The U.S. Environmental Protection Agency (EPA) has issued final guidance on linking cancers to chemical agents and radiation. Titled Lymphohematopoietic Cancers Induced by Chemicals and Other Agents: Overview and Implications for Risk Assessment, the guidance addresses cancers related to bone marrow, spleen, lymph nodes, thymus, and the production of blood cells. The document asserts that lymphohematopoietic cancers are most commonly linked to chemical exposure, pharmaceuticals, infectious agents, and other nonenvironmental agents. The guidance was prepared to help agency scientists understand how to apply detailed biological information from toxicity studies to assessments of whether chemicals cause human leukemia and related cancers. It acknowledges the difficulty in determining which lymphohematopoietic cancers should be grouped and provides examples of different groupings that authoritative bodies, such as the International Agency for Research on Cancer, have used.