Risk Factors

ALL in Children. In 2005, experts estimated that about 3,970 cases of acute lymphocytic leukemia would be diagnosed in the US, with about 2,670 of them in children and adolescents younger than age 20. Until recently, most studies listed it as the most common childhood cancer. (Some recent evidence suggests that cancers in the central nervous system may be surpassing ALL in children.) The disease typically develops in children ages 1 to 10 years old, but the disease can strike from infancy to old age.

ALL in Adults. About 30% of ALL cases occur in adults. Adults who develop ALL are usually male and over 50 years old, with the highest risk being above age 70.

Ethnicity and ALL

Caucasian and Asian children have a much higher risk for ALL than African-American children, although African-American and Hispanic children who develop it do not appear to fare as well. Socioeconomic factors and unequal access to healthcare may account for some of these differences.

Hereditary Disorders

Certain inherited disorders can increase the risk for leukemia. For example, children with Down's syndrome have a 20-fold greater risk of developing acute leukemia than the general population. Other rare genetic disorders associated with increased risk include Bloom syndrome, Fanconi's anemia, ataxia-telangiectasia, neurofibromatosis, Schwachman syndrome, IgA deficiency, and congenital X-linked agammaglobulinemia.

People Exposed to Radiation

Children treated with radiation and chemotherapy for Hodgkin's disease are at higher risk for acute leukemia within 2 to 13 years after treatment (usually of the myeloid variety). Children under 10 are most susceptible to acute leukemia following exposure to radiation treatments. Susceptibility decreases between the ages of 10 and 19 then increases slowly again through age 50. After 50, a person is again at high risk of developing acute leukemia following ionizing radiation.

Most people who are not treated for cancer have low exposure to radiation, so radiation from other sources is not a significant cause of leukemia. The following are some situations that may increase risk from radiation:

  • Fetal exposure to diagnostic x-rays (not ultrasound) before birth increases the danger of developing ALL by the age of 15 years.
  • One study of children who lived near a nuclear waste processing plant in France found an increased risk for leukemia, particularly if they ate local fish.
  • Reports of increased incidence in leukemia in peacekeepers and military personnel who were stationed in Bosnia have sparked investigation of certain weapons that use depleted uranium, which were employed in the Balkan wars. Military officials say the risk is unlikely, but more research is needed.

Indoor radon also does not appear to increase the risk for leukemia. (Radon does increase the risk for lung cancer, however, particularly in smokers).

People Highly Exposed to Toxic Chemicals

Decades of research show that those who work in the petroleum industry (where benzene is derived) have a two to threefold increased risk of developing leukemia (most often acute myeloid). Others who may be at some risk for leukemia and lymphomas include painters, agricultural workers, distillers, dye users, furniture finishers, and rubber workers.

People Exposed to Electromagnetic Fields

Because people's exposure to electromagnetic fields varies widely over the course of time, it is very difficult to determine any risk. The following are some observations from studies on determining who, if anyone, might be at risk for leukemia from exposure to electromagnetic fields:

  • Evidence is mixed on any risk for living near high-power electrical lines. A 2001 study reported a small increase in risk for people living near high-voltage cables. Others have found no evidence of risk. In any case, the risk is still very small.
  • One 2000 study suggested that people living in homes with wiring at very high current levels had a risk for ALL that was about 20% above average.
  • Most studies have found that exposure to low-energy waves from household appliances does not increase the risk of childhood ALL.
  • A 2000 study of workers highly exposed to wireless communication devices found no risk for leukemia or other cancers.

A major study is under way to determine if there is any association between magnetic field exposure and survival in children with ALL.

Review Date: 12/17/2005
Reviewed By: Harvey Simon, MD, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital