WASHINGTON - A House committee warned the Centers for Disease Control and Prevention on Thursday not to fire a whistleblower who was involved in a controversial draft report that suggested pollution is causing health problems in parts of the Great Lakes region.

Representatives John Dingell and Bart Stupak (D-Mich.) wrote CDC Director Dr. Julie Gerberding that they were concerned the agency might be taking steps to terminate the scientist in charge of the project, Christopher De Rosa.

The House Energy and Commerce Committee, which Dingell chairs, is investigating the draft report, which was produced by CDC scientists and later released after allegations of a cover-up.

CDC administrators have distanced themselves from the research, arguing that some of the science is weak. They have asked an independent scientific advisory organization, the Institute of Medicine, to review the drafts and provide an assessment of the work's quality.

CDC spokeswoman Bernadette Burden said they had not yet received the letter and could not immediately comment.

De Rosa was reassigned last year and Dingell and Stupak said the CDC took a formal step toward termination in February. Some legislators have said they believe De Rosa was reassigned because he pushed for release of important information.

The legislators noted that De Rosa "has been a key figure in more than one issue that may have caused embarrassment to CDC management," including allegations the Federal Emergency Management Agency manipulated scientific research to play down dangers posed by formaldehyde in trailers issued to the victims of hurricanes Katrina and Rita.

"It is imperative that CDC take no action that might be viewed as retaliation against any employee involved in any of the aforementioned studies, especially Dr. De Rosa," Dingell and Stupak wrote.