Cyclohexanethiol

Endpoint summary

Description of key information

In the key acute oral toxicity study, the LD50 in rats was determined to be 1200 mg/kg bw (Lifestream Laboratories, 1970).
In the key acute vapour inhalation toxicity study, the LC50 in rats was determined to be between 5.6 and 13.3 mg/l (Lifestream Laboratories, 1970).
In the key acute dermal toxicity study, the LD50 in rats was determined to be 7.82 g/kg (Lifestream Laboratories, 1970).

Key value for chemical safety assessment

Acute toxicity: via oral route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Dose descriptor:

LD50

Value:

1 200 mg/kg bw

Quality of whole database:

Two acute oral toxicity studies are available for the registered substance. Neither of these was conducted according to OECD test guidelines or in compliance with GLP. However, the key study followed a protocol that resembled current test guidelines and was considered to be reliable. The supporting study is from a publication with limited details available.

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

adverse effect observed

Quality of whole database:

Two acute vapour inhalation toxicity studies are available for the registered substance. Neither of these was conducted according to OECD test guidelines or in compliance with GLP. However, the key study followed a protocol that resembled current test guidelines and was considered to be reliable. The supporting study was a limit test in which all animals died and no LC50 could be established.

Acute toxicity: via dermal route

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

7 820 mg/kg bw

Additional information

Two acute oral toxicity studies are available. The key study (Lifestream Laboratories, 1970) was selected since it closely resembled current test guidelines and was well-reported. The supporting study (Schaefer and Bowles, 1985) is a publication of a dietary study in mice in which only limited details were reported, defines the LD₅₀ as >1000 mg/kg. In the key acute oral toxicity study, the LD₅₀ in rats was determined to be 1200 mg/kg bw (Lifestream Laboratories, 1970). Significant clinical signs were lethargy and ataxia. All animals appeared normal by Day 2. In animals that died, necropsy findings included darkened liver and kidneys. There were no abnormal necropsy findings in animals that survived until the end of the 14-day observation period.

Two acute vapour inhalation toxicity studies are available. The key study (Lifestream Laboratories, 1970) was selected since it closely resembled current test guidelines and was well-reported. The supporting study (Lifestream Laboratories, 1969) was a limit test in which all test animals died and no LC₅₀ could therefore be established. In the key acute vapour inhalation toxicity study, the LC₅₀ in rats was determined to be between 5.6 and 13.3 mg/l (Lifestream Laboratories, 1970). 8 out of 10 rats at 13.3 mg/l died during exposure. The remaining 2 died between 2 and 25 hours after the exposure period. All rats survived at 5.6 mg/l. At 13.3 mg/l lethergy and/or general weakness, lacrimation and ataxia were noted within 60 minutes of the start of the exposure period. Rhinorrhea was noted 60 to 90 minutes from start of exposure. Hyperemia of liver and lungs and presence of blood in the gastro-intestinal tract were noted for animals at 13.3 mg/l. There were no remarkable findings in animals at 5.6 mg/l.

Only one acute dermal toxicity study is available (Lifestream Laboratories, 1970). The test protocol resembled OECD 402 but only two animals were used per sex per dose level. 4/4 rabbits at 15.380 g/kg died, 2 between 6 and 22 hours following dosing and 2 by Day 10. 3/4 rabbits at 10.25 g/kg died by Day 12. 1/4 rabbit at 6.834 g/kg died between 6 and 22 hours following dosing and 1/4 rabbit at 4.556 g/kg died by Day 5. The LD₅₀ was determined to be 7.82 g/kg. Generalised weakness, edema, erythma and drying of the skin at the application sites was noted in all groups. Ischemic lungs, hyperemic liver and necrosis of the skin at the application site were noted in all groups except 3.038 g/kg.

Justification for selection of acute toxicity – oral endpoint
The selected study is the more reliable of two available acute oral toxicity studies.

Justification for selection of acute toxicity – inhalation endpoint
The selected study is the more reliable of two available acute inhalation toxicity studies.

Justification for selection of acute toxicity – dermal endpoint
The selected study is the only acute dermal toxicity study that is available for the registered substance.

Justification for classification or non-classification

Based on the available acute oral and inhalation studies, cyclohexylmercaptan is classified in Acute Toxic Category 4 (oral) with hazard statement H302 "Harmful if swallowed" and Acute Toxic Category 3 (vapour) with hazard statement H331 "Toxic if inhaled" according to the criteria of Regulation (EC) No 1272/2008.

Based on the available acute dermal study, no classification is required for dermal toxicity.