"In fact, the radiation risk is discussed several times in these documents," she said.
The DHS did not immediately respond to a request for comment.
In 2006, the DHS conducted a Rail Security Pilot project at the Port Authority Trans Hudson Exchange Place station in New Jersey to test the viability of using different types of body scanner technologies to detect concealed explosives.
Apart from that test, there has been no public word that the DHS has conducted similar tests at public transit locations, McCall said.
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