Acute Exposure Guideline Levels (AEGLs)
AEGLs are exposure guidelines designed to help responders deal with emergencies involving chemical spills or other catastrophic events where members of the general public are exposed to a hazardous airborne chemical. (Acute exposures are single, non-repetitive exposures that don't exceed 8 hours.)
What are AEGLs?
AEGLs estimate the concentrations at which most people鈥攊ncluding sensitive individuals such as old, sick, or very young people鈥攚ill begin to experience health effects if they are exposed to a hazardous chemical for a specific length of time (duration). For a given exposure duration, a chemical may have up to three AEGL values, each of which corresponds to a specific tier of health effects.
The three AEGL tiers are defined as follows:
- AEGL-3 is the airborne concentration (expressed as parts per million [ppm] or milligrams per cubic meter [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.
- 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-1 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 notable discomfort, irritation, or certain asymptomatic nonsensory effects. However, the effects are not disabling and are transient and reversible upon cessation of exposure.
All three tiers (AEGL-1, AEGL-2, and AEGL-3) are developed for five exposure periods: 10 minutes, 30 minutes, 60 minutes, 4 hours, and 8 hours. See example of how the chlorine AEGL values vary with exposure durationSee example of how the chlorine AEGL values vary with exposure duration
听Final AEGLs for Chlorine (in parts per million)
| 听 | 听10 minutes | 30 minutes | 60 minutes | 4 hours | 听8 hours |
|---|---|---|---|---|---|
| 听AEGL-1 | 听0.50 | 0.50 | 0.50 | 0.50 | 0.50 |
| 听AEGL-2 | 2.8听 | 2.8 | 2.0 | 1.0 | 0.71 |
| 听AEGL-3 | 50 | 28 | 20 | 10 | 7.1 |
Typically, the AEGL values will be different for each exposure duration (such as the AEGL-3 values in the table above). This is because the physical effects are typically related to dose (that is, concentration over exposure duration). However, in some cases, the AEGL values will be the same for all durations. This situation usually occurs at the AEGL-1 level (as in the table above), because it is a threshold for non-disabling effects; some effects (for example, whether people will be able to smell the chemical) depend only on concentration鈥攏ot on the length of time people are exposed.
For More Information
- How are AEGLs chosen?How are AEGLs chosen?
The AEGL development process changed in November 2011; a brief summary of the process鈥攑resent and historical鈥攊s included below. To find out more specific details, go to the
听website.New AEGL Process (November 2011 to Present)
In November 2011, the National Advisory Committee for AEGLs was eliminated and the AEGL development process was modified.
Future development work on the AEGLs will focus on finalizing interim AEGLs through the National Academy of Sciences.
Old AEGL Process (1996 to October 2011)
In the past, AEGLs were developed by the National Advisory Committee for AEGLs. The committee established detailed guidelines for developing uniform, meaningful emergency response standards for the general public.
Each AEGL was developed independently by a team of scientists who assigned priority to current data from human and animal studies. The process was exhaustive and the guidelines were thoroughly reviewed. As a result, AEGLs represent the best public exposure guidelines available to date.
As part of the development process, interim AEGL values were established鈥攆ollowing review and consideration of public comments鈥攂y the National Advisory Committee for AEGLs. Interim AEGLs are available for use by organizations while awaiting peer review and publication of final AEGLs by the National Research Council of the National Academy of Sciences.
- What substances have AEGLs?What substances have AEGLs?
About 175 substances have final AEGLs and about 80 substances have interim AEGLs. To see the current list of substances with AEGLs, go to the
听website. You can also search for specific substances in CAMEO 365bet娱乐; if available, AEGLs are shown in the Physical Properties section of the chemical datasheet. - How should AEGLs be used?How should AEGLs be used?
AEGLs should be used to help protect the public when there has been a chemical release that is short-term in duration.
AEGLs estimate how the general public would react to a release of this nature, so they can be used to identify areas where a hazard exists if the concentration of hazardous gas is exceeded for the specified exposure duration. For example, in areas with concentrations just above the AEGL-1, most people would experience temporary, non-disabling effects. On the other hand, in areas with concentrations just above the AEGL-2, most people would experience significant鈥攂ut not life-threatening鈥攈ealth effects.
Each defined chemical has AEGL values for five exposure durations, and you should use the duration that is appropriate for your release.
AEGLs shouldn't be used as:
- Guidelines for workers who are routinely exposed to chemicals for longer durations. In such cases, you should use workplace exposure limits, because they contain safety factors specific to that type of exposure.
- Guidelines for members of the public who are exposed to background chemical releases for longer durations. In these types of air quality issues, values such as the 听should be used rather than emergency response guidelines.
AEGL Information Online
- 听Read all about AEGLs on this Environmental Protection Agency site, which contains a list of current AEGLs and details about AEGL development.