Decan-1-ol

Endpoint summary

Additional information

Short-term toxicity

Reliable short-term toxicity tests results are available for freshwater fish (Pimephales promelas) and invertebrates (Nitocria spinipes) and effect levels in green algae have been estimated using QSAR and read-across approaches.

The relevant short-term values are:

Fish: weight of evidence: LC₅₀ (120 h): 3.4 mg/l (OECD 236) and LC₅₀ (96 h): 2.4 mg/l (OECD 203)

Invertebrates: EC₅₀ (48 h): 3.1 mg/l

Algae: EC₅₀ in the range 1 - 10 mg/l (estimated by read-across from other taxonomic levels; Fisk et al., 2009); ErC₅₀ 1.5 mg/l (Category QSAR, Fisk et al., 2015)

Long-term toxicity

Due to the rapid biodegradability by a range of organisms, maintaining substance concentrations throughout long-term tests is extremely challenging. The only results that can be considered reliable are those from studies in which significant non-standard methodologies were developed to maintain the substance in solution as far as possible, whilst minimising stress to the test animals.

The relevant long-term values are:

Fish: EC₁₀ (33-day) 0.43 mg/l (based on survival) and NOEC 0.26 mg/l (based on growth (total length)) (mean measured)

Invertebrates: EC₁₀ (21-day): 0.21 mg/l and NOEC 0.11 mg/l (mean measured) for effects on reproduction

Algae: ErC₁₀ 0.7 mg/l (Category QSAR, Fisk et al., 2015)

At these concentrations decanol is expected to be fully dissolved.

 

Toxicity to microorganisms

At or above the limit of water solubility, the registered substance has no significant inhibitory effects on respiration of activated sludges or specific microbial strains relevant to WWTP, based on consistent category evidence for C6-24 aliphatic alcohols. There is no hazard for WWTP microorganisms.

Sediment

A 6 d EC₅₀ value of 150 mg/kg dw soil (1.3% organic carbon) has been determined for the effects of decanol on population numbers and survival of the ostracod H. incongruens.

 

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 octan-1-ol (CAS 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.