end point for AEGL-1 and AEGL-2 (headache), and no data on the relationship between concentration and exposure duration are available for the end point of convulsions, the more conservative values of n=3 and n=1 were used to scale from 6 h to the shorter (30-min and 1- and 4-h) and longer time periods, respectively. The 10-min AEGL-3 was set equal to the 30-min AEGL-3. The values are supported by the results of additional studies with squirrel monkeys and dogs by Jones et al. (1972). Monkeys and dogs exposed continuously at approximately 15 ppm for 90 days (d) showed no overt clinical signs; systemic toxicity consisted of biochemical and/or non-life-threatening histological changes in the liver, spleen, and kidneys.

The values appear in Table 2–1.

Otto Fuel II is a liquid propellant used exclusively by the U.S. Navy in MK-46 and MK-48 torpedoes and other weapon systems (Rivera 1974; Gaworski et al. 1985). It is a mixture of three synthetic compounds. The primary component is the explosive, 1,2-propylene glycol dinitrate (PGDN) (approximately 75%); dibutyl sebacate (23%) is added as a desensitizer, and because pure PGDN is unstable, 2-nitrodiphenylamine (2%) is added as a stabilizer (ATSDR 1995). PGDN, a nitrated ester, is a volatile liquid with a disagreeable odor. Its primary use is as a propellant in Otto Fuel II (Forman 1988). No information on production was located. Wiltshire Chemical Company in Gardena, California, was the only identified producer (ATSDR 1995).

Neither Otto Fuel II nor its components are highly acutely toxic, as indicated by oral toxicity data. The oral LD₅₀ for Otto Fuel II in male HA/ICR mice was 1.6 mL/kg (2.24 g/kg) (Litton Bionetics 1979). For PGDN, oral LD₅₀ values for the rat ranged from 0.25–1.19 g/kg (Clark and Litchfield 1969; Jones et al. 1972; Andersen and Mehl 1979). About 10% of topically applied PGDN is absorbed through the skin (Clark and Litchfield 1967). Dibutyl sebacate, a food flavoring agent and plasticizer, has a very low acute oral toxicity; the oral no-effect level for lethality was 16 g/kg in the rat (Bisesi 1994). The low vapor pressure of 3 mm Hg at 180°C severely limits its risk as an inhalation hazard. ATSDR (1995) reported an oral LD₅₀ value for 2-nitrodiphenylamine in rats of 6.15 g/kg. In addition to its use in Otto Fuel II, 2-nitrodiphenylamine is an orange-colored solvent dye (Sudan yellow 1339) with a low vapor pressure of 1×10⁻⁵ mm Hg at 25°C (Baughman and Perenich 1988; ATSDR 1995).