CAS RN: 75-28-5

Toxicity Summary

IDENTIFICATION AND USE: Isobutane is a colorless gas. It is used in organic synthesis, as a refrigerant, in motor fuels, and as aerosol propellant, as well as in synthetic rubber, and in instrument calibration fluid. HUMAN STUDIES: Isobutane is a simple asphyxiant. Acute exposure may cause tachypnea and tachycardia. In severe cases, hypotension, apnea, and cardiac arrest develop. Direct contact with the liquid produces chemical burns. Toxicologically, the vapor exerts no effect on skin and eyes. A case of ventricular fibrillation due to isobutane toxicity after unintentional inhalation of air freshener has been reported. The intentional inhalation of a volatile substance ("sniffing") causing euphoria and hallucinations is a form of substance abuse in children and adolescents with a high morbidity and mortality. Sudden death can be caused by cardiac arrhythmia, asphyxia or trauma. Fatal cases of isobutane sniffing of cigarette lighter refill containing isobutane has been reported. ANIMAL STUDIES: Studies in rabbits exposed through the eyes to undiluted hairspray containing 22% isobutane showed that irritation of the eye was immediately evident with transient iritis and mild conjunctivitis. Acute exposure in dogs to 55 mg/L isobutane was fatal, and 45 mg/L caused anesthesia. Two-hour exposures of mice to 41 mg/L isobutane caused death in 60% of the exposed animals, whereas exposure to 52 mg/L was lethal to 100% of the animals within an average of 28 min. Isobutane is a CNS depressant in the mouse at 15% in 60 min, and at 23% in 26 min. Isobutane caused apnea and finally cardiac arrest in anesthetized rats. Isobutane tested negative in the Ames Salmonella mutagenicity assay.
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