Acute Exposure Guideline Levels Program

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What is an AEGL?

Acute Exposure Guideline Levels (AEGLs) are threshold exposure limits for the general public that are applicable to emergency exposure ranging from 10 minutes to 8 hours. In other words, AEGLS represent exposure levels below which adverse health effects are unlikely to occur in the general public, including infants, children, and other susceptible populations.

Three levels – AEGL-1, AEGL-2, and AEGL-3, are developed for each of five exposure periods (10min, 20min, 1hr, 4h, and 8 h) and are distinguished by varying degrees of severity of toxic effects. The three AEGLs are defined as follows:

AEGL-1 is the airborne concentration, expressed as parts per million or milligrams per cubic meter (ppm or mg/m3) of a substance above which it is predicted that the general population, including susceptible individuals, could experience notable discomfort, irritation, or certain asymptomatic nonsensory 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 susceptible subpopulations, such as infants, children, the elderly, persons with asthma, and those with other illnesses, it is recognized that individuals, subject to unique or idiosyncratic responses, could experience the effects described at concentrations below the corresponding AEGL.

The US EPA maintains a chemical priority list for extremely hazardous substances and the interim AEGL values for these high-priority, acutely toxic chemicals initially developed by the NAC. Information on AEGL chemical priority lists and interim AEGL values can be found on the EPA AEGL Program website.