2-mercaptoethanol

Endpoint summary

Justification for classification or non-classification

Acute oral toxicity:

SNEA (1993) reported an OECD guideline 401 study with sodium-2-mercaptoethanol (CAS: 37482-11-4). The toxicity of the sodium salt of 2-mercaptoethanol is similar to that of the unchanged substance. Male and female rats were given orally doses (gavage) of 86, 150 and 250 mg/kg. The mortality rate was 20% at 86 mg/kg, 50% at 150 mg/kg and 100% at 250 mg/kg. Hypoactivity, sedation, rapid breathing, muscular weakness, tremor, convulsions, cyanosis, and protraction were observed in rats as clinical symptoms of toxicity. Macroscopic post-mortem examination of the main organs of the animals found dead during the study or sacrificed at the end of the study revealed no abnormalities. The LD50 value for male and female rats was found to be 98 - 168 mg/kg bw.

BASF reported an oral LD50 value of < 112 mg/kg for rabbits (study from 1967) and an oral LD50 value of 336 mg/kg for rats (study from 1964). These two studies are less well described.

Classification proposal regarding acute oral toxicity: T; R25. under DSD. Category 3 (H301) under GHS/CLP.

Acute inhalation toxicity:

DuPont (1992) estimated an inhalative LC50 value of about 2 mg/l/air for 4 hours. Male rats were given vapour concentrations of 975, 2030, 4060, 8100 and 16200 mg/m3. The findings observed indicated effects on central nervous system, respiratory and circulatory systems and possibly on the liver. All rats survived the low concentration group; all rats died at concentrations > 4060 mg/m3.

In an inhalation hazard test (BASF, 1964) 3/12 rats died during 0.5 hour exposure, 2/12 rats died during 1-hour exposure and all rats died during the 3-hour and 8-hour exposures. Escape behaviour, irritation of mucosa membranes, tremor, stilted gait, apathy, abdominal position and dyspnea were found as clinical signs. Gross pathology showed in some cases petechia.

Classification proposal for acute inhalation toxicity: T; R23. under DSD. Category 3 (H331) under GHS/CLP.

Acute dermal toxicity:

BASF (1965) reported an acute dermal LD50 value of about 112 - 224 mg/kg bw for male and female rabbits. The undiluted test substance was applicated occlusive in doses of 56, 112 and 224 mg/kg (= 0.05, 0.1, 0.2 ml/kg). All animals (3/3) died in the high dose group with no specific resorptive intoxication symptoms. One animal (1/3) died in the mid dose group showing apathy, local reddening and edema as clinical signs. No animal (0/3) died in the low dose group showing apathy and local inflammation.

Phillips Petroleum Co. (1992) reported a minimum lethal dose of < 200 mg/kg for male and female rabbits under occlusive conditions. 6 rabbits were found dead by 24-h postapplication. Clinical signs reported were labored respiration and depression. Gross pathology showed a dark red zone between the cortex and medulla of the kidneys as well as red-speckled areas on the outer surface of the kidneys.

Classification proposal for acute dermal toxicity: T; R24. under DSD. Category 2 (H310) under GHS/CLP.