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

Toxicity to aquatic algae and cyanobacteria

Description of key information

Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-9 branched alkyl esters (CAS 125643-61-0): EL50(72h) > 100 mg/L, NOECR: 100 mg/L (Mead and Hill, 2007) 

Additional information

The growth inhibition effect of Benzenepropanoic acid, 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-,C7 -9 branched alkyl esters (CAS 125643 -61 -0) as well as Butyl 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxybenzenepropanoate (CAS 52449 -44 -2) and Benzenepropanoic acid 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-2 -ethyl-hexylester (CAS 144429 -84 -5) on the green algae species Desmodesmus subspicatus was investigated according to OECD guideline 201 and EU Method C.3 as static freshwater tests. All available studies were conducted under certificated GLP compliance. Benzenepropanoic acid,3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-,C7 -9 branched alkyl esters (Z72) and Butyl 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxybenzenepropanoate (Z44) are known as poorly water soluble substances, therefore, a modification of the standard method for the preparation of aqueous media was performed. An approach endorsed by several important regulatory authorities is to expose organisms to filtered Water Accommodated Fractions (filtered WAFs) of the test material in cases where the test material is a complex mixture and is poorly soluble in water and in the permitted auxiliary solvents and surfactants. Using this approach, aqueous media are prepared by mixing the test material with water for a prolonged period.

The experiment with Benzenpropanoic acid, 3,5 -bis(1,1 -dimethylehtyl)-4 -hydroxy-,C7 -9 branched alkyl esters (CAS 125643 -61 -0) resulted in an Effective Loading rate (EL50) > 100 mg/L loading rate WAF with a corresponding No Observed Effect Loading rate of 100 mg/L (Mead and Hill, 2007). Following a preliminary range-finding test, the test organisms were exposed to a Water Accomodated Fraction (WAF) of the test material at a single nominal loading rate of 100 mg/L (six replicate flasks) for 72 hours under constant illumination and shaking. The temperature was held constant at 24 +/- 1 °C. Samples of the algal population were collected daily and cell concentrations determined for each control and treatment group using a Coulter Multisizer Particle Counter or haemocytometer and light microscope. Potassium dichromate was used as reference material, whereby this positive control test is conducted approximately every six months.

In the study conducted with Butyl 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxybenzenepropanoate (CAS 52449 -44 -2) a filtered Water Accommodated Fraction (WAF) of the test material at a nominal loading rate of 1000 mg/L (six replicate flasks) was prepared for the definitive test (Mead and Mullee, 2000). The exposure time was 96 hours with constant illumination and shaking at a temperature of 24 +/- 1°C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter Multisizer 11 Particle Counter.The following results were reported: EL(Effective Loading rate)50 > 1000 mg/L loading rate filtered WAF and correspondingly the No Observed Effect Loading rate (NOELR) was 1000 mg/L loading rate filtered WAF. Analysis of the test solutions at 0 hours showed the measured test concentrations to be in the range of 1.57 mg/L to 1.58 mg/L. At 96 hours analysis showed the measured test concentrations to be in the range of 0.913 mg/L to 0.917 mg/L. This decline was in line with pre-study stability analyses conducted so was considered to be due to the unstable nature of the dissolved components in culture medium. During the pre-study analyses, the dissolved components in the filtered WAF were shown to be due to a combination of test material and degradation products. Therefore, given that toxicity cannot beattributed to the test material as a whole or to its degradation products, the results are based on nominal loading rates only.

The toxicity of Benzenepropanoic acid 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-2 -ethyl-hexylester (CAS 144429 -84 -5) was tested at concentration levels of 6.25, 12.5, 25, 50 and 100 % v/v with three replicate flasks per concentration in the definitive experiment (Vryenhoef and Mullee, 2009). The exposure period was 72 hours with constant illumination and shaking at a temperature of 24 +/- 1 °C. Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter Multisizer Particle Counter. A positive control conducted approximately every six months used potassium dichromate as the reference material. Thereby Desmodesmus subspicatus was exposed to an aqueous solution of the reference material at concentrations of 0.0625, 0.125, 0.25, 0.50 and 1.0 mg/L (three replicate flasks per concentration) under the same conditions as in the definitive test. The results from the positive control were within the normal range for this reference material. The definitive test gave the following results for the test material: based on the geometric mean measured test concentrations gave EC50 values of greater than 0.00018 mg/L. The Lowest Observed Effect Concentration (LOEC) based on growth rate, yield and biomass integral was 0.00018 mg/L, and the No Observed Effect Concentration (NOEC) was 0.00014 mg/L. Although the concentrations found in the 0-Hour test samples were in some instances only just above that of the LOQ the results obtained were considered to be valid. However, caution should be taken when using values around the LOQ and any such results should always be assessed on a case by case basis. In this particular case procedural recoveries were run alongside the test samples to account for any analytical variation that may have occurred. Whilst these results were outside of the normal acceptance criteria of 80 - 120 % they were considered to show that the sensitivity of the method of analysis was satisfactory at the low test concentrations employed and that therefore the measured test concentrations obtained were valid.