Air-quality testing is planned to begin next Friday on government-issued trailers housing hurricane victims in Louisiana and Mississippi, federal officials said Thursday.

About 500 occupied trailers and mobile homes will be tested for formaldehyde levels under the plan announced by the Federal Emergency Management Agency and the U.S. Centers for Disease Control and Prevention.

Formaldehyde is a common preservative and embalming fluid found in building materials for manufactured homes. It can cause respiratory problems and has been classified as a carcinogen by the International Agency for Research on Cancer. Many trailer occupants are blaming ailments on formaldehyde.

Testing is expected to take about five weeks, with a summary of findings to follow the testing and data analysis. Officials hope to release a final report of those findings next year.

Henry Falk, director of the CDC Coordinating Center for Environmental Health and Injury Prevention, said Thursday that there are no existing standards for gauging air quality in trailers and “no sharp, direct way” of predicting the health impact of formaldehyde.

“Some people will react at higher levels. Some people might react to formaldehyde at lower levels,” he told reporters in New Orleans.

There are an estimated 46,700 households still in travel trailers or mobile homes along the Gulf Coast, more than two years after hurricanes Katrina and Rita damaged or destroyed tens of thousands of homes.