(Z)-octadec-9-enol

Endpoint summary

Additional information

Short term toxicity

There are no reliable measured short-term toxicity test results available for freshwater fish, invertebrates or algae. QSARs have been used to predict short-term toxicity to fish, invertebrates and algae. Read-across data from studies with structurally similar substances have also been considered.

 

The relevant short-term values are:

 

Fish: A reliable 96 h LC₅₀ value of >100 mg/L has been calculated for the effects of the test substance towards Oncorhynchus mykiss. Therefore the test substance has been predicted to be non-toxic at the limit of solubility, so the LC₅₀ is >0.042 mg/L.

A 96h LC₅₀ value of >1000 mg/L has been read-across from a supporting substance C16-18 and C18 Unsaturated (CAS 68002-94-8). The study is reliability 4 since only a summary report was available for review. However it does support the view that the (z)-octadec-9-enol is non-toxic at the LoS.

 

Invertebrates: (Z)-octadec-9-enol has been predicted to be non-toxic at the limit of solubility, so the EL₅₀ is >0.042 mg/L. This is the only value available for this endpoint and therefore has been selected as key.

A reliable 48 h EC₅₀ value of 70 mg/L has been determined for the effects of Alcohols, C14-18 and C16-18-unsaturated (CAS 68002-94-8) on mobility of the freshwater invertebrate Daphnia magna. The study supports the view that the substance is non-toxic at the LoS.

 

Algae: (Z)-octadec-9-enol has been estimated, by expert judgement based on read-across from other taxonomic groups and the alcohols Category, to be non-toxic at the limit of solubility to the algal taxonomic group. Therefore the EC₅₀ value is >0.042 mg/L.

 

Long term toxicity

Fish: (Z)-octadec-9-enol has been determined by expert judgement to be non-toxic at the limit of solubility.

 

Invertebrates: (Z)-octadec-9-enol has been determined by expert judgement to be non-toxic at the limit of solubility.

A 21-d EC₁₀ value of 0.012 mg/l (reproduction of Daphnia magna) has been read across from pentadecan-1-ol (CAS 629-76-5, C15). This study has been read across for the purpose of setting indicative aquatic PNECs for use in assessing risk to the sediment and terrestrial compartments using the equilibrium partitioning method, because no aquatic toxicity is expected at chain lengths >C15.

 

Toxicity to Micro-organisms

In waste-water treatment plant micro-organisms, (z)-octadec-9-enol does not cause inhibition at the limit of water solubility. In view of the ready biodegradability, further information is not required in REACH. A data waiver is in place for the activated sludge respiration inhibition as the substance is readily biodegradable and the applied test concentrations are in the range that can be expected in the influent to a sewage treatment plant. Existing data is, however, available, for the species Pseudomonas putida. A 30 minute EC₁₀ of >10000 mg/L was determined.

 

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

Many short-term aquatic toxicity tests have been carried out on this family of long chain aliphatic (LCAAs), addressing toxicity to organisms from three trophic levels; fish, invertebrates and algae. For studies in which the test substance had a single carbon chain length, a key study has been identified for each taxonomic level. Where there were two or more reliable studies of the same quality but on different species within the same taxonomic group, the lower toxicity value (highest level of toxicity) was chosen. For studies in which the test substance was a multi-constituent LCAAs (commercial products) and where there was more than one type of the substance a key study was identified for each type.

 

The results of short-term tests performed on single carbon chain length LCAAs are generally reported in terms of the nominal or measured dissolved concentration of the alcohol in the test medium and are identified as EC₅₀ or LC₅₀ values. However there are also instances where the reported effect concentration exceeded the solubility of the LCAA. These instances are distinguished in the results tables either by the result being reported as an LL₅₀ or EL₅₀, implying that the test medium was a water accommodated fraction (WAF), or by a note indicating that the test substance loading exceeded the solubility of the LCAA. In the latter case it has had to be assumed (because it is not apparent from the test report) that undissolved LCAA may have been present in the test medium and that there was the potential for physical (rather than toxicity) effects to occur.

For studies using multi-constituent substances it is possible to interpret the results on the basis of measured dissolved concentrations of the LCAA constituents but they cannot be directly related to the concentration of the multi-constituent substance itself. This is because the test medium does not contain dissolved concentrations of the constituents in the same ratio as present in the substance itself. The toxicity data for mixed carbon chain length LCAAs are therefore also expressed using different conventions. Where the effect concentrations occurred at concentrations below the solubility limit of a multi-constituent substance they are reported as nominal or measured concentrations and are again identified as EC₅₀ or LC₅₀ values. In cases where the test media were WAFs, or where the loading of a multi-constituent substance exceeded the solubility of one or more of its constituents, the result is reported either as an LL₅₀ or EL₅₀, denoting that the test medium was a Water Accommodated Fraction (WAF), or by a note indicating that the test substance loading exceeded the solubility limit of the multi-constituent substance. Once again in the latter case it has had to be assumed (because it is not apparent from the test report) that undissolved LCAA may have been present in the test medium and that there was the potential for physical (rather than toxicity) effects to occur.

In Section 4 it was highlighted that biodegradation is likely to be a significant loss mechanism from aquatic media for the LCAAs under review. If loss of test substance from aquatic test media is significant it will undermine the results of tests where analysis of exposure was not performed. For example, exposure concentrations of 1-octanol (No. 111-87-5) in a 7-day test with the fathead minnow (Pimephales promelas) declined by >90% in the unspecified period between media renewals (Pickering et al., 1996). However the NOEC has been expressed relative to nominal concentrations and must represent a significant overestimate of the true value and therefore an underestimate of the true toxicity. Similarly, the exposure concentration of the same substance that corresponded to the NOEC determined in a 21-day semi-static long-term test with Daphnia magna, declined by >35% over the 3-4 day period between media renewals (Kuhn et al., 1989). This suggests that exposure concentrations, expressed as nominal values, would have significantly overestimated the actual concentrations. The above examples highlight that test results expressed only in terms of nominal concentrations must be treated with considerable caution and may underestimate the toxicity of the substance.

Trends in results, described in this section, are supported by reliable measured data for branched LCAAs which are members of the Oxo Alcohols Category. For full details please refer to the Oxo alcohols SIAR and SIDS dossiers.

Where there were no available data for a linear LCAA the data has been read-across (see CSR section 1.4) from reliable data for the closest linear alcohols with a smaller carbon chain length.

For multi-constituent substances lacking measured short-term toxicity data, the data has been read-across from the major constituent linear LCAAs in cases where these formed >90% of the multi-constituent substance. This approach is deemed valid because it is considered very unlikely that the minor constituents present at <10% will contribute significantly to short-term effects. This approach has not been adopted for long-term toxicity data because here the potential for the minor constituents to contribute to effects is much greater.

In the absence of suitable read-across data for linear and multi-constituent LCAAs, validated QSAR methods have also been developed to fill data gaps for short-term toxicity to fish and invertebrates. QSARs for linear alcohols have also been developed to fill data gaps for long-term toxicity to invertebrates.

References:

Kuhn, R., Pattard, M., Pernak, K., and Winter, A. (1989). Results of the harmful effects of water pollutants to Daphnia magna in the 21 day reproduction test. Wat. Res. 23(4): 501-510.

Pickering, Q.H., Lazorchak, J.M., and Winks, K.L. (1996). Subchronic sensitivity of one-, four-, and seven-day-old fathead minnow (Pimephales promelas) larvae to five toxicants. Environ. Toxicol. Chem. 15(3): 353-359.