Officials with the Federal Emergency Management Agency say they’re "confident" about the safety of temporary housing units sent to Iowa flood and tornado victims. The response follows a report by Cedar Rapids TV station KGAN, claiming tests it had conducted of 20 FEMA mobile homes contained formaldehyde levels above the state’s standard of .04 parts-per-million.

David Garrett, with FEMA, says only trailers that tested below that state standard were sent to Iowa this summer. "That testing was done by an independent industrial hygiene company and FEMA stands behind those tests," Garrett said in a conference call with reporters Tuesday. "We believe that those tests are the most rigorous and accurate tests of formaldehyde over time in a mobile home or a park model."

Garrett says FEMA tests the units before they are occupied, so the formaldehyde levels can rise depending on what people bring into the home. "The occupants can introduce any number of variables into these units," Garrett said. "Activities such as cooking, smoking or the introduction of various forms of household products can all elevate formaldehyde in a mobile home."

There are more than 560 Iowa families living in temporary housing provided by FEMA. Garrett says he does not feel it’s necessary to re-test the formaldehyde levels in any of those units. "There are probably very few units anywhere in the United States that have been scrutinized, tested, and validated more than the units that FEMA is providing to disaster victims across this country," Garrett said.

The formaldehyde issue first surfaced in 2006, when Gulf Coast residents displaced by Hurricanes Katrina and Rita complained of breathing difficulties, nosebleeds, and headaches after living in the FEMA trailers. Tests conducted by the CDC later confirmed potentially hazardous levels of formaldehyde in many of those trailers.