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Sediment toxicity

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Reference
Endpoint:
sediment toxicity: long-term
Data waiving:
other justification
Justification for data waiving:
other:
Justification for type of information:
JUSTIFICATION FOR DATA WAIVING
In respect of test design and feasibility:
- Standard sediment studies are designed to assess the effects of prolonged exposure to substances which persist in sediments over long time periods. The standard OECD guideline methods for long-term sediment ecotoxicity require spiking of substrate with the test substance initially, with an equilibration phase and in-life exposure phase of several weeks duration, and replenishment during the test is not realistic.
- It is expected that test organism exposure could not be consistently maintained for test substance in a bioavailable form, or primary degradation products, for the duration of a long-term test, due to very rapid biodegradation and mineralisation of bioavailable alcohol in a sediment-water system.
- Considerable technical difficulties would be expected in the conduct of either short or long-term sediment ecotoxicity tests, due to the expected very rapid biotic removal (primary degradation and mineralisation) of bioavailable substance from such a test system.
- Sediment simulation studies (Federle and Itrich, 2010; Itrich, 2010) have demonstrated the very short sediment half-life for the 'readily bioavailable' alcohol 'pool' (see Section 5.2.2); similarly rapid degradation rates are anticipated for other substances in the carbon chain length range C6-24, including this substance.
- for tetradecan-1-ol, in two different natural sediments: half-life 0.04 days and 0.08 days (primary degradation); 0.4 days and 0.15 days (mineralisation)
- for octadecan-1-ol, in two different natural sediments: half-life 1.1 days and 0.04 days (primary degradation); 1.7 days and 0.2 days (mineralisation).
It is considered that this would prevent maintenance of ‘readily bioavailable’ alcohol in pore-water for the duration of a standard long-term test (28 days duration for OECD 225), or even a shorter-term test. (While the sorbed alcohol ‘pool’ has a longer biodegradation half-life (for tetradecan-1-ol, in two different natural sediments: half-life 11.4 days and 23.1 days; for octadecan-1-ol, in two different natural sediments: half-life 17.3 days and 34.7 days (primary degradation)), alcohols are also ‘less bioavailable’ in the sorbed state).
- Please refer to discussion of the long-term aquatic invertebrate and fish studies which were complicated by the rapid degradation in the test system (Section 6.1.2 and 6.1.4).
- Please refer to discussion of the method development for the adsorption/desorption study (decan-1-ol) with natural soils, which was complicated by the rapid removal of test substance in non-sterilised soils (Section 5.4.1 and 5.2.3).

In the context of the chemical safety assessment:
- The substance is readily biodegradable and is very rapidly degradable in all compartments relevant to the environment (please refer to discussion in Section 5.2 of the IUCLID technical dossier for further information).
- In the wider environment, sediment biota are adapted to exposure to fatty alcohols from natural sources (please refer to Section 5.5 of the IUCLID technical dossier for further information).
- The exposure assessment indicates in the course of normal use some releases of alcohols to waste water is possible from both local and wide-dispersive uses. However, investigations have demonstrated that for both freshwater and marine sediments, LCAAs from anthropogenic sources are a minor proportion (1% or less in river environments) of the total present (see Section 5.5 on monitoring data).
- In general it is reasonable to conclude that natural freshwater and marine sediment biota would already be well-adapted to the presence of fatty alcohols from exposure to the many natural sources and the additional exposure to anthropogenic alcohols would not be expected to be a significant concern particularly given that biodegradation would be rapid following release. As such in accordance with column 2 in REACH Annex X, the chemical safety assessment does not indicate a need to investigate further the effects of the substance and/or relevant degradation products on sediment organisms.
Reason / purpose:
data waiving: supporting information
Reason / purpose:
data waiving: supporting information
Reason / purpose:
data waiving: supporting information
Reason / purpose:
data waiving: supporting information

Description of key information

Key value for chemical safety assessment

Additional information

Testing for sediment toxicity is not considered necessary because:

In accordance with Annex XI, section 2, the long-term toxicity effects studies to sediment dwelling organisms (required in Section 9.5.1) do not need to be conducted as the study is technically not possible. This is due to the very short sediment half-life once desorbed (see the discussion of Biodegradation in water and sediment for further details), preventing maintenance of exposure concentrations for the duration of either a standard short-term or long-term test. Therefore, sediment hazard assessment is based on the EQPM PNECs derived from the aquatic data.

PNECsediment has been calculated from PNECfreshwater on the basis of the equilibrium partitioning method.

The aquatic data used to derive the PNECaquatic for docosan-1-ol is based on the 21-d EC10 value of 0.012 mg/l, for long-term toxicity of pentadecan-1-ol (CAS 629-76-5) to aquatic invertebrates. This substance is used for deriving the aquatic PNEC for alcohols >C15, based on the conclusion in the SIAR that "For substances of chain length greater than C15, no long-term effects would be expected" (for water). The PNECs derived using this approach are only indicative limits, not true values, therefore the PNECaquatic for docosan-1-ol is a conservative value.