Washington ? A former Food and Drug Administration scientist said Tuesday his job was eliminated after he raised concerns about the risks of radiation exposure from high-grade medical scanning.

Dr. Julian Nicholas said at a public hearing that he and other FDA staffers “were pressured to change their scientific opinion,” after they opposed the approval of a CT scanner for routine colon cancer screening. Nicholas said that he objected to exposing otherwise healthy patients to the cancer risks of radiation.

After FDA officials pushed ahead with plans to clear the device, Nicholas, now a physician at the Scripps Clinic in San Diego, said he and eight other staffers raised their concerns with the division’s top director Dr. Jeffrey Shuren last September. The device apparently is still under review.

“Scientific and regulatory review process for medical devices was being distorted by managers who were not following the laws,” Nicholas said. A month later Nicholas’ position was terminated, he said.

Nicholas does not think there was undue influence by the manufacturer in his ouster, but that his more cautious stance was in opposition to that of FDA higher-ups.