The toxicity of chloroform as determined by single and repeated exposure of laboratory animals

The acute and chronic toxicity of chloroform has been studied in laboratory animals. An acute oral LD50 of 2.0 (1.0-3.8) g/kg was determined for male rats. When applied to the skin of rabbits, chloroform produced slight to moderate irritation and delayed healing of abraded sking. Absorption of chloroform through the skin of rabbits was apparent but absorption is not expected to present a practical acute hazard. Liquid chloroform produced slight injury to the eyes of rabbits which took over a week to heal. Repeated 1-hour exposures five days per week for six months to either 85.50 or 25 ppm of the vapor of chloroform resulted in adverse effects in all or some species studied: rats, rabbits, guinea pigs and dogs. The effects at 25 ppm were slight and reversible. Rats exposed to 25 ppm for 4.2 or 1 hour/day for 6 months were not adversely affected. Based on experimental data and published reports on human experience as well as industrial experience with carbon tetrachloride, the authors suggest that when worker's exposures can be expected to be repeated and prolonged, the exposure concentrations be maintained below 25 ppm vapor and that the time weighted average not exceed 10 ppm.