High level of formaldehyde have been detected in trailers and mobile home occupied by victims of Hurricane Katrina, says a report by the U.S. Centers for Disease Control and Prevention (CDC). Formaldehyde, a preservative commonly used in construction materials, is carcinogenic and can cause breathing problems.

The trailers were provided by the Federal Emergency Management Agency (FEMA) to hurricane victims in 2005. The agency no longer provides them, but the mobile homes are still in use.

The Lawrence Berkeley National Laboratory in California was tasked by CDC to measure formaldehyde concentrations in trailers and emissions from specific parts of each trailer, such as walls, floors, ceilings, tables and cabinets of four vacant, never-used trailers provided by FEMA. The four trailers emitted formaldehyde fumes ranging from 173 to 266 micrograms per meter per hour in the morning to 257 to 347 micrograms per meter per hour in the afternoon due to increasing temperatures.

CDC has recommended that FEMA use different building materials to produce emergency housing.

Processed wood products such as particleboard and plywood have been detected as the main source of formaldehyde, which can irritate the skin, eyes, nose and throat. High exposure levels may cause cancer.

Nearly 15,000 people displaced by hurricanes Katrina and Rita along the U.S. Gulf Coast in 2005 are still living in such trailers, FEMA said.