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

Short-term toxicity to aquatic invertebrates

Description of key information

EL50 (48 h): > 25 mg/L for Daphnia magna (OECD 202)

Additional information

One experimental study is available investigating the short term effects of Propanoic acid, 2-hydroxy-, C12-13-branched-alkyl esters to aquatic invertebrates (Cattapan, 2008). The study was performed according to OECD 202 (GLP) with the water flea Daphnia magna. Three different preparation methods of test solutions were performed in the study. Either the test substance was added directly to the test vessels without a filtration step, or the test item was diluted in acetone or Water Accommodated Fractions (WAF) were prepared for testing. 100% inhibition of mobility was observed after 48 h in the solution prepared by direct addition of the test substance. This effect is most likely caused by physical effects rather than intrinsic effects of the dissolved fraction of the test substance (micelles were observed that trapped Daphnia).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 2.5, 5, 10, 25, 50, 75 and 100 mg/L were tested. After 48 h an EL50 of 22.37 mg/L was reported. This EL50 was not considered to be valid based on the raw data presented in the report. 50% inhibition was recorded only at a concentration of > 25 mg/L. Thus, an EL50 of > 25 mg/L was selected for the assessment. Since this effect concentration is above the water solubility limit and 50% immobilization was not recorded in nominal WAFs of 2.5, 5, 10 and 25 mg/L which are in the range and above the water solubility (water solubility: 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 (physical entrapment of organisms due to undissolved test material). For a final assessment a chronic study with Daphnia magna according to OECD 211 was performed.