Oligomerisation products of beta-pinene

Endpoint summary

Additional information

In water, pinene oligomers are not readily biodegradable (8% degradation after 28 days in OECD 301D test). Testing with a mixed and adapted inoculum (otherwise OECD 301B test method) found negligible biodegradation, but adsorption of test substance onto vessel walls prior to testing made bioavailability uncertain. The ready biodegradation test was repeated in accordance with OECD 301B due to limitations in the above testing and included enhancement measures alongside an inherent test (OECD 302C). Both tests indicated negligible degradation.

Read-across to the analogue limonene (readily biodegradable) and other considerations, including reports of extensive microbial metabolism of mixed phytoterpenes by marine microbes lead to a weight-of-evidence conclusion of inherent biodegradability (not fulfilling specific criteria).

Biodegradation of close chemical analogues of pinene oligomers by soil microbes is confirmed in a study using both liquid phase and soil slurry tests. Other publications provide supporting evidence of the wide distribution of phytoterpenes and the ability of bacteria and microfungi to metabolise them. It is concluded that pinene oligomers will be biodegraded by soil microbes: half-life in soil cannot be accurately predicted, but seems likely to be weeks or months according to local conditions.

These predictions of microbial biodegradation are justified by the following consideration. Although the covalent binding of monomer units within pinene oligomers seems likely to decrease the rate of unit degradation via microbial metabolism, the availability of sites for enzymic attack and general terpenoid chemistry is largely unaffected by the polymerisation process: slower but otherwise similar biodegradation to that seen in tests of the terpene monomer units can thus be expected for pinene oligomers.