Dueling Docs: Are Airport Body Scanners Safe?

"Just flying in a plane exposes people to many times more radiation from than an X-ray scanner does," according to Johns Hopkins professor Dr. Mahadevappa Mahesh.
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The Issue
Body scans at the airport

The facts

Usually there's a medical reason for getting an x-ray. But now, to ensure that air travelers aren't packing explosives, the U.S. government is gearing up to require body scans on anyone who flies. The Transportation Security Administration (TSA) already has 40 scanners in 19 airports nationwide. In six of those airports, the machine is used for primary screening; at the others they're used for follow-up searches if there's a suspicion of wrong-doing.

Scanners, dubbed by some as "virtual strip searches," have been used on products, not people, entering the U.S ports for years. But for today's traveling public, there are two types of approved scanners. One uses radio-wave technology, which employs radio waves tens of thousands of times lower than those in cell phone technology--and which experts agree are largely benign. The other scanners use x-rays. They may allow for better images, but they've also created the most stir over any health effects on frequent flyers.

The government is convinced the x-rays scanners are good for the security of the flying public, but are they okay for you?

Two experts debate the issue: Dr. Mahadevappa Mahesh, chief physicist and radiology professor at Johns Hopkins University Medical School and Arjun Makhijani, nuclear engineer and president of the Institute of Energy and Environmental Research in Maryland.

The Debate

Dr. Mahesh:

"The medical risk of airport body scanners is negligible," says Mahesh. "I don't have any vested interest in defending these scanners. I'm trying to discuss the science. The radiation used in these machines is low-intensity and doesn't even transmit through the body; it reflects off the skin. The scanners go through clothes only. They can catch explosive taped to the body or hidden under clothes. They don't see into the body."

Mahesh explains that the dose of radiation of each scan is .05 to .1 micro-sieverts. (micro-sieverts is a measure of radiation dose). "A chest x-ray is equivalent to 100 micro-sieverts. That means a person would have to have 1000 to 2000 airport scans to add up to the radiation he would get from just one chest x-ray."

Moreover, says Mahesh, the radiation must be viewed in context. "Just flying in a plane exposes people to radiation. The average radiation exposure at 100,000 ft in the air is 4 micro-sieverts an hour, many times more than the radiation from a scanner. And the general population, including people who don't fly, are exposed to background radiation of about 3,100 micro-sieverts every year."

Can the scanner's operator make a mistake that would harm the passenger? "No," says, Mahesh. "There are no settings for the operators to confuse. It's push-button technology. Whether the traveler is a small child or an obese patient, the machine's settings don't have to be changed. Truth is, for those people who are totally paranoid about radiation, there's no convincing them that scanners are OK.

"But," says Mahesh. "It's highly important that these machines are tested yearly by a qualified person not associated with the manufacturer to make sure they are operating properly.

"There are privacy concerns, to be sure. The machine can distinguish between natural tissue and silicone. So if someone's had a breast implant, it will show up. But there is nothing like a perfect security system."

Arjun Makhijani:

"I'm not saying scanners should not be used, I'm saying there should be a public process," says Makhijani. "The use of scanners needs to be debated before you impose even a de minimis risk on the public. We have about 600 million air passengers every year. On average each person takes two flights. In order for scanners to be effective, the effort would have to be global. We're talking about a couple of billion scans a year--that's a lot of scans. And it's nonsense to say that the radiation of these scanners don't absorb through the body.

"By the conventional methods of calculation, once you expose billions of people to these very low doses of radiation, you will induce some cancers, and a few cancer deaths every year. They may be non-detectible, but they will be there."

Makhijani goes on: "We really need to look at what benefit we're getting from these scanners. Certain kinds of plastic explosives will remain undetectable. People can also swallow an explosive or hide them in body cavity like the anus or vagina and that won't be detectable."

Makhijani worries that use of scanners would actually introduce new risks. "Who will look at these pictures? It may be possible that the job will attract a small minority of people who could be child abusers, for example. They will be able to figure out how to store these images.

"What's more, in many societies, particularly in parts of the Islamic world, modest clothing for women is very important and yet, with these scanners, a silhouette of the body can be seen. We will be forcing people from Islamic countries to go through these machines. We are putting this on a society that is already antagonistic to the US.

"We must ask ourselves as part of a debate. 'How would the Muslim world perceive such a thing?' We have to look at whether scanners could actually increase terrorist risk because of the extreme anger that they might induce. We simply have not debated any of this. And we must.

"If you're close to the needle in the haystack, do you want to increase the size of the haystack or figure out how to grab that needle? We are putting into place machinery that increases the haystack. I'm not saying they should never be deployed. All I'm saying is that the decision to spend the money to buy and operate these machines in a hasty fashion, without consideration of any potential increase of terrorism risk or collateral risks, such as child pornography, for example, is not the way to go. We need to open this up to public debate."

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