Lithium isooctadecanoate

Biodegradation in water: screening tests

Description of key information

Lithium isooctadecanoate is considered to be readily biodegradable. 

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A ready biodegradation test on lithium isooctadecanoate is currently ongoing.

Lithium isooctadecanoate is considered readily biodegradable based on data read across from lithium 12 -hydroxystearate and isooctadecanoic acid, both of which are considered to be readily biodegradable. Lithium isooctadecanoate consists of a lithium cation and an organic fatty acid anion. According to column 2 of REACH Annex VII, ready biodegradability studies do not need to be conducted for inorganic substances and therefore biodegradation is not considered to be relevant for the lithium cation. Biodegradation of the substance is relevant only to the organic component and therefore data are presented for isooctadecanoic acid, the organic component (and raw material for) lithium isooctadecanoate. Data are also presented for lithium 12 -hydroxystearate, which also consists of a lithium cation and an organic fatty acid anion, to show that the lithium ion does not impact the degradation of the organic component. Further testing on lithium isooctadecanoate itself is currently ongoing to support this endpoint.

The ready biodegradability of lithium 12 -hydroxystearate was determined in a GLP-compliant modified MITI test, following OECD guideline 301C (Ministry of International Trade and Industry, Japan -MITI 1999). The biodegradation of lithium 12 -hydroxystearate was 78% on day 28, and the substance is considered to be readily biodegradable. The study was published as part of a regulatory database and is considered to be reliable and relevant for use for this endpoint.

The data on lithium 12 -hydroxystearate are supported by results from a regulatory review document (American Petroleum Institute - API 2008), which states that lithium 12-hydroxystearate is considered to be readily biodegradable, based on a US EPA 560/6-82-003 CO2 evolution test showing 74.7% biodegradation in 28 days and meeting the 10-day window (Stonybrook Laboratories 1992). Only a summary of the study is available, but as the results are taken from a regulatory document, the data are considered reliable and relevant for use for this endpoint. Data were submitted by the American Petroleum Institute as part of the US EPA High Production Volume Challenge Program. The EPA website states that the EPA’s OPPT uses methods established in EPA guidance, which are similar to those described in Klimisch et al. (1997), to evaluate data submitted under the HPV Challenge Program for its quality and completeness. A two-tier assessment is used to assess overall scientific integrity of the information, with initial screening followed by a more rigorous evaluation. Therefore, the values presented here are acceptable as they are from a reliable secondary source.

An OECD guideline, GLP compliant study conducted on isooctadecanoic acid (Coenen, 1990) showed it to be readily biodegradable after 28 days. Annex I to the OECD Guideline for Testing of Chemicals 'Revised introduction to the OECD guidelines for testing chemicals, section 3' (OECD, March 2006) states that the 10-day window, should not be considered for UVCB substances. Therefore, despite the substance not meeting the 10-day window this conclusion is considered acceptable due to isooctadecanoic acid being a UVCB, a complex of a mixture of fatty acids.

The experimental data on lithium 12 -hydroxystearate (lithium salt of C18-OH) and isooctadecanoic acid (C18-branched) have been read across to lithium isooctadecanoate (lithium salt of C18-branched). As data are available showing the ready biodegradability of lithium 12 -hydroxystearate and isooctadecanoic acid, lithium isooctadecanoate is considered to be readily biodegradable.