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Short-term toxicity to aquatic invertebrates

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Description of key information

 EC50 > 211.2 mg/L acute Daphnia magna immobilization (OECD 202)

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
211.2 mg/L

Additional information

For the assessment of the EC50 for freshwater invertebrates, three acute Daphnia studies are available, one key study with B-TEGME (BASF 1988), one key study with a mixture of methyl borate esters which contains 22% B-TEGME (Shell 1999b) and one supporting study with a brake fluid containing 17% B-TEGME (Shell 1987b).

In the non-GLP (key) study from BASF (1988) the acute toxicity of B-TEGME to Daphnia magna was determined in a 48 hour static study. The study was performed according to the EU C.2 test guideline. Restrictions of this study are: (1) the study was conducted non-GLP, (2) the purity of B-TEGME is not provided, (3) dose verification analysis was not performed. The advantage of this study is that the study was performed with B-TEGME as test item itself and not with a B-TEGME containing mixture. The nominal test concentrations were 0 (control), 31.25, 62.5, 125, 250 and 500 mg B-TEGME/L. The control and each test group was started with 4 replicates (5 daphnids each). At start of the exposure, the daphnids were younger than 24 hours. Within 48 hours of exposure, none of the daphnids from the control and treated test groups was immobilized. The 24 and 48-hour EC0 was 500 mg B-TEGME/L and the EC10, EC50 and EC100 were all > 500 mg B-TEGME/L.

In the GLP compliant (key) study from Shell (1999) the acute toxicity of methyl borate esters (containg 22% B-TEGME) 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-TEGME containing mixture and not with B-TEGME as pure substance itself. The nominal test concentrations were 0 (control) and 1000 mg methyl borate esters/L, corresponding to 0 (control) and 220 mg B-TEGME/L. The mean measured concentration was 960 mg methyl borate esters/L, corresponding to 211.2 mg B-TEGME/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 211.2 mg B-TEGME/L, respectively. Thereafter, no further immobilization was observed. The 24 and 48 -hour EC50 were both >211.2 mg B-TEGME/L.

In the GLP compliant (supporting) study from Shell (1987b) the acute toxicity of a brake fluid (which contains 17% B-TEGME) 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-TEGME and other components. The nominal test concentrations were 0 (control), 3.4, 8.5, 17, 34, 85, and 170 mg B-TEGME/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 17, 34 and 170 mg B-TEGME/L test groups. The 24 and 48 -hour EC50 values were both >170 mg B-TEGME/L.

 

The key study of BASF (1988) and Shell (1999) shows EC50 of > 500 mg B-TEGME/L and >211.2 mg B-TEGME/L, respectively. Due to the above given restrictions, the EC50 of BASF is considered less reliable than the EC50 value of Shell (1999). Moreover, the EC50 of Shell (1999) is more conservative than the EC50 of BASF. The supporting study of Shell (1987) provides an EC50 value of > 170 mg B-TEGME/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 211.2 mg B-TEGME/L is considered reliable and sufficiently conservative to assess the toxicity of B-TEGME on aquatic invertebrates.

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