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Biodegradation in water: screening tests

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Description of key information

Under test conditions, none of the substances in the category Rosin Esters would be considered to be readily biodegradable. However, biodegradation studies conducted with UVCB substances are not always relevant, as individual constituents within a UVCB will have different biodegradation potential.

For the purposes of persistence assessment, a screening assessment has been conducted assessing the biodegradation potential of constituents within the UVCB. Based on the results of this screening assessment, direct ready biodegradation testing is underway to assess the degradation potential of the mono-ester fraction of rosin ester substances.

Key value for chemical safety assessment

Additional information

Biodegradation studies are available for the following category members: Resin acids and rosin acids, Me esters; Resin acids and rosin acids, esters with pentaerythritol; Resin acids and rosin acids, esters with glycerol; Resin acids and rosin acids, hydrogenated esters with glycerol; Resin acids and rosin acids, hydrogenated, esters with pentaerythritol and Resin acids and rosin acids, esters with diethylene glycol (Inveresk, 2002a). All studies are GLP-compliant and follow standard guidelines. They are considered acceptable for use and have been given Klimisch scores of 1. Results of testing of representative members of the category of Rosins Esters have failed to demonstrate ready biodegradation in OECD 301B, 28 day ready biodegradation screening studies. 

A GLP-compliant study following OECD guideline 301B was conducted for Resin acids and rosin acids, hydrogenated, Me esters (Notox, 1988a). The study used test item concentrations of 10 mg/L and 20 mg/L, with 17.7 and 28.3% degradation respectively over 28 days. A biodegradation study is available for Resin acids and rosin acids, Me esters, which followed guideline 301B. Harlan (2012a) determined 40% degradation of the test item after 28 days.

Two studies are also available, for Resin acids and rosin acids, hydrogenated, esters with glycerol and Resin acids and rosin acids, hydrogenated, esters with pentaerythritol (Notox, 1988b; Notox, 1988c). Both studies are GLP-compliant and follow a standard guideline, but the study reports provide limited test details only. These studies determine that neither test item would be considered readily biodegradable.

A GLP study was conducted according to the OECD TG 310 (2014) to assess the ready biodegradation potential of the registered test item (Resin acids and rosin acids, hydrogenated with glycerol). The old test item attained a mean level of biodegradation (based on % ThIC) of 37% after 28 days and 42% after 45 days, and the results showed good replication. Less than 60% biodegradation was achieved, so the old test substance cannot be classified as readily biodegradable under OECD TG 310. The new test item attained a mean level of biodegradation (based on % ThIC) of 52% after 28 days and 67% after 45 days, and the results showed good replication. Less than 60% biodegradation was achieved within the 28 days, so the new test item cannot be classified as readily biodegradable under OECD TG 310, however the new test item exhibited the potential for rapid degradation and can be classified as inherently biodegradable.

The ready biodegradability of the test item Monoesters of hydrogenated rosin with glycerol was determined with a mixed inoculum of the aqueous phase of non-adapted activated sludge and pre-treated, non-adapted standard soil in the Headspace Test following OECD 310 (Noack Laboratorien 2017a). The ultimate biodegradation of the test item was 34% after 28 days and 35% after 60 days, based on CO2 production. Primary biodegradation of the monoester fraction reached 74% after 7 days, 89% after 28 days and 95% after 60 days. The test item is not readily biodegradable based on the ultimate degradation determined in the study. Nevertheless, the test item reveals a considerable potential for biodegradation, as the determination of the primary degradation of the monoester fraction as well as the determination of mineralisation shows.

The maximum percent of biodegradation across 9 reliable studies was 52% after 28 days. Therefore, Rosin Esters are not considered to be readily biodegradable. However, biodegradation studies conducted with UVCB substances are not always relevant, as individual constituents within a UVCB will have different biodegradation potential.

 

For the purposes of persistence assessment, a screening assessment has been conducted assessing the biodegradation potential of constituents within the UVCB. Based on the results of this screening assessment, direct ready biodegradation testing is underway to assess the degradation potential of the mono-ester fraction of rosin ester substances.