Transportation Security Administration employees participate in a demonstration of new body scanner software that uses a stick figure to represent the passenger being scanned, rather than an actual image of the person, at the TSA Systems Integration Facility at Washington's Reagan National Airport in Arlington, Virginia, February 1, 2011. REUTERS/Jonathan Ernst

WASHINGTON (Reuters) - New tests of full-body scanners deployed at airports found that the radiation they emit was within acceptable levels, the Transportation Security Administration said on Tuesday after previous checks found some anomalies in results.

The machines, which have provoked health concerns about excessive radiation exposure, have been deployed at dozens of airports to thwart attacks on the U.S. aviation system which has continued to be a prime target of al Qaeda militants.

“The latest reports confirm previous testing and show that every backscatter unit currently used for passenger screening in U.S. airports is operating well within applicable national safety standards,” said TSA spokesman Nicholas Kimball.

There are about 486 full-body scanners in 78 airports in the United States, of which 247 are so-called backscatter machines made by Rapiscan Systems, a unit of OSI Systems Inc. They expose a person to about 0.0025 millirem of radiation.

Test results released by TSA in March showed some anomalies, such as missing data or calculation errors unrelated to safety. The agency ordered new tests for the scanners as well as other X-ray equipment used to screen baggage that had problematic reports.

The machines cannot produce more than 0.005 millirem per scan, according to TSA. In comparison, a chest X-ray will expose someone to 10 millirem of radiation and the maximum recommended exposure to radiation from man-made sources is 100 millirem per year, according to TSA.

TSA posted the new test results on its website: here.

TSA has accelerated deploying full-body scanners and other machines to detect explosives after a Nigerian man tried but failed to detonate a bomb hidden in his underwear on a flight from Amsterdam as it approached Detroit on Christmas Day 2009.

The full-body scanners have also provoked a backlash among some travelers who were upset because they produce revealing body images.