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Ecotoxicological information

Toxicity to microorganisms

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Description of key information

NOEC = 1000 mg/L; EC10 and EC50 > 1000 mg/L

Key value for chemical safety assessment

Additional information

In the GLP compliant (key) study from BASF (1999) the effect of B-TEGME on the oxygen consumption of activated sludge was determined in a limit test with 1000 mg B-TEGME/L. The study is considered compliant with OECD 209, ISO 8192 and C.11. The inoculum was obtained from laboratory wastewater plants treating municipal waste water. The inoculum was washed, adjusted to 5g dry mass/L and subsequently aerated for 24 hours. Three controls and one replicate for the treated test solution was set up. Non-replicated positive controls were set up with 1, 10 and 100 mg 3,5 -dichlorophenol/L The respiration measurements were performed 30 minutes after start of the exposure.

The test with 3,5 -dichlorophenol resulted in an EC50 of 8.8 mg 3,5 -dichlorophenol/L. The variation between 3 controls was < 15%. The findings from the positive controls render the test as valid. At 1000 mg B-TEGME/L, the respiration was increased by 6% relative to the average respiration in the control. Therefore, the EC0 = 1000 mg B-TEGME/L and the EC10, EC20, EC50 and EC80 are > 1000 mg B-TEGME/L

and consequently B-TEGME is considered to have no effect on microorganisms.

In the GLP compliant (supporting) study from Shell (1986), the microbial inhibition of a brake fluid (which contains 17% B-TEGME) to Pseudomonas fluorescens was determined in a microbial inhibition test. The test design was based on the method described in "Degradability, Ecotoxicity, and Bioaccumulation, TNO, Delft, The Netherlands, 1977". The nominal test concentrations were 0 (Control), 10, 32, 100, 320, and 1000 mg brake fluid/L (nominal concentrations), corresponding to 0 (control), 1.7, 5.44, 17, 54.4, and 170 mg B-TEGME/L, respectively. Sodium pentachlorophenate was used as positive control. Growth curves were constructed of the optical density of the inoculated media versus time and the rate determined as the slope of the exponential growth phase. The reference substance, sodium pentachlorophenate inhibited with an EC50 =18 mg/L while the brake fluid caused a maximum of 19% inhibition at 1000 mg brake fluid/L, corresponding to 170 mg B-TEGME/L, the highest concentration tested. Therefore, the EC50 is > 170 mg B-TEGME/L. The exposure duration, environmental conditions like temperature and details on the measurements of the optical density and the origin of the cultures were not reported. Due to the limited information provided the results of this study are considered to have only limited relevance and the study was considered to be supporting.

The GLP (key) study with B-TEGME (BASF, 1999) provided an EC20 and EC50 of > 1000 mg B-TEGME/L. The advantage of this study is that it was performed with B-TEGME itself and not with a B-TEGME containing brake fluid as in the study from Shell (1986) where other additives may have affected microbial growth. The (supporting) study from Shell (1986) provided an EC50 of > 170 mg B-TEGME/L, the highest tested concentration. Due to the above restrictions the test results from Shell (1986) were not considered as relevant for the risk assessment.

In conclusion, the EC10 and EC50 values of >1000 mg B-TEGME /L are considered reliable and sufficiently conservative to assess the toxicity of B-TEGME on microorganisms.