I am a biochemist working in the field of biophysics. Specifically, the lab I work in (as well as many others) has spent the better part of the last decade working on the molecular mechanism of how mutations in the breast cancer susceptibility gene, BRCA2, result in cancer. The result of that work is that we now better understand that people who have a deficient BRCA2 gene are hypersensitive to DNA damage, which can be caused by a number of factors including: UV exposure, oxidative stress, improper chromosomal replication and segregation, and radiation exposure. The image below shows what happens to a chromosome of a normal cell when it is exposed to radiation. It most cases, this damage is repaired; however, at high doses or when there is a genetic defect, the cells either die or become cancerous.
Quite some time ago, I posted a short educational video that describes how BRCA1 and BRCA2 mutations cause cancer. In short, when a person who has a mutation in one of these genes is exposed to environmental factors that cause DNA damage, they simply don’t repair the damage with the same efficiency as the general population. Over the course of their lifetime, the incremental exposures to relative small and seemingly safe doses of ionizing radiation (which is everything from UV light to X-rays to gamma radiation) statistically accumulate damage (or the effects of damage and improper repair) until the probability of developing cancer becomes almost certain. This is because BRCA1 and BRCA2 are both part of a molecular process that is very similar to the spell-check on your word processor (in oncology parlance, these genes are known as caretakers of the genome for this specific reason). When these genes don’t work, mutations accumulate faster and eventually results in cancer.
Its because of my interest in this aspect of cancer biology that I felt compelled to review the safety reports released on the TSA website here. However, my interest is not only professional, but also personal. My grandmother died of breast cancer in 2005 after being in remission for 20+ years. While she was never tested for either BRCA1 or BRCA2, her family history indicates that there is a strong probability of one of these mutations running in my family. Including my grandmother, at least four of her siblings developed cancer: two died of breast cancer, one developed a rare form of leukemia and another died of skin cancer. All of her female siblings had cancer, and its noteworthy that her mother died of a very young age (maybe 30’s or early 40’s) of an unknown (to me) cause. For these reasons, I fear that inadequate safety evaluation of these machines could unduly expose my family (and myself) to levels of radiation that might be harmful should this high familial cancer rate in fact be hereditary.
Last spring, a group of scientists at the University of California at San Francisco (UCSF) including John Sedat Ph.D., David Agard Ph.D., Robert Stroud, Ph.D. and Marc Shuman, M.D. sent a letter of concern to the TSA regarding the implementation of their ‘Advanced Imaging Technology’, or body scanners as a routine method of security screening in US airports. Of specific concern is the scanner that uses X-ray back-scattering. In the letter they raise some interesting points, which I’ve quoted below:
- “Our overriding concern is the extent to which the safety of this scanning device has been adequately demonstrated. This can only be determined by a meeting of an impartial panel of experts that would include medical physicists and radiation biologists at which all of the available relevant data is reviewed.”
- “The X-ray dose from these devices has often been compared in the media to the cosmic ray exposure inherent to airplane travel or that of a chest X-ray. However, this comparison is very misleading: both the air travel cosmic ray exposure and chest X-rays have much higher X-ray energies and the health consequences are appropriately understood in terms of the whole body volume dose. In contrast, these new airport scanners are largely depositing their energy into the skin and immediately adjacent tissue, and since this is such a small fraction of body weight/vol, possibly by one to two orders of magnitude, the real dose to the skin is now high.”
- “In addition, it appears that real independent safety data do not exist.”
- “There is good reason to believe that these scanners will increase the risk of cancer to children and other vulnerable populations. We are unanimous in believing that the potential health consequences need to be rigorously studied before these scanners are adopted.”
Read moreReview of the TSA X-ray backscatter body scanner safety report: hide your kids, hide your wife