Acute Exposure Guideline Levels


Acute Exposure Guideline Levels set levels of chemical concentration that pose a defined level of risk to humans. These levels are used in preventing and responding to disasters. These guidelines are ascertained for one, short exposure by the air. The AEGL values are determined for varying times of exposure, such as ten minutes, thirty minutes, one hour, four hours and eight hours.
The AEGL values describe the expected effects of inhalation exposure to certain compounds. Each AEGL is determined by different levels of a compound's toxicological effects, based on the 4 Ds: detection, discomfort, disability and death. There are three levels of AEGL-values: AEGL-1, AEGL-2 and AEGL-3. AEGL-1 is the airborne concentration above which notable discomfort or irritation could be experienced. However, the effects are not disabling and reversible once exposure stops. AEGL-2 is the airborne concentration above which irreversible or other serious, long-lasting adverse health effects or an impaired ability to escape could be experienced. AEGL-3 is the airborne concentration above which life-threatening health effects or death could be experienced. An example is shown below for chlorine gas AEGLs:
10 min30 min60 min4 hours8 hours
AEGL-10.500.500.500.500.50
AEGL-22.82.82.01.00.71
AEGL-3502820107.1

In this example, several trends can be observed. First, as one moves from AEGL-1 to AEGL-3, the concentrations increase, based on the dose predicted to produce the respective effects. Second, as one moves from shorter exposures to longer, the overall concentration allowed decreases due to the effects of cumulative dose. This is not always the case for AEGL-1 values, however, since they represent a threshold for non-disabling outcomes and sometimes only depend on air concentration.