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 concentrations that could 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 concentrations for the general public, including susceptible subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.

SUMMARY

n-Hexane is a colorless liquid with a slightly disagreeable, gasoline-like odor. It dissolves slightly in water. The lower explosive limit of n-hexane is 1.1%. n-Hexane is produced from natural gas and crude oil. Its main use in industry is in products known as solvents. The major uses for these solvents are in food processing to extract vegetable oils from crops, as cleaning agents in the printing, textile, furniture, and shoemaking industries (used in special glues), and in the manufacture of pharmaceuticals. Because of their easily accessibility, solvents and glues containing n-hexane are often used in inhalant abuse.

Human data on the acute toxicity of n-hexane are extremely limited and are insufficient for setting AEGL values. The data show that the acute toxicity of n-hexane is very low. No cases of lethality were reported after inhalation of n-hexane or n-hexane-containing mixtures, not even in solvent abuse. Furthermore, no severe clinical signs were reported in human volunteers after acute exposure to n-hexane both at rest and during physical exercise. Genotoxic and carcinogenic effects of the chemical have not been examined in humans. Chronic exposure to n-hexane frequently results in degenerative distal axonopathy in the peripheral nervous system, but this effect is not relevant for acute exposures.

Two LC50 (lethal concentration, 50% lethality) values for n-hexane have been reported for rats, but the original studies from which they were derived could not be obtained. Findings in toxicokinetic studies appear to have discrepancies with the LC50s. Visible signs of acute toxicity from n-hexane are generally associated with effects on the nervous system, such as reduced respiration, ptosis, myoclonic seizures, ataxia, decreased motor activity, sedation, laying



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