One of the most established causes for childhood leukemia is the presence of ionizing radiation. Ionizing radiation is responsible for causing chromosomal abnormalities. This is truer in the case of AML rather than ALL; however it is also the only known cause of CML. The effect of the exposure can occur during, before or after pregnancy during the postnatal period. Exposure to the radiation can be a risk factor if it occurs before conception. Diagnostic exposure to X-rays increases the potential risk of leukemia by 40% when in utero.In terms of chemicals the most commonly associated are hydrocarbons and pesticides. Hydrocarbons are found in many household compounds such as solvents and paint thinners. Benzene exposure has a strong association with AML. Lower exposures have also shown excess risk for leukemia. If there is maternal exposure to paints or solvents during the postnatal period this increases the risk for ALL. In terms of Pesticides the children can be contaminated by agricultural products, food contaminants, parental occupation or pet products. It is associated with both ALL and AML. When talking about alcohol, cigarette and drug use there is a particular link to AML associated with use during pregnancy. There are certain diseases that cause a higher incidence of AML than ALL among children. They include inherited diseases such as Fanconi anemia, Bloom syndrome, ataxia telangiectasia, Down syndrome, Shwachman syndrome and neurofibromatosis. AML incidence is also increased due to immunosuppression, Polycythemia vera, thrombocythemia and refractory anemia. The risk for ALL is not increased in those families with a history of leukemia. However a genetic disposition towards it has been confirmed. There is a significantly higher risk to those children who were born when their fathers were above 40 years of age and their mother was above 35 years of age. An increased birth weight has also been linked due to a higher rate of cell proliferation putting the child at risk for malignancy (Belson, Kingsley, & Holmes, 2007).