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Environmental fate & pathways

Biodegradation in water and sediment: simulation tests

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Description of key information

A half-life of 4.5 days was determined for hydrogenated rosin alcohols in an OECD 309 pelagic study. It was not possible to identify the degradation products produced in the study, but a QSAR modelling approach using EAWAG’s BBD Pathway Prediction System has identified a number of initial degradation products, which match the initial degradation products produced from resin acids which make up the starting material in the manufacture of hydrogenated rosin alcohols. PACT assessments for the substances rosin and hydrogenated rosin which are composed of these resin acids concluded that these substances are not PBT or vPvB, and therefore the degradation products are not considered to be PBT.

Key value for chemical safety assessment

Half-life in freshwater:
4.5 d
at the temperature of:
22.6 °C

Additional information

An OECD 309 pelagic study and subsequent metabolite identification (Harlan 2013, Envigo 2015) was conducted with 3H-labelled test item, at concentrations of 0.2 and 0.8 µg/L. A half-life of 4.5 days was determined. Two main metabolites (M1 and M3) were found at concentrations above 10% but it was not possible to identify these using liquid chromatography-mass spectrometry (LC-MS), due in part to the low test concentrations.

Following a request from ECHA, further work to identify these degradation products has been carried out. Testing options were explored and the solubility of the constituent groups was assessed in the natural water that would be used in an OECD 309 study (Scymaris 2020). It was found that only dehyroabietyl alcohol constituents were soluble at >100 µg/L (370 µg/L), the concentration noted in the OECD 309 guideline as often being required for the identification of degradation products, with the least soluble constituents, rosin, hydrogenated, methyl esters, being far below this (3 µg/L). Therefore, even if a sample of hydrogenated rosin alcohols was tested it is likely that any degradation products identified would relate to dehydroabietyl alcohol constituents only, when the whole substance should be considered for PBT assessment.

A testing approach is further complicated by the need to prepare a labelled sample for testing; although an OECD 309 study can be conducted with non-labelled material, a labelled test item is necessary for the identification of degradation products as requested in the final decision letter. The previous OECD 309 study used a 3H-labelled test item, which was considered to contain constituents similar to those in the registered substance, but it is not possible to confirm the exact composition of the material tested. In addition the HPLC analysis carried out in the study was not able to differentiate between constituents of the test item, showing a single peak for the parent material. New trials were conducted to try to prepare a labelled sample, but GC-MS analysis was unable to confirm the same composition for the labelled material and the registered substance. A testing approach is therefore considered to be technically not feasible for identification of degradation products for the test item and instead a modelling approach assessing individual constituents has been followed.

QSAR modelling, conducted using the EAWAG-BBD Pathway Prediction System with representative structures for each of the constituent groups present in hydrogenated rosin alcohols, shows that degradation products are similar between different constituents of hydrogenated rosin alcohols and that predicted degradation products for hydrogenated rosin alcohol constituents match initial degradation products produced from resin acids, which make up the starting material in the manufacture of hydrogenated rosin alcohols. Available data for resin acids, and for the substances rosin and hydrogenated rosin that are composed of these resin acids, can be used for PBT assessment of the degradation products of hydrogenated rosin alcohols. PACT assessments carried out for rosin and hydrogenated rosin concluded that these substances are not PBT or vPvB, and therefore degradation products of hydrogenated rosin alcohols are also not considered to be PBT or vPvB.