Alcohols, C20-30 (even numbered)

Toxicity to microorganisms

Description of key information

Alcohols, C20-30 (even numbered), is characterized as comprising long chain alcohols of which constituents include tetracosan-1-ol, hexacosan-1-ol, and octacosan-1-ol.  In accordance with Column 2 of REACH Annex VIII, the activated sludge respiration inhibition study (required in Section 9.1.4) does not need to be conducted as the substance and its constituents is readily biodegradable and the applied test concentrations are in the range that can be expected in the influent to a sewage treatment plant.

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 Column 2 of REACH Annex VIII, the activated sludge respiration inhibition study (required in Section 9.1.4) does not need to be conducted as the substance is readily biodegradable as detailed below and the applied test concentrations are in the range that can be expected in the influent to a sewage treatment plant. 

 

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).

 

The findings are consistent with very high levels of removal in other types of test systems where very fast degradation and metabolism in microorganisms and a range of trophic levels has been identified for alcohols in the range C6-24. Ready biodegradability means that the test substance will rapidly be unavailable for uptake and bioaccumulation in biological organisms.

 

In summary, the data requirement for microorganism studies is waived on the evidence of ready biodegradability and the applied test concentrations are in the range that can be expected in the influent to a sewage treatment plant.