Acute Exposure Guideline Levels Program

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How are AEGLs developed?

The AEGL development process is the most comprehensive ever used for the determination of short term exposure limits for accutely toxic chemicals. The process consists of four basic stages identified by the review level and concurrent status of the AEGL values:  (1) draft AEGLs, (2) proposed AEGLs, (3) interim AEGLs, and (4) final AEGLs. 

Stage 1: Draft AEGLs
Draft AEGL reports are prepared by ad hoc development teams consisting of a chemical manager, two chemical reviewers, and a staff scientist of the NAC contractor. The development team conducts a comprehensive search of the published scientific literature and relevant unpublished data through industry-trade associations and from individual companies in the private sector.
The draft documents are submitted to and reviewed by the NAC. Concensus or a two-thirds majority vote of the NAC is required to elevate the draft AEGLs  to "proposed" status.

Stage 2: Proposed AEGLs
Proposed AEGL reports are published in the Federal Register for a 30-day public review and comment period. The NAC reviews public comments, and addresses and resolves relevant issues. Concensus or a two-thirds majority vote is required to elevate proposed AEGLs to "interim" status.  


 Stage 3: Interim AEGLs
The interim AEGL status represents th best efforts of the NAC to establish exposure limits, and the avlues are available for use by regulatory agencies and the private sector on an interim basis. The interim AEGLs and the supporting scientific rationale are sent to the NRC AEGLs committee for independent review. The NRC review involves oral and written presentations to the committee by the authors of the AEGL reports. The NRC committee provides advice and recommendations for revisions to ensure scientific validity and consistency with the NRC guidlines. Concurrence of the NRC committee is required to raise the interim AEGLs to "final" status.

Stage 4: Final AEGLs 
AEGL values are considered final when the NRC AEGLs committee reaches consensus on scientific validity and conformance to NRC guidelines of the AEGL values and supporting documentation.  Final AEGL values may be used on a permanent basis by all federal, state and local agencies, and private organizations. It is possible that new data will become available from time to time that challenge the scientific credibility of final AEGLs. If that occurs, the chemical will be resubmitted to the NAC and recycled through the review process.



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.