Federal health experts will initiate air testing next week on several hundred trailers offered to people displaced by Hurricane Katrina in 2005 after complaints were made of health problems attributed to exposure to formaldehyde.

U. S. health officials said Thursday that approximately 500 of the nearly 46,000 trailers and mobile homes provided by the government to people in Louisiana and Mississippi who lost their homes in the aftermath of Hurricane Katrina will be tested for formaldehyde.

The U. S. Centers for Disease Control and Prevention will begin to test indoor air-quality on Dec. 21 and testing is expected to last five weeks.

The CDC was requested to conduct the analysis by the U.S. Federal Emergency Management Agency. Jim Stark, director of the FEMA Transitional Recovery Office of New Orleans, said approximately 3,700 people had expressed fears that the health problems they have been experiencing are due to exposure to formaldehyde in their trailers.

These people have been offered housing alternatives. “In most cases, this will mean a trip to a motel or a hotel until appropriate rental units can be found,” Stark said.

Air quality tests were supposed to be performed last month but were postponed. Questions over possible dangerous levels of formaldehyde had appeared as long as a year ago. Results of the upcoming testing should be disclosed by mid-February, officials said.

Formaldehyde is a common preservative and embalming fluid, and a chemical used in the manufacture of the trailers. It can cause respiratory problems such as bronchitis and is known to cause cancer; formaldehyde has been classified as a carcinogen by the International Agency for Research on Cancer.

Tens of thousands of people were displaced by Hurricanes Katrina and Rita and were provided with temporary housing by the government. Nearly 48,000 households continue to live in the trailers and mobile homes.

Henry Falk, director of the CDC's Coordinating Center for Environmental Health and Injury Prevention, said standards do not exist at the moment indicating air quality in trailers.

The federal government does not have a “single, safe, line-in-the-sand level of formaldehyde level exposure that is acceptable,” Howard Frumkin, director of the CDC's National Center for Environmental Health, said.

Questionnaires will be handed to residents of trailers exploring how the trailers are used. Officials will also be looking for other possible reasons for the health problems, such as heavy mold.

In November, the FEMA suspended the sale of its used trailers to residents and said that these constructions would no longer be used in the case of future disasters.