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Acute Exposure Guideline Levels for Selected Airborne Chemicals: Volume 8
asymptomatic, non-sensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.
AEGL-2 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience irreversible or other serious, long-lasting adverse health effects, or an impaired ability to escape.
AEGL-3 is the airborne concentration (expressed as ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience life-threatening health effects or death.
Airborne concentrations below the AEGL-1 represent exposure levels that can produce mild and progressively increasing but transient and nondisabling odor, taste, and sensory irritation or certain asymptomatic, nonsensory effects. With increasing airborne concentrations above each AEGL, there is a progressive increase in the likelihood of occurrence and the severity of effects described for each corresponding AEGL. Although the AEGL values represent threshold levels for the general public, including sensitive subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that certain individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.
Hydrazine (m.w. 32.05) is a liquid at room temperature with a vapor pressure of 14.4 mm Hg at 25°C. This simple diamine (H2NNH2) is a powerful reducing agent. The chemical acts as an oxygen scavenger and is highly reactive with many other chemicals. Hydrazine is used in various chemical manufacturing processes (production of flexible and rigid foams, pesticides) and by the military as a missile and rocket propellant, and in power sources. U.S. production is estimated at 20 million pounds and world-wide production at 80 million pounds. Hydrazine has an ammonia-like odor with an odor threshold of 3.0 to 4.0 ppm.
Human data on the toxicity of hydrazine following acute inhalation exposure are limited to anecdotal accounts that lack definitive exposure data. The utility of this information is compromised by non-quantitative exposures, concurrent exposure with other chemicals, and involvement of simultaneous multiple exposure routes.
Data from animal studies indicate that hydrazine may be metabolized to acetylhydrazine, diacetylhydrazine, ammonia, and urea, and may form hydrazones with pyruvate and 2-oxoglutarate. The biotransformation of hydrazine is mediated, at least in part, by hepatic monooxygenases. The role of metabolism and absorption/excretion kinetics is uncertain regarding immediate portal-of-