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Short-term toxicity to aquatic invertebrates

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Description of key information

Benzenepropanoic acid, 3,5-bis(1,1-dimethylethyl)-4-hydroxy-C7-9 branched alkyl esters (CAS 125643-61-0): EC50(48h) > 0.323 mg/L, NOEC: 0.323 mg/L (based on peak area); EC50(48h) > 0.224 mg/L, NOEC: 0.224 mg/L (based on peak area attributed to test material) (Mead and Mullee, 2007) 

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
0.224 mg/L

Additional information

The acute toxicity to invertebrates 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) was investigated according to OECD guideline 202 and EU Method C.2 as static freshwater test with Daphnia magna used as test species. 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.

For Benzenepropanoic acid,3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-,C7 -9 branched alkyl esters (CAS 125643 -61 -0) a WAF nominal loading rate of 100 mg/L was prepared (Mead and Mullee, 2007). 1st instar animals were used, obtained by in-house laboratory cultures and less than 24 h old. The lightening cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Potassium dichromate was used as reference substance. Analysis of the test samples were performed by Gas Chromatography (GC) including a flame ionisation detector (FID). The dissolved oxygen content ranged from 8.7 - 8.8 mg O2/L (96 - 98 % ASV, Air Saturation Value), no aeration was performed during the 48 h exposure period. As results a 48-Hour EL50 (Effective Loading rate) value of greater than 100 mg/L loading rate WAF was determined. Correspondingly the No Observed Effect Loading Rate was 100 mg/L loading rate WAF. The EC50 value and associated confidence limits at 48 hours were calculated by the trimmed Spearman-Karber method (Hamilton et. al., 1977) using the ToxCalc computer software package (ToxCalc, 1999), giving the following results: Based on peak area the EC50 was found to be greater than 0.323 mg/L with a corresponding NOEC of 0.323 mg/L. Based on peak area attributed to test material the EC50 is greater than 0.224 mg/L, thus resulting in a NOEC of 0.224 mg/L after 48 h test period.

The same type of test animals were used in the experiment with Butyl 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxybenzenepropanoate (CAS 52449 -44 -2) (Wetton and Mullee, 2000). Following a range-finding study the WAF nominal loading rate of 10, 18, 32, 56, 100 , 180, 320, 560 and 1000 mg/L were prepared. The lightening cycle was controlled to give a 16 hours light and 8 hours darkness cycle with 20 minute dawn and dusk transition periods. Potassium dichromate was used as reference substance. Analysis of the test samples were performed by High Performance Liquid Chromatography (HPLC) with UV/VIS detection. The dissolved oxygen content ranged from 7.9 - 8.2 mg O2/L , no aeration was performed during the 48 h exposure period. As result a 48-Hour EL50 (Effective Loading rate) value of 110 mg/L loading rate WAF with a 95 % Confidence limits of 93 - 120 mg/L loading rate filtered WAF was determined. The corresponding No Observed Effect Loading Rate (NOELR) was 56 mg/L loading rate filtered WAF.

Benzenepropanoic acid 3,5 -bis(1,1 -dimethylethyl)-4 -hydroxy-2 -ethyl-hexylester (CAS 144429 -84 -5) was tested as an aqueous preparation with a concentration of 100 % v/v saturated solution (Goodband and Mullee, 2009). Potassium dichromate was used as positive control. Following a preliminary range-finding test, twenty daphnids (4 replicates of 5 animals) were exposed to the test material for 48 h at a temperature of 21°C. Immobilisation and any adverse reactions to exposure were recorded after 24 and 48 hours. Analysis of the freshly prepared media at 0 h showed measured concentrations of 0.0303 and 0.0191 mg/L. Analysis of the old media after 48 h showed measured concentrations of 0.00287 and 0.00258 mg/L. These results showed a decline in measured concentration over the 48 h test period. The results showed a decline in measured concentration, which can be explained of the test materials partition coefficient of logPow 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 unstable in the light and dark at ambient temperatures. Therefore the loss of the test material over the 48-Hour test 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 geometric mean measured test concentrations of the test media (0.0082 mg/L) in order to give a "worst case" analysis of the data. This results in an EC50(48h) value greater than 0.0082 mg/L, with a corresponding No Observed Effect Level (NOEC) of 0.0082 mg/L. This study showed that there were no toxic effects at saturation. The results from the positive control with potassium dichromate were within the normal range for this reference material. The mean 48-Hour EC50 value calculated from all positive controls was 0.79 mg/L (sd = 0.23).

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