Thioglycolic acid (CAS No. 68-11-1) was evaluated for acute inhalation toxicity in Wistar albino rats (5/sex/group) administered continuous whole-body exposures to measured concentrations of 0 (control), 0.068, 0.172, 0.338 and 0.582 mg/l for 4 hours. Despite respective atmospheric deviations during 4-hour exposures of 21, 48, 53 and 22%, study authors reported an LC50 of 0.21 mg/l with a standard error of 0.040 mg/l. Mortality occurred in treatment groups administered exposures to 0.172 mg/l (2/5M, 2/5F), 0.338 mg/l (3/5M, 4/5F) and 0.582 mg/l (5/5M, 5/5F). Clinical signs of irritative respiratory toxicity during exposures includedpartial closure of eyes, wetness about eyes and mouth, abnormal respiration, restlessness, and hunched posture. Abnormal respiration, brown-stained snout and jaws, and sensitivity to touch persisted from 3-13 days of 14-day observation in a dose-related manner. Transient reduced food and water consumption was noted in both male and female rats of 0.172 and 0.338 mg/l exposures, and transient (up to 3 days) reduced bodyweight gains reflected effects of increasing exposure levels. Upon necropsy of study lethalities, lungs were found congested and of increased weight relative to controls. Terminal necropsy of all surviving rats at allexposure concentrations revealed no grosschanges in the lungs. Detailed microscopic evaluation of decedent rats and rats surviving 2-week recovery confirmed lung congestion among study lethalities of 0.172, 0.338 and 0.582 mg/l exposures.