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Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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Description of key information

The data requirement for bioaccumulation studies in aquatic and terrestrial organisms is waived on the evidence of technical difficulties, ready biodegradability and the absence of toxicity in aquatic organisms and mammals. For completeness, bioconcentration factors (log BCF) for the Alcohols, C20-30 (even numbered), constituents, icosan-1-ol, docosan-1-ol and tetracosan-1-ol, were estimated to be 1.64, 0.97 and 0.4, respectively. Log BCFs of 0.5 kg/L using a Log Kow of 15 were also predicted for tetracosan-1 -ol, hexacosan-1 -ol and octacosan-1 -ol. However, predicted BCFs for long chain alcohols are considered to be overestimates by orders of magnitude due to the natural ability of biochemical systems in organisms to metabolise alcohols.

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.

 

The REACH requirement in Annex IX for a study on bioaccumulation in aquatic species is not needed if the substance has a low potential for bioaccumulation and/or a low potential to cross biological membranes. The waiver argumentations are based on the technical difficulties associated with conducting bioaccumulation studies, the ready biodegradability of the test substance, the low toxicity in aquatic organisms and the low toxicity in mammals resulting in the unlikely potential for secondary poisoning, as presented in more detail below:

 

Study not technically feasible

The requirement to conduct bioaccumulation studies for long chain alcohols is waived due to technical difficulties in performing such a test. Guideline (standard) studies of bioaccumulation in fish 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 Alcohols, C20-30 (even numbered), as biodegradation in the test system was almost complete within the 24-hr test media renewal period.

 

Biodegradation

Substances that are themselves constituents of and analogous to other primary constituents of Alcohols, C20-30 (even numbered), (eicosan-1-ol (C20), docosan-1-ol (C22), 2-decyltetradecanol (C24) and tetradecyloctadecan-1-ol (C32)) were assessed for ready biodegradability in reliable (Klimisch 1 or 2) OECD Guideline 301B studies (Ready Biodegradability: CO2 Evolution Test). 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. In other studies, 2-decyltetradecanol (C24) degraded by 84%, docosan-1-ol (C22) by 87.9% and 87.5% and eicosan-1-ol (C20) by 88.4% in 28-day tests confirming the ready biodegradability of these long chain alcohols (Flach (2012b), Federle (2009), Flach (2012a) and Federle (2009), respectively).

 

All of the experimental studies and evidence from the published literature demonstrate that constituents and analogues of Alcohols, C20-30 (even numbered) will degrade in the aquatic environment. It is concluded that given the very close similarity between LCA Category alcohols, 2-decyltetradecanol and tetradecyloctadecan-1-ol, as well as similar physico-chemical properties and structure, it is fully expected that Alcohols, C20-30 (even numbered) will rapidly and readily biodegrade in the environment.

 

Toxicity to Aquatic Organisms

Generally the short-term aquatic toxicity of the constituent substances (icosan-1-ol and docosan-1-ol) is low. According to the OECD SIDS Report for Long Chain Alcohols (2006) long-term toxicity is also considered to be very low and greater than the limit of solubility for alcohols ≥ C15 in chain length.

 

Toxicity to Mammals

There is no requirement in REACH to conduct a secondary poisoning assessment in view of the lack of toxic effects in mammals. Chronic and sub-chronic mammalian toxicity studies have shown that long chain alcohols 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. This evidence indicates 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.

 

Summary

The data requirement for bioaccumulation studies in aquatic and terrestrial organisms is waived on the evidence of technical difficulties, ready biodegradability and the absence of toxicity in aquatic organisms and mammals. For completeness log BCF’s for the main constituents, represented by eicosan-1-ol, docosan-1-ol and tetracosan-1-ol, were estimated to be 1.64, 0.97 and 0.4 kg/L, respectively. Log BCFs of 0.5 kg/L using a Log Kow of 15 were also predicted for tetracosan-1-ol, hexacosan-1-ol and octacosan-1-ol. Predicted BCFs for long chain alcohols are considered to be overestimates by orders of magnitude due to the natural ability of biochemical systems in organisms to metabolise alcohols (OECD SIDS Initial Assessment Report (2006); Veith et al (1979) and Connell and Hawker (1988)).

 

References

SIDS Initial Assessment Report on Long Chain Alcohols (2006). Organisation for Economic Cooperation and Development (OECD).

Veith GD, Defoe DL and Bergstedt BV (1979). Measuring and estimating the bioconcentration factor of chemicals in fish. J. Fish. Board Can. 36: 1040-1048.

Connell DW and Hawker DW (1988). Use of polynomial expressions to describe the bioconcentration of hydrophobic chemicals by fish. Ecotox. Environ. Safety 16: 242-257.