The U.S. Environmental Protection Agency (EPA) issued guidelines for assessing human risk from exposure to environmental carcinogens. The guidelines set forth principles and procedures to guide EPA scientists in the conduct of Agency risk assessments, to promote high scientific quality and Agency-wide consistency, and to inform Agency decision-makers and the public about these scientific procedures. In publishing the guidance, EPA emphasized that one purpose of the guidelines was to 'encourage research and analysis that will lead to new risk assessment methods and data,' which in turn would be used to revise and improve the guidelines. Thus, the guidelines were developed and published with the understanding that risk assessment is an evolving scientific undertaking and that continued study would lead to changes.