(Z)-octadec-9-enol

Endpoint summary

Additional information

There are no terrestrial data available for (Z)-octadec-9-enol (C18 unsaturated - CAS 143-28-2). ECHA guidance on the integrated testing strategy and screening assessment for soil (ECHA 2014, R.7c) indicates that this substance falls into Hazard Category 3. This is due to the high log K_ow (7.07) of the substance indicating potential for high adsorption, but the substance showing no toxicity during the aquatic tests. This 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 (Z)-octadec-9-enol is based on the 21-d EC₁₀ value of 0.012 mg/l, for long-term toxicity of pentadecan-1-ol (CAS 629-76-5) to aquatic invertebrates. This substance is used for deriving the aquatic PNEC for alcohols >C15, based on the conclusion in the SIAR that "For substances of chain length greater than C15, no long-term effects would be expected" (for water). The RCRs derived using this approach are only indicative limits, not true values, therefore the PNECaquatic for (Z)-octadec-9-enol 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 microorganisms

In accordance with Column 2 of REACH Annex IX, the toxicity test with terrestrial microorganisms (required in Section 9.4.2) does not need to be conducted as direct and indirect exposure of the soil compartment is unlikely. In the absence of toxicity data for soil organisms, the equilibrium partitioning method has been applied to assess the hazard to soil organisms.

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.

Long-term toxicity

In accordance with Column 2 of REACH Annex X, long-term toxicity testing with terrestrial organisms (required in Section 9.4) 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.

Toxicity to terrestrial plants

In accordance with Column 2 of REACH Annex X, long-term toxicity testing with terrestrial plants (required in Section 9.4.5) 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.

Toxicity to birds

In accordance with Column 2 of REACH Annex X, long-term and reproductive toxicity testing with birds (required in Section 9.6) is not needed as the chemical safety assessment according to Annex I indicates that this is not necessary.

Testing for toxicity to terrestrial organisms is not considered necessary because:

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