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Toxicity to soil microorganisms

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Description of key 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. 
The REACH requirement in Annex IX for studies on soil microorganisms is waived on the basis of direct or indirect exposure of the soil compartment being unlikely.

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.

 

Study data, where available, for each substance that are themselves constituents of as well as analogous to the primary constituents of Alcohols, C20-30 (even numbered) has been evaluated and considered together. In a conservative approach the most sensitive study result from substances that are themselves constituents of as well as analogous to the primary constituents would be identified and used to address the endpoint in question, although no terrestrial studies were available for the test substance. The REACH requirement in Annexes IX and X for studies on terrestrial organisms is waived if direct or indirect exposure of the soil compartment is unlikely. In particular, substances that are unlikely to be persistent in the environment do not require long-term terrestrial testing.

 

Terrestrial testing is waived based on the unlikely direct or indirect exposure to soils, technical difficulties associated with conducting studies, the ready biodegradability of the test substance, the low toxicity in aquatic organisms and the low toxicity in mammals resulting in the unlikely direct or indirect exposure of terrestrial organisms to the test substance, as presented in more detail below:

 

Exposure to soils

It is unlikely that soil organisms will be exposed to the test substance as there is no intended use involving the direct application of Alcohols, C20-30 (even numbered), to soil. In addition, it is unlikely that indirect exposure will occur, via the application of sewage sludge to land, as the test substance is expected to biodegrade through the sewage treatment process.

 

Study not technically feasible

The requirement to conduct terrestrial toxicity studies for Alcohols, C20-30 (even numbered), and its constituent long chain alcohols 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 (tetracosan-1-ol, hexacosan-1-ol, and octacosan-1-ol) 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 soils.

 

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 constituent substances (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 terrestrial organisms.

 

Toxicity to Mammals

The requirement for long-term avian testing is waived in view of the lack of toxic effects in mammals. Chronic and sub-chronic mammalian toxicity studies have shown that long chain alcohols (LCA) are of low toxicity. Furthermore, combined repeated-dose studies with developmental endpoints, as well as reproductive and developmental studies, showed no effects at the highest dose tested. Using this evidence it is assumed that the test substance is not considered to be toxic (in PBT terms) to mammals and secondary poisoning is unlikely to occur in the environment.

 

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