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Sediment toxicity

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Description of key information

Behenyl Bottoms is characterized as Alcohols, C18 -22, distillation residues.  The REACH requirement in Annex X for studies on sediment organisms is waived based on technical difficulties associated with conducting studies due to its low solubility and the low to no toxicity in aquatic organisms.  No reliable measured ecotoxicity data are available for sediment organisms.

Key value for chemical safety assessment

Additional information

Behenyl Bottoms is characterized as Alcohols, C18-22, distillation residues and the data requirement for sediment studies is waived. The REACH requirement in Column 2 of Annex X for studies on sediment organisms can be waived if long-term toxic effects to sediment organisms are unlikely. Testing for sediment organisms is waived based on technical testing difficulties associated with conducting studies, the lack of evidence for persistence and the absence of toxicity in aquatic organisms as presented in more detail below:

Study not technically feasible

The requirement to conduct long-term sediment studies for Alcohols, C18-22, distillation residues is waived due to anticipated technical difficulties in performing such a test. The water solubility of the substance is below the limit of quantification based on experimental evidence by Cartee and Schaefer (2009) where the limit of solubility was <1 mg/L. Further evidence provided in this dossier suggests that the maximum solubility for Alcohols, C18-22, distillation residues will be 0.007 mg/L, based on a conservative approach. The low solubility of the substance means that it is technically unfeasible to undertake a guideline (standard) study of long-term sediment ecotoxicity where the test substance would need to be maintained in solution for up to nine weeks (depending on test species) to be available for uptake by sediment organisms. Therefore, Behenyl Bottoms are considered to be unavailable for uptake by sediment organisms.

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Persistence

Results of the ready biodegradability tests with Behenyl Bottoms demonstrate that it is inherently biodegradable in fresh water (Schaefer & Matthews, 2010). The test substance biodegraded to an extent of 84.1% after 60 days and can be regarded as inherently biodegradable. According to ECHA Guidance, when the half-life is greater than 40 days in freshwater, the substance is considered to be persistent. Based on an average of three replicates and the steady rate of biodegradation, it can be assumed that the half-life of the substance is below the persistence (P) criterion when 50.3% of the substance biodegraded in a freshwater environment by day 37 of the test (Schaefer & Matthews, 2010). In accordance with ECHA Guidance (Chapter R.11, PBT Assessment), Behenyl Bottoms does not fulfil the PBT or vPvB criteria for Persistence (P).

Toxicity to Aquatic Organisms

Generally the short-term aquatic toxicity of Behenyl Bottoms (Alcohols, C18-22, distillation residues) is low based on experimental evidence presented in this dossier. The short-term toxicity of Behenyl Bottoms to invertebrates and fish was reported by Palmer et al., (2009) in OECD guideline and GLP compliant studies resulting in LC50s of >100 mg/L. In addition, long-term toxicity is considered to be below the limit of solubility (LoS) for alcohols > C15 in chain length based on evidence presented in the Long Chain Alcohols SIDS report (2006). It is unlikely that the substance would be available for uptake from the aquatic compartment. Therefore, long-term toxicity to sediment organisms is waived based on technical testing difficulties due to low solubility of the test substance and the absence of short-term toxicity to aquatic organisms at the limit of solubility.

In summary, the data requirement for studies for sediment organisms is waived on the evidence of testing technical difficulties, lack of persistence in the environment and the absence of toxicity in aquatic organisms.