The vast majority of leukemias occur as a result of genetic mutations in the blood forming cells. Exposure to anything that increases damage to DNA, such as chemotherapy or radiation as a treatment for other cancers can increase an individual's risk for developing leukemia. Additionally, chemicals such as benzene or formaldehyde are known toxins that can lead to the development of leukemia. Advancing age is one of the most common risk factors for leukemia, though leukemias can develop at any age. Some rare genetic disorders, such as neurofibromatosis, Shwachman-diamond syndrome and Down syndrome are all associated with a higher risk of leukemia.