( CNN ) -- Rep. Nick Lampson , D-Texas , said Tuesday that Federal Emergency Management Agency tried to control the outcome of a scientific study on formaldehyde in trailers used to house victims of Hurricane Katrina . FEMA trailers are shipped to the Gulf Coast by train in March 2006 . `` Someone from one of the agencies , the CDC , came to our committee and reported that he had information that indicated that good science was n't followed when a decision was made to allow people to live in basically travel trailers that were not designed to be lived in , '' said Lampson , chairman of the Energy and Environment Subcommittee of the House Committee on Science and Technology . In addition , the chairman of the House Homeland Security Committee -- Rep. Bennie G. Thompson , D-Mississippi -- cited medical experts who said prolonged exposure to high levels of formaldehyde can cause ailments ranging from respiratory irritation to cancer . The committee recently obtained internal CDC e-mail which showed that `` despite the efforts of CDC professionals to bring these health risks to the public 's attention , those concerns were thwarted by CDC leadership for roughly eight months , '' Thompson said . FEMA denies that it has suppressed any report , including one about formaldehyde prepared by a branch of the Centers for Disease Control . `` The health and safety of residents has been and continues to be our primary concern , '' FEMA said in a statement issued Monday . Watch why the trailers are such a big concern » . `` Any and all allegations that FEMA ignored or manipulated formaldehyde-related research are unfounded and false . Such activities are completely contrary to our mission and our commitment to the victims of disaster , '' said Carlos Castillo , FEMA 's assistant administrator for disaster assistance during the House Homeland Security Committee hearing Tuesday afternoon . Almost 150,000 households have lived in FEMA trailers at some point since Hurricanes Katrina and Rita devastated the Gulf Coast in 2005 . FEMA says about 40,000 families are still living in the travel trailers . Formaldehyde is a preservative used in construction materials like plywood . The Environmental Protection Agency classifies it as a probable human carcinogen , according to the EPA Web site . The site says the chemical can also be an irritant to the respiratory tract and the eyes . FEMA and the CDC say the Agency for Toxic Substances and Disease Registry , an arm of the CDC , did an initial assessment for FEMA that was n't intended to address the long-term effects of extended exposure to formaldehyde . `` ATSDR 's original response focused on the acute health effects of formaldehyde exposure -- to meet the urgent needs expressed by FEMA in its original request , '' said a CDC statement . `` The initial consultation with ATSDR was intended to determine effective mitigation measures , and did not discuss long-term health impacts , '' a FEMA statement agreed . `` FEMA wanted to be able to put people into these trailers for long periods of time , '' Lampson said . `` They gave a report that apparently said that it was safe to go in for a couple of weeks and allowed people to go in . Well , it 's been way past a couple of weeks and now people have been in them a year or 18 months . '' `` One person [ from the CDC ] who came to us told us they would n't write the report , '' he said . `` That person was circumvented and another person at the agency agreed to write a report to say that levels of formaldehyde were safe for a couple of weeks . '' FEMA received that initial report in February 2007 . `` That study showed that ventilating the units is effective in reducing levels of formaldehyde , '' according to a FEMA fact sheet . FEMA and the CDC said it became apparent that more study was needed , so ATSDR went back to work and issued a new report in October . `` This revised report supports the initial report in that ventilation of travel trailers was effective in lowering formaldehyde levels , '' according to the FEMA statement issued Monday . `` It was revised to include a number of caveats relating to potential health impacts of long term exposure . '' FEMA says it has offered everyone living in a travel trailer the option of moving to a hotel until alternative housing can be found . Meanwhile , the CDC has been doing a separate study of formaldehyde in the trailers . The results of that research are expected next month . FEMA pointed to that more comprehensive study in its statement issued Monday about the controversy , and added , `` In addition , FEMA already had begun an aggressive outreach campaign to occupants advising them of potential exposure to formaldehyde and offered those residents an option for immediate relocation to alternative housing , '' the FEMA statement said . Lampson said his subcommittee has requested copies of communications between FEMA and the CDC on the subject . `` Not following good science in advising people to do things as they try to recover from one tragedy is indeed a much greater tragedy this is compounding , '' he said . `` This appears perhaps to be the tip of an iceberg . '' E-mail to a friend . CNN 's Sean Callebs and Eric Marrapodi contributed to this report .
FEMA denies allegations it suppressed report on trailers used by Katrina victims . The agency has been criticized for its handling of the disaster, which killed more than 1,800 people in New Orleans and left tens of thousands homeless or without homes. FEMA , CDC say studies were short-term , more comprehensive study in the works .