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Long-term toxicity to fish

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Description of key information

No toxicity is expected at the limit of solubility (expert judgement)

Key value for chemical safety assessment

Additional information

No reliable measured data are available for long-term toxicity of (z)-octadec-9-enol to fish.

In an expert statement based on ecotoxicological information available on the alcohols category no toxicity is expected at the limit of solubility.

The only reliable test data that provide an indication of long-term toxicity to fish are for 1-octanol, branched 1-pentadecanol and decan-1-ol:

  • For 1-octanol a NOEC of between 0.75 and 3.0 mg/L has been determined for growth reduction in a 7-day test with larval fathead minnows (Pimephales promelas) (Pickering et al., 1996). The result has been assigned reliability 2.
  • For 1-pentadecanol branched a NOEC of ≥140 µg a.i./L has been determined for growth, survival and reproduction in a 35-day test with larval fathead minnows (Pimephales promelas) (ABC 1999). The result has been assigned reliability 2.
  • For decan-1-ol a NOEC of 0.26 mg/l based on growth (total length), and EC10 of 0.43 mg/l based on mortality, have been determined in a 33-day test with larval fathead minnows (Pimephales promelas). The result has been assigned reliability 1.

The result from Pickering et al. is expressed relative to nominal exposure concentrations and it is significant to note that measured concentrations declined by >90% over the period between media renewals (not specified in the source document). The true toxicity is therefore likely to have been greater than that expressed due to the observed loss of test substance concentration in the old media. Additionally, the duration of this test is too short for it to be considered a true long-term study.

The result from ABC is expressed relative to the arithmetic mean of measured concentrations; it should be noted that measured concentrations may vary as much as 10-fold in the same treatment level.

The test result from Wildlife International is expressed relative to arithmetic mean measured concentrations. Measures were taken to prevent significant biodegradation losses of substance in the test system. Measured concentrations were within 80% of nominal concentrations. 

These three test results do not provide sufficient data to determine a trend in long-term toxicity across the category. However, short-term data for fish and invertebrates indicate that the toxicity of linear alcohols decreases with increasing chain length and that alcohol’s with chain lengths ≥C13 are not toxic to fish, and those with chain lengths ≥C15 are not toxic for invertebrates, at their solubility limit. Invertebrates appear to be rather more susceptible than fish in short-term tests and it is reasonable to assume that a similar relationship exists in long-term tests.

Long-term invertebrate (Daphnia) toxicity data for a linear alcohol with a carbon chain length of C15 show it to be toxic at a concentration below its solubility limit (Schaefers, 2005). However data for a C18 linear alcohol show it to be non-toxic at its solubility limit (Guhl, 1992). Schaefers et al (2009) have analysed these data and concluded that linear alcohols with carbon chain lengths >C15 are not toxic to invertebrates at their solubility limit. Given the relative susceptibilities of fish and invertebrates in short-term tests it is reasonable to conclude that alcohols with carbon chain lengths >C15 would also not be toxic to fish in long-term tests.

Testing for long term toxicity to fish is not considered necessary because:

A recent long-term toxicity test has been carried out with the structurally analogous substance decan-1-ol. There was intensive method development to attempt to overcome very significant biodegradation losses of substance in the test system. Whilst testing is not technically impossible, it requires very significant efforts which are disproportionate to the need for data.

The freshwater PNEC has been derived from the data with long-term toxicity to invertebrates (Daphnia). The three available NOEC values for toxicity to fish indicate that they are in the range of the NOEC values determined in the long-term invertebrate tests. The risk characterisation ratios (RCRs) based on the PNECfreshwater derived from the long-term toxicity to invertebrates data are <1, therefore no further testing is considered necessary.