There are 244 full-body “backscatter” X-ray scanners in use at 36 airports in the United States. They operate almost nonstop, according to the Transportation Security Administration. Other airports use millimeter wave scanners, which look like glass telephone booths and do not use radiation, or metal detectors.”
X-Ray Scans at Airports Leave Lingering Worries
Even before she was pregnant, Yolanda Marin-Czachor tried to avoid the full-body X-ray scanners that security officers use to screen airport passengers. Now she’s adamant about it: She’ll take a radiation-free pat-down instead any day.
“I had two miscarriages before this pregnancy,” Ms. Marin-Czachor, a 34-year-old mother and teacher from Green Bay, Wis., recalled, “and one of the first things my doctor said was: ‘Do not go through one of those machines. There have not been any long-term studies. I would prefer you stay away from it.’ ”
There are 244 full-body “backscatter” X-ray scanners in use at 36 airports in the United States. They operate almost nonstop, according to the Transportation Security Administration. Other airports use millimeter wave scanners, which look like glass telephone booths and do not use radiation, or metal detectors.
Most experts agree that as long as the X-ray backscatter machines are functioning properly, they expose passengers to only extremely low doses of ionizing radiation.
But some experts are less sanguine, and questions persist about the safety of using X-ray machines on such a large scale. A recent study reported that radiation from the machines can reach organs through the skin. In another report, researchers estimated that one billion X-ray backscatter scans per year would lead to perhaps 100 radiation-induced cancers in the future. The European Union has banned body scanners that use radiation; it is against the law in several European countries to X-ray people without a medical reason.
The machines move a narrowly focused beam of high-intensity radiation very quickly across the body, and David Brenner, director of the Center for Radiological Research at Columbia University Medical Center, says he worries about mechanical malfunctions that could cause the beam to stop in one place for even a few seconds, resulting in greater radiation exposure.
For security reasons, much about how the machines work has been kept secret. The T.S.A. says the full-body scanners have been assessed by the Food and Drug Administration, the United States Army Public Health Command and the Johns Hopkins University Applied Physics Laboratory.
But researchers at these institutions have not always had direct access to the scanners in use, and some of the published reports about them have been heavily redacted, with the authors’ names removed. Independent scientists say limited access has hampered their ability to evaluate the systems.
John Sedat, emeritus professor of biochemistry and biophysics at the University of California, San Francisco, believes that the effective dose could be 45 times as high as the T.S.A. has estimated, equivalent to about 10 percent of a single chest X-ray.
T.S.A. officials scoff at scientists’ statements that measuring the effective radiation dose received by passengers is very complex, saying that it is not difficult, that the machines are inspected for problems at least once a year, and that they are equipped with fail-safe shutoff systems.
The machines, though, have had mechanical problems. A recent T.S.A. report said that between May 2010 and May 2011, there were 3,778 service calls concerning mechanical problems in backscatter X-ray machines. Radiation safety surveys were conducted after only 2 percent of the calls.
In a letter to the federal Department of Health and Human Services dated Oct. 12, 2010, the scientists said that “the casual nature for maintenance of these devices is alarming to us. These machines are capable of delivering large X-ray doses.
They added, “Hospitals usually check for problems on X-ray machines daily.”
Most of what is known of the risks of radiation has been extrapolated from disease trends in Japan after World War II.
T.S.A. officials say that these low doses of radiation are safe for everyone, including pregnant women, infants and young children, even though children are significantly more sensitive to radiation’s effects.
Those at greatest risk, however, may be T.S.A. employees and others who work in the terminals and go through security daily. A 2004 National Institute for Occupational Safety and Health study of T.S.A. baggage screeners urged the agency to have employees wear film badges to monitor ongoing exposure systemically, as many hospital and lab employees do, and to label machines more prominently. The agency has not done so.
While the risk to the average passenger may be low, here are some suggestions for those who wish to reduce their exposure.
¶ Get to the airport early. That gives you extra time to opt for a pat-down if you want.
¶ If you are pregnant or think you may be pregnant, tell a T.S.A. agent. You may be allowed to pass through a metal detector without additional screening.
¶ The younger children are, the more sensitive to radiation. T.S.A. employees have been known not to require children under 13 to go through an X-ray machine, although the agency denies there is any policy on this.
¶ If you have any concerns about medical conditions, you have the right to opt for a pat-down by a T.S.A. employee.