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Sediment toxicity

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Description of key information

Alcohols, C20-30 (even numbered), is characterised as comprising long chain alcohols with constituents including tetracosan-1-ol, hexacosan-1-ol, and octacosan-1-ol. The REACH requirement in Annexes XI for studies on sediment organisms is waived based on technical difficulties associated with conducting studies, the ready biodegradability of the test substance and its constituents, and no toxicity in aquatic organisms.  No reliable measured ecotoxicity data are available for sediment organisms.

Key value for chemical safety assessment

Additional information

Alcohols, C20-30 (even numbered), is a UVCB substance that comprises several linear long chain alcohols, predominantly tetracosan-1-ol (C24), hexacosan-1-ol (C26), and octacosan-1-ol (C28). Together, these substances make up approximately 70% of the composition of Alcohols, C20-30 (even numbered). Other constituents include, to a much lesser extent, secondary long chain alcohols and complex mixtures of long chain carboxylate esters. On this basis, study data, where available, for each of the long chain alcohol constituents has been evaluated and considered together; this is consistent with the Category approach applied for Long Chain Alcohols (LCA) under REACH.  In a conservative approach the most sensitive study result from the constituents of the LCA category have been identified and used to address the endpoint in question.

 

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, readily biodegradable and exerts low to no toxicity to aquatic organisms. The technical infeasibility is due to the very short sediment half-life once desorbed (see CSR for further details), which do not allow for the studies to be conducted. No reliable predicted or measured toxicity to sediment organism’s data are available for Alcohols, C20-30 (even numbered). The requirement to conduct sediment studies for this substance is being waived based on technical infeasibility, ready biodegradation and low toxicity to aquatic organisms as detailed below.

 

Study not technically feasible

The requirement to conduct long-term sediment toxicity studies for Alcohols, C20-30 (even numbered), is waived due to anticipated technical difficulties in performing such a test. The requirement to conduct long-term toxicity studies for long chain alcohols, such as Alcohols, C20-30 (even numbered) or its primary constituents tetracosan-1-ol, hexacosan-1-ol, and octacosan-1-ol, is waived due to anticipated technical difficulties in performing such a test. Guideline (standard) studies for long-term toxicity testing would be confounded by the technical difficulties of maintaining the test alcohols in solution, as was demonstrated in long-term invertebrate studies reported in the OECD SIDS Report for Long Chain Alcohols (2006). Severe difficulties were encountered when studies were conducted with ≥C15 alcohols, which are similar to constituents of the Alcohols, C20-30 (even numbered), as biodegradation in the test system was almost complete within the 24-hr test media renewal period. It is reasonable to assume that similar biodegradation would occur in sediment.

 

Biodegradation

Reliable experimental studies (Klimisch scores 1 and 2) were performed in accordance with OECD Guidelines on eicosan-1-ol (C20), docosan-1-ol (C22), 2-decyltetradecanol (C24) and tetradecyloctadecan-1-ol (C32) that are constituents of and analogous to primary constituents of Alcohols, C20-30 (even numbered) and the LCA Category. The key study by Flach (2014) reported 90% biodegradation of tetradecyloctadecan-1-ol in an OECD 301B CO2-evolution test over 28 days. More than 60% of tetradecyloctadecan-1-ol had degraded within the 10-day study window. The key study demonstrates that tetradecyloctadecan-1-ol, a C32 long chain alcohol, is readily biodegradable. Supporting studies also confirmed the ready biodegradability of LCAs including constituents and analogue constituents of Alcohols, C20-30 (even numbered).

 

Toxicity to Aquatic Organisms

Generally the short-term aquatic toxicity of the constituent substances (including tetracosan-1-ol, hexacosan-1-ol, and octacosan-1-ol) is low and long-term toxicity is considered to be greater than the limit of solubility (LoS) for alcohols > C15 in chain length. In addition, the ready biodegradability of the test substance means long-term exposure to aquatic organisms is unlikely. It is reasonable to assume that similarly low toxicities would be seen in sediment organisms.

 

In summary, the data requirement for sediment studies is waived on the evidence of technical difficulties, ready biodegradability and the absence of toxicity to aquatic organisms.