In the aftermath of Hurricane Katrina, FEMA provided travel trailers, park models and mobile homes to Gulf Coast residents who had lost their homes in the hurricane. CDC has been working with FEMA and other agencies to investigate the levels of formaldehyde in the trailers and mobile homes.

“These two studies provide much helpful information,” said Michael McGeehin, director of the Division of Environmental Health Hazards at CDC. “But the findings are only applicable to those trailers distributed by FEMA in the Gulf Coast Region; they do not apply to other trailers in use elsewhere in the country. However, taken together, the two studies indicate that manufacturers of travel trailers and the government agencies that influence their design, should consider using construction materials that emit lower levels of formaldehyde as well as designs that increase outside air ventilation.”

McGeehin noted that, as CDC previously recommended, families that include children, the elderly, and those with chronic diseases such as asthma should make relocating to permanent housing a priority.

The results of both studies are available at http://www.cdc.gov/nceh/ehhe/trailerstudy/.

Assessment of Unoccupied Travel Trailer Building Materials and Components (newly released study)

In an effort to identify and better understand factors that could foster high levels of formaldehyde and other volatile organic compounds, CDC had the Lawrence Berkeley National Laboratory (LBNL) measure air formaldehyde concentrations in whole trailers and emissions from specific parts of each trailer, such as walls, floors, ceilings, tables and cabinets. Four vacant, never-used trailers were provided by FEMA, including two trailers that were specifically designed to be used as temporary emergency housing and thus not commercially available.

“Even with a limited sample of trailers, this study affirms what would be expected, that construction materials that emit high concentrations of formaldehyde, when part of a relatively small structure that has poor ventilation, have the potential to produce elevated levels of formaldehyde in the indoor air,” McGeehin, said. “This suggests that efforts to design and build emergency housing units may be able to greatly improve indoor air quality by using different construction materials and ensuring that ventilation systems let in fresh air.”

Formaldehyde emissions from the four whole trailers studied ranged 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. Median formaldehyde emissions in previously studied, newer (six months or less) site-built and manufactured homes were 31 and 45 micrograms per meter per hour, respectively. Researchers also found phenol, and TMPD-DIB ¹ (which is used to make plastic) at levels higher in the trailers than commonly found in site-built or manufactured homes. Though elevated, neither phenol nor TMPD-DIB levels were found at high enough levels to pose health hazards.

McGeehin stressed that the CDC study, because it only examined four travel trailers, did not provide results that could be applied to all FEMA-supplied travel trailers or to other types of temporary housing, such as park models or mobile homes. He noted the FEMA-supplied trailers were different from other types of housing because they contain extensive wood surface areas packed into relatively small spaces, and often let in less fresh air than site-built or manufactured houses.

“This detailed analysis does help us identify the sources of formaldehyde and other volatile organic compounds that may make the largest contributions to poor indoor air quality,” McGeehin said. “It also indicates that, even though individual construction materials can meet standards that are generally accepted by the construction industry and others, the amount of space and the amount of ventilation also affect the concentrations found in the air.”

After taking whole-trailer measurements at FEMA′s Purvis, Miss., storage yard, CDc and LBNL staff took each trailer apart - then collected, packaged and shipped the parts to their California laboratory. Laboratory staff tested the individual parts in small chambers to determine the type and extent of formaldehyde and 32 other volatile organic compounds each part emitted. Only formaldehyde, phenol and TMPD-DIB1 were found at higher levels in the trailers than commonly found in site-built or manufactured homes. Though elevated, neither phenol nor TMPD-DIB ¹ levels were found at high enough levels to pose health hazards.

Assessment of Indoor Formaldehyde Levels in Occupied Travel Trailer (previously released study)

As reported in February 2008, in many of the travel trailers, mobile homes, and park models tested, formaldehyde levels were elevated relative to typical levels of U.S. indoor exposure. Formaldehyde levels varied by model, but all types of trailers tested had high levels. The average level of formaldehyde in all units was about 77 parts per billion (ppb.) Levels measured from 3 ppb to 590. It was determined that health could be affected at the levels seen in many of the trailers.

Indoor temperature was a significant factor for formaldehyde levels in this study, independent of trailer make or model; other factors such as humidity, temperature, the presence of more than one square foot of mold, and poor ventilation also were associated with formaldehyde. Nearly one in five residents reported mold in their trailers. Higher indoor air temperature and relative humidity were also associated with an increase in formaldehyde levels, regardless of the type or brand of trailer.

These conclusions affirmed CDC′s previous recommendation that Gulf Coast families still living in travel trailers and mobile homes spend as much time outdoors in fresh air as possible. Residents should open windows to let fresh air in whenever possible, and try to maintain the temperature inside the travel trailers or mobile homes at the lowest comfort level. Higher temperatures can cause greater release of formaldehyde. Persons who have health concerns are encouraged to see a doctor or another medical professional.

¹ 2,2,4-Trimethyl-1,3-pentanediol diisobutyrate

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DEPARTMENT OF HEALTH AND HUMAN SERVICES