Registration Dossier

Environmental fate & pathways

Endpoint summary

Administrative data

Description of key information

Additional information

3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate (CAS 59219-71-5) is readily biodegradable according to the OECD criteria (91% in 28 d, read across). The substance is characterised by low water solubility (1.5-4.4 µg/L at 20 °C), low vapour pressure (0.0193 Pa) and a log Koc 3.94. Hydrolysis is not expected to be a relevant degradation pathway for the substance as indicated by QSAR calculations performed with the HYDROWIN v2.00 program resulting in estimated half-lives in water > 1 year.

The volatilization potential of the substance is negligible, based on a vapour pressure of 0.0193 Pa at 20°C.

3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate is expected to be extensively eliminated in conventional sewage treatment plants. In the case insoluble chemicals enter a standard Sewage Treatment Plant (STP), they will be extensively removed in the primary settling tank and fat trap and thus, only limited amounts will get in contact with activated sludge organisms. Moreover based on the results of the ready biodegradation test, it is expected that activated sludge will rapidly mineralize the substance. So the concentration of the substance in conventional STP effluents is expected to be low, and the release to the aquatic environment is considered as negligible (Guidance on information requirements and chemical safety assessment, Chapter R.7b (ECHA, 2014).

If released to the aquatic environment, due to insolubility and potential of adsorption on the organic matter, 3,5,5-trimethylhexyl 3,5,5-trimethylhexanoate is not expected to be present in the water column.

Considering the adsorption potential, low volatilization potential and low water solubility, the substance is expected to distribute preferably to soil and sediment if released to the environment. Nevertheless, due to the ready biodegradability of the substance, a rapid and ultimate mineralisation in all environmental compartments is anticipated. Therefore the exposure of soils through activated sludge spreading, as well as the exposure of sediments from the water column, are both considered as low.  

Due to the rapid environmental biodegradation and metabolization via enzymatic hydrolysis a relevant uptake and bioaccumulation in aquatic organisms is not expected. Enzymatic breakdown will initially lead to the free fatty acid and C9 iso-alcohol. From literature it is well known, that these hydrolysis products will be metabolised and excreted in fish effectively (Tocher, 2003). This is supported by BCF/BAF values ranging from 152.9/703.9 L/kg (BCFBAF v3.01, Arnot-Gobas, including biotransformation, upper trophic). Please refer to IUCLID Section 5.3.1 for a detailed overview on bioaccumulation of the substance.

A detailed reference list is provided in the technical dossier (see IUCLID, section 13) and within the CSR.