Propanoic acid, 2-hydroxy-, C12-13-branched alkyl esters

Toxicity to aquatic algae and cyanobacteria

Description of key information

EL50 (72 h): 62.58 mg/L for Selenastrum capricornutum (OECD 201)

Additional information

One experimental study investigating the toxicity of Propanoic acid, 2-hydroxy-, C12-13-branched-alkyl esters to freshwater algae is available (Cattapan, 2008). The study was performed according to OECD 201 under GLP conditions with the freshwater algae Selenastrum capricornutum. Two different preparation methods of test solutions were performed in the study: either the test substance was diluted in acetone or Water Accommodated Fractions (WAF) were prepared for testing. Using acetone as solvent for media preparation is not appropriate for the substance as it is a complex UVCB. According to OECD Guidance 23 (OECD, 2000) the use of solvents can give preferential dissolution of one or more components and thereby affect the toxicity. Therefore, the WAF approach was considered to be the most appropriate media preparation method for this study. WAFs of nominal 25, 50 and 100 mg/L were tested. After 72 h of incubation an EL50 (72 h) of 62.58 mg/L was calculated. At a nominal WAF of 25 mg/L no significant inhibition of growth was recorded. This concentration is already above the water solubility of the substance which is reported to be 4 - 5 mg/L. It is likely that the effects might have been caused by an oversaturated solution. It might be possible that a component of the UVCB substance tends to from micro-micelles with increasing loading rates. They are capable to pass through the filter due to the small size and can cause physical effects. For a final assessment and decision for PNEC derivation, the long-term study with Daphnia magna according to OECD 211 is considered to be necessary. This study is still ongoing and the Chemical Safety Assessment according to Annex I of Regulation (EC) No 1907/2006 will be re-evaluated based on the outcome of the study.