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In all the controversy over the deployment of full-body scanners in U.S. airports, the health effects of the millimeter wave and backscatter machines has been a muted part of the debate. The backscatter X-ray machines deliver a very small amount of radiation. The millimeter wave machines use radio waves that (as in the case of cell phones) are to pose any risk. Even so, about the health effects, and at the ÀÏ°ÄÃÅ¿ª½±½á¹û we have often been asked questions about those effects by people who regard government claims with a lot of skepticism or who just worry that, as so often in the past, there are risks scientists don't yet understand.

What about real X-ray machines? The current body scanners cannot see below the skin, and we have previously pointed out the possibility of explosives being hidden in body cavities, in the context of asking just how far the United States is prepared to go in pursuing privacy-violating security measures. Of course, regular X-rays, like those used when you break your arm, can see below the skin — but because the radiation doses they deliver are significant, those would be a nonstarter in the airline security context.

Or would they? We were surprised to that some agency of the U.S. government is purchasing genuine, "through-body X-Ray" machines for African countries for the purposes of airport security — the kind that can see through flesh, and which deliver real doses of radiation.

The U.S.-supplied scanners have apparently been deployed at one airport in Ghana and four in Nigeria. the X-ray machine supplier OD Security, the machines will be used to "scan selected passengers who have been identified as posing a possible security risk."

The scanners, the company says, offer

a much more effective, cheaper and less disruptive security procedure than mass screening and relying on the inferior image quality of microwave and Backscatter scanners. The Soter will detect any metallic or non-metallic objects, such as narcotics, explosives, precious stones, plastic weapons or other contraband, hidden under clothes or in natural cavities within the human body. Other than the conventional intrusive strip searches there is no other way of detecting these items carried internally.

Well there's no doubt that a real X-ray machine can see things that won't be picked up by other scanning technologies. All kinds of things, in fact. But what about all that radiation? OD Security calls its devices "low dose" X-rays. But what do they mean by "low"? A fact sheet at the web site (PDF) at least, uses "low dose" to refer to any X-ray other than a super-high-dose procedure such as a CT scan. Low dose X-rays are "those that involve only films taken by a technologist" — in short, what everyone thinks of as a regular medical X-ray.

Throughout the 20th century, the experts' definition of a "safe" dose of radiation was constantly downward, until finally it was concluded that there is "no safe dose." RadiologyInfo.org also recommends "if you have had frequent X-ray exams," that it "is a good idea to keep a record of your X-ray history for yourself" so that the "potential risk from radiation" can be balanced against the "likelihood of benefit" from an X-ray. Perhaps travelers in these African countries will need to include their trips through security in those records. Pity the local traveler whose name is on a watch list and gets X-rayed every time. . .

This story, assuming it's accurate, leaves several questions begging to be answered:

• Is Homeland Security considering the use of "through-body X-ray" machines domestically?
• How much radiation do these human-targeted airport X-ray machines deliver?
• Who are they being used on in Nigeria and Ghana? Everyone selected for secondary screening, or only those for whom a body cavity search is deemed justified? Is the United States monitoring their use or did it set any conditions on their use?
• In the medical context, technicians are trained to use the minimal radiation dose required for a particular image. Are airport X-ray operators similarly trained, or are they just blasting passengers away with radiation to minimize the chances of missing contraband?
• Are the X-rays, which can reveal an enormous amount of intimate information about passengers' bodies, being viewed in a separate room, or will passengers' every internal and external bodily quirk, condition, and deformity be exposed to agents standing right there?
• Is the U.S. government encouraging the use of these machines in other countries? Any countries in other areas of the world, such as Europe, Asia, and Latin America?

Ultimately, the biggest question raised by this story is whether the U.S. security agencies behind this program have considered the health effects on African travelers of these machines. If true, this situation just might evoke inevitable comparisons to the fictional plot of the John LeCarré novel and movie , in which an evil pharmaceutical company conducts drug tests on African children, or to the real-life . When Westerners deploy devices with questionable health effects in Africa that they won't or don't deploy at home, it doesn't look good.