Registration Dossier

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

Currently viewing:

Administrative data

Link to relevant study record(s)

Description of key information

The toxicity of lithium myristate to algal growth showed no effects at a water accommodated fraction loading rate of 160 mg/L. The toxicity of lithium 12-hydroxystearate and lithium behenate showed no effects at up to 100 mg/L WAF. Therefore, the 72 hour ErL50 is determined to be > 160 mg/L WAF for lithium myristate and > 100 mg/L WAF for lithium 12-hydroxystearate and lithium behenate. The 72 hour NOErLR is 160 mg/L WAF for lithium myristate and 100 mg/L WAF for lithium 12-hydroxystearate and lithium behenate.

 

Further testing on algal growth inhibition is currently ongoing for fatty acids C16-18 (even numbered) saturated and C16-20 (even numbered) unsaturated lithium salts.

Key value for chemical safety assessment

Additional information

The toxicities to algal growth were determined in GLP-compliant, static, freshwater tests (Harlan 2013) following OECD guideline 201. The algal growth inhibition test on lithium myristate was conducted at10, 20, 40, 80 and 160 mg/L WAF and no effects were observed at any of the test concentrations. Lithium 12-hydroxystearate was tested at concentrations of 1, 3.2, 10, 32 and 100 mg/L WAF alongside a blank control and no effects were observed at any concentrations. The definitive toxicity to algal growth test on lithium behenate was conducted as a limit test at 100 mg/L alongside blank controls and no toxicity was observed. 

 

Algae were exposed to water accommodated fractions of lithium myristate, lithium 12-hydroxystearate and lithium behenate for 72 hours in standard ecotoxicity media adjusted to a hardness of approximately 150 mg/L CaCO3. Observations of algal biomass were made in triplicate at 24, 48 and 72 hours and the test solutions analysed for lithium content and total organic carbon at test initiation and termination. 

 

Lithium myristate, the shortest carbon chain length substance in the category, has a 72 hour ErL50 of >160 mg/L WAF and a 72 hour NOErL of at least 160 mg/L WAF to algae. Lithium 12-hydroxysterate, with intermediate carbon chain length, and lithium behenate, the longest carbon chain length substance in the category, have 72 hour ErL50s of >100 mg/L WAF and 72 hour NOErLRs of at least 100 mg/L WAF to algae. As none of these substances are acutely toxic to algae, it can be justifiably expected that the remaining substances in the category with intervening carbon chain lengths will not be acutely toxic to algae either.

 

The toxicities of lithium myristate, lithium 12-hydroxystearate and lithium behenate to algae, aquatic invertebrates and fish were investigated in GLP-compliant guideline short-term toxicity studies (Harlan 2013). While ensuring that media were compatible with the water chemistry requirements of the test species, the ecotoxicity tests for all three trophic levels were all conducted in media with the same hardness, approximately 150 mg/L CaCO3, in order to reduce effects observed from variations in the formation of micelles due to the soap-like structure and surface activity of the substances in the category.

 

However, as there are concerns that water chemistry (such as hardness) influences the (bio)availability of the substances and that surfactants may precipitate out of solution, it has been recommended that testing follows harmonised test guidelines and non-standard testing approaches, such as changes to water hardness, are avoided.

Additional testing is currently being commissioned for lithium salts of monocarboxylic acids substances and therefore it is proposed that these new studies are conducted following standard guidelines at the recommended water hardness levels for each species. As some studies were previously conducted at different water hardness levels to those in the new testing program, it is proposed that the algae studies in the new testing program are conducted at both the guideline (e.g. 15-24 mg/L CaCO3) and increased (e.g. 150 mg/L CaCO3) water hardness levels in order to provide a comparison of results and to provide further evidence of the potential impact of water hardness on the solubility and thus bioaccessibility and bioavailability of the substances.

 

In addition to the long-term toxicity data on category members, assessments of metal salts should consider the inorganic moiety if the substances dissociate rapidly or both the inorganic moiety and the substances themselves if the dissociation rate is unknown. As there is currently no experimental data on the rate of dissociation of the substances in the lithium salts of monocarboxylic acids C14-C22 category, data are presented here on the lithium ion for completeness.

 

In aqueous environments, the substances in the lithium salts of monocarboxylic acids C14-C22 category would dissociate into fatty acids and lithium ions. The fatty acids used for the formation of the salts in this category are readily biodegradable and are considered to be non-hazardous. Fatty acids of natural origin have a long history of safe use in foods and, under the REACH regulation Annex V, natural C6 to C24 fatty acids are exempt from registration. Data on the lithium component of the salts are available in the dossiers for soluble lithium salts such as lithium carbonate and lithium hydroxide. In a toxicity test with lithium hydroxide on algae, an EC50 of 87.57 mg/L and a NOEC of 5.71 mg/L for lithium hydroxide anhydrous (equivalent to 153.44 mg/L and 10.0 mg/L for lithium hydroxide monohydrate) were determined, which are equivalent to 856.8 and 55.8 mg/L for lithium myristate. In a toxicity test with lithium carbonate on algae, an EC50 of 400 mg/L, an EC10 of 90 mg/L and a NOEC of 50 mg/L for lithium carbonate were determined, which are equivalent to an EC50 of 2531 mg/L, an EC10 of 571 mg/L and a NOEC of 317 mg/L for lithium myristate. The lowest result, a NOEC of 55.8 mg/L for lithium myristate has been read across to all substances in the lithium salts of monocarboxylic acids C14 - C22 category, following a worst-case approach as lithium myristate is the shortest chain length substance in the category and contains the highest proportion of lithium, calculated as 2.96% lithium.

 

Most of the substances in the category are surface active and form stable dispersions rather than being truly soluble. As such, definitive water solubility values could not be determined in the physico-chemical testing but the substances are expected to have very low solubility in water. A water solubility value of ≤0.000046 g/L (equivalent to ≤0.046 mg/L) was determined for lithium behenate (C22), and the other category members with shorter chain lengths would be expected to have similarly low water solubilities. As the water solubility of substances in the category is likely to be low (e.g. <1 mg/L), the long-term toxicity of the substances to invertebrates, based on the NOEC of 55.8 mg/L for lithium myristate, recalculated from the result for lithium hydroxide and read across to all substances in the lithium salts of monocarboxylic acids C14 - C22 category, would be above the water solubility and therefore, no effects are expected at the limit of solubility.