Fatty acids, tallow, zinc salts

Biodegradation in water: screening tests

Description of key information

93% biodegradation in 28 days (OECD 301 D, O2 consumption); read-across

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

No studies are available on the biodegradation of Fatty acids, tallow, zinc salts. Therefore, in accordance to Regulation (EC) No 1907/2006 Annex XI, 1.5, the assessment of biodegradability was based on studies conducted with the structurally similar read-across substances Fatty acids, C16-18, zinc salts (CAS No. 91051-01-3) and Zinc-12-Hydroxystearate (CAS No. 35674-68-1). The two read-across substances are both salts of fatty acids and zinc, as Fatty acids, tallow, zinc salts. Also the fatty acids in all three substances are similar. Fatty acids, tallow, zinc salts mainly contains saturated fatty acids of chain lengths C16 and C18 and monounsaturated C18 fatty acids. C16-C18 fatty acids are also present in the first read-across substance. The second read-across substance mainly consists of saturated C18 fatty acids with a hydroxyl group. The single double bond of the C18 unsaturated fatty acids of Fatty acids, tallow, zinc salts is not expected to significantly slow down the biodegradation of the substance compared to the read-across substances. For further justification see the overall endpoint summary in section 5 and the read-across aproach justification in section 13 of the technical dossier.

The key ready biodegradability study carried out with Fatty acids, C16-18, zinc salts (CAS No. 91051-01-3), was performed following the OECD Guideline 301 D (TÜV Bayern Sachsen E.V., 1992). During the 28-day test period, biodegradation reached 93%, based on O2 consumption. As the test substance is a mixture of constituents with different chain-lengths, sequential (instead of concurrent) biodegradation takes place. Thus, referring to Annex I to the OECD Guideline for The Testing of Chemicals 'Revised introduction to the OECD guidelines for testing of chemicals, section 3' (OECD, March 2006), the 10-day-window should not be considered for the test substance. Due to a degradation of > 60% within 28 days the test substance can be regarded as readily biodegradable according to the OECD criteria.

The key ready biodegradability study carried out with Zinc bis[12-hydroxystearate] (CAS No. 35674-68-1), was performed following the OECD Guideline 301 B (Rudolf, 2003). During the 28-day test period, biodegradation reached 71%, based on CO2 evolution. The pass level of 60% was reached, but the 10-day window was not met.

Thus, based on these results and the structural similarity of the substances, Fatty acids, tallow, zinc salts can be considered readily biodegradable according to OECD criteria.