Registration Dossier

Administrative data

Endpoint:
phototransformation in air
Type of information:
read-across based on grouping of substances (category approach)
Adequacy of study:
key study
Study period:
2018
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
study well documented, meets generally accepted scientific principles, acceptable for assessment
Justification for type of information:
MTDID 22327 is a member of the Perfluorinated Organic Chemicals, C5-C18, category. Unlike most members of the category, MTDID 22327 is a UVCB consisting mostly of perfluoro-N-methylmorpholine, a mixture of C5-C7 perfluoroamines, and perfluorohexane isomers. However, all of these chemicals 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, 3.04 for nitrogen 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. For example, strong electron withdrawing in perfluorinated tertiary amines results in a molecule with essentially no lone pair reactivity or availability for protonation or hydrogen bonding, and which has chemistry more similar to a branched, perfluorinated alkane than any other structure. Because these substances exhibit similar physicochemical properties they can be considered to constitute a chemical category. Phototransformation in air can therefore be addressed by many-to-one read-across between category members.

See section 13 for a fuller discussion of the category approach.

Data source

Reference
Reference Type:
other: Read across from other internal studies
Title:
Unnamed
Year:
2018
Report date:
2018

Materials and methods

Test guideline
Qualifier:
according to guideline
Guideline:
other: REACH Guidance on QSARs and grouping of chemicals
Version / remarks:
May/July 2008
Deviations:
no
GLP compliance:
no
Remarks:
all studies were done before January, 2014

Test material

Constituent 1
Reference substance name:
Reaction mass of perfluoro(dimethyl - N - Butylamine ) and perfluoro (methyl - di - N - propylamine) and perfluoro (dimethyl - N - propylamine and 2,2,3,3,5,5,6,6, octafluoro-4-(trifluoromethyl)morpholine and perfluoro-N-pentane
EC Number:
908-205-5
Cas Number:
2187449-42-7
IUPAC Name:
Reaction mass of perfluoro(dimethyl - N - Butylamine ) and perfluoro (methyl - di - N - propylamine) and perfluoro (dimethyl - N - propylamine and 2,2,3,3,5,5,6,6, octafluoro-4-(trifluoromethyl)morpholine and perfluoro-N-pentane
Specific details on test material used for the study:
Readacross is from category members:
Perfluorohexanes, PFHx, CAS# 1064697-81-9
Perfluoro-N-methylmorpholine, PMM, CAS# 382-28-5
Perfluorotripropylamine, PTPA, CAS# 338-83-0

Results and discussion

Dissipation half-life of parent compound
Key result
DT50:
> 1 100 - < 2 800 yr
Test condition:
Bracketing by category member data. Lower limit is from atmospheric lifetime of Perfluoro-N-methylmorpholine. Upper limit is from Perfluoropentane

Any other information on results incl. tables

In general, perfluorinated compounds are chemically inert. The sole known phototranformation pathway is direct photolysis in the upper atmosphere. Bracketing by category members was used to establish the range of phototransformation lifetimes (i.e, 1/rate constant).

Perfluorohexanes lifetime: 3200 years. Perfluorohexanes were not subject to indirect phototransformation in photochamber tests. Accepted lifetime published by Intergovernmental Panel on Climate Change.

Perfluoro-N-methylmorpholine lifetime: 1600-4000 years. Perfluoro-N-methylmorpholine was not subject to indirect phototransformation in photochamber tests. Minimum lifetime was set by phototransformation test detection limit. Maximum was set by accepted lifetime of Perfluoropentanes (4000 years) published by Intergovernmental Panel on Climate Change.

In addition, data for perfluorotriethylamine was read across to perfluorotripropylamine. Perfluorotriethylamine was not subject to direct photo transformation at long UV wavelenghts, nor to indirect phototransformation by atomic oxygen or hydroxyl radical (data ). A lifetime >2000 years was assigned based on upper limit of rate constant.

Applicant's summary and conclusion

Conclusions:
Atmospheric lifetime of MTDID 22327: 1600-4000 years by read-across from category members.
Executive summary:

The atmospheric lifetime of MTDID 22327 was determined using a category approach wherein the experimental lifetimes of similar substances with similar physical and chemical properties are used to define the upper and lower bound atmospheric lifetime. The resulting range is 1600 - 4000 years.

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, cannot undergo bioactivation by normal enzymatic processes, and are inert to chemical degradation processes, they can be considered to constitute a chemical category. Data gaps for fate properties can therefore be addressed by read-across and/or trend analysis between category members. The read-across is considered reliable with restrictions and the result is suitable for use in Risk Assessment, Classification & Labelling, and PBT Analysis.