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Environmental fate & pathways

Biodegradation in water: screening tests

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Description of key information

All the substances in the lithium salts of monocarboxylic acids C14 -C22 category are considered to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

All of the substances in the lithium salts of monocarboxylic acids C14-C22 category are considered to be readily biodegradable in water. 

The ready biodegradability of lithium behenate was determined in a GLP-compliant CO2evolution study following OECD guideline 301B (Harlan 2013). Non-adapted, activated sludge from the aeration stage of sewage treatment plant which treats predominantly domestic sewage was exposed to lithium behenate at 13 mg/L for 28 days and the carbon dioxide evolution was assessed. The study was run alongside a reference substance, a blank control and a toxicity control, which indicated that lithium behenate is not inhibitory to aquatic micro-organisms at 13 mg/L. Lithium behenate reached 97% degradation after 28 days, meeting the 10 day window, and therefore is considered to be readily biodegradable. 

 

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 is considered readily biodegradable. The study was published as part of a regulatory database and is considered reliable and relevant for use for this endpoint.

 

This is 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 CO2evolution 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. The 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. 

 

The biodegradability of long-chain fatty acids has been read across from a non-GLP, non-guideline, batch respirometric study (Mizuki et al. 2010). The results suggest that the soap-based fire-fighting agent (58.9% sodium oleate, 40.5% potassium laurate, 0.6% potassium palmitate) is readily biodegradable. As only a summary is available, there are limitations in design and/or reporting, but the data are taken from published, peer-reviewed literature and are considered reliable and relevant for use. Mizuki et al. have shown that a mixture of ~60% sodium oleate (C18) and ~40% potassium laurate (C12) is readily biodegradable, indicating that shorter carbon chain length substances are expected to have the same properties as those of longer chain substances.

 

Ready biodegradation studies are currently being conducted on lithium myristate in order to bracket the category and fatty acids C16-18 (even numbered) saturated and C16-20 (even numbered) unsaturated lithium salts to provide data on unsaturated structures (Covance 2020).

 

Proprietary data are available for lithium behenate showing ready biodegradability (Harlan 2013). Published data are available on lithium 12-hydroxystearate from regulatory reviews (MITI 1994, API 2008) showing ready biodegradability. The results from these studies also indicate that the lithium ion is not inhibitory to microorganisms, and does not prevent the ready biodegradation of the fatty acid component. Additional supporting data have also been included for other metal salts of fatty acids across the carbon number range of the category. 

 

The experimental data on category members and data on other metal salts of fatty acids in the carbon number range of the category has been read across to substances in the lithium salts of monocarboxylic acids C14-C22 category. Substances with shorter carbon chain lengths are expected to be more water soluble and therefore more bioavailable to aquatic microorganisms for degradation. Reading across from longer chain length substances to shorter chain length substances is therefore considered valid. As data are available showing the ready biodegradability of lithium behenate, all of the substances in the lithium salts of monocarboxylic acids C14-C22 category are considered to be readily biodegradable.