In the injection solution after intravenous injection, 35S-thioglycolate was mainly distributed in the kidney, lung and spleen of female monkeys, and the small intestine and kidney of rats. Residual 35S plasma concentrations in rats did not exceed 5.3% 0.5 to 7 hours after injection. Significant concentrations of dithioglycolate were detected in the urine of rabbits 24 hours after intraperitoneal injection of thioglycolic acid. Thioglycollate was detected in negligible concentrations.
In a study conducted according to OECD Guideline 401, oral administration of thioglycolic acid to male and female rats resulted in an LD50 of 73 mg/kg bw. In the OECD Guideline 423 study, the LD50 of its ammonium (71% solution) and sodium salts administered orally in male and female rats ranged from 50 to 200 mg/kg bw. Behavioral abnormalities and in some cases gastrointestinal irritation were the most common findings following oral ammonium thioglycolate administration. In a study conducted according to OECD Guideline 403, exposure of male and female rats to a vapor/aerosol mixture of thioglycolic acid resulted in an LC50 of 2.172 mg/l for males and 1.098 mg/l for females. Clinical signs include severe irritation of the airways and mucous membranes as well as abnormal behavior and discoloration of the lungs at autopsy. Male rats showed no signs of death or clinical toxicity following inhalation of saturated vapor produced at 125°C or ambient temperature for 7 hours. In a non-guideline acute dermal toxicity study, the LD50 for thioglycolic acid in male and female rabbits was 848 mg/kg bw. Clinical signs were limited to skin irritation and necrosis at the application site. For the ammonium salt (71% solution) and the sodium salt, in a study conducted according to OECD Guideline 402, the LD50 was > 2000 mg/kg bw and 1000 to 2000 mg/kg bw in male and female rats, respectively. Clinical signs of toxicity were reported.
Thioglycolic acid was corrosive to the skin in the EpiDerm skin model study according to Directive 2000/33/EC, B.27. It was also corrosive to the eyes in a rabbit study in compliance with OECD Guideline 405. Ammonium and sodium salts were only mildly irritating to the skin and eyes of rabbits in the OECD Guideline 404 and 405 studies, respectively. Respiratory irritation was observed in rats exposed to high concentrations of vapor/aerosol mixtures, but not when exposed to saturated vapors only.