Exposure to high-priority, acutely toxic chemicals for prolonged periods can potentially manifest into adverse health effects and deadly outcomes. Thus, to identify, review, and interpret relevant toxicological and other scientific data and to develop acute exposure guideline levels (AEGLs), the National Advisory Committee (NAC) established applications for federal, state, and local governments, as well as for the private sector. These guidelines frame emergency-response plans in case extremely hazardous substances (EHSs) are released from accidents or terrorist activities.

In 1991, the U.S. Environmental Protection Agency (EPA) and the Agency for Toxic Substances and Disease Registry (ATSDR) asked the National Research Council (NRC) to provide technical guidance for establishing community emergency expose levels for extremely hazardous substances. In response to that request and continued efforts to provide current advisory material, the Twentieth Interim Report of the Committee on Acute Exposure Guideline Levels: Part B is the second of a two part report that reviews the proposed AEGLs for scientific validity, completeness, internal consistency, and conformance to prior National Research Council guideline reports. This report also reviews NAC's research recommendations and identifies additional priorities for research to fill data gaps.