Dilithium azelate

Toxicity to terrestrial arthropods

Administrative data

Endpoint:

toxicity to terrestrial arthropods: short-term

Data waiving:

exposure considerations

Justification for data waiving:

the study does not need to be conducted because direct and indirect exposure of the soil compartment is unlikely

Justification for type of information:

Terrestrial toxicity studies are not considered to be scientifically relevant for the substances in the lithium salts of dicarboxylic acids C6-C10 category. The substances have very low vapour pressures, are readily biodegradable, have low potential for bioaccumulation, and show no classifiable acute or chronic aquatic toxicity. No data are available on the adsorption/desorption of these substances and the requirement for testing this endpoint was waived on the basis that the substances are readily biodegradable. However, the substances are expected to have low potential for adsorption to sediment or soil based on their low octanol-water partition coefficients. The log Kow values for dilithium adipate (C6), dilithium azelate (C9) and dilithium sebacate (C10) range from <-0.9 to -3.3 based on the dicarboxylate ion and <-3.1 to <-4.0 based on the lithium ion. The lithium salts of dicarboxylic acids are expected to dissociate in the aquatic environment into lithium cations and dicarboxylic acid anions. The acids have been registered themselves under REACH, so the hazard profile of such substances is well-documented. The dissociation and biodegradation in the environment of the substances would result in carbon dioxide, water and lithium ions. Lithium ions are expected to remain in solution in the aqueous environment. Lithium is a naturally occurring element, “found in small amounts in nearly all igneous rocks and in the waters of many mineral springs” (Lide 2009) and the adsorption/desorption of lithium in the environment is not expected to be scientifically relevant.
The toxicity to terrestrial organisms studies do not need to be conducted because direct and indirect exposure of the soil compartment is unlikely. When soil exposure is considered negligible, i.e. where there is low likelihood of land spreading of sewage sludge, or aerial deposition of the substance and other pathways such as irrigation or contact with contaminated waste are equally unlikely, then neither a PEC, nor PNEC can or need be calculated and no soil toxicity data are necessary
The substances in this category are used as thickeners in greases (see sections 9 and 10 of the CSR) and none of the identified uses involves direct application to soil. The substances are not expected to enter the water system in significant quantities and there is no expectation that any waste from these substances would reach the terrestrial environment. The substances are not expected to enter the sewage system in significant quantities and, of the amount which occurs in sewage sludge, the acid components of lithium salts are readily biodegradable and the lithium ion is not expected to partition to sludge or soil but to remain in solution. Therefore, these compounds are not expected to be present in any sewage sludge applied in agriculture. The vapour pressure of the lithium fatty acid salts in the category are estimated to be below 1.3 x 10 (-8) Pa at 20°C and 2.9 x 10 (-8) Pa at 25°C and as the substances have very low volatility, they are not expected to enter the atmosphere. Thus, aerial deposition of the substances will be negligible and is not expected to be a relevant route of exposure.
The identified uses of the substances in the lithium salts of dicarboxylic acids C6-C10 category relate to their use as thickeners in formulated greases. For these uses, the substances are typically manufactured in situ in base oil so exposure to the isolated thickeners would not occur. Additionally, although greases are considered to have wide, dispersive uses, with professional and consumer downstream users, most grease-lubricated parts are sealed. The majority of greased parts are designed to keep the grease within the contact zone. A large proportion of light to medium duty grease-lubricated parts are sealed for life and the user will not interact with the grease during any time of the part’s use from purchase to disposal. Due to the nature of the grease as a semi-solid, it will remain within the part and not be released, even in the event of catastrophic failure. Some applications require a grease to be used as a total loss lubricant, such as on rail tracks, heavy duty trucks, spindles on agricultural crop pickers and marine applications. In these applications, there are voluntary/compulsory schemes in place that limit the type of product used based on its toxicity, ecotoxicity and biodegradability (e.g. Nordic Swan, Ecolabel, Blaue Engel, VGP). Therefore, the potential for human or environmental exposure to the formulated grease is limited and the potential for exposure to the thickener itself would be even further reduced.
Given this, the concentrations of the substances which would be available for adsorption to soil or sediment would be reduced. Leaching studies have been undertaken (see leaching summary in dossier and CSR) on dilithium adipate in the form in which is it manufactured and used (i.e. with other thickener substances in base oil). The tested grease consisted of 3.6% dilithium adipate, the maximum concentration that is manufactured and used, and 9.4% lithium 12-hydroxystearate in distillates (petroleum), hydrotreated heavy naphthenic (CAS: 64742-52-5). It was concluded that dilithium adipate leaches into water, but the grease base appears to limit the bioaccessibility of the substance to less than 20% of the theoretical maximum dilithium adipate concentration as measured in the WAF. Toxicity screens using Daphnia magna and MicroTox™ were conducted alongside the leaching study to screen for ecotoxicity. No toxic effects were observed in these tests, i.e. L(E)C50 values were >100% v/v WAF.