The vapor pressures of the three components of Otto Fuel II differ considerably. During vapor generation studies with Otto Fuel II, PGDN was the only component vaporized into inhalation exposure chambers in sufficient quantity to allow direct analysis (Stewart et al. 1974; MacEwen and Vernot 1982). In light of the low toxicity of dibutyl sebacate and 2-nitrodiphenylamine and the fact that they do not vaporize to a detectable extent at test compound generation temperatures up to 45°C, the toxicity of Otto Fuel II has been evaluated in terms of PGDN. Chemical and physical data for PGDN are listed in Table 2–2.

At low concentrations, PGDN has been reported to cause cardiovascular, irritant, and central nervous system effects including headaches, nasal congestion, eye irritation, and dizziness in humans (Stewart et al. 1974; Hovath et al. 1981). In animal studies that used higher concentrations, methemo-globinemia occurred (Jones et al. 1972). The acute and subchronic effects of PGDN were studied in monkeys, dogs, rats, and guinea pigs. Several studies with humans as well as with monkeys and rats addressed neurotoxicity. The air-odor threshold in healthy subjects is 0.2 ppm, but warning properties are poor inasmuch as olfactory fatigue sets in after as little as 5 min (Stewart et al. 1974).