What price security? Now skin is under attack

Backscatter scanners are one of the newest devices employed by the TSA to scan airline travelers. The machines use Compton scattering of ionizing X-rays which are absorbed in the skin. This has the potential to increase skin cancer risk. Should travelers be compelled by the TSA to submit to X-ray radiation exposure?

Recently, several University of California San Francisco scientists wrote a letter to John Holdren, Assistant to the President for Science and Technology. They expressed concern that the amount of radiation emitted by airport backscatter scanners has not been calculated properly and that the dose and safety have not been independently investigated.

The main concern is that the radiation dose given for the devices was calculated as if it was absorbed by the volume of the body, not just the skin. “Unlike other scanners, these new devices operate at relatively low beam energies (28keV). The majority of their energy is delivered to the skin and the underlying tissue,” they wrote. Also, they state in the letter; “it appears that real independent safety data do not exist.”

The TSA website states “advanced imaging technology screening is safe for all passengers.” They also state that backscatter technology was independently evaluated by the FDA, NIST (National Institute for Standards and Technology), and the Johns Hopkins University Applied Physics Laboratory. However, as the authors from UCSF point out, the testing was done using an indirect test, which emphasizes whole body exposure.

The TSA responded that they did study the dose the skin received, and the “modeling results revealed that the dose to the skin is approximately twice the effective dose.” Concluding, “as a result of these evidence-based, responsible actions, we are confident that full-body X-ray security products and practices do not pose a significant risk to the public health.” But how much of a risk is “significant?” Ionizing radiation is inherently dangerous: it causes cancer in humans.

Although the radiation dose to the skin may be fairly low even with corrected calculations, the impact of this radiation exposure is unknown. Have calculations been made across the population exposed to the radiation? Has the impact to children and persons with history of skin cancer been evaluated? How much will this affect the incidence of skin cancer over time? Is the populace being endangered by the TSA in the name of safety?

Moreover, a safer alternative is concurrently in use; the millimeter wave scanner. Millimeter-wave scanners use radio waves, which do not cause mutations and cancer. According to NPR “the images are comparable in quality to the X-ray scanners, the TSA says. The cost is also comparable.”

If an apparently safe alternative exists, why use X-ray radiation? NPR reported that the TSA plans to deploy roughly equal numbers of the X-ray and millimeter-wave machines because the TSA’s strategy is to use multiple vendors. Or in other words, the TSA would rather preserve their scanning options than use a safer alternative.

Dermatologists should advise their patients with history of skin cancer, prior X-ray treatments, or conditions such as basal cell nevus syndrome to be especially wary. Go through millimeter wave scanners, or submit to a pat-down; do not go through X-ray backscatter scanners.