Radiation Causes Cancer, but rarely

A pair of new studies published in July 2005 indicates that even low doses of radiation - such as those delivered during medical imaging studies - are likely to increase a person's risk of developing cancer.

Exposure to everyday sources of radiation, mostly medical x-rays, raises the risk of cancer but not by much, according to the National Research Council.

People should think twice about having unnecessary high-dose x-rays such as the full-body CT scans being offered by some clinics, the panel advised, but otherwise should be reassured by the findings.

Most sources of radiation are natural -- gamma rays from space, and radon from the ground, air, and water. "These sources account for about 82% of human exposure," the report reads. The 18% of human-made radiation comes mostly from medical radiation but also tobacco, televisions, and smoke detectors.

The National Research Council is part of the National Academy of Sciences, an independent organization set up by Congress to guide government on matters of health and science.
The second study, published in the British Medical Journal, examined nuclear industry workers in 15 countries who had been exposed to low doses of radiation over an extended period of time, finding that these workers had a slightly higher risk of cancer death.

"We have shown that even low doses of radiation cause cancer," said Dr. Elisabeth Cardis, head of the radiation group at the International Agency for Research on Cancer (IARC) in Lyon, France.
In its commentary, PBS News reported that a full-body scan is equivalent to 100 times a mammogram. If you had a full-body scan annually beginning in middle age, you would have a 1/50 (2%) chance of dying of cancer. That's about the same as your risk of dying in an automobile accident. David Ropeik of the Harvard Center for Risk Analysis says that he is actually reassured by the report. "Yes, radiation does cause cancer, but doesn't cause very much compared to a lot of other things that can. And I'm reassured to find that in the most updated findings here."

References: National Research Council, "Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2," and Frijheid et al, "Risk of cancer after low doses of ionising radiation: retrospective cohort study in 15 countries." BMJ. 2005 Jul 9;331(7508):77. Epub 2005 Jun 29. Additional information from PBS News, from Reuters Health, and from the X-ray Digital Community (AuntMinnie.com) was used in the preparation of this article. Full text is available at www.pubmed.com, PMID 15987704.

As printed in the VHL Family Forum 13:2, August/September 2005. For permission to reprint, please contact VHL Family Alliance, editor@vhl.org. Further information is available from the VHL Family Alliance, info@vhl.org.