Hexan-1-ol

Endpoint summary

Additional information

There are no terrestrial data available for hexan-1-ol (C6, CAS 111-27-3).

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

Further testing for toxicity to terrestrial organisms is not considered necessary because:

In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in long-term terrestrial toxicity studies because, as indicated in guidance R.7.11.6 (ECHA 2016), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio is well below 1, and therefore the risk is already adequately controlled and further testing is not justifiable.

Hexan-1-ol is highly water soluble and has a low log K_ow value and therefore, exposure of the soil compartment is expected to be low. The substance has low potential for adsorption and low bioavailability (based on log K_ow <3 (2.5)) and low toxicity (EC/LC₅₀ >1 mg/l). Based on these properties, the substance is classed as having a soil Hazard Category 1 (Table R.7.11-2, ECHA 2017), according to which if the PEC/PNEC_screen < 1, no further testing on soil organisms is needed.

The PNEC was derived from the Equilibrium Partitioning Method for the purpose of deriving a chemical safety assessment and the risk characterisation ratios are below 1.

The occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies would be considered unlikely.

In addition, using stable isotope signatures of fatty alcohols in a wide variety of household products and in environmental matrices sampled from river catchments in the United States and United Kingdom, it has been estimated that 1% or less of fatty alcohols in rivers are from waste water treatment plant (WWTP) effluents, 15% is from in situ production (by algae and bacteria), and 84% is of terrestrial origin (Mudge et al., 2012). Further, the fatty alcohols discharged from the WWTP are not the original fatty alcohols found in the influent. While the compounds might have the same chain lengths, they have different stable isotopic signatures (Mudge, 2012). See IUCLID section 5.5.1 for further details.

Overall it is concluded that the risk characterisation conclusion is sufficiently conservative in respect of any uncertainties and therefore further in is not considered necessary.

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0 and Chapters 9 and 10 of the Chemical Safety Report, respectively.

 

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

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). 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.

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.

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. 

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.

ECHA 2017, Chapter R.7c: Endpoint specific guidance, Version 3.0 - June 2017.

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.