What causes leukemia?

Experts say that different leukemias have different causes. The following are either known causes, or strongly suspected causes:

• Artificial ionizing radiation
• Viruses - HTLV-1 (human T-lymphotropic virus) and HIV (human immunodeficiency virus)
• Benzene and some petrochemicals
• Alkylating chemotherapy agents used in previous cancers
• Maternal fetal transmission (rare)
• Hair dyes
• Genetic predisposition - some studies researching family history and looking at twins have indicated that some people have a higher risk of developing leukemia because of a single gene or multiple genes.
• Down syndrome - people with Down syndrome have a significantly higher risk of developing leukemia, compared to people who do not have Down syndrome. Experts say that because of this, people with certain chromosomal abnormalities may have a higher risk.
• Electromagnetic energy - studies indicate there is not enough evidence to show that ELF magnetic (not electric) fields that exist currently might cause leukemia. The IARC (International Agency for Research on Cancer) says that studies which indicate there is a risk tend to be biased and unreliable.