Leukemias represent 3% of all malignant neoplasms. Ionizing radiation, benzene, and cytotoxic drugs are known causes of acute leukemia. In atomic bomb survivors, the incidence of acute leukemias peaked at 2 to 5 years and declined after 10 years. After chemotherapy, the incidence peaks at 5 to 8 years. Acute lymphocytic leukemia (ALL) is limited mainly to the first 2 decades of life. (Rosenstock, p. 746-7) Occupational exposure to benzene >200 ppm per year is associated with leukemia, specifically AML. [Sullivan, p. 756-7] There is strong evidence for associations between the following and occupational leukemia: boot and shoe manufacture and repair, benzene, and ionizing radiation. [Siemiatycki, p. 334] "There were reports from Sweden among producers and some users of ethylene oxide that hinted at excess risks of leukemia. But larger American studies have subsequently shown no such risk." [Boffetta, p. 3] In studies of ionizing radiation and leukemia, strong associations were found for Japanese A-bomb survivors, radiation treatments for spondylitis, and use of Thorotrast as a contrast agent. Meaningful associations were found for radiologists working in past decades and Mayak workers. Negative associations were found for radium dial painters, underground miners, uranium processors, and Chernobyl cleanup workers. For nuclear workers the association is a "suggested but unconfirmed or questionable association." Ionizing radiation increases risks for acute lymphocytic and acute myeloid leukemias and chronic myeloid leukemia, but not for chronic lymphocytic leukemia. [Boice, p. 261, 268]
Myelodysplastic syndrome (MDS) and AML are often evaluated together in epidemiology studies; they are sometimes considered a single entity. [Schottenfeld, p. 845] MDS probably precedes leukemia in a large percentage of cases; it has the same causal risk factors as AML. [Rosenstock, p. 467, 749] The median survival for patients with MDS is 12 months. Patients either develop leukemia or die from complications of cytopenias. [LaDou, p. 272] See the definition of MDS and the WHO classification of AML at www.cancer.org. [Hyperlink]
"Patients with certain blood disorders seem to be at increased risk for getting AML. These include chronic myeloproliferative disorders such as polycythemia vera, essential thrombocytopenia, and idiopathic myelofibrosis." [www.cancer.org] Causes of bone marrow fibrosis include myeloid disorders like primary myelofibrosis, lymphoid disorders, and nonhematologic disorders. [Cecil, Table 169-7] Causes of nonhematologic myelofibrosis include cancer with bone marrow metastases, osteomyelitis, and tuberculosis. [Merck Manual, p. 1165t]
"There is limited evidence in humans for a causal association of ethylene oxide with lymphatic and haematopoietic cancers (specifically lymphoid tumours, i.e. NHL, MM and CLL), and breast cancer." [IARC 2012: Ethylene Oxide] "There is sufficient evidence in humans for a causal association of formaldehyde with leukemia." [IARC 2012: Formaldehyde] "Findings from this re-analysis do not support the hypothesis that formaldehyde is a cause of AML." [
PMID 26147546] "Studies from the styrene-butadiene industry show an excess of leukaemia, and a dose-response relationship with cumulative exposure to butadiene, while studies from the monomer industry show an excess of haematolymphatic malignancies in general, attributable both to leukaemia and malignant lymphoma." [IARC 2012: 1,3-Butadiene]