Odds are you'll get more radiation during your flight than from an airport scanner—assuming the scanners are working properly.

RODALE NEWS, EMMAUS, PA—As the world waits nervously to see what happens with the nuclear reactors in Japan, many people are worried about nuclear radiation drifting across the Pacific and contaminating food, air, and water here. But last November and December, the American public was much more concerned about a totally different kind of radiation, and one that, according to a new study, isn't as dangerous as was feared.

As of last November, the Transportation Security Administration had distributed two forms of full-body airport body scanners to major airports nationwide: millimeter-wave body scans that use energy waves to create images and backscatter X-ray scanners, which use ionizing radiation to create images. Based on a study published in last month's issue of the Archives of Internal Medicine, that radiation shouldn't be a huge concern.

"We get exposed to radiation and ionizing radiation from lots of different sources," says Rebecca Smith-Bindman, MD, professor of radiology and biomedical imaging at the University of California– San Francisco, and lead author of the study. "The doses [from backscatter machines] are very low, and I don't think people should be suspicious that it's dangerous." However, she adds, "I'm in no way an expert on how these machines are used in practice, but if there's any possibility for malfunction, it could be a different story." It's that last "but" that has a lot of politicians up in arms again.

THE DETAILS: Based on previous tests on airport body scanners, Dr. Smith-Bindman calculated that the amount of radiation a person is exposed to from one scan is equivalent to the amount of radiation you'd receive in three to nine minutes of time spent outside or simply going about your daily business. Using computer modeling, she calculated that of the 750 million trips taken by 100 million people every year, the radiation exposure from backscatter scans would lead to a total of six cancers over their lifetimes, compared with 40 million cancers that could develop from underlying causes such as genetics and lifestyle factors.

She then broke her analysis down into frequent flyers and 5-year-old female frequent flyers (children are far more susceptible to radiation damage than adults, and girls are more susceptible than boys). One million frequent flyers who took 10 airplane trips a week for an entire year would see four cases of cancer from backscatter machines and 600 cases of cancer from the radiation received from flying at high elevations, compared with 400,000 cases of cancer from underlying factors. As for the young girls, the authors estimated that, for every 2 million girls who make one airplane round-trip per week, one additional breast cancer could occur from these scans over their lifetimes, while 250,000 of those same girls would develop breast cancer during their lifetimes due to high incidence rates and other factors.

WHAT IT MEANS: Dr. Smith-Bindman, who admits she was skeptical of these machines and usually avoided them before doing her study, says that airport backscatter body scans are no longer a concern for her. "I no longer avoid that line; the doses are truly trivial," she says.

"It’s true that we want to do everything we can to lower the risk of cancer," she adds, "but avoiding airport body scanners is not going to do that." People are exposed to higher levels of radiation during a flight itself, due to your closer proximity to the sun. "So if you're truly concerned about radiation exposure, you should reconsider the amount of flying you do."

Dr. Smith-Bindman isn't giving these machines a total hands-down recommendation, though. In her study she writes that though the actual levels of radiation emitted are low, there's no way to control for machine settings that get changed after installation or if the machines undergo software or mechanical malfunctions. On top of that, "the TSA has not been generous in allowing access to these machines," she says, adding that she wasn't allowed to test them independently. And based on recent reports of TSA tests, she isn't alone in her opinions of the agency.