Perfluamine

Endpoint summary

Additional information

Releases of PTPA are anticipated to be primarily to the atmospheric compartment. This compound is unlikely to partition to terrestrial or aquatic compartments from the atmosphere based on partition coefficients (see below).

The experimental vapor pressure (3.87 mm Hg) and categorical Henry’s Law constant range (140000 to 166000 dimensionless; or 3.45E+08 to 4.07E+08 Pa∙m³/mol; or 3400 to 4020 atm∙m³/mol [based on readacross from category members]) suggests that PTPA is expected to partition from wet or dry terrestrial surfaces into the atmosphere. Soil volatilization half-lives are estimated to be 25.6 for agricultural soils and 1.6 hours for grassland and industrial soils. The category member perfluoro-N-methylmorpholine has an experimental soil-atmosphere partitioning half life of 66.1 ± 16.0 minutes (substantially shorter than that predicted by EUSES), which indicates that it will be removed from soil and sediments quickly. This half life may underestimate the atmospheric partitioning from natural soils due to the layer of water on soils particulates (volatilization driven by water-atmosphere partitioning rather than soil-atmosphere partitioning).

Henry’s Law constant (HLC) is used to describe the tendency for a substance to partition from water to air, the higher the value the greater the tendency for partitioning from water to air. For PTPA, the categorical dimensionless HLC range of 140000 to 166000 dimensionless indicates that it is likely to volatilize from the aquatic compartment into the atmosphere.

The logarithm of the normalized organic carbon adsorption coefficient (log Koc) is used to describe the tendency for a substance to partition from water to soils or suspended solids. The experimental water solubility of PTPA is slight (0.381 µg/L) and the log Koc range of PTPA was calculated⁽¹⁾ to be 4.4 to 5.0 based on log Kow range (5.3 to 6.11 [based on readacross from category members]). Based on these data PTPA is anticipated to partition from water to soils and suspended solids for a short period of time. Given the rapid partitioning to the atmosphere from soils and from water, the overall net partitioning will be to the atmosphere.

The logarithm of the octanol air partition (log Koa) coefficient is used to describe the tendency of a substance to partition from air into the lipid rich tissues of air breathing organisms. The categorical octanol air partition coefficient (Koa) of PTPA was calculated to be 1.2 to 9.3 (log Koa = 0.1 to 1.0) based on the categorical Henry’s Law constant range of (140000 to 166000 dimensionless) at 22 °C and the log Kow range of 5.3 to 6.1 at 23 °C. This log Koa value indicates that PTPA has a low potential to partition from air to the lipid rich tissues of air-breathing organisms.

All of the members of this category stem from the same manufacturing process, have similar physicochemical properties including high vapor pressure and low water solubility relative to the hydrocarbon analogs (e. g., hexanes v. perfluorohexanes), and also lack any chemically reactive groups, which forms the technical basis for the category. Members of this category are fully fluorinated, meaning that fluorine, rather than hydrogen, is bonded to all carbon atoms in the molecule. Fluorine is the most electronegative of the elements (fluorine has an electronegativity of 3.98 on the Pauling scale, as compared to 2.55 for carbon or 2.20 for hydrogen). This electronegativity is expected to dominate over all other aspects of substance chemistry and is the underlying basis for similarity of substances in this category. Because these substances exhibit similarity in their physicochemical properties and toxicological properties in mammals, and because available data indicates that parent molecules are not reactive toward biological molecules and cannot undergo bioactivation or indeed any reaction by normal enzymatic processes, they are considered to constitute a chemical category. Data gaps for transport and distribution can therefore be addressed by read-across between category members. Please see Appendix A for the category justification and a matrix of physicochemical and distribution data for members of the Perfluorinated Organic Chemicals C5-C18 category.

(1) European Chemicals Bureau: Technical Guidance Document of Risk Assessment, Chapter 4.