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Environmental fate & pathways

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With the exception of biodegradation, all endpoints in the environmental fate section are covered by the substances itself. Only for biodegradation, studies from category members were used for read across purposes. On the basis of the available studies, all members of the category PFAE fumarates are assessed as either readily biodegradable or readily biodegradable, but failing 10- day window. The available studies on biodegradation cover the outer borders of this category so that this endpoint is covered by interpolation (i.e. studies are available for the lower alcohol chain length (C12, C14) and highest alcohol chain length (C18/C22), respectively). Only two constituents, i.e. C8 and C10 fatty acid ester components of 2-Butenedioic acid (E)-, di-C8-18-alkyl esters (CAS 68610-90-2) are not enclosed by the available data. However, the C-chain length is a determining factor in biodegradation – the shorter the faster - so the biodegradability for these two components is even expected to be faster compared to higher chain lengths fumarates and therefore can be covered by extrapolation. 2-Butenedioic acid (E)-, di-C18-22-alkyl esters (CAS 68921-53-9) represents the higher end of the category consisting of the longest fatty alcohol chain lengths and therefore represents a worst case for biodegradation since, the C-chain length of the fatty alcohol is the determining factor for biodegradation. Thus, the assumption that all members of the PFAE fumarates category are either readily biodegradable (in case of UVCBs) or readily biodegradable, but failing 10 -day window (in case of monoconstituent substances) is clearly underlined by the result for this substance (readily biodegradable). Consequently, the category members will not be persistent in the environment since they will be ultimately and completely biodegraded.

Evaporation into air and the transport through the atmospheric compartment is not expected since the category members are not volatile based on the low vapour pressure (VP: < 1 Pa). Since all substances are not likely to be present in the atmosphere, indirect photolysis is not to be expected. Abiotic hydrolysis is not relevant, since all members of the PFAE fumarates category are insoluble in water (< 0.15 mg/l in aqua dest.) and well biodegradable and thus expected to be primarily eliminated through biodegradation. Additionally, estimated rates of hydrolysis are very low.

All substances, including their main constituent’s exhibit log Kow values > 8 and will mainly distribute into soil and sediment exclusively. Due to the biodegradability, however, all members of the category will not be persistent in sediment and soils. Based on the rapid environmental biodegradation and metabolism via enzymatic hydrolysis, relevant uptake and bioaccumulation in aquatic organisms is not to be expected. Enzymatic breakdown will initially lead to the free fumaric acid and the free alcohol. From literature it is well known, that these hydrolysis products will be metabolised and excreted in fish effectively (for detailed information please see chapter 5.3 of the technical dossier). This is supported by low calculated BCF values estimated for all category members (BCF < 1 - 10 l/kg ww, BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic).

A detailed reference list and justification for read-across is provided in section 13 of IUCLID and within CSR.

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