Body scanners are a little weird at airports, but have been deemed necessary by the TSA to protect the friendly skies. A question arises though: Are they safe for you on the ground or do they present a cancer risk?

Whole body X-ray backscatter scanners have been used in U.S. airports since 2007, though in more limited capacity. After the Christmas 2009 attempted airline bombing, AIT (advanced imaging technology) scanner use was shifted from secondary to primary screening status. Currently 486 AIT units are used at 78 U.S. airports.

Backscatter technology involves scanning the body with a pencil beam of 50 or 120-kVp X-rays (depending on the manufacturer). Millimeter wave units use low-power (non-ionizing) millimeter waves, and the reflected signals are analyzed with a holographic imaging algorithm. Most machines in the U.S. currently use backscatter technology.

The most likely risk from the airport scanners is the most common type of skin cancer called basal cell carcinoma. It rarely metastasizes or kills, but because it can cause significant destruction and disfigurement, it is still considered malignant by invading surrounding tissues.

Statistically, approximately 3 out of 10 Caucasians may develop a basal cell cancer within their lifetime. In 80% of all cases, basal-cell cancers are found on the head and neck. There appears to be an increase in the incidence of basal-cell cancer of the trunk (torso) in recent years.

Prognosis is excellent if the appropriate method of treatment is used in early primary basal cell cancers. Recurrent cancers are much harder to cure, with a higher recurrent rate with any methods of treatment. Although basal cell carcinoma in fact rarely spreads, it grows locally with invasion and destruction of local tissues. The cancer can impinge on vital structures like nerves and result in loss of sensation or loss of function or rarely death. The vast majority of cases can be successfully treated before serious complications occur. The recurrence rate for the above treatment options ranges from 50% to 1% or less.

New research conducted by David J. Brenner, PhD, DSc, director of the Center for Radiological Research at Columbia University Medical Center, said that according to some estimations, the fatal cancer risk from going through a backscatter scanner twice a year is one in 10 million. Using the same set of assumptions, he wrote that getting scanned before 200 or more flights per year could result in a one in 100,000 fatal cancer risk. Frequent flyers might want to opt for a pat-down instead.

Brenner continues:

"There is no need to limit the number of individuals screened or, in most cases, the number of screenings an individual can have in a year. In the present context, if a billion X-ray backscatter scans were performed each year, one might anticipate 100 cancers each year resulting from this activity. Super frequent fliers or airline personnel, who might go through the machine several hundred times each year, might wish to opt for pat-downs. The more scans you have, the more your risks may go up, but the individual risks are always going to be very, very small."

Although even with a low risk, the long-term consequences of the collective population getting scanned up to one billion times per year is unknown. A small individual risk could still mean that cancers could develop in the overall population as a result of the airport scanning.

Source: Radiology, Volume 259: pp 12-16

Sy Kraft, B.A.