Alcohols, C9-11-branched and linear

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

no hazard identified

Marine water

Hazard assessment conclusion:

no hazard identified

STP

Hazard assessment conclusion:

no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:

no hazard identified

Sediment (marine water)

Hazard assessment conclusion:

no hazard identified

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

Alcohols, C9-11 branched and linear (CAS 85711-26-8) is a multi-constituent long-chain aliphatic alcohol (LCAA) liquid substance composed of approximately 10-30% C9, 30-50% C10, and 30-50% C11. It has an estimated whole substance water solubility of 44 mg/l as a water accommodated fraction (WAF) at a loading rate of 1000 mg/l, at 20°C. Whilst water solubility for a multi-constituent or UVCB substance is not meaningful scientifically for the purpose of assessment of exposure or risk, an indicative value is useful for reference. Exposure and risk are assessed on the basis of water solubility of the individual constituents. Water solubility values of 128 mg/l, 39.5 mg/l and 8.0 mg/l were obtained (literature source values used in exposure modelling) for the constituents C9, C10 and C11, respectively.

 

The whole substance has a partition coefficient in the range of 3.8 - 4.7. Similar to water solubility, partition coefficient for a multi-constituent or UVCB substance is not meaningful scientifically for the purpose of assessment of exposure or risk. Exposure and risk are assessed on the basis of log K_ow of the individual constituents. Log K_ow values of 3.77, 4.57 and 4.72 were obtained (literature source values used in exposure modelling) for the constituents C9, C10 and C11, respectively.

 

Alcohols, C9-11 branched and linear has no hydrolysable structural features and would be expected to be stable in water. All constituents are rapidly biodegradable.

 

A full set of reliable measured data are not available for Alcohols, C9-11 branched and linear (CAS 85711-26-8). However, short-term toxicity data are available with the closely related substance Alcohols, C9-11 linear only. The type of branched structure occurring in Alcohols, C9-11 branched and linear is termed 'essentially linear' and the physicochemical, toxicological and ecotoxicological properties and behaviour do not differ significantly between such structures and their linear analogues. It is therefore possible to read-across between the substances. Additionally, these isomeric substances have an identical molecular weight. The difference in composition is dependent on the manufacturing process which may create linear alcohols or simple mono-branched structures. The presence of branched structures does not appear confer aliphatic alcohols any different environmental properties compared to the linears only substances, therefore the data is freely read-across between branched and linear substances. Direct read-across between Alcohols, C9-11 branched and linear (CAS 85711-26-8) and Alcohols, C9-11 (CAS 66455-17-2) is scientifically justified.

 

Constituents of commercial multi-constituent LCAAs in the environment will distribute and degrade in accordance with their intrinsic environmental fate and toxicity properties, and so exposure assessment is conducted on the basis of the single cuts. Exposure and risk are assessed on the basis of each constituent of the substance.

 

Alcohols, C9-11 branched and linear is a member of a category of long chain aliphatic alcohols (LCAAs) with a carbon chain length range of C6-C24. The hypothesis is that the long chain linear aliphatic alcohol Category has, at its centre, an homologous series of increasing carbon chain length alcohols. The category members are structurally very similar. They are all primary aliphatic alcohols with no other functional groups. The category members are mainly linear; and the remainder are “essentially linear”; largely 2-methyl branched, or with a single short-chain branch in another position in the chain. The majority of the category members have saturated alkyl chains.

 

The category members are biochemically very similar. The metabolic synthesis, degradation pathways and products are well established and considered to be similar for branched and linear structures (Mudge, 2005; DAR, 2009).

 

The structure of the Category is associated with a consistency and predictability in the physicochemical, environmental, and toxicological property data across its members. In addition, certain branched and unsaturated structures are considered to have such similar properties that their inclusion in the category is well justified.

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.

 

Long-term tests have not been deemed necessary as long-term data are available for the individual constituents of the substance.

 

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 EC_x 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 Alcohols, C9-11.  

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
Conclusion	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 Alcohols, C9-11 branched and linear 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

Reliable short-term toxicity data for fish, invertebrates and algae of 6.3-10 mg/l (freshwater) and 5.8 mg/l (marine water); 7 mg/l (freshwater) and 4.6 mg/l (marine water); and 2.7 mg/l, respectively, are read-across from Alcohols, C9 -11 (CAS 66455 -17 -2; EC 266 -367 -6), pending availability of data for the substance itself. It has a NOEC value of 1.0 mg/l in algae.

 

There are no long-term data available for Alcohols, C9-11 branched and linear as a whole substance. Long-term invertebrate toxicity data are available for the each of the linear constituents:

C9: 21-d EC₁₀ value of 0.4 mg/l (lowest calculated value).

C10: 21-d EC₁₀ value of 0.21 mg/l.

C11: 21-d EC₁₀ value of 0.075 mg/l (lowest calculated value).

 

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: Category Chronic 3.