Dilithium azelate

Endpoint summary

Additional information

No data are available for the toxicity to terrestrial organisms. Category members exhibit no classifiable short-term or long-term aquatic toxicity (lowest EC50 of 23 mg/L and NOEC of 3.2 mg/L) and have low potential for adsorption/desorption to soil (Log Kow <0). The substances are expected to dissociate to carboxylic acids and lithium ions, and the substances are readily biodegradable, with ultimate degradation products of carbon dioxide, water and lithium.

 

Lithium has a low potential for adsorption; based on the partitioning of other metals (i.e. Na, K, and Ca), lithium ions are expected to remain in solution in the aqueous environment and as lithium is a naturally occurring element, its adsorption/desorption is not expected to be scientifically relevant. The lithium ions have a low potential to partition out of water, with a Kd value for soil of 280 L/kg (see Dissemination Portal). Lithium ions also have a low potential for bioaccumulation, with a BCF of 8 L/kg (Barker et al. 2006).

 

As the substances are readily biodegradable, they have a low potential for persistence and, based on the data for lithium, the substances have a low potential for adsorption. The substances are not very toxic to aquatic organisms (lowest E/LC50 >1 mg/L) and therefore the substances would meet the criteria for soil hazard category 1 and the conduct of soil toxicity testing is not required.

 

Exposure

 

Chapter R7.c. (ECHA 2017) states that “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”. Chemicals can reach the soil via several routes: 

 

- Application of sewage sludge in agriculture - The substances in this category are used as thickeners in greases and are not expected to enter the sewage system in significant quantities (see sections 9 and 10 of the CSR). 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. 

 

- Direct application of chemicals - The substances in this category are used as thickeners in greases and none of the identified uses involves direct application to soil (see sections 9 and 10 of the CSR). 

 

- Deposition from the atmosphere - 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.

 

- Irrigation or contact with contaminated waste - The substances in this category are used as thickeners in greases and are not expected to enter the water system in significant quantities (see sections 9 and 10 of the CSR). Given the uses of the substances, there is no expectation that any waste from these substances would reach the terrestrial environment.

 

The terrestrial toxicity endpoints can be waived if it can be demonstrated that direct and indirect exposure of soil is unlikely to occur. In the case of readily biodegradable substances which are not directly applied to soil, it is generally assumed that the substances will not enter the terrestrial environment and as such there is no need for testing of soil organisms. The substances are readily biodegradable, with ultimate degradation products of carbon dioxide, water and lithium. The substances are produced and used solely in base oil as grease thickeners and the substances are not applied directly or indirectly to soil so there is expected to be no exposure of the terrestrial environment and testing of terrestrial ecotoxicity endpoints is not required. 

 

Exposure to the isolated substance 

 

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. 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. 

 

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). 

 

The isolated thickener is unlikely to come in contact with the terrestrial environment. Thus, the derivation of terrestrial toxicity data on the isolated thickeners is not considered to be relevant to the potential exposure of these substances in the environment. 

 

Conclusion for terrestrial toxicity 

 

The acid components of these thickeners are readily biodegradable and the lithium ion is not expected to partition to sewage sludge or soil. The thickeners have low volatility (so aerial deposition is unlikely) and are not applied directly to soil. Thus, terrestrial exposure of lithium salts of dicarboxylic acids C6-C10 is considered to be unlikely and, as the terrestrial toxicity would not be environmentally relevant, these tests have not been conducted.