The Department of Health and Human Services (DHHS) has determined that benzene is a known human carcinogen. Breathing benzene can cause drowsiness, dizziness, and unconsciousness; long-term benzene exposure causes effects on the bone marrow and can cause anemia and leukemia.

Air around hazardous waste sites or gas stations will contain higher levels of benzene. A major source of benzene exposure is tobacco smoke. Animal studies have shown low birth weights, delayed bone formation, and bone marrow damage when pregnant animals breathed benzene.