A risk factor is anything that makes you more likely to get a disease. Most people who have leukemia do not have any known risk factors. But things that increase your risk of having leukemia include:

• Smoking or using other tobacco products. This risk factor is linked to some cases of acute myelogenous leukemia (AML).⁷
• Exposure to high levels of radiation. People who were close to atomic bomb explosions in Japan during World War II and people who were close to the 1986 nuclear plant accident in Chernobyl, have higher rates of some kinds of leukemia.
• Exposure to chemicals, such as benzene and formaldehyde. Sometimes people are exposed to these chemicals where they work.
• Chemotherapy or radiation used to treat a previous cancer.
• Conditions caused by abnormal chromosomes, such as Down syndrome.
• Infection with a type of HIV known as HTLV-1.
• Other blood diseases, such as myelodysplastic syndromes.
• Your family history. In some cases, chronic lymphocytic leukemia (CLL) runs in families.¹