Methyl 3-mercaptopropionate

Endpoint summary

Description of key information

High quality eye and skin irritation studies comparable to OECD guidelines 404 and 405 are available.

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)

Additional information

A skin irritation study of sufficient quality and tested with methods similar to a standard acceptable guideline indicated that MMP was not irritating to the skin. Therefore, no classification is required for the skin irritation endpoint for MMP.

In one eye irritation study of sufficient quality and tested with methods similar to a standard acceptable guideline except that treated eyes were washed 4 seconds after exposure, corneal opacity and iritis were noted in only one out of six rabbits. Conjunctival redness was noted in all six rabbits at one hour. However, the conjunctival redness cleared in three rabbits by 24 hours, in three rabbits by 48 hours and reoccurred in one rabbit from 48 hours to Day 4. Conjunctival chemosis was noted in three rabbits at one hour only, and in one rabbit on Day 4 only. At Day 7, the conjunctivae was back to normal in all animals. The total mean conjunctivae score of the 24, 48 and 72 hour time points was less than 2 in any animal.

In another eye irritation study of sufficient quality and tested with methods similar to a standard guideline and the treated eyes were not washed, corneal opacity, involving up to 50% of the cornea, was noted in five rabbits at 24 hours and in one rabbit at 48 hours. The opacity persisted in one rabbit to 48 hours and in three rabbits to Day 4. Iritis was noted in one rabbit at 24 hours only and in two rabbits at 48 and 72 hours and on Day 4. Conjunctival redness was noted in all six rabbits from 1 to 72 hours postinstillation and persisted in four rabbits to Day 4. Conjunctival chemosis and conjunctival discharge were noted in five rabbits at 1 hour postinstillation and persisted in one rabbit to 24 hours. The conjunctival discharge occurred in one rabbit at 24 hours only and reoccurred in another rabbit at 48 hours. Phonation upon instillation was noted in three rabbits and excessive blinking and rubbing upon instillation was noted in five rabbits. All ocular lesions had cleared by Day 7. Because individual eye irritation scores on corneal opacity, conjuctival redness, and conjunctival chemosis are not presented in the study report, classification could not be made due to insufficient data.

Available skin and eye irritation studies indicated a lack of corrosivity.

In an acute inhalation study of sufficient quality and tested with methods similar to OECD Guideline 403, male and female rats were exposed to MMP at dose levels of 1.35 -2.60 mg/l for 4 hours. Animals that survived showed only non-specific clinical signs that didn't represent any characteristic toxic syndrome and pathological profiles were similar to the controls. There were no findings suggestive of respiratory irritation. In another acute inhalation study of sufficient quality and tested with methods similar to OECD Guideline 403, male and female rats were exposed to MMP at dose levels of 1.19 -4.75 mg/L for 4 hours. The majority of animals (26/30) exposed to 1.81 mg/l and above died during the study. All surviving animals (9/10) exposed to 1.63 mg/l experienced labored respiration. There were no reported gross pathological effects indicative of respiratory irritation in the surviving groups of animals. In a respiratory irritation study of sufficient quality, but no established guideline, male mice were exposed to MMP at dose levels of 1.19 -4.75 mg/L for one minute, followed by room temperature for ten minutes and then a second one minute MMP exposure. The results of the study indicated that exposure to the test substance at dose levels of 1.63 mg/L and above resulted in slight to moderate depression in respiratory rates with inconsistent indications across the groups of slight to moderate upper respiratory irritation. The data further suggests that no upper respiratory irritation was produced in the mice exposed to 1.19 mg/L of the test substance. No human data on respiratory tract irritation is available. The evaluation of respiratory irritation should be based primarily on human data. Due to the lack of human data and the inconsistency of animal study results, classification could not be made.

Effects on eye irritation: irritating

Effect level: empty Endpoint conclusion: Adverse effect observed

Justification for classification or non-classification

Skin Irritation/Corrosion - Reason for no classification: conclusive but not sufficient for classification

Eye Irritation - Reason for no classification: inconclusive

Respiratory Irritation - Reason for no Classification: data lacking