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Short-term toxicity to aquatic invertebrates

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Description of key information

Two reliable acute studies are available for the structurally related substance TMAOH:
In the key study, the nominal 48h-EC50 value to Daphnia magna was 3.0 mg/L (95% CI 2.7 - 3.3 mg/L). When this result is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal 48h-EC50 value of 3.6 mg/L (95% CI 1.2 - 4.0 mg/L) for TMAC.

Key value for chemical safety assessment

EC50/LC50 for freshwater invertebrates:
3.6 mg/L

Additional information

Justification for use of the study performed with TMAOH for determination of the acute toxicity to Daphnia magna of TMAC is given in the attached Read Across document.

An acute toxicity test with Daphnia magna was carried out according to OECD 202 and GLP under static conditions. The nominal 48h-EC50 value of TMAOH to Daphnia magna was 3.0 mg/L (95% CI 2.7 - 3.3 mg/L). When this result is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal 48h-EC50 value of 3.6 mg/L (95% CI 1.2 - 4.0 mg/L) for TMAC. The recovery rates based on DOC measurements of samples taken at the start and the end of the test were > 80% and therefore it is deemed acceptable to express the test results as nominal concentrations. (Noack, 2001).

An acute toxicity test with Daphnia magna was carried out according to OECD 202 under static conditions. The nominal 48h-EC50 value of TMAOH to Daphnia magna was 13.9 mg/L (95% CI 12.2 - 15.8 mg/L) (Sachem, Inc., 1999). When this result is corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal 48h-EC50 value of 16.6 mg/L (95% CI 14.6 - 18.9 mg/L) for TMAC. The nominal concentrations were not confirmed by analytical measurements. However, due to the high water solubility and the fact that analytical measurements in the algae test by the TMAOH Consortium (2005) indicate that the substance is stable in water, it is deemed acceptable to express the test results as nominal concentrations.

In none of the acute Daphnia studies with TMAOH, nominal concentrations were confirmed by specific analyses. In the test by Noack (2001) a recovery of >80% was determined with DOC analyses of samples taken from 4 concentrations at the beginning (0h) and at the end (48h) of the test. Furthermore, in the algae study by the TMAH Consortium (2005) in which specific analytical measurements were carried out, measured concentrations at the beginning (0 h) and the end (72 h) of the test were ranged within 91.4-96.3% and 93.8-101% of the nominal concentrations, respectively. This indicates that the test substance was also stable in the other aquatic toxicity tests.

Since the study by Noack (2001) revealed the lowest LC50 value of 3.6 mg/L (converted for TMAC), this study was selected as a key study.

In the 11d-chronic toxicity study of TMAC with Daphnia Magna (Dow Chemical Co.,1991), a 48h-LC50 value of 1.86 mg/L was determined, which is in the same range as the key study from Noack (2001).