reaction mass of isomers of: C7-9-alkyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate

Short-term toxicity to fish

Description of key information

Benzenepropanoic acid 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-2 -ethyl-hexylester (CAS 144429-84-5): LC50(96h) > 0.0011 mg/L, NOEC: 0.0011 mg/L (Goodband and Mullee, 2009)
Butyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate (CAS 52449-44-2): LL50: 1500 mg/L (WAF), NOELR: 560 mg/L (WAF) (Wetton and Mullee, 2000) / LC50(96h) > 5 mg/L (Mino, 2002)

Additional information

Regarding acute toxicity to fish of Benzenepropanoic acid, 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-,C7 -9 branched alkyl esters (CAS 125643 -61 -0) neither experimental nor predicted results are available.

The substance Benzenepropanoic acid 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-2 -ethyl-hexylester (CAS 144429 -84 -5) can be considered as one read-across possibility. The substance was tested according to OECD guideline 203 in a semi-static freshwater test, using rainbow trout (Oncorhynchus mykiss) as test organisms (Goodband and Mullee, 2009a). The study was conducted under certificated GLP compliance. The test duration was 96 hours with a substance concentration of 100 mg/L; whereby the substance was considered as "difficult substance" as defined by the OECD Guidance Document on Aquatic Toxicity Testing of Difficult Substances and Mixtures (2000) due to the very low water solubility. No reference substance was used since it is not essential according to the guideline description. A temperature of 14 °C was held constant, the mean pH value range was 7.7 - 8.1 and the water hardness was measured as 140 mg/L (CaC03). The dissolved oxygen content was measured as 9.5 - 10.2 mg O2/L (92 - 99 % ASV; Air Saturation Value). The test solutions were replaced every 24 hours. The untreated control sample at 0 (fresh media), 24 and 48 hours (old media) showed measured concentrations of 0.000228 to 0.000499 mg/L. These results were considered to be due to post sampling contamination rather than a contaminated test vessel although analysis of some of the frozen duplicate samples showed measured concentrations of the test material. As the study showed no mortality at the limit of saturation for the test material it was considered unnecessary to repeat the test due to ethical considerations. The test samples were also analysed after centrifugation at 40000 g for 30 minutes to determine the dissolved, and hence bioavailable, concentration of the test material. Analysis of the centrifuged samples from the freshly prepared media at 0, 24, 48 and 72 hours showed measured concentrations to range from less than the LOQ (Limit of Quantitiation) to 0.00331 mg/L. Analysis of the old media centrifuged samples at 24, 48, 72 and 96 hours showed measured concentrations to range from less than the LOQ to 0.00211 mg/L. The results showed a general decline in measured concentration over each 24 hour period. A study to determine the General Physico-Chemical properties of the test material (Safepharm Laboratories Project number: 0525/0750) gave a partition coefficient, log Pow of 7.18 indicating a high potential for the test material to adsorb to organic matter and/or bioaccumulate in the test organisms. Preliminary stability analysis showed that the test material was stable in the light and dark at ambient temperatures. Therefore the loss of the test material over each 24 hour dosing period was considered to be due to possible bioaccumulation and/or adsorption of the test material to the test organisms and/or their organic waste products. Given this decline in measured test concentrations it was considered justifiable to base the results on the time-weighted mean measured test concentrations of the centrifuged test media to give a "worst case" analysis of the data. The 96-Hour LC50 based on the time-weighted mean measured test concentrations of the centrifuged test media was greater than 0.0011 mg/L and correspondingly the No Observed Effect Concentration was 0.0011 mg/L.

Another read-across possibility is given with Butyl 3,5-bis(1,1-dimethylethyl)-4-hydroxybenzenepropanoate (CAS 52449 -44 -2). Two experimental results are available (key and supporting study, both reliability 2), described as followed: According to the key study, the substance was tested in a semi-static freshwater test with rainbow trout (Oncorhynchus mykiss) as test organisms (Wetton and Mullee, 2000). The study was conducted according to OECD guideline 203 and with certificated GLP compliance. The test duration was 96 hours with substance concentrations of 180, 320, 560, 1000 and 1800 mg/L; whereby Water Accommodated Fractions (WAFs) were prepared due to the low aqueous solubility and complex nature of the material. No reference substance was used since it is not mandatory according to the guideline description. A temperature of 16 °C was held constant, the mean pH value was measured as 7.9. The water hardness was determined to be 100 mg/L as CaCO3 as well as a dissolved oxygen content of equal or greater than 9.6 mg O2/L. The Lethal Loading rate, LL50, was determined to be 1500 mg/L (nominal value), whereby the 96 h LC50 value can be assumed to be greater than the limit of water solubility of the test substance. The corresponding NOELR (No Observed Effect Loading rate) was 560 mg/L loading rate filtered WAF. Filtration was conducted as undissolved test material was observed throughout the water columns at the end of the stirring and settlement periods. Sub-lethal effects of exposure were observed at loading rate filtered WAFs of 1000 and 1800 mg/L. These responses were fish swimming at the bottom of the test vessels and loss of equilibrium.

Second experimental data is available out of a preliminary test for a bioaccumulation study and was conducted also according to OECD guideline 203 (Mino, 2003). In this case Oryzias latipes (Medaka) was used as test organisms in a semi-static freshwater test. The aim was to confirm that the LC50 (96h) value is greater than 5 mg/L, which was achieved.