The U.S. Centers for Disease Control and Prevention and the Department of Homeland Security's Office of Health Affairs are to begin air quality testing in the trailers Tuesday.
"Potential buyers/recipients will be fully advised of the concerns regarding formaldehyde levels in travel trailers," FEMA spokesman Aaron Walker said Friday in an e-mail message to The Associated Press.
FEMA drew the ire of Congress last week after documents revealed that the agency's lawyers discouraged investigating reports that the trailers had high formaldehyde levels.
In May, CBS News chief investigative correspondent Armen Keteyian of the nearly 86,000 families with rising health problems still living in FEMA trailers across the Gulf.
Formaldehyde, a common preservative and embalming fluid, sometimes is found in building materials that are used in manufactured homes. The chemical can cause respiratory problems and possibly cancer in high doses or with prolonged exposure.
FEMA provided about 120,000 travel trailers to victims of 2005 hurricanes Katrina and Rita. More than 56,000 of them are still occupied in Mississippi and Louisiana, and others are being held in reserve for future disasters, Walker said.
"Before FEMA sells any more of these or gives these to people ... each trailer needs to be tested. If it comes in over the limit, it shouldn't be sold or given away until the formaldehyde is remediated," said Becky Gillette of the Mississippi chapter of the Sierra Club.
Walker said FEMA has disposed of 18,562 travel trailers "through authorized disposal methods." The General Services Administration handles the sale or donation of the trailers.