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EC number: 205-597-3
CAS number: 143-28-2
(Z)-octadec-9-enol (C18 unsaturated - CAS 143-28-2) has low predicted
water solubility (0.042 mg/l at 25˚C), and high predicted log Kow
(7.07). It has no hydrolysable structural features and would be
expected to be stable in water. It is rapidly biodegradable.
(Z)-octadec-9-enol is a member of a category of long chain aliphatic
alcohols (LCAAs) with a carbon chain length range of C6-C24. The
Category is limited to linear and essentially-linear aliphatic alcohols.
As carbon number increases, short- and long-term aquatic toxicity
generally increase (i.e. decreasing E(L)C50 and NOEC values
observed) up to a threshold carbon number, above which there are no
effects at the limit of solubility. For short term effects the threshold
is between C13 and C14; for chronic effects it is between C15 and C16.
The observed threshold in carbon number is associated with limitations
on the degree to which predictable effects are expressed at the limit of
solubility, which is low for the longer-chain alcohol structures in the
Evidence across the Category of C6-24 long-chain aliphatic alcohols
(LCAAs) supports the conclusion that a similar level of susceptibility
is exhibited for all three taxonomic groups in the short-term data set.
Alcohols in the Category have toxicity consistent with non-polar
narcosis effects, in line with the very many organic non-polar narcotic
organic substances that have been extensively studied and described in
literature by various authors. Therefore the LCAAs in this category
should be considered in the context of neutral organics.
Long-term toxicity testing across the category has been carried out with
fish and Daphnia. However, significant biodegradation losses of
substance in the test system still occurred, despite measures taken to
prevent this. A full report detailing properties and trends across the
LCAAs category, as well as further discussion on measures to prevent
test substance losses is available: ECOTOXICITY Alcohols C6-24 Category
Data have been read across from a supporting substance C16-18 and C18
Unsaturated (CAS 68002-94-8) to fulfil short-term toxicity to fish and Daphnia
endpoints, as well as toxicity to microorganisms. It is possible to
read-across from CAS 68002-94-8 to CAS 143-28-2 since these two
substances are closely related. CAS 68002 -94 -8 is a mixture of C16-18
and C18 unsaturated. The physicochemical, toxicological and
ecotoxicological properties and behaviour do not differ significantly
between the two substances.
Where measured data is lacking or of unassignable reliability,
quantitative structure-activity relationships ((Q)SAR’s) and expert
judgement have been used to calculated predicted E(L)C50 and
NOEC values for short and long-term toxicity to fish, invertebrates and
algal endpoints. Further details are described in the ECOTOXICITY
Alcohols C6-24 Category report.
Reduced assessment factors have been used to derive PNECs.
Basis for setting of assessment factor
The purpose of assessment factors is to take a laboratory result and
estimate a PNEC that applies to the environment itself. In summary, and
as is well-known, the purpose of the factors is to account for
1. Intra-laboratory variability
2. Inter-laboratory variability
4. Sensitivity of the environmental ecosystem relative to the range
or organisms actually tested.
For one substance standing alone, the factor of 10 is considered in the
Guidance to apply to three long term NOECs or ECx values for the aquatic
compartment. Similarly an assessment factor of 50 is specified when
deriving a PNEC when two long-term NOECs or EC10s for
different taxonomic groups are available.
Why is the Guidance default of 10 a reasonable number for long-term
data? A reasoned discussion is set out in the table below, along with an
application of the same logic to (Z)-octadec-9-enol.
Table 1 A basis of understanding assessment factors and application to
long-term studies with alcohols
General rationale when three trophic levels have been studied
Members of the C6-24 Alcohols Category
1. Intra-laboratory variability
For well-performed studies with good chemical analysis point 1 is negligible
2. Inter-laboratory variability
A factor of 2 to 5 would be realistic
For the long-chain alcohols, the inter-laboratory variation is much lower, because the substances are archetypal exemplars of non-polar narcotics.
When a full set of long-term NOECs or ECxvalues are available, the contributing factor associated with point 3 (duration) is relatively minor, and can be ignored.
This is definitely the case for the ecosystem, in which alcohols are ubiquitous, so duration is irrelevant.
4. Sensitivity of the environmental ecosystem
For point 4 (ecosystem sensitivity), a value of 2 to 5 is realistic
For non-polar narcotics, many species of organism have been studied, so the uncertainty regarding lab to field extrapolation should also be reduced. The ecosystem is adapted to alcohols.
The geometric mean of the range of the two contributing factors is 10. Whilst not set out in Guidance, such a breakdown is a reasonable basis of the factors and is consistent with such extrapolations in mammalian toxicology.
AF = 1*2*1*2.5 = 5 is implied
Although in the case of (Z)-octadec-9-enol specifically, a
full set of long-term results are not available, the predictability of
trends across the category, the low acute-to-chronic ratio and the
potential for metabolism mean that the duration factor (point 3) does
not need to be inflated. On the basis of this logic, the registrants
of (Z)-octadec-9-enol have proposed an assessment factor of 5 for
extrapolation from the lowest NOEC or ECx value to PNEC.
For further discussion please refer to the attached ECOTOXICITY Alcohols
C6-24 Category report.
(Z)-octadec-9-enol has reliable short- and long-term predicted data for
fish, Daphnia and algae. The substance is predicted to be
non-toxic at the limit of solubility, therefore the short- and long-term
E(L)C50 and NOEC values are all >0.042 mg/l.
The substance is readily biodegradable and very rapidly biodegraded in
These data are consistent with the following classification under
Regulation (EC) No 1272/2008 (as amended) (CLP):
Acute toxicity: Not classified.
Chronic toxicity: Not classified.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.Reproduction or further distribution of this information may be subject to copyright protection. Use of the information without obtaining the permission from the owner(s) of the respective information might violate the rights of the owner.
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