The International Agency for Research on Cancer (IARC) has determined that benzene is a human carcinogen, and can cause various forms of cancer from prolonged exposure. According to the IARC, benzene is often considered "the mother of all carcinogens," as a large number of carcinogens have structures that include benzene rings. Occupational studies of workers exposed to high levels of benzene show association with leukemia cancer; including acute myelogenous leukemia, acute lymphocytic leukemia, and chronic myelogenous leukemia. Benzene related leukemias have been reported to develop in as short as nine months, and can remain dormant for as long as 25 years after initial exposure.
Even a small amount of benzene exposure can cause temporary nervous system disorders, immune system depression and anemia. Short term affects include skin, eye, and respiratory tract irritation, headache, stomach irritation, drowsiness and dizziness. High levels of exposure can result in a rapid heart rate, excessive bleeding, tremors, vomiting, unconsciousness and death. Benzene can cause harmful effects on bone marrow, and can cause a decrease in red blood cells leading to myelofibrosis and myelodysplastic syndrome.