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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

The lithium salts of monocarboxylic acids C14-C22 category are readily biodegradable and are considered not inhibitory to micro-organisms at up to 13 mg/L.

Key value for chemical safety assessment

Additional information

The lithium salts of monocarboxylic acids C14-C22 category are readily biodegradable. As the concentrations tested are in excess of their water solubility, and therefore higher than concentrations that may be expected in the influent of a sewage treatment plant, the toxicity to aquatic micro-organisms studies have not been conducted.

The toxicity of lithium behenate to aquatic micro organisms was taken from the inhibition control of a GLP-compliant ready biodegradability test following OECD guideline 301B (Harlan 2013). 39.6 mg of lithium behenate was dispersed in 400 mL mineral medium by high shear mixing (approximately 7500 rpm) for 15 minutes and 51.4 mL sodium benzoate stock solution were added to mineral medium inoculated with 30 mg/L suspended solids mixed population of activated sewage sludge and adjusted to 3 L, giving a final concentration of 13.2 mg/L lithium behenate and 17.1 mg/L sodium benzoate. The test vessels were sealed, the evolved carbon dioxide collected and samples from the carbon dioxide absorber vessels analysed on days 0, 2, 6, 8, 10, 14, 21, 28 and 29 for calculation of the percentage degradation. This toxicity control vessel attained 74 % degradation after 14 days and 83 % degradation over 28 days, which are above the 25 % required for substances to be considered as non-inhibitory, thereby confirming that lithium behenate was not toxic to sewage treatment micro-organisms used in the test.

Although data are only available for lithium salts of fatty acids at C22, substances in the category with shorter carbon chain lengths are expected not to be inhibitory to micro-organisms either. All of the substances in the category are considered to be readily biodegradable with no toxicity to fish, Daphnia or algae at up to 100 mg/L and the similarities in environmental fate and ecotoxicity properties across the category indicate that reading across the toxicity to aquatic micro-organisms is justified. Further testing is currently ongoing on the ready biodegradability of lithium myristate and fatty acids C16 -18 (even numbered) saturated and C16 -20 (even numbered) unsaturated lithium salts and the toxicity to microorganisms endpoint will be updated once the results become available.