Registration Dossier

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Please be aware that this old REACH registration data factsheet is no longer maintained; it remains frozen as of 19th May 2023.

The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Administrative data

Description of key information

The study is waived based on the corrosiveness of the substance (see skin irritation/corrosion).

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (corrosive)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no study available

Additional information

An acute dermal irritation /corrosion test according to OECD 404 with 2.38% TMAH was performed under GLP circumstances. No dermal irritation was observed following application for 3 minutes. Application for one hour elicited well-defined dermal irritation. Application for 4 hours resulted in well-defined to severe dermal irritation in all animals, with necrosis in one animal. Due to the severity in this animal and the irreversibility of the effect, the 2.38% TMAH-solution was shown to be corrosive to the skin, category 1C (according to EC regulation No 1272/2008).

The pH of a 10% TMAH solution in water is 13.6.

According to the Corrositex database, TMAOH pentahydrate should be classified as packing group II for transport (ADR/DOT) based on experimental results from Corrositex testing. Based on the fact that the criteria for packing group II are identical to the criteria for the classification as skin corrosive 1B from OECD guideline 435, TMAOH pentahydrate is classified as skin corrosive 1B.

Taking into account the above data and in view of the hygroscopicity of the substance, anhydrous tetramethylammonium hydroxide is considered to be skin corrosive 1B.

Justification for selection of skin irritation / corrosion endpoint:
No study was selected. The endpoint conclusion is derived by weight of evidence. One study is available done with 2.38% TMAH (aqueous solution) resulting in classification 1C. TMAH is a strong alkaline substance with a pH 13.6 at 10% solution. Furthermore, TMAH (99% or neat) is classified in Packing group II for transport (ADR/DOT), which is equivalent to category 1B classification according to EC Regulation 1272/2008.

Justification for selection of eye irritation endpoint:
TMAH is a strong alkaline substance with a pH 13.6 at 10% solution, therefore no study available.

Effects on skin irritation/corrosion: corrosive

Justification for classification or non-classification

Based on the above data, anhydrous TMAH is classified as corrosive 1B according to CLP Regulation (EC) No. 1272/2008. Based on the available data on skin corrosion and the strong alkalinity, TMAH is classified for eye damage (cat. 1) according to CLP Regulation (EC) No. 1272/2008.