Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

Acute aquatic toxicity

None of the substances in the lithium salts of monocarboxylic acids C14-C22 category are considered to be acutely toxic to fish, invertebrates or inhibitory to algal growth as all of the substances have acute LL or EL50s of >100 mg/L.

Published data

The literature search identified two pieces of ecotoxicological data for lithium 12-hydroxystearate; a study on acute toxicity to fish and a study on toxicity to aquatic microorganisms. The API (2008) and HPV Characterisation (2003, 2009) data indicate that lithium 12-hydroxystearate has an LC50 of greater than 2000 mg/L for fish. The original reference (Stonybrook 1992b) is proprietary, and as we were not able to obtain a copy of the original fish study, our assessment was based on data reported in the review documents, with the API document giving a Klimisch score of 2, “test not conducted under full GLP regulations”. As only a summary of the study from a secondary source is available, this is not considered reliable enough for use as a key study.

The HPV used experimental data as well as a combination of calculated data, read across data from similar substances within the categories and technical discussion (HPV 2009) to conclude on the potential aquatic toxicity of lithium salts of monocarboxylic acids. The HPV concluded that QSAR predicted data from ECOSAR and measured data for lithium hydroxystearate, whole greases and metal fatty acid salts were consistent, with both calculated and measured data indicating that the substances are not likely to be acutely toxic at the limits of water solubility.

Proprietary data

Due to the lack of experimental ecotoxicity data for members of lithium salts of monocarboxylic acids C14-C22 category novel testing was undertaken. Where testing has been conducted to generate data in order to complete ecotoxicity endpoints, testing of lithium myristate (C14), at the lower end of the category, lithium 12-hydroxystearate (C18), as a hydroxylated member, and lithium behenate (C22), at the upper end of the category of the category was considered the most efficient approach. The data for the longest and shortest carbon chain lengths and for a hydroxylated substance in the middle of the category were generated to bracket the possible range properties across the category and to show that substance properties are consistent across the range of carbon chain lengths specified. The testing of three substances at strategic points in the category is designed to ensure that the most conservative results are identified and, where appropriate, provide a classification which covers all of the substances in the category.

Due to the low aqueous solubility, the substances were tested as Water Accommodated Fractions. Amounts of test item were added to the surface of the dilutent at the appropriate loading rates. After the addition of the test item, the media was stirred by a magnetic stirrer using a stirring rate such that a vortex was formed to give a dimple at the water surface. The stirring was stopped after 23 hours and the mixtures allowed to stand for 1 hour. A wide bore glass tube, covered at one end with Nescofilm was submerged into the vessel, sealed end down, to a depth of approximately 5 cm from the bottom of the vessel. A length of Tygon tubing was inserted into the glass tube and pushed through the Nescofilm seal and the WAFs removed by mid-depth siphoning (the first approximate 75-100 mL discarded), using a glass wool plug if dispersed test item was seen in the aqueous phase, to give the WAFs. 

While ensuring that media were compatible with the water chemistry requirements of the test species, the tests on the three taxa were conducted using water from the same source with similar characteristics. As the water solubility of the substances in the category are likely to be influenced by the hardness of the water, the ecotoxicity tests were all conducted in media with the same hardness, approximately 150 mg/L CaCO3. The changes from the standard test media were employed to reduce effects observed from variations in the formation of soap scum between the tests for different species. As far as possible, tests were also conducted concurrently in order to reduce the variation in the solubility and stability of the substance between the different tests. As the substances could not be analysed directly, both the lithium and the total organic carbon were measured in the exposure media.

The acute toxicities of lithium myristate, lithium 12-hydroxystearate and lithium behenate to fish and Daphnia and toxicity to algal growth showed no effects at a water accommodated fraction loading rate of 100 mg/L. Therefore, for fish the 96 hour LL50 is > 100 mg/L WAF, for Daphnia the 48 hour EL50 is >100 mg/L and for algal growth inhibition the 72 hour EL50 is >100 mg/L for all three substances. The acute toxicities to fish, Daphnia and toxicity to algal growth were determined in GLP-compliant, limit tests following OECD guidelines 203, 202 and 201 respectively (Harlan 2013).

Summary

The acute ecotoxicity data for lithium myristate, the shortest carbon chain length substance in the category, lithium 12-hydroxysterate, with intermediate carbon chain length, and lithium behenate, the longest carbon chain length substance in the category have been read across to the remaining substances in the category. As data are available for the end members of the category and a substance in the centre of the category is shown to have the same properties, the interpolation of these properties to other substances with intervening chain lengths is considered to be justified.

Lithium myristate, lithium 12-hydroxysterate and lithium behenate all have 96 hour LL50s of >100 mg/L WAF to fish, 72 hour EL50s of >100 mg/L WAF to algae growth and 48 hour EL50s of >100 mg/L WAF to Daphnia when conducted in ecotoxicity media at ~150 mg/L CaCO3(Harlan 2013). As none of these substances are acutely toxic to fish, Daphnia or algae, it can be justifiably expected that the remaining substances in the category with intervening carbon chain lengths will not be acutely toxic to aquatic organisms either.

This is supported by the data reviewed in the API (2008) and HPV Characterisation (2003, 2009) documents, reporting a 96 hour LC50 to fish of >2000 mg/L for lithium 12-hydroxystearate. The HPV used experimental data as well as a combination of calculated data, read across data from similar substances within the categories and technical discussion (HPV 2009) to conclude that alkali metal salts of fatty acids are unlikely to be acutely toxic at the limits of water solubility.

Chronic aquatic toxicity

None of the substances in the lithium salts of monocarboxylic acids C14-C22 category are considered to show chronic toxicity to fish, invertebrates or inhibitory to algal growth at their limit of solubility.

Proprietary data

Algal studies report both acute and chronic endpoints and therefore the data collected from the algal growth inhibition study will be used to provide chronic data for this trophic level. As discussed under acute aquatic toxicity above, the toxicity of lithium myristate to algal growth showed no effects at a water accommodated fraction loading rate of 160 mg/L and lithium 12-hydroxystearate and lithium behenate showed no effects at 100 mg/L WAF. Therefore, the 72 hour NOErLR is 160 mg/L WAF for lithium myristate and 100 mg/L WAF for lithium 12-hydroxystearate and lithium behenate (Harlan 2013).

No data are available for the long-term toxicity to aquatic species of the lithium salts of monocarboxylic acids C14-C22. Testing is proposed for the long-term toxicity to Daphnia using lithium 12 -hydroxystearate, lithium myristate, lithium docosanoate, and fatty acids C16 -18 (even numbered) saturated and C16 -20 (even numbered) unsaturated lithium salts. The data from these studies will be read across to other substances in the lithium salts of monocarboxylic acids C14 -C22 category. The substances in the category are considered to be similar on the basis that they have common structures of a lithium ion varying only by the length of the fatty acid chain and the presence of unsaturated and/or hydroxyl functional groups. As a result, it is predicted that the substances will have similar, predictable properties. Due to the close structural similarity and the narrow range of carbon chain numbers covered by the category, the aquatic ecotoxicity is expected to be similar across the category.

The substances in the lithium salts of monocarboxylic acids C14-C22 category are readily biodegradable and have low potential for bioaccumulation. It was not possible to measure the water solubility of the substances as they are not truly soluble in water but form stable dispersions instead. In environmental media, the substances form a scum dispersed within the water and it is therefore expected that the substances have limited bioaccessibility. In realistic use scenarios, the thickeners will be contained in base oil, with the formulated greases specifically designed to minimise the leaching of the thickener. Therefore, during use, the concentrations of the substances which would be bioaccessible are further limited. The leaching investigations undertaken on these substances support that the substances would not be bioaccessible - for further information see section 5.6 of IUCLID.

Additional testing is currently being conducted with long-term toxicity to Daphnia studies on lithium myristate, lithium docosanoate, lithium 12 -hydroxystearate and fatty acids C16 -18 (even numbered) saturated and C16 -20 (even numbered) unsaturated lithium salts, and a long-term toxicity to fish study on lithium 12 -hydroxystearate.

Sediment toxicity

No data are available for the toxicity to sediment organisms. Sediment toxicity data is not a data requirement at the registered tonnage band.

References

ECHA (2011) Guidance on information requirements and chemical safety assessment – Chapter R.5: Adaptation of information requirements. European Chemicals Agency, ECHA-2011-G-15-EN

ECHA (2012) Guidance on information requirements and chemical safety assessment – Chapter R.7b: Endpoint Specific Guidance. European Chemicals Agency

HPV(High Production Volume Chemical Challenge Program) (2003) Test plan: Fatty acids, lithium and calcium salts used as grease thickeners. Submitted to the US EPA by the Petroleum HPV Testing Group. Consortium Registration. Report reference: 201-15019A. 31st December 2003.

HPV (High Production Volume Chemical Challenge Program) (2009) Lubricating Grease Thickeners CAD. Category analysis and hazard characterisation: Fatty acids, lithium and calcium salts used as lubricating grease thickeners. Submitted to the US EPA by the Petroleum HPV Testing Group. Consortium registration number 1100997. 9th February 2009.