This booklet contains two page fact sheets on some of the common radionuclides found at hazardous waste sites across the nation. It is meant to help you understand more about the various radionuclides and to assist the public in understanding how the federal government may apply legal requirements in the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA). The CERCLA requirements and regulations described in this document contain legally binding requirements. The information in this booklet is not a substitute for those requirements and regulations, nor is it a regulation itself. Thus, it does not impose legally-binding requirements on any party, including EPA, States, or the regulated community, and may not apply to a particular situation based on the circumstances. EPA and State decision makers retain the discretion to adopt approaches on a case-by-case basis that differ from this booklet where appropriate. Any decisions regarding a particular facility will be made based on the applicable statutes and regulations. Therefore, interested parties are free to raise questions and objections about the appropriateness of the application of this booklet to particular situation, and EPA will consider whether or not the recommendations or interpretations in the booklet are appropriate in that situation. EPA may change this booklet in the future.