One of the green terms we touched on briefly (Define Your Terms - What is Green, September 19) is off-gassing, a major contributor to indoor air pollution.  To restate the definition, off-gassing is the release of chemicals into the air from non-metallic materials.  Paints, stains, building materials, even fabrics are capable of releasing volatile organic compounds (VOCs) and there is a long list of these chemicals although some are, as far as we know, harmless.

One of the substances that is found in virtually every home and that we know is far from harmless is urea-formaldehyde (UF.)  Anyone who has ever taken a biology class knows how vile the odor from formaldehyde is, but even in amounts that cannot be detected by the human nose it can cause a wide range of health problems such as watery or burning eyes, burning sensations in the throat, fatigue, eczema, wheezing and coughing.  It can increase the incidence of asthma attacks and may cause cancer in humans.  The Occupational Safety and Health Administration (OSHA) reports studies linking formaldehyde exposure to nasopharyngeal cancer although at higher levels than would usually be found in a home. 

Air levels in excess of 0.1 parts per million are considered to be elevated.  Most older homes, except perhaps those that are treated with Urea-formaldehyde foam insulation (more about UFFI later) come in below the 0.1 ppm level, however, newer homes with significant amounts of pressed word products may test over 0.3 ppm.

It is the glue used to produce these pressed wood products such as hardwood plywood wall paneling, particleboard, fiberboard, and furniture and cabinetry made with pressed wood products that contribute the greatest level of off-gassed formaldehyde, but paint (where UF is used as a preservative,) permanent pressed fabrics (UF gives them their no-iron properties) smoking, and improperly vented fuel burning heaters and appliances also contribute to formaldehyde levels.

Older homes may contain UFFI which was widely used in the 1970s in new construction and in retrofitting existing homes during the energy crises of that decade.  UFFI could be sprayed into interior wall cavities through small holes and it would expand to fill the void.  The types of medical reactions listed above made it unpopular, some states outlawed its use and banks sometimes refused to write mortgages on homes containing UFFI.   Off-gassing from the foam diminishes over time and 30 years later probably contributes only a tiny amount to elevated formaldehyde levels.

Off-gassing from all UF-containing products decreases over time, but according to the Environmental Protection Agency, when the products are new high ambient temperatures and humidity levels can cause these emissions to increase.

The cure for high levels of UF is basically the same as for other VOCs - increased ventilation and control of humidity - but by far the best way to prevent problems is to eliminate formaldehyde from the home.

  • Some types of pressed wood products such as oriented strand board and softwood plywood are made using phenol-formaldehyde (PF) which usually emits formaldehyde at a much lower rate than UF. While these products are produced for exterior use and tend to be more expensive than products intended for interior applications, there is nothing to preclude their use in the home.
  • Ask about the UF content of products such as building materials, cabinetry, furniture, and draperies at the point of purchase. If the sales person cannot provide adequate information ask for a phone number or website for the manufacturer and inquire of it directly.
  • According to the EPA, there is some indication that coating wood products with polyurethane may seal in formaldehyde fumes. The finish must cover all of the wood including the edges and remain intact. Be sure that the coating does not also contain high levels of formaldehyde.

For more information on formaldehyde, you can call the EPA Toxic Substance Control Act Assistance Line (202)554-1404 or get the Occupational Safety and Health Administration's fact sheet on the subject at