For an upcoming column, I reviewed the safety of the whole body scanners being deployed nationwide. There are two broad types of scanners: millimeter wave or backscatter x-ray. While there is little reason to be concerned about the health risks of millimeter wave exposure at this time, the backscatter x-ray scanners are of concern.

A recent, open, letter to the White House by UCSF professors Sedat, Shuman, Agard, and Stroud [PDF] concisely summarizes the (still unaddressed) concerns:

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


Our colleagues at UCSF, dermatologists and cancer experts, raise specific important concerns:
• A) The large population of older travelers, >65 years of age, is particularly at risk from the mutagenic effects of the X-rays based on the known biology of melanocyte aging.

• B) A fraction of the female population is especially sensitive to mutagenesis- provoking radiation leading to breast cancer. Notably, because these women, who have defects in DNA repair mechanisms, are particularly prone to cancer, X-ray mammograms are not performed on them. The dose to breast tissue beneath the skin represents a similar risk.

• C) Blood (white blood cells) perfusing the skin is also at risk.

• D) The population of immunocompromised individuals—HIV and cancer patients (see above) is likely to be at risk for cancer induction by the high skin dose.

• E) The risk of radiation emission to children and adolescents does not appear to have been fully evaluated.

• F) The policy towards pregnant women needs to be defined once the theoretical risks to the fetus are determined.

• G) Because of the proximity of the testicles to skin, this tissue is at risk for sperm mutagenesis.

• H) Have the effects of the radiation on the cornea and thymus been determined?

In short, the safety of backscatter x-ray whole body scanners, like those currently deployed at Seatac, has not been adequately demonstrated at this time. (In contrast, the millimeter wave scanners used elsewhere do not have these sorts of safety concerns.) The FDA's tepid response to these concerns is utterly unconvincing.

The deployment of these scanners represents a gigantic, unconsented, radiation exposure experiment on travelers. You should opt-out of any backscatter x-ray whole body scanning until the safety of these devices is definitively demonstrated.