Petroleum hydrocarbon toxicity studies. IV. Animal and human response to vapors of Rubber Solvent

Abstract

The suggested hygienic standard for inhalation of Rubber Solvent for man is 1.7 mg/liter (430 ppm) based upon inhalation studies with rats and dogs and the sensory response of human subjects. The LC50 for rats by 4 hr inhalation is 61 mg/liter (15,000 ppm). A concentration of 11 mg/liter (2800 ppm) caused no visible signs of discomfort in rats in 4 hr while for dogs the corresponding concentration was 5.9 mg/liter (1500 ppm). Cats exhibited signs judged to be indicative of central nervous system depression after a 4-hr inhalation of 49 mg/liter (12,000 ppm) but survived. At the highest concentration obtainable, 180 mg/liter (45,000 ppm), the Lt50 for rats was 4.3 min. Convulsions were produced in about 2 min. Rats and dogs inhaled measured concentrations of 7.9, 3.7, 1.9, and 0.0 mg/liter (2000, 930, 480, and 0.0 ppm) for 6 hr/day, 5 days/wk for 13 wk. The rats tolerated the highest level without any meaningful disturbances in the various criteria of effect that were followed. The only disturbing finding in the dogs was the dosage related granulation nodules found in the lungs. There is no evidence that the nodules were caused by the inhalation of Rubber Solvent but we cannot deny the condition may have been some-what exacerbated by the solvent vapor. This statement is based upon the 4-hr LC50 of 61 mg/liter (15,000 ppm) for rats and the lack of any similar lung pathology in rats that inhaled the same vapor: air mixtures in company with the dogs, for 13 wk. The odor of the solvent is detectable at 0.04 mg/liter (10 ppm) and 15-min periods of inhalation by human subjects resulted in good acceptance of the recommended hygienic standard.