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Toxicity to microorganisms

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The toxicity of the structurally related substance TMAOH  to microorganisms was determined in a 3 h activated sludge respiration inhibition study carried out with TMAOH pentahydrate according to OECD guideline No. 209 and GLP principles.The EC50 exceeded the highest test concentration of 1000 mg/L, corresponding with a TMAOH concentration of 503 mg/L and no NOEC could be determined. When the EC50 is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal EC50 value of >602 mg/L for TMAC.

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Additional information

Justification for use of the study performed with TMAOH for determination of the toxicity of TMAC to micro-organisms is given in the attached Read Across document.

The toxicity of the structurally related substance TMAOH to microorganisms was determined in a 3 h activated sludge respiration inhibition study carried out with TMAOH pentahydrate according to OECD guideline No. 209 and GLP principles.

In a combined limit/range-finding test, microorganisms in activated sludge were exposed to the test substance at a concentration of 10, 100 and 1000 mg/L under static conditions. Under test conditions TMAOH pentahydrate significantly inhibited the respiration rate of waste water (activated sludge) at 1000 mg/L. However, the EC50 exceeded the highest test concentration of 1000 mg/L, corresponding with a TMAOH concentration of 503 mg/L and no NOEC could be determined. When the EC50 is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal EC50 value of >602 mg/L for TMAC.

All criteria for acceptability of the test were met and this study was considered to be valid. The present toxicity study is classified as reliable without restrictions according to the OECD guideline No. 209.

The effects of TFT-LCD wastewater on nitrification activity was evaluated with batch experiments. The NOEC of the structurally related substance TMAOH (see read-across justification in IUCLID section 13) to nitrification was 50 mg/L. When this result is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a NOEC of 60 mg/L for TMAC.Since adapted sludge was used, the results of this experiment are considered as less relevant for the evaluation of toxicity to a STP treating predominantly domestic waste water.

Since adapted sludge was used in the test by Whang (2008), this study is considered as less relevant for municipal sewage treatment plants. Furthermore the study from Desmares-Koopmans (2013) is carried out according to OECD and GLP guidelines and is therefore considered as a key study.