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# 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 agenci es, 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 develo pment. Based on the findings of the workshop, the idea to establis h a combined effort for the future development of short-term guideline levels was co nceived and a program was implemented.

In September, 1989, OPPT and the Agency for Toxic Substa nces 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 th e NAS Committee on Toxicology to articulate specific uses of, and requirementsfor, short-term exposure guideline levels. In June, 1993, the NAS published its report, entitled Guidelines forDeveloping 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 suppo rt and participation from federal and state agencies and organization s in the private sector to establis h a joint committee to develop the exposure guideline levels. The AEGL Committee was formed an d 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 prio rity chemical lists. Th e last meeting of the AEGL committee was in April 2010 and the charte r of the FACA committee expired in October 2011. Although the work of th e AEGL committee has ended, the AEGL program is still operational and works with the Nation al Academies to publish final AEGLs.
During its operation, the AEGL/NAC committ ee was fortunate to have dedicated members that contributed to set the standard for a ne w and fruitful way to develop a single high quality scientific product required by many fe deral and state agencies as well as private sector groups.
Some of the key accomplishments of th e AEGL committee are the following:

z Represented a major pooling of resources fr om the public sector (federal and state
a g encies ) and the p rivate sector ( academic , non- p rofit or g anizations , and p rivate industry)

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5 / 19 /201 4 htt p ://www.ep a. g ov/o pp t/ae g l/ p ubs/histor y .htmThis provided greater scientific validity of th e exposure guideline levels developed as a result of greater resources for more comprehensive data gathering and the utilization of a broader base of scientific kn owledge and expertise.

z Represented a significant cross-se ction 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 enti re scientific community.

z Resulted in the establishment of national, standardized acute exposure guideline levelsfor 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 developi ng 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 pr oductivity in the development of exposure guideline levels. This approach eliminated duplication of effort and, through the use of pooled financial and staff reso urces and the overlap of priori ty lists of chemicals from various agencies and organizations, substant ially reduced the cost of developing the exposure guideline levels per ch emical 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 concur rence and publication of the values by NAS. 

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# Definitions AEGLs represent threshold exposure limits fo r the general public and are applicable to emergency exposure periods ranging from 10 mi nutes to 8 hours. AEGL-2 and AEGL-3, and AEGL-1 values as approp riate, will be developed for each of five exposure periods (10 and 30 minutes, 1 hour, 4 hours, and 8 hours) and wi ll 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 ha ve 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, co uld experience notable discomfort, irritation, or certain asymptomatic nonsen sory effects. However, the ef fects are not disabling and are transient and reversible up on 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 popula tion, including susceptible individuals, could experience irreversible or other serious, long-l asting 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 popula tion, 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 no ndisabling odor, taste, and sensory irritation or certain asymptomatic, nonsenso ry 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 valu es represent threshold levels for the general public, including suscepti ble subpopulations, such as infants, children, the elderly, persons with asthma, and those wi th other illnesse s, it is recognized that individuals, subject to unique or idiosyncra tic responses, could ex perience the effects described at concentrations below the corres p ondin g AEGL

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# 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 acci dental 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 primarilyon acute toxicology data and not subchronic or chronic data. The guidance therefore does no t 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 consid ered in the development of workplace exposure levels. Users of the AEGL TS Ds should first determine if there are legally enforceable standards that a pply to the situation. Other organizations may also have recommended levels of exposu re 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 subjec t chemical and the basis for the development of the AEGL values. From this review one will have the information to de termine the applicability of the AEGL to their particular situation. 

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