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Short-term toxicity to aquatic invertebrates

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Description of key information

 EC50 >422.4 mg/L acute Daphnia magna immobilization (OECD 202)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
422.4 mg/L

Additional information

For the assessment of the EC50 for freshwater invertebrates, two acute Daphnia studies are available, one key study with a mixture of methyl borate esters which contains 44% B-TTEGME (Shell 1999) and one supporting study with a brake fluid containing 35% B-TTEGME (Shell 1987).

In the GLP compliant (key) study from Shell (1999) the acute toxicity of methyl borate esters (containing 44% B-TTEGME) to Daphnia magna was determined in a static 48 h toxicity limit test. The test was performed according to OECD 202. No relevant restrictions appeared and the only disadvantage of this study is the fact that the study was performed with a B-TTEGME containing mixture and not with B-TTEGME as pure substance itself. The nominal test concentrations were 0 (control) and 1000 mg methyl borate esters/L, corresponding to 0 (control) and 440 mg B-TTEGME/L. The mean measured concentration was 960 mg methyl borate esters/L, corresponding to 422.4 mg B-TTEGME/L. The control and the treated test group was started with 2 replicates (10 daphnids each). Within the first 24 hours of exposure, 0 and 4 out of 20 daphnids were immobilized in the control and at 422.4 mg B-TTEGME/L, respectively. Thereafter, no further immobilization was observed. The 24 and 48 -hour EC50 were both >422.4 mg B-TTEGME/L.

In the GLP compliant (supporting) study from Shell (1987) the acute toxicity of a brake fluid (which contains 35% B-TTEGME) to Daphnia magna was determined in a static 48 h toxicity test. The test design was similar to OECD 202. Restrictions of this study are (1) no specific guideline was followed (2) dose verification analysis was not performed (3) the temperature of 18- 22°C exceeded the maximum allowable variation of +/- 1°C as given in the OECD 202 test guideline. Furthermore, the test substance was a mixture of B-TTEGME and other components. The nominal test concentrations were 0 (control), 7, 17.5, 35, 70, 175, and 350 mg B-TTEGME/L, applied as 0 (control), 20, 50, 100, 200, 500, and 1000 mg brake fluid /L. For the control and each of the treated test groups three replicates with 10 daphnids younger than 24 hours were set up. Within the 48 hour exposure period, 1 out of 30 daphnids was immobilized in the 35, 70, and 350 mg B-TTEGME/L test groups. The 24 and 48 -hour EC50 values were both >350 mg B-TTEGME/L.

 

The key study of Shell (1999) shows an EC50 of >422.4 mg B-TTEGME/L The supporting study of Shell (1987) provides an EC50 value of > 350 mg B-TTEGME/L. Due to the above given restrictions, this value is considered less reliable than the value provided by Shell (1999).

In conclusion, the EC50 value of 422.4 mg B-TTEGME/L is considered reliable and sufficiently conservative to assess the toxicity of B-TTEGME on aquatic invertebrates.

The above value is higher than the limit for classification and labeling, i. e., higher than 100 mg B-TTEGME/L.