'U.S. law enforcement agencies are exposing people to radiation in more settings and in increasing doses to screen for explosives, weapons and drugs. In addition to the controversial airport body scanners [2], which are now deployed for routine screening, various X-ray devices have proliferated at the border, in prisons and on the streets of New York.

Not only have the machines become more widespread, but some of them expose people to higher doses of radiation. And agencies have pushed the boundaries of acceptable use by X-raying people covertly, according to government documents and interviews.'

Read more: Drive-by Scanning: Officials Expand Use and Dose of Radiation for Security Screening