Source:http://linkedlifedata.com/resource/umls/id/C0542271
NCI: Studies to identify or characterize the mechanism of action of non-infectious exogenous agents, conditions, or procedures that initiate, promote, or otherwise contribute to the development of cancer. Although infectious agents are excluded from this definition, extrinsic factors that increase exposure to these agents (e.g., occupation, sexual activity, needle sharing, transfusion) are considered environmental.