The Federal Emergency Management Agency failed to speedily react to a public health threat posed by formaldehyde-contaminated trailers it provided to Hurricane Katrina victims, according to a report (PDF) released Thursday night by the inspector general of the Department of Homeland Security.

The report bolsters the findings of a ProPublica investigation published last year, which found that FEMA misused a flawed Centers for Disease Control and Prevention study to suppress public concerns about the formaldehyde problem.

Our investigation found that CDC officials who studied formaldehyde levels in the trailers used the wrong safety standard to determine exactly how harmful the fumes were.

Formaldehyde is considered a probable carcinogen by the CDC and can increase the risk of asthma attacks and other respiratory problems in people who inhale it.

The CDC’s own standards say that people exposed to as a little as 30 parts of formaldehyde per billion parts of air for more than two weeks can suffer constricted airways, headaches and rashes. The trailers that the CDC studied all measured above that level.

But the scientists who conducted the CDC study used a much higher standard to evaluate the formaldehyde in the trailers: Instead of 30 parts per billion, they said health dangers wouldn't occur until the substance reached 300 ppb, 10 times as great as the long-term standard. According to the CDC, people exposed to that amount for just a few hours can suffer respiratory problems and other ailments.

Not long after that study was provided to FEMA, Christopher De Rosa, a senior CDC scientist, sent FEMA a letter (PDF) saying it was inaccurate and misleading. ProPublica found that the letter was received by a FEMA attorney, who didn't share it with anyone else because he thought "everything in that letter was already known to FEMA."

The inspector general's report confirms that the attorney kept the letter to himself and suggests that the attorney’s involvement “may have caused or allowed FEMA officials to make assurances about the safety of the FEMA trailers that were later shown to be incorrect.”

While trailer-occupants repeatedly complained about headaches, rashes and burning eyes, FEMA officials continued to cite the CDC study to make their case that the formaldehyde levels weren’t high enough to harm people.

At a May 2007 congressional hearing (PDF), then-FEMA administrator David Paulison told Congress that “we've been told that the formaldehyde does not present a health hazard."

For its part the CDC never formally corrected FEMA’s public statements, even though top CDC officials knew the study they provided to FEMA was flawed. ProPublica found that Dr. Howard Frumkin, head of the CDC division that produced the study, received several e-mails mentioning FEMA's public statements, and attended over a dozen meetings where formaldehyde or trailers were listed as a topic of discussion. But in interviews with ProPublica Frumkin said that he was not aware how FEMA was using the study.

The inspector general's report also sheds light on an even earlier study (PDF, see p. 20) produced in October 2005 by the Occupational Safety and Health Administration, which should have raised red flags about the formaldehyde fumes. The report was done in response to complaints from workers who were setting up the trailers. According to the inspector general's report, high formaldehyde levels were present in several trailers that OSHA tested, and the results of those tests were provided to a FEMA contractor overseeing the setup and maintenance of the trailers, but never to FEMA itself.

The report also notes that FEMA and the CDC have invested $14 million on a health registry and children's health study to examine how children who lived in these trailers may have been affected by the formaldehyde.

In November 2008, ProPublica found that the Children's Health Study was also muddled by delays and confusion, and that the agencies hadn’t yet begun to recruit people for the study.

In November, Michael McGeehin, the CDC official who is leading the study, told ProPublica that the final bill for the study could reach $87 million, far more than the $14 million the inspector general said has been committed so far.

The inspector general's report’s recommendations to FEMA include the suggestions that the agency needs a more effective process to deal with health complaints lodged by disaster housing occupants and that it should provide better guidelines to the contractors that build mobile homes and trailers that the agency provides to disaster victims.

In its response to the report, FEMA said that it is following the inspector general’s recommendations. The former acting director of FEMA, Robert Farmer, said in a May 2009 letter to the inspector general that the report doesn’t fairly describe how other federal agencies like the CDC and the EPA shared responsibility for the government’s lethargic response.

The inspector general's report came as a result of an amendment to the Department of Homeland Security appropriations bill passed last year.

The lawmakers responsible for the amendment, led by Joe Lieberman, the Senate Homeland Security and Governmental Affairs chairman, said in a letter (PDF) to FEMA that the report is a "disturbing testament of FEMA's missteps and delays that might well have had a detrimental effect on the health and safety of those living in the trailers."

Many of the documents referenced in this story are available on our interactive feature: Timeline of CDC's and FEMA's Response to Formaldehyde Danger