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Administrative data

Hazard for aquatic organisms


Hazard assessment conclusion:
no hazard identified

Marine water

Hazard assessment conclusion:
no hazard identified


Hazard assessment conclusion:
no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:
PNEC sediment (freshwater)
PNEC value:
157 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:
PNEC sediment (marine water)
PNEC value:
15.7 mg/kg sediment dw
Extrapolation method:
equilibrium partitioning method

Hazard for air


Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms


Hazard assessment conclusion:
PNEC soil
PNEC value:
31.4 mg/kg soil dw
Extrapolation method:
equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Icosan-1-ol (C20, CAS 629-96-9) has low predicted water solubility of 0.001 mg/l at 23˚C and high log Kow (7.75). It has no hydrolysable structural features and would be expected to be stable in water. It is rapidly biodegradable.

Icosan-1-ol 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 category.

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 report.

No experimental data are available for icosan-1-ol. Short-term data for toxicity to fish have been read across from octadecan-1-ol (CAS 112-92-5) and docosan-1-ol (CAS 661-19-8). A QSAR prediction is also available. Data have not been read across for short-term toxicity to invertebrates and algae. The endpoints have been filled using QSAR predictions. Data waivers are in place for long-term toxicity to fish and invertebrates.

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 uncertainty in:

1.     Intra-laboratory variability

2.     Inter-laboratory variability

3.     Duration

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 icosan-1-ol.  

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

This applies.

Use 1

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.

Use 2

3. Duration


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.

Use 1

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.

Suggest 2.5


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 icosan-1-ol 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, an assessment factor of 10 is very conservative for deriving PNECs in the chemical safety assessment of this substance. However, an assessment factor of 10 has been applied to the lowest NOEC or ECx value to derive aquatic PNECs.

For further discussion please refer to the attached ECOTOXICITY Alcohols C6-24 Category report.

Conclusion on classification

Icosan-1-ol has reliable read-across or predicted short-term 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)C50and NOEC/EC10 values are all >0.001 mg/l.

The substance is readily biodegradable and very rapidly biodegraded in non-sterilised systems.  

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.