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Toxics AEGLs History

History of the AEGL Program 

In 1986, the National Advisory Committee for the Development of Acute Exposure Guideline 

Levels for Hazardous Substances (AEGL/NAC Committee or AEGL Committee) was formed to 

develop and recommend AEGLs for hazardous chemicals for use in chemical emergency 

programs. These levels can be used by federal, state and local agencies, the private sector 

and foreign organizations for emergency planning, prevention and response activities related 

to the accidental release of hazardous substances.

EPA has been actively involved since 1988 in a program leading to the development of shortterm exposure guidelines for accidental air-borne chemical releases. In April, 1988, EPA's 

Office of Pollution Prevention and Toxics (OPPT) organized and held a National Workshop to

determine the status of short-term exposure guideline level development. Based on the 

findings of the workshop, the idea to establish a combined effort for the future development 

of short-term guideline levels was conceived and a program was implemented.

In September, 1989, OPPT and the Agency for Toxic Substances and Disease Registry 

(ATSDR) provided funding for a cooperative agreement with the National Academy of 

Sciences (NAS) to develop a methodology that could be used to develop short-term exposure 

guideline levels. The NAS commenced work on this task in October, 1990. From October, 

1990 until February, 1993, OPPT staff continually met with the NAS Committee on Toxicology 

to articulate specific uses of, and requirements for, short-term exposure guideline levels. In 

June, 1993, the NAS published its report, entitled Guidelines for Developing Community 

Emergency Exposure Levels for Hazardous Substances.

With the methodology now available, OPPT initiated the next series of steps to develop the 

concept of a working committee and solicit support and participation from federal and state 

agencies and organizations in the private sector to establish a joint committee to develop the 

exposure guideline levels. The AEGL Committee was formed and first met in June, 1996. For

15 years, the AEGL committee discussed over 300 chemicals and developed AEGL values for 

at least 273 of the 329 chemicals on the AEGL priority chemical lists. The last meeting of the 

AEGL committee was in April 2010 and the charter of the FACA committee expired in October 

2011. Although the work of the AEGL committee has ended, the AEGL program is still 

operational and works with the National Academies to publish final AEGLs.

During its operation, the AEGL/NAC committee was fortunate to have dedicated members 

that contributed to set the standard for a new and fruitful way to develop a single high 

quality scientific product required by many federal and state agencies as well as private 

sector groups.

Some of the key accomplishments of the AEGL committee are the following: 

z Represented a major pooling of resources from the public sector (federal and state 

agencies) and the private sector (academic, non-profit organizations, and private industry). 

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This provided greater scientific validity of the exposure guideline levels developed as a

result of

greater resources for more comprehensive data gathering and the utilization of a broader 

base of scientific knowledge and expertise.

z Represented a significant cross-section of scientists in toxicology and related fields from 

both the public and private sectors as well as the international community. This fostered 

consensus among the entire scientific community. 

z Resulted in the establishment of national, standardized acute exposure guideline levels 

for all federal and state agencies in the public sector and all private companies and nonprofit organizations in the private sector. This prevented individual federal and state 

agencies and private industry from developing their own individual exposure guideline 

levels, which would result in the publication and use of different values and cause major

confusion and controversy among regulatory agencies, private industry and confusion and 

concern among the general public. 

z Resulted in greater efficiency and greater productivity in the development of exposure 

guideline levels. This approach eliminated duplication of effort and, through the use of

pooled financial and staff resources and the overlap of priority lists of chemicals from 

various agencies and organizations, substantially reduced the cost of developing the 

exposure guideline levels per chemical per agency or entity. 

z Fostered the acceptance of the exposure guideline levels by all participating agencies and 

organizations in the public and private sectors as well as foreign countries, since they are 

both the creators and users of the exposure guideline levels. Also, the AEGL committee 

fostered confidence among the general public with the concurrence and publication of the 

values by NAS.

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Toxics AEGLs Defintions

Definitions

AEGLs represent threshold exposure limits for the general public and are applicable to

emergency exposure periods ranging from 10 minutes to 8 hours. AEGL-2 and AEGL-3, and 

AEGL-1 values as appropriate, will be developed for each of five exposure periods (10 and 30 

minutes, 1 hour, 4 hours, and 8 hours) and will be distinguished by varying degrees of 

severity of toxic effects. It is believed that the recommended exposure levels are applicable 

to the general population including infants and children, and other individuals who may be 

susceptible. The three AEGLs have been 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.

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Toxics AEGLs Application of AEGL Values 

Application of AEGL Values

The Acute Exposure Level Guidelines have been developed primarily to provide guidance in 

situations were there can be a rare, typically accidental exposure to a particular chemical that 

can involve the general public. They, therefore, differ from PELs, TLV®s, WEEL®s, RELs or 

MAK values etc. in that they are based primarily on acute toxicology data and not subchronic 

or chronic data. The guidance therefore does not reflect the effects that could result from 

frequent exposure. Also, they are designed to protect the general population including the 

elderly and children, groups that are generally not considered in the development of 

workplace exposure levels. Users of the AEGL TSDs should first determine if there are legally 

enforceable standards that apply to the situation. Other organizations may also have 

recommended levels of exposure that more appropriately apply to the scenarios under 

evaluation.

It is however recognized that there may be an occasion where it may seem desirable to use

these values for other exposure scenarios. In these cases, one should consult the technical 

support document. This document contains a comprehensive review of all identified acute 

toxicology data on the subject chemical and the basis for the development of the AEGL 

values. From this review one will have the information to determine the applicability of the 

AEGL to their particular situation.

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