Docosan-1-ol

Endpoint summary

Additional information

In accordance with Column 2 of REACH Annex X long-term terrestrial toxicity testing is not needed as the chemical safety assessment according to Annex I indicates that this is not necessary.

Moreover, considerable technical difficulties would be expected in the conduct of such a test, due to the very rapid biotic removal of the substance from the test system. Please refer to discussion of the long-term aquatic invertebrate and fish studies, and evidence of rapid removal in non-sterilised soils during method development for the adsorption/desorption study with natural soils in the environmental fate section.

 

PNECsoil has been calculated from PNECfreshwater on the basis of the equilibrium partitioning method;the risk characterisation ratio (RCR) based on PNECsoil derived from this method is <1.

 

ECHA guidance on the integrated testing strategy and screening assessment for soil (ECHA 2017, R.7c) indicates that this substance falls into Hazard Category 3 (based on high potential for adsorption (Log Kow >5), low persistence (readily biodegradable) and low toxicity to aquatic organisms (EC 50 >1 mg/L)). This soil Hazard Category would usually trigger screening assessment based on the equilibrium partitioning method (EQPM) as well as a confirmatory long-term soil toxicity test.However,the rapid degradation of the substance means that long-term toxicity testing in soil is not possible.The rapid degradation also indicates that the absolute quantity of partitioning to soil is expected to be small. Therefore terrestrial hazard is based on the EQPM PNECs derived from the aquatic data.

 

The aquatic data used to derive the PNECaquatic for docosan-1-ol is based on the 21-d EC10v alue of 0.012mg/l, for long-term toxicity of pentadecan-1 -ol (CAS629 -76 -5) to aquatic invertebrates.This substance is used for deriving the aquatic PNEC for alcohols >C15, based on the trends observed in the category that for linear LCAAs with carbon numbers ≥C15 long-term effects on aquatic invertebrate would be above the solubility limit (Schäfers et al. 2009).The PNECs derived using this approach are only indicative limits, not true values, therefore the PNECaquatic for docosan-1-ol is a conservative value.

Discussion of trends in the Category of C6-24 linear and essentially-linear aliphatic alcohols:

The experimental data set for terrestrial toxicity across the category is limited. There are no long-term data on the toxicity of LCAAs to soil-dwelling organisms. However, the absolute quantity of partitioning to soil is expected to be small, and rapid degradation is anticipated, particularly in view of the rapid degradation seen in short-term studies using soils.

It is notable that significant technical difficulties were encountered during method development for a recent study with decan-1-ol of adsorption/desorption (OECD 106, Wildlife 2015) using natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples. During method development in preparation for this study, the laboratory reported that after equilibration with soils for 15-minute to 24-hour periods, decan-1-ol dosed into the test vessels was partly or completely transformed into a more polar product, which was clearly distinguishable from the starting material as clear and well separated peaks in the chromatograms. The rate of transformation depends on the soil type. Only after a very short (5-minute) equilibration the parent material remained intact (personal communication, 8 January 2015 from Wildlife International laboratory). Half-lives were not explicitly derived, but chromatograms presented would indicate the half-life of decan-1-ol in the soil test samples was approximately 30 min - 1 hour (silt loam soil); 1 - 2 hours (loamy sand), and 15 - 30 minutes (clay loam). In view of this, it is not technically feasible to attempt any further terrestrial toxicity testing and the absence of existing long-term study data is understandable.

Toxicity to terrestrial microorganisms

The terrestrial chemical safety assessment has been conducted using the Equilibrium Partitioning method (EQPM). It is recognised that the aquatic PNEC used in the EQPM does not take into account any indicator for effects in aquatic microorganisms. However, analogous alcohols within the Category are very rapidly biodegradable and show no significant inhibitory effects on respiration of activated sludge or specific microbial strains relevant to WWTP, at or above the limit of solubility (based on inhibition tests and lack of toxicity in ready biodegradability test).A lack of toxicity to soil microbiota was suggested by a recent experimental finding associated with a recent study of adsorption/desorption (OECD 106, Wildlife International, 2015) using decan-1-ol. Significant technical difficulties were encountered during method development for this study using natural standard soils, in that it was not possible to detect sufficient substance and establish equilibrium in non-sterilised soil samples. Therefore it is unlikely that the PNECterrestrial based on aquatic ecotoxicity test results would not be protective for terrestrial microorganisms. The chemical safety assessment using EQPM does not suggest any unacceptable risks for the terrestrial compartment.

Therefore, further toxicity testing with terrestrial microorganisms does not need to be conducted.

Toxicity to birds

In accordance with Column 2 of REACH Annex X, studies on long-term and reproductive toxicity to birds (required in Section 9.6) do not need to be conducted due to the availability of relevant existing data.

References:

 

Schäfers, C. Boshof, U. Jürling, H. Belanger, S.E. Sanderson, H. Dyer, S.D. Nielsen, A.M. Willing, A. Gamon, K. Kasai, Y. Eadsforth, C.V. Fisk, P.R. Girling, A.E., 2009. Environmental properties of long chain aliphatic alcohols. Part 2: Structure-activity relationship for chronic aquatic toxicity of long-chain alcohols. Ecotoxicology and environmental safety. 72(4): 996-1005.