Petroleum hydrocarbon toxicity studies: XIII. Animal and human response to vapors of Toluene Concentrate

The suggested hygienic standard for human inhalation of Toluene Concentrate, based upon results of these inhalation studies with rats and dogs and the sensory response of human subjects, is 1.9 mg/liter (480 ppm). The LC50 for rats that inhaled Toluene Concentrate for 4 hr was 35 (31 to 38) mg/liter or 8800 (7800 to 9600) ppm. Rats tolerated 6.8 mg/liter (1700 ppm) for 4 hr and dogs 3.0 mg/liter (760 ppm) for 6 hr without any signs of discomfort. Four cats that inhaled 31 mg/liter (7800 ppm) for 6 hr developed signs suggestive of central nervous system effects, including mydriasis, mild tremors, prostration in 80 min, and light anesthesia after 2 hr. One of four died as a result of pneumonic infection within 14 days. Rats and dogs that inhaled 3.9, 1.9, or 0.95 mg/liter of Toluene Concentrate for 13 weeks, 6 hr/day, were not statistically significantly different from their air-exposed controls in any of the criteria of injury that were monitored including hematology, clinical chemistry, and micropathology. The odor threshold as determined by a sniff test involving two trials with six human subjects is approximately 0.01 mg/liter (2.5 ppm). Six of six people indicated their willingness to work in a concentration of 1.9 mg/liter (480 ppm) which is equivalent to 0.87 mg/liter or 220 ppm of contained toluene, the limiting concentration recommended for the hygienic standard. Only the response of people in the workplace can determine whether the toxic and irritative effects of the components of this mixture are additive or less than additive, as the evidence presented suggests to us that they are not greater than additive.