AP NEWS A federal scientist said Tuesday his bosses ignored pleas to alert Gulf Coast hurricane victims earlier about severe health risks from formaldehyde in government-issued trailers and once told him not to write e-mails about his concerns.

Christopher De Rosa, who until recently was one of the government's top toxicologists, told a congressional panel that he repeatedly raised concerns early last year that the Centers for Disease Control and Prevention was not adequately informing the public of the hazard, even as symptoms of dangerous exposure were surfacing.

As a result, tens of thousands of families displaced by hurricanes Katrina and Rita remained in the trailers without full knowledge of the risks, he said.

"I stated that such clinical signs were a 'harbinger of a pending public health catastrophe,'" De Rosa said in written testimony, quoting one series of e-mails he wrote to superiors last summer. "I stressed the importance of alerting the trailer residents to the potential reproductive, developmental and carcinogenic effects ... (but) the only response I received was that such matters should not be discussed in e-mails since they might be 'misinterpreted.'"

De Rosa's comments came Tuesday at a House Science and Technology subcommittee hearing on how the CDC and its sister agencies handled complaints about trailers issued by the Federal Emergency Management Agency.

Committee Democrats accuse FEMA of manipulating scientific research to downplay the dangers. They say the CDC and the Agency for Toxic Substances and Disease Registry, where De Rosa worked, went along with the effort.

"Your agency failed to protect public health," said Nick Lampson, D-Texas.

When complaints of possible formaldehyde poisoning surfaced, FEMA officials insisted in early 2006 that the trailers were safe. But after coming under increasing pressure, FEMA enlisted the CDC's help to test them.

Formaldehyde, well known as a preservative and embalming fluid, is commonly used in building materials. Prolonged exposure can lead to breathing problems and is also believed to cause cancer.

The CDC initially said in February 2007 that, with proper ventilation, formaldehyde levels were safe in the short-term. FEMA immediately began citing the advisory as evidence that the trailers were safe.

De Rosa said he protested immediately that the CDC should more aggressively address the matter and that the advisory didn't include broader warnings about longer-term health risks, including for cancer.

But it wasn't until February 2008 that the CDC released preliminary results from additional testing showing that FEMA trailers and mobile homes had formaldehyde levels that were, on average, about five times higher than in most modern homes.

The CDC urged people to move as quickly as possible, prompting FEMA to say it would rush to find new housing for some 35,000 families still living in the trailers.

As they have done previously, De Rosa's bosses at the toxic substances agency, director Howard Frumkin and deputy director Thomas Sinks, acknowledged that the agency took too long to address the formaldehyde hazard, in part because little is known about its risks.

But they said there was never any effort to silence De Rosa or mislead the public.

"I regret that our initial work on formaldehyde in trailers did not meet our own expectations," Frumkin said. "In some respects, we could and should have done better."

The agency is reviewing its procedures, he said, and is planning a five-year study of children who lived in the trailers in Alabama, Louisiana, Mississippi and Texas.

Subcommittee Chairman Brad Miller, D-N.C., called De Rosa a whistleblower, noting that the nearly 30-year employee was recently removed from his job and assigned to another division.

Frumkin said De Rosa, who also has gained attention as the author of a controversial study on pollution around the Great Lakes, was transferred for internal personnel reasons, not as a result of his work on the trailers.

Meanwhile, test results obtained by The Associated Press Tuesday showed that some of the thousands of mobile homes being stored for possible use by future disaster victims have formaldehyde levels rivaling those used after the 2005 hurricanes.

Testing conducted by FEMA show that three of 32 mobile homes tested for use in Arkansas had levels high enough to put possible residents at an increased risk of cancer and respiratory illnesses. More than half the homes tested had levels higher than the average.

FEMA had a contractor test some of the units to see if they were suitable for storm victims in the region, which was hit by deadly tornadoes on Feb. 5.