Paul and Melody Stewart have a similar story to tell about their health problems, which began shortly after moving into a FEMA trailer at the site of their storm-ravaged house. "When we got here, it smelled bad," says Paul, a former Waveland, Mississippi, policeman. Melody woke up the first night they stayed in the trailer, gasping for air. "Within a week," he says, "we both had nosebleeds."

One morning the Stewarts found their cherished pet cockatiel lethargic and unable to stand. They rushed the bird to the vet, who said the cockatiel would die if he were kept in the trailer. Stewart began doing research and discovered that the wood products used to make cabinets, walls and other interior parts could emit formaldehyde, especially in hot, humid climates.

He bought a testing kit for airborne contaminants and sent it back for analysis. In winter, with windows open and the air conditioner on, the test showed, the formaldehyde level in the Stewarts' trailer was more than two times the EPA's limit. Still, FEMA refused to replace the trailer until a story about the Stewarts' formaldehyde problems ran on the local television news. FEMA called the next day to say they were bringing a new trailer.

When the new trailer arrived, the couple could smell formaldehyde before they opened the door. Another was delivered with mold covering the walls. The Stewarts lived in their truck until they took what remained of their insurance settlement and their retirement savings to buy a new trailer at a dealer's lot. This one was made with low-formaldehyde-emitting materials. Their respiratory problems are gone, but plans to rebuild their home are on hold.

Hilda Nelson, 75, of Coden, Alabama, was not as lucky as the Stewarts. When she moved into a FEMA trailer at the site of her former house, she was in good health, says her son, Paul. Three weeks later, he says, "she was having trouble breathing." Not long after, she was diagnosed with pneumonia, then congestive heart failure, a chronic illness that can cause breathing difficulties.

In June 2006 Paul Nelson ordered a kit to test his mother's trailer for formaldehyde. The results showed the level of the chemical inside her trailer was 50 percent over the EPA's recommended limit.

Scientists familiar with toxics agree that elderly people, like infants, are highly susceptible to the hazards of formaldehyde, particularly if they have underlying illnesses. "We started testing in Alabama," explains Becky Gillette, co-chair of the Mississippi Sierra Club, "because we got reports from social workers there that so many elderly people living in the trailers were being hospitalized for respiratory conditions. And many of them were dying."

In October 2006, at the age of 76, Hilda Nelson died, one year and one month after moving into her FEMA trailer. Doctors "never had an answer" as to why her health deteriorated so quickly, says her son. "But I have my suspicions. I point the finger at the formaldehyde."