The major issue addressed in this document involves the nature and magnitude of the inhalation risk of cancer to humans exposed to low levels of benzene. Occupational studies continue to provide the bulk of evidence of benzene's carcinogenicity. This document reconfirms that benzene is a 'known' human carcinogen by all routes of exposure. This finding is supported by evidence from human epidemiologic studies, animal data, and an improvement in understanding of mechanisms(s) of action. Human epidemiologic studies of highly expose occupational cohorts have demonstrated that inhalation exposure to benzene can cause acute nonlymphocytic leukemia and other blood disorders, that is preleukemia and aplastic anemia. Additionally, changes in blood and bone marrow consistent with hematotoxicity are recognized in humans experimental animals. Currently, there is insufficient evidence to deviate from using an assumption of a linear dose-response curve for benzene, hence, the Agency's past approach of using a model with low-dose linearity is still recommended.