Docosanoic acid

Endpoint summary

Additional information

Studies on soil toxicity of docosanoic acid (CAS 112-85-6) to terrestrial organisms are not available.

The target substance is characterized by a low water solubility (0.016 mg/L at 25 °C), a high potential for adsorption to organic soil particles (log Koc = 5.64, KOCWIN v2.00) and ready biodegradability.

All reliable aquatic acute (fish, invertebrates, algae) and aquatic chronic data (fish, invertebrates, algae) for the target substance and suitable source substances indicate no effects up to the water solubility limit. Thus, as the water solubility of the substance is < 1 mg/L (0.016 mg/L at 25 °C)) and no long-term effects to aquatic organisms were observed up to the substance solubility limit, this fact can be used as part of a Weight-of-Evidence argument to waive the data requirement of Annex X for terrestrial toxicity according to chapter R. 7c of the ‘Guidance on information requirements and chemical safety assessment' (ECHA, 2017).

 

In addition, based on the readily biodegradability of the substance, docosanoic acid is expected to be eliminated in sewage treatment plant to a high extent. As mentioned in the Guidance on Information Requirements and Chemical Safety Assessment, Chapter R.7b (ECHA, 2017), the ready biodegradability of a substance can be an indication of rapid and ultimate degradation in most environments, including biological sewage treatment plants (STP). Thus, the substance will be extensively removed by microorganisms in biological sewage treatment plants. Moreover, degradation studies cited in the Draft Assessment Report (DAR, Volume 1 and 3, 2008) show DT50 values of 1.5 to – 3 days for Fatty Acids (C7-C20), indicating rapid primary degradation of fatty acids by microbial organisms in the soil environment. Besides, due to the high adsorption potential of the substance (log Koc = 5.64, KOCWIN v2.00), a removal from the water column to a significant degree by adsorption to sewage sludge can be expected (Guidance on information requirements and chemical safety assessment, Chapter R.7b, (ECHA, 2017)). Thus, discharged concentrations of the substance into the soil compartment are likely to be negligible. Overall, the bioavailability of docosanoic acid (CAS 112-85-6) in the soil environment is expected to be low, which reduces the probability of exposure, in particular long-term exposure, of soil organisms in general.

 

Furthermore, Fatty acids generally occur naturally in soils and are part of physiological pathways. Fatty acids are used by soil organisms as an energy source and for anabolic processes as well. According to Draft Assessment Report (DAR), low toxicity of a fatty acid formulation was demonstrated in several tests on soil macroorganisms, terrestrial non-target arthropods and terrestrial plants (DAR, Volume 1, 2008). Thus, toxic effects to soil organisms caused by docosanoic acid (CAS 112-85-6) are negligible.

 

 In conclusion, due to the following reasons no study on the effects on terrestrial organisms need to be conducted for docosanoic acid (CAS 112-85-6):

- absence of long-term effects in aquatic organisms up to the water solubility limit

- a rapid primary degradation of fatty acids by microbial organisms in the soil environment

- a removal from the water column to a significant degree by adsorption to sewage sludge

- a low bioavailability

- fatty acids are part of the physiological pathway

- low toxicity demonstrated for fatty acid formulation

References:

Draft Assessment Report (DAR) for Fatty Acids (C7-C29) (Volume 1, August 2008)

Draft Assessment Report (DAR) for Fatty Acids (C7-C29) (Volume 3, Annex B, Part 4, B.8, August 2008)