Petroleum hydrocarbon toxicity studies. II. Animal and human response to vapors of varnish maker's and painters' naphtha.

Abstract The suggested hygienic standard for inhalation of Varnish Maker's and Painters' Naphtha (VM&P naphtha) for man is 2.0 mg/liter (430 ppm) based upon inhalation studies with rats and dogs and the sensory response of human subjects. Inhalation of substantially saturated vapor for more than a few minutes constitutes a hazard to life. Rats tolerated saturated vapor at room temperature for 7.5 min but loss of coordination and convulsions occurred in 15 min or more. The single 4-hr inhalation LC50 for rats was 16 mg/liter (3400 ppm), and the highest concentration producing no visible signs of discomfort was 4.4 mg/liter (940 ppm). Rats that survived the 65-day inhalation schedule of 5.8, 2.8, and 1.3 mg/liter (1200, 600, and 280 ppm) were challenged with 27 mg/liter (5800 ppm) for 6 hr. All treated rats were more resistant in terms of mortality than were either their air controls or naive controls of the same age and sex. Only the rats at the 2.8-mg/liter level showed any tendency to prolong the median time to death. Cats responded with signs indicative of severe central nervous system effect when subjected to 19 mg/liter (4100 ppm) for 4 hr. All cats survived the 4-hr exposure, which indicates they are at least as resistant as rats to single 4-hr inhalation. There were no dosage-related statistically significant differences between the controls and the rats and beagles that inhaled 2.8 mg/liter or 1.3 mg/liter for 6 hr daily, 5 days each week for 13 wk. The odor threshold for VM&P naphtha as determined in sniff tests by a panel of six people was found to be on the order of 0.004 mg/liter (0.86 ppm). During a 15-min inhalation period, four of seven subjects had upper respiratory tract irritation and three of seven eye irritation at 4.1 mg/liter (880 ppm). Olfactory fatigue occurred but 10 min in fresh air restored acuity.