A new federal study says cheap materials and poor oversight exposed thousands of evacuees to toxic levels of formaldehyde in government-issued trailers following Hurricane Katrina. Researchers found toxic levels at between four to eleven times higher than those in average US homes. At least one death has been linked to toxic exposure in the Katrina evacuee trailers. More than 11,000 health complaints were filed over the trailers, leading government officials to move more than 4,000 families.