioaccumulation in
their tissues.
9.5 Environmental Concentrations of TFA
TFA is ubiquitous in the environment with the possible exception of preindustrial age fresh water. It is found in deep ocean water to remote Polar
Regions although it is more concentrated in urban areas where there are
more potential sources. However, TFA generated from HFC degradation has
changed over time as the usage of the HFCs has increased, further complicating matters. This has changed the deposition of TFA on a global basis.
There are also specifc hot spots near point sources of the precursors to TFA.
For this analysis, the reported environmental TFA concentrations will be
assigned to specifc conditions that they represent, namely, oceanic, remote
hemispheric background, populated regions, terminal waterbodies, and
point sources of TFA.
9.5.1 Oceans
The discovery of TFA in the oceans was not anticipated since TFA was originally considered to be an anthropogenic pollutant. However, numerous
studies by multiple research groups have verifed the presence of TFA in the
oceans. In general, TFA concentrations range from 1 to 250 ng/L (Table 9.3)
although there seems to be a trend to higher concentrations in the Atlantic
and Arctic Oceans compared to the Pacifc Ocean (Scott et al., 2005). Many of
these water samples were from deep ocean currents whose water was dated
to preindustrial times, thus suggesting that there is a natural source of TFA
that has accumulated in the oceans for millennia. Geothermal vents were
shown to have elevated concentrations of TFA over them, so this identifes at
least one of the natural sources of TFA in the oceans (Scott et al., 2005). The
uniformity of TFA concentrations in the water column also suggests that TFA
is very stable due to the slow mixing of the ocean waters (Frank et al., 2002).
Trifuoroacetic Acid from CFC Replacements
(Cahill et al., 2001). The NOEC was determined for a series of terrestrial plants
with crop species being the most common test organisms. The NOEC for the
root uptake mechanism ranged from approximately 1 to 32 mg/L (Table 9.2).
The average NOEC over several species was 7.2 mg/L although this is an
underestimate since a large number of the toxicology data are reported as
lower limits. This is considerably lower than the estimated NOEC for aquatic
plants at 520 mg/L since the aquatic plants lacked evaporative bioconcentration. Given the affnity of TFA for water, it is expected that aquatic plants are
more likely be exposed to elevated TFA concentrations. However, terrestrial
plants associated with water systems, and terminal water systems in particular, may suffer from both elevated concentrations and bioaccumulation in
their tissues.
9.5 Environmental Concentrations of TFA
TFA is ubiquitous in the environment with the possible exception of preindustrial age fresh water. It is found in deep ocean water to remote Polar
Regions although it is more concentrated in urban areas where there are
more potential sources. However, TFA generated from HFC degradation has
changed over time as the usage of the HFCs has increased, further complicating matters. This has changed the deposition of TFA on a global basis.
There are also specifc hot spots near point sources of the precursors to TFA.
For this analysis, the reported environmental TFA concentrations will be
assigned to specifc conditions that they represent, namely, oceanic, remote
hemispheric background, populated regions, terminal waterbodies, and
point sources of TFA.
9.5.1 Oceans
The discovery of TFA in the oceans was not anticipated since TFA was originally considered to be an anthropogenic pollutant. However, numerous
studies by multiple research groups have verifed the presence of TFA in the
oceans. In general, TFA concentrations range from 1 to 250 ng/L (Table 9.3)
although there seems to be a trend to higher concentrations in the Atlantic
and Arctic Oceans compared to the Pacifc Ocean (Scott et al., 2005). Many of
these water samples were from deep ocean currents whose water was dated
to preindustrial times, thus suggesting that there is a natural source of TFA
that has accumulated in the oceans for millennia. Geothermal vents were
shown to have elevated concentrations of TFA over them, so this identifes at
least one of the natural sources of TFA in the oceans (Scott et al., 2005). The
uniformity of TFA concentrations in the water column also suggests that TFA
is very stable due to the slow mixing of the ocean waters (Frank et al., 2002).