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Specific investigations: other studies

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Studies involving specific investigations (ie. mode of action studies) are summarised and discussed in the relevant sections.

Effects on the endocrine system

Three in vitro studies were conducted under GLP and to standardised guidelines to assess the effects of tertiary butyl alcohol on the endocrine system. The overall assessment was that tertiary butyl alcohol and its parent substance methyl tertiary butyl ether, were classified as non-binders to the androgen receptor, were classified negative for effects on testosterone and estradiol in the steroidogenesis assay, and were classified as non-inhibitors of aromatase activity. 

The first study (CeeTox, Inc., 2013a) investigated the ability of tertiary butyl alcohol and its parent substance methyl tertiary butyl ether to interact with the androgen receptors (ARs) isolated from rat prostates following U.S. EPA OPPTS 890.1150. Under the conditions of the assay, tertiary butyl alcohol was classified as a “non-binder” to the androgen receptor in all three independent runs and thus has a final classification of “non-binder” according to the test guideline.  

The second study (CeeTox, Inc., 2013b) investigated the ability of tertiary butyl alcohol and its parent substance methyl tertiary butyl ether to affect the steroidogenic pathway, specifically by inhibiting catalytic activity of aromatase, the enzyme responsible for the conversion of androgens to estrogens, using a human recombinant test system following U.S. EPA guideline OPPTS 890.1200. Under the conditions of the assay, tertiary butyl alcohol was classified as a non-inhibitor, with mean aromatase activity of 102.3 % (± 1.7 % SD), at the highest test concentrations at 10-3 M.

The third study (CeeTox, Inc., 2013c) investigated the ability of tertiary butyl alcohol and its parent substance methyl tertiary butyl ether to affect the steroidogenic pathway, affecting the production of testosterone or estradiol was investigated in a H295R steroidogenesis assay following U.S. EPA guideline OPPTS 890.1550. The OECD 456 (H295R Steroidogenesis Assay) guideline was used to provide additional guidance in evaluation of the results. Under the conditions of this assay, tertiary butyl alcohol did not cause changes compared to the controls in the production of testosterone or estradiol in accordance with the US EPA guideline. Furthermore, based on the OECD guidelines, tertiary butyl alcohol should be classified as negative for effects on testosterone or estradiol in this H295R steroidogenesis assay. While statistically significant effects were observed, they were observed in only one run of the assay for the test substance and were not reproducible.

The authors concluded that tertiary butyl alcohol does not directly impact the steriodogenic pathway involved in estrogen and androgen production.

The following information is taken into account for any hazard / risk assessment:

The most recent in vitro assays on endocrine interactions (CeeTox, 2013a, 2013b, 2013c) were conducted with a specific aim of investigating potential for tertiary butyl alcohol and its parent substance methyl tertiary butyl ether to cause effects on the endocrine system. From these studies, there was no evidence of endocrine interactions.