Tuesday, April 05, 2011

Any Dose Of Radiation Increases Risk For Cancer

Radiation damages cells and DNA. The good news: DNA can be repaired by proteins encoded by DNA repair genes.1, 2

Some people have a reduced capacity to repair DNA owing to inherited mutations in their DNA repair genes. Inherited tendencies to colon, breast, and ovarian cancers can involve reduced capacity to repair DNA. Apart from inherited mutations, DNA repair genes themselves can be damaged. DNA repair also naturally diminishes as we age.1, 2

All ionizing radiation damages cells. There is no level of exposure below which changes to a cell do not occur.3 Some of this damage can be repaired. Some will result in cancer:

"FIGURE PS-4 In a lifetime, approximately 42 (solid circles) of 100 people will be diagnosed with cancer (calculated from Table 12-4 of this report). Calculations in this report suggest that approximately one cancer (star) per 100 people could result from a single exposure to 0.1 Sv of low-LET radiation above background." 3

X-rays and computed tomographic (CT) scans employ ionizing radiation. They are now the major source of medical radiation in this country. A single dose of 10 mSv (the dose from a typical CT scan of the chest, abdomen, or pelvis) produces a lifetime risk of developing a solid cancer or leukemia of 1 in 1000.3

This study estimated that approximately 29,000 future cancers could be related to CT scans performed in 2007 alone:
Projected Cancer Risks From Computed Tomographic Scans Performed in the United States in 2007, Archives of Internal Medicine, 2009

Much of the radiation to which we're exposed can't be controlled.4 Radiation from medical imaging ... we control.

1 Wikipedia: DNA Repair
2 Retired Harvard Professor John Kimball's Biology Pages: DNA Repair
3 Health Risks from Exposure to Low Levels of Ionizing Radiation: BEIR VII Phase 2, National Academies Press, 2006
4 Report No. 160 - Ionizing Radiation Exposure of the Population of the United States (2009)
Pie chart from DiagnosticImaging.com

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