Diane Rehm hosted a discussion about the new TSA screening procedures. The conversation touched on privacy, the efficacy of the full-body scanning machines and the invasiveness of pat-downs.

Privacy issues have typically dominated stories about the TSA, though more and more news outlets have begun looking into the health effects of so-called backscatter scanning machines. the New York Times explored the issue of radiation in airport scans:

The T.S.A. says that the technology has been evaluated by the Food and Drug Administration’s Center for Devices and Radiological Health, the National Institute for Standards and Technology, and the Johns Hopkins University Applied Physics Laboratory. The results, the agency said, confirmed that radiation doses for individuals “were well below the dose limits specified by the American National Standards Institute.”

According to the agency, “a single scan using backscatter technology produces exposure equivalent to two minutes of flying on an airplane,” where slightly higher levels of radiation are routine. These safety issues are discussed at www.TSA.gov.

But others who have studied the technology argue that repeated low-dose exposure to radiation at airport checkpoints is a cumulative risk, and that the safety of the backscatter technology has not yet been adequately demonstrated by impartial research.

In a letter on May 28, several organizations and individuals, including the American Civil Liberties Union and Ralph Nader, asked Congress to stop deployment of the devices pending “an independent review of the devices’ health effects.”

While it’s not our place to debate science fact (whatever the eventual verdict on backscatter scanners may be), it’s interesting to note that Nader and several Republican Senators have been wondering why the whole controversy can’t be sidestepped. The TSA, they say, should look into other types of scanners that either use less radiation, are more effective or are more private. One such device is in use in America, it uses millimeter radio waves instead of radiation. The other is being used in Amsterdam.

That technology identifies potentially threatening objects on a person without actually showing naked body images and also “avoids exposing passengers to radiation,” the senators said.

But for now, the agency is committed to the backscatters and millimeter wave machines.

To me, the obvious question is: Given that the two types of machines are both deemed effective by the T.S.A., why doesn’t the agency just abandon backscatters and use the millimeter wave machines, which don’t pose radiation issues?

“I’ll tell you what the T.S.A. told us when we asked,” Mr. Nader said. “They said, ‘We want to stimulate competition in order to get the best price.’ ”

What are your thoughts? Are the scanners and more thorough pat-downs necessary?