No one knows the exact causes
of leukemia. Doctors can seldom explain why one
person gets this disease and another does not.
However, research has shown that people with certain
risk factors are more likely than others to develop
leukemia. A risk factor is anything that increases
a person's chance of developing a disease.
Studies have found the following risk
factors for leukemia:
* Very high levels of radiation —People
exposed to very high levels of radiation are
much more likely than others to develop leukemia.
Very high levels of radiation have been caused
by atomic bomb explosions (such as those in
Japan during World War II) and nuclear power
plant accidents (such as the Chernobyl [also
called Chornobyl] accident in 1986).
Medical treatment that uses radiation can
be another source of high-level exposure. Radiation
used for diagnosis, however, exposes people
to much lower levels of radiation and is not
linked to leukemia.
* Working with certain chemicals—Exposure
to high levels of benzene in the workplace can
cause leukemia. Benzene is used widely in the
chemical industry. Formaldehyde is also used
by the chemical industry. Workers exposed to
formaldehyde also may be at greater risk of
patients treated with certain cancer-fighting
drugs sometimes later develop leukemia. For
example, drugs known as alkylating agents are
associated with the development of leukemia
many years later.
* Down syndrome and certain other
genetic diseases—Some diseases
caused by abnormal chromosomes may increase
the risk of leukemia.
* Human T-cell leukemia virus-I (HTLV-I)—This
virus causes a rare type of chronic lymphocytic
leukemia known as human T-cell leukemia. However,
leukemia does not appear to be contagious.
* Myelodysplastic syndrome—People
with this blood disease are at increased risk
of developing acute myeloid leukemia.
In the past, some studies suggested exposure
to electromagnetic fields as another possible
risk factor for leukemia. Electromagnetic fields
are a type of low-energy radiation that comes
from power lines and electric appliances. However,
results from recent studies show that the evidence
is weak for electromagnetic fields as a risk