This story was also published in the Atlanta Journal-Constitution and is a followup to ProPublica's investigation into the CDC response to formaldehyde findings in FEMA trailers.

A government study to track the health of children who lived in FEMA trailers after Hurricane Katrina is still stuck in the planning stages, three years after families first began complaining about health problems related to formaldehyde in their temporary homes. See interactive timeline

The Centers for Disease Control, which is supposed to conduct the study, hasnât figured out how it will find the children, many of whom moved out of the trailers months or even years ago. It also hasnât settled on a scientific methodology, according to interviews and documents obtained by ProPublica, a nonprofit investigative newsroom.

Before the work can actually begin, the study must be approved by the White Houseâs Office of Management and Budget. The CDC also must get money from the Federal Emergency Management Agency to fund the study. The final bill could reach $87 million, according to Michael McGeehin, who is leading the study.

Families moved into 140,000 FEMA trailers after Hurricane Katrina hit the Gulf Coast in August 2005. In February 2008, the CDC urged people to move out of the trailers because formaldehyde levels were high enough to cause health problems. Today only about 10,000 trailers remain occupied.

Children and the elderly are particularly vulnerable to the harmful effects of formaldehyde, which can increase the risk of cancer and asthma attacks and can cause severe skin, ear, nose, and throat irritations. The chemical is found in the glue that is used to make plywood and particleboard in most trailers.

Heidi Sinclair, a Baton Rouge-based pediatrician who treated dozens of children for symptoms related to formaldehyde exposure, said many of her patients have moved to different parts of the country.

"CDC should have started doing this a year before they wanted to start the study," said Sinclair, who got an email from the CDC in October asking her to join a panel that will help find the children. "These people are going to be impossible to track down. Most of them have pay-as-you-go cellphones and have already moved."

The CDC hopes to enroll 6,000 children and monitor their health for as long as six years.

Brad Miller (D-NC), chair of a House subcommittee that has issued several reports slamming the CDCâs handling of the formaldehyde problem, said the agencyâs approach to the childrenâs health study is "unconscionable."

"The longer it takes to launch this study, the more difficult it will be to locate participants, characterize their exposures accurately, and identify life-changes since leaving the trailers that might influence health outcomes down the road," Miller said in a statement to ProPublica. "We owe those children, whose health may have been compromised due to the public housing provided them, a better effort than this."

The CDC began talking about doing a childrenâs study more than a year ago. It highlighted the study last month in its response to a report by Millerâs subcommittee and a story by ProPublica, blaming the CDC for producing a flawed study that FEMA used to suppress public concerns about formaldehyde. But the news release gave few details and did not mention a start date.

McGeehin hopes to get enough money from FEMA by the end of the year to allow contractors to begin bidding on the project. Heâd like to award the contract in the spring.

"Itâs a long process to get this going unfortunately, but it needs to be done," he said. "One concern we have is tracking people who were in the area and where they live now, but there are methods to do that and we will do the best we can."

David Williamson, the CDC official in charge of developing a registry of the trailer occupants, said FEMA has their names and their pre-Katrina addresses, but has no information about where they live now. He said the CDCasked FEMA for its data in June, but he doesnât know when it will be delivered.

"There is a set of procedures to keep peopleâs information confidential and secure, and we are going through that with FEMA now," Williamson said.

Lindsay Huckabee, whose five children experienced frequent nosebleeds and other respiratory problems whiletheylived in a FEMA trailer, isnât surprised by the studyâs slow pace.

"Itâs part of the way things have been going with this. Talks get started a year after you find out about a problem, and then it takes another year for the problem to be addressed," Huckabee said. "Not that I want to knock progress, but it is discouraging to see how things are going."

During her familyâs year in a FEMA trailer, Huckabee said her daughter developed asthma so severe that she was often hospitalized. The health of all her children has improved since they moved, Huckabee said, but sheâs worried they might have problems in the future. People exposed to high levels of formaldehyde can develop cancer decades later.

"Itâs frustrating not knowing what to expect," Huckabee said. "Some people say that the formaldehyde could cause problems for life. Others say my kids should be fine now that they are out of the trailer."

After the CDC settles on the studyâs scientific methodology and on a contractor to do the work, the Office of Management and Budget still has to weigh in. OMB reviews are standard for large projects, McGeehin said.

The OMB has been criticized by some in Congress for injecting politics into federal scientific studies and rulemaking. Earlier this year CDC chief Julie Gerberdingâs congressional testimony on climate change was edited by the OMB to minimize the health consequences of waterborne diseases, extreme weather events and intense heat.

The OMB also played a role in delaying EPA studies of the health risks of formaldehyde and many other contaminants, according to a report released this year by the Government Accountability Office, the investigative arm of Congress.

"The problem with that review is that there are no scientific experts at OMB that would be reviewing this," said Rick Melberth, director of regulatory policy at OMB Watch, a Washington D.C.-based nonprofit. "I think the public will be outraged to know there is a White House review of this study by non-scientists."

A CDC scientist who has had many studies reviewed by OMB said the review process is "characterized by endless review and re-review."

"Itâs like listening to fingernails on a chalkboard," said the scientist, who did not want to be quoted by name for fear of retribution. "There is just an unprecedented level of scrutiny by a range of vested interests."

ProPublica obtained a PowerPoint presentation (see last page) from a May meeting of the CDCâs Board of Scientific Counselors indicating that OMB would begin reviewing the childrenâs study in July of this year and the results would be published in January 2015. But McGeehin said he wonât send the study to OMB until the projectâs contractor is selected and has had time to review it.

Scott Needle, who was running a clinic in Bay St. Louis, Miss. when Katrina hit, has been waiting more than two years for the government to do a comprehensive childrenâs study.

Many of his patientsâ families moved into FEMA trailers after they lost their homes, and children soon began showing up at his clinic with cold and flu symptoms that never seemed to subside no matter how many times he treated them. In April 2006, when news reports began linking formaldehyde to those symptoms, he asked the Mississippi State Department of Public Health to investigate whether formaldehyde was causing the problem. He said he was told that the state didnât have the resources for such a study and that he should contact the CDC, which he did.

In July 2007 the CDC agreed to evaluate 144 children living in FEMA trailers, but the methodology didnât directly address Needleâs concerns.

The study was restricted to children who had respiratory problems before the hurricane and it focused only on how many times they had been hospitalized. Researchers found that children who lived in the trailers were hospitalized a bit more often than children who didnât, but the difference was so slight that they didnât draw any conclusions. The final report didnât mention the word formaldehyde.

Needle, who now practices medicine in Florida, has doubts about the new study, too.

"If the study had been done earlier, maybe we could have teased out some answers," he said. "Now I donât know if there would be any way to know."