Perfluamine

Endpoint summary

Additional information

Perfluorotripropyl amines (PTPA) is of very low water solubility (0.381 µg/L at 23 °C) and is volatile (vapor pressure, 3.87 mm Hg at 20 °C).  A range of Henry's Law constants (expressed as the ratio of vapor phase partial pressure of PTPA over aqueous phase concentration) of 3.45E+08 Pa∙m³/mol (3400 atm∙m³/mol) to 4.07E+08 Pa∙m³/mol (4020 atm∙m³/mol) at 22 °C was established by readacross from the most relevant category members.  A value for log K_OW of 5.3 – 6.1 at 23 °C for PTPA was similarly established by readacross.  However, it is not expected that PTPA will have a significant presence in the aquatic compartment, and bioaccumulation in aquatic organisms is not expected.

 

PTPA is not expected to partition from the atmosphere to moist soils or surface waters.  Based on its uses, PTPA will not be released to aquatic systems or soils.  Upon direct release of PTPA to the aquatic compartment, the chemical would be expected to volatilize rapidly.  However, as noted PTPA release under registered uses is entirely to the atmosphere.  PTPA is not expected to partition to aquatic compartments from the atmosphere, therefore no exposure to aquatic organisms is expected.

We have proposed adaptation of the data requirement for bioconcentration factor of PTPA.  Based on a log K_OW range of 5.3 – 6.1, the chemical would be considered bioaccumulative in aquatic organisms.  However, substantial bioaccumulation of PTPA in aquatic organisms is not expected due to lack of exposure in aquatic systems.  PTPA is expected to reside entirely in the atmospheric compartment, so air breathing organisms were evaluated for bioaccumulation potential.  According to Chapter R.7.10.3.4 of the Technical Guidance (Other indication of bioaccumulation potential):

 

For air-breathing organisms, respiratory elimination occurs via lipid-air exchange, and such exchange declines as the octanol-air partition coefficient (K_OA) increases, with biomagnification predicted to occur in many mammals at a log K_OA above 5. Such biomagnification does not occur if the substance and its metabolites are rapidly eliminated in urine (i.e. have a log K_OW of around 2 or less). Thus the bioaccumulation potential in air-breathing organisms is a function of both log K_OW and log K_OA. In contrast, respiratory elimination in non-mammalian aquatic organisms occurs via gill ventilation to water, and this process is known to be inversely related to the log K_OW (hence an increase in log K_OW results in a decrease in the rate of elimination and hence increase in the accumulation potential). 

A log octanol-air partition coefficient (log K_OA) range 0.1 – 1.0 at ca. 23 °C was calculated for PTPA using the relationship:

K_OA(unitless) = K_OW / K_AW

Where K_OW is octanol:water partition coefficient and K_AW is the dimensionless Henry’s Law constant.  As per Kelly and Gobas⁽¹⁾, chemicals with log K_OA <4 do not biomagnify regardless of the K_OW because of efficient elimination via air exhalation (or, in this case, extremely inefficient absorption via air inhalation).  According to the classification scheme proposed in Chapter R7.10.3.4, PTPA is a non-polar volatile (high log K_OW and low log K_OA), and is not expected to bioaccumulate in air-breathing organisms.  As stated, the potential to accumulate in aquatic organisms is mitigated by the lack of relevance of the aquatic exposure pathway. Therefore, bioaccumulation of PTPA in terrestrial or aquatic organisms is not expected.

 

Reference:

 

1) Kelly, B.C. and F.A.P.C. Gobas.  2003.  An Arctic Terrestrial Food-Chain Bioaccumulation Model for Persistent Organic Pollutants.  Environ. Sci. Technol Vol. 37, No. 13, pp 2966–2974.