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Key value for chemical safety assessment

Additional information

An AMES test was conducted according to OECD guideline 471 and GLP principles.Considerable growth inhibition was observed in all strains treated at the highest concentrations of tetramethylammonium hydroxide. However, no increase in the number of revertant colonies was observed in either strain (S. typhimurium TA98, TA100, TA1535, TA1537, or E.coli WP2 uvrA) treated at any concentrations of tetramethylammonium hydroxide with or without metabolic activation (S9 mix).These results have led to the conclusion that tetramethylammonium hydroxide is negative for mutagenicity in the bacterial reverse mutation assay (Ames test) regardless of metabolic activation.

A chromosomal aberration test was conducted according to OECD guideline 473 and GLP principles. Chinese hamster lung (CHL/IU) cells were exposed to 228, 455 or 910 ug/ml with and without metabolic activation.No considerable inhibition of cell growth was observed up to the highest dose.No increase in the number of polyploid cells or cellswith structural genetic aberrations were found after treatmentwith the test substance for 24 hr in the absence of metabolic activation or shortly for 6 hr with the test substance in the presence or absence of metabolic activation.Based on these findings, tetramethylammonium hydroxide was considered negative in the induction of chromosomal aberrations.

A mouse lymphoma assay was conducted according to OECD 476 guideline and GLP principles. The spontaneous mutation frequencies in the solvent-treated control cultures were between the minimum and maximum value of the historical control data range Positive control chemicals, methyl methane sulfonate and cyclophosphamide induced appropriate responses. In the absence of S9-mix, TMAH did not induce a significant increase in the mutation frequency in the first experiment. This result was confirmed in an independent repeat experiment with modifications in the duration of treatment time. In the presence of 8% v/v S9-mix, TMAH did not induce a significant increase in the mutation frequency in the first experiment. This result was confirmed in an independent repeat experiment with 12% v/v S9 for metabolic activation. It is concluded that TMAH is not mutagenic in the mouse lymphoma L5178Y test system under the experimental conditions described in this report.


Justification for selection of genetic toxicity endpoint
No study was selected, since all three in vitro studies were negative.

Short description of key information:
Three in vitro tests were performed (AMES test, chromosome aberration test and MLA assay). TMAH was shown to be negative with and without metabolic activation in all tests, therefore TMAH is considered not to be genotoxic ( weight of evidence approach).

Endpoint Conclusion: No adverse effect observed (negative)

Justification for classification or non-classification

Based on the available data, TMAH is not classified for genotoxicity according to CLP Regulation (EC) No. 1272/2008.