Registration Dossier

Administrative data

Description of key information

One key study was identified to evaluate the dermal irritation potential of 2-methylpropane-2-thiol.  The test material was not identified as a dermal irritant in rabbits following 4 hour occlusive exposure.  No key data examining eye irritation was available for 2-methylpropane-2-thiol; however a read-across study from the structural analogue, propane-1-thiol, was identified.  Propane-1-thiol was identified as a slight ocular irritant in rabbits. No key data examining respiratory irritation was available for 2-methylpropane-2-thiol; however acute inhalation data from studies in rats and mice indicates that 2-methylpropane-2-thiol is not a respiratory irritant.

Key value for chemical safety assessment

Skin irritation / corrosion

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Eye irritation

Endpoint conclusion
Endpoint conclusion:
adverse effect observed (irritating)

Respiratory irritation

Endpoint conclusion
Endpoint conclusion:
no adverse effect observed (not irritating)

Additional information

Skin Irritation

A key primary dermal irritation study (Latven, 1976; Klimisch score = 2) was identified to evaluate the skin irritation potential of 2-methylpropane-2-thiol. In this study, six albino rabbits were dermally exposed to 0.5 mL 2-methylpropane-2-thiol under occlusive wrap for 4 hours. The animals were subsequently observed for a period of 3 days. There was no evidence of dermal irritation at any of the treatment sites and the overall irritation score (24, 48, and 72 hour mean) was 0. 2-methylpropane-2-thiol was not considered to be irritating to the skin of rabbits.

Eye Irritation

No key data were available to evaluate the eye irritation potential of 2 -methylpropane-2-thiol. However, a read across primary eye irritation study (Moon, 1981c; Klimisch score = 2) with rabbits was identified to evaluate the eye irritation potential of propane-1-thiol, a structural analog of 2 -methylpropane-2-thiol. Although this study was conducted prior to adoption of GLP and guidelines, there was sufficient detail to consider it comparable to OECD TG405.  A 0.1 mL dose was instilled into one eye of six rabbits, the eye was held closed for 4 seconds and irritation was scored at 1, 24, 48 hours and 7 days. At the 1-hour scoring interval, five of six animals showed slight to dark redness, discharge was observed in four, chemosis was observed in three and one animal had a lesion. At the 24-hour interval, three animals had returned to normal and remained normal through study termination (day 7). Two of three affected animals showed redness through the 4-day scoring interval. One of these animals (lesion-bearing) had chemosis through the 72-hour reading. The remaining animal had redness that resolved after the 24-hour reading. By the 7-day observation period, the treated eyes of all animals were normal. The mean Draize score was 3.3/110. 2-methylpropane-2-thiol was considered to be slightly irritating to the eyes.

Respiratory Tract Irritation

There are no respiratory irritation data available for 2-methylpropane-2-thiol. However, acute inhalation toxicity data available from studies conducted in rats (Daly, 1986) and mice (Fairchild and Stokinger, 1958) appear to indicate that exposure to 2-methylpropane-2-thiol does not cause respiratory irritation.


Effects on eye irritation: slightly irritating

Justification for classification or non-classification

2-methylpropane-2-thiol does not meet the criteria for classification and labelling as a skin irritant under EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008.

 

2-methylpropane-2-thiol does not meet the criteria for classification and labelling as an eye irritant as defined by EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008 based on read-across to studies of structural analogues which were not irritating to the eyes of rabbits.

2-methylpropane-2-thiol does not meet the criteria for classification and labelling as a respiratory irritant under EU Dangerous Substances Directive 67/548/EEC or CLP EU Regulation 1272/2008.