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Wednesday, October 13, 2010

X-ray Exposure Linked to Childhood Leukemia

Researchers at the University of California Berkeley just published a paper in which they report that exposure to as little as three X-rays in childhood is associated with an almost doubled incidence of childhood leukemia of a particular type – acute lymphoblastic (or lymphocytic or lymphoid) leukemia – ALL for short. In fact, exposure to just one X-ray increased the incidence of another form of leukemia, called B cell leukemia (B cells are a type of lymphocyte involved with recognition of objects – bacteria, viruses, foods, antigens – foreign to the body). The concern about exposure to CT scans is even greater, since they deliver up to 500 times as much radiation as conventional X-rays.

The study included 827 children up to age 15 diagnosed with either ALL or AML. The children with leukemia were each compared with other children randomly selected from the California birth registry who were matched by factors such as age, gender, ethnicity and maternal race.

Interviews were conducted with mothers within four months of the diagnosis of leukemia, and the mothers were asked to report on the number of X-rays received by the child at least 12 months or more before the leukemia diagnosis. Mothers were also asked about their exposures to X-rays during pregnancy and the year prior to pregnancy. Dental X-rays were not included.

Dr. Grout's comment:

With the incidence of childhood cancers rising since 1975, it is important to realize that our children are being exposed to increasing amounts of toxicity throughout their gestation and early in their lives. ALL is known to be increased by prenatal exposure to radiation, as well as exposure to pesticides during gestation, infancy and childhood. This is the first study which shows that it is also increased by exposure to X-rays outside the womb. Remember the EWG study which showed that newborns have an average of 200 toxic chemicals in their umbilical cord blood? These chemicals had to have been downloaded from their mothers, which means that their mothers have been exposed as well. Once the DNA is weakened, because of abnormal methylation – a chemical process which turns genes off and on – it is much easier to develop a further mutation that may lead to abnormal bone marrow cells. These cells are extraordinarily sensitive to radiation – remember the atom bomb and Nagasaki and the huge increase in thyroid and bone marrow cancers? So it’s no wonder that any exposure to radiation could increase the incidence of cancer. As early as 1972, questions were being raised in the New England Journal of Medicine.  We are still attempting to answer them.

That’s not to say that we should never use X-ray as a diagnostic tool. It is, in fact, very helpful. But do we really need to take a chest X-ray every time a child has a cough? Do we in fact have to confirm with X-ray what we can hear with our ears, if we listen? Persistent rales (crackles) in a given area of the lungs is pretty much diagnostic of pneumonia, and doesn’t necessarily need to be confirmed by X-ray. CYA is probably not the safest course to take for the child – although it may make the doctor feel that he/she is standing on firmer legal ground.

And speaking of B cell leukemias – one has to wonder about the relationship between X-ray exposure and multiple myeloma, a cancer of the B cells that develops within the bone marrow in older people. But that’s a question for another study.

And we are asking travelers to go through X-ray scanning every time they get on an airplane? I personally plan to opt for the pat-down version of scanning. 

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