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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Description of key information

There are two studies available, carried out with the structurally related substance TMAOH. In the key study, the nominal 72h-ErC50 value and NOECr value to Pseudokirchnerella subcapitata were 96.3 and 6.25 mg/L, respectively.  When the results are corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal 72h-ErC50 value and NOECr value of 115 and 7.5 mg/L, respectively for TMAC. 

Key value for chemical safety assessment

EC50 for freshwater algae:
115 mg/L
EC10 or NOEC for freshwater algae:
7.5 mg/L

Additional information

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

A toxicity test with Pseudokirchnerella subcapitata was carried out by the TMAH Consortium (2005) according to OECD 201 and GLP under static conditions. Analytical monitoring was conducted. The TMAOH concentrations in test solutions were maintained within ± 20% of nominal concentrations throughout the test. Thus the value was estimated with nominal concentrations. The nominal 72h-ErC50 value and NOECr value of TMAOH were 96.3 and 6.25 mg/L, respectively. When the results are corrected for molecular weight (TMAC/TMAOH = 109/91), this corresponds with a nominal 72h-ErC50 value and NOECr value of 115 and 7.5 mg/L, respectively for TMAC.

A toxicity test with Desmodesmus subspicatus was carried out by Scheerbaum (2001) in accordance with OECD 201, EU Method C.3 (Algal Inhibition test) and GLP. The nominal 72h-ErC50 value and NOECr value of TMAOH to Desmodesmussubspicatus were >251 and 31 mg/L, respectively. The recovery rates of samples taken at the start and the end of the test based on DOC measurements were > 80% and therefore it is deemed acceptable to express the results as nominal values. As no significant effects was observed in neutralised solution of 251 mg/L TMAOH (pH control), it can be concluded that the effects are pH dependent. When the results are corrected for molecular weight (TMAC/TMAOH = 109/91), the nominal 72h-ErC50 value is >301 and the NOEC is 301 mg/L for TMAC. The converted NOEC for TMAC was based on the NOEC of neutralised solution of TMAOH of 251 mg/L. This NOEC is assumed to better reflect the toxicity of TMAC, due to the pH effects that were not observed in the neutralised solution.

The study from TMAH Consortium (2005) was selected as a key study because the EC50 and NOEC values were lower. Probably Pseudokirchnerella subcapitata is more sensitive to TMAOH than Desmodesmus subspicatus. Furthermore, the nominal concentrations in the study from the TMAH Consortium (2005) were confirmed by specific analytical measurements, whereas in the study by Scheerbaum (2001) DOC measurements were carried out, which was a reason to assign a lower reliability to it.