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 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.
Butane is a colorless gas with a faint disagreeable odor, although it is considered to be odorless by some. It is poorly soluble in water. The lower explosive limit is 1.9%. Butane is produced from natural gas. Its main uses are in the production of chemicals like ethylene and 1,3-butadiene, as a refrigerant, as an aerosol propellant, as a constituent in liquefied petroleum gas, and as the main component of gas lighter refills. Because it is easily accessible, butane is often used in inhalant abuse.
The toxicity of butane is low. Huge exposure concentrations can be assumed in butane abuse. The predominant effects observed in abuse cases are central nervous system (CNS) and cardiac effects. Case studies also reveal that serious brain damage and underdeveloped organs can occur in fetuses in case of high single exposures during the week 27 or 30 of pregnancy. Quantitative data for setting AEGL values are sparse. Quantitative human data include an old study with human volunteers focused on the warning properties of butane.
Mortality from butane in mice and rats is preceded by CNS effects. Some data are available on cardiac effects in dogs, but they are insufficient for setting AEGL values. Data on CNS effects are available for mice and guinea pigs. Butane was negative in the bacterial reverse-mutation assay (Ames test). Carcinogenicity studies and studies on reproductive toxicity are lacking.