(USA TODAY) -- Controversial full-body X-ray scanners at U.S. airports underwent more than 700 inspections last year with all tests showing radiation levels below standards used by their manufacturer and the Transportation Security Administration, according to a USA TODAY review of the recently released reports.
While the TSA and scanner-maker Rapiscan Systems say the reports offer additional proof of safety, some critics remain unconvinced. Regardless, the TSA is in the final phases of removing the last of Rapiscan's backscatter scanners from airport checkpoints by June. Full-body scanners using a different technology that does not involve ionizing radiation, called millimeter wave, will remain in use to screen passengers.
"We're very pleased with the results of the latest batch of inspection reports," said Peter Kant, Rapiscan's executive vice president. "It's yet another set of test results that show the systems are operating exactly as we said they would, that they are well below safety limits."
The TSA did not respond to interview requests since Tuesday. The agency issued a brief statement Thursday night that said in part: "All scientific testing on this technology thus far has proven to be well within nationally recognized standards and safe for all passengers."
The TSA has said it was privacy concerns - not radiation - that resulted in the agency canceling its contract with Rapiscan in January. Rapiscan, unlike the maker of the millimeter-wave machines, was unable to meet TSA's deadline to develop software to convert the nude-like images produced by their machines into stick-like figures, the agency has said.
The TSA has repeatedly sought to assure the public that the radiation exposures delivered by the machines are tiny, the equivalent to what passengers receive during two minutes of a typical flight. According to the Health Physics Society, passengers on a flight from New York to Los Angeles are exposed to about 4,000 microrem of cosmic radiation and a chest X-ray can deliver 10,000 microrem. The full-body scanners deliver less than 5 microrem of radiation per screening, according to Rapiscan.
Critics have questioned the wisdom of adding to passengers' radiation exposure when other types of scanners are available that don't use X-rays. The governing body of the European Union has banned the use of X-ray body scanners in order "not to risk jeopardizing citizens' health and safety."
The reports involve about 715 inspections and generally covered radiation tests from December 2011 through December 2012. USA TODAY's review found:
• USA TODAY reviewed the latest airport X-ray scanner inspection reports, which TSA recently posted on its website and said are a response to a February 2011 Freedom of Information Act request filed by the newspaper. USA TODAY filed the request after the agency refused repeated requests in the fall of 2010 - by the newspaper and members of Congress - to voluntarily release the reports.• While all reports showed radiation measurements below Rapiscan's standard of 5 microrem, the amount of radiation measured varies by machine. Eleven inspections showed radiation exposures of 1.3 microrem or less; 47 inspections showed radiation exposures at or above 2.6 microrem.
• Three body scanners had radiation readings of 3 microrem or higher. At Pittsburgh's airport a December 2011 inspection of one machine showed 3.9 microrem. In San Antonio, a scanner had radiation readings in February 2012 of 3 and 3.1 microrem. In Columbus, Ohio, tests showed a scanner delivering 3.3 and 3.4 microrem in December 2011.
• Measurements of radiation leakage outside the scanners rarely detected anything during a 10-scan test. In a few cases, tests detected 1 microrem of radiation leakage, below Rapiscan's standard of 2 microrem.
The radiation inspections, performed by Rapiscan employees and contractors, use a device to measure the amount of radiation delivered and whether it is less than the company's standard of 5 microrem. Kant noted that Rapiscan's inspection standard is far less than the 25 microrem per screening dose limit for such devices set by the American National Standards Institute.
Kant said the variations in radiation readings recorded by his firm's inspectors likely reflect how the measurement was taken, such as slight differences in the placement of the measuring device in the scan chamber.
But some scientists have said the device Rapiscan uses in its tests isn't designed to accurately measure the low-level radiation used by the scanners. "Their measurements are probably flawed," John Sedat, a professor emeritus of biochemistry and biophysics at the University of California, San Francisco, said of the latest inspection reports. Sedat was among a group of scientists who have sent letters of concern to federal officials over the years about the scanners.
The first batch of inspection reports, released by TSA in March 2011, were riddled with what the TSA and Rapiscan said were clerical and math errors that in some cases showed radiation levels 10 times higher than expected,USA TODAY reportedat that time. The TSA had repeatedly assured the public and lawmakers that the machines had passed all inspections, but USA TODAY found that the agency hadn't reviewed the reports until after the newspaper began calling for their release. The TSA required Rapiscan to retrain its employees and contractors who conduct the radiation inspections.