The process of installing the foam involved taking liquid monomer and reacting it so that it becomes a solid. This process is called polymerization. In the process of polymerization, some formaldehyde is released into the atmosphere. As the foam is setting up, smaller amounts of formaldehyde may be released to the air. However, there is a finite amount of formaldehyde that is available for off-gassing, so over time, the formaldehyde being emitted decreases steadily. Studies have shown that within two years of application, with an air exchange rate of 0.3 (i.e. in one hour, 30% of the air in the attic space has been replaced by outside air), half of the available formaldehyde has been released. Since it has been nearly 20 years since the insulation was installed, it is entirely probable that little or no available formaldehyde remains in the insulation.
Urea-formaldehyde insulation is not the only source of formaldehyde in the home. Many products use formaldehyde during the manufacturing process. Formaldehyde consistently ranks among the top 50 manufacturing chemicals by volume. It is a common ingredient in many household furnishings and consumer products. In household furnishings, it is a component of carpeting, particle board, vinyl products, and foam used in furniture and construction; in consumer products, it is used as a preservative in cosmetics, in room deodorants, disinfectants and fumigants, and numerous medicinal applications such as athlete's foot treatment, mouthwash, spermatocide cream, skin disinfectants, and cough drops. It is also a component in cigarette smoke; it is used as a disinfectant in mattresses; and as a component of "permanent press" fabric finishes. Finally, formaldehyde is synthesized within the human body as a natural metabolite of methanol. Because this is so, the human body has built in mechanism to metabolize formaldehyde. This metabolic pathway must be overwhelmed before adverse affects are observed. Because each person reacts differently, it is hard to say at exactly what level of exposure adverse affects begin to occur.
Adverse health affects associated with formaldehyde, particularly in occupational settings, include irritation of the eyes, nose, and throat. It can cause bronchial spasm and pulmonary irritation, particularly in sensitive individuals (e.g. asthmatics). Occasionally individuals may have acute severe reaction to formaldehyde, but rarely it is life threatening. Since the most severe acute symptoms of formaldehyde exposure is associated with inhaling it, individuals with compromised respiratory systems may wish to limit their exposure to products from which formaldehyde may off-gas (for example, an asthmatic may avoid ironing permanent press fabrics as the heating action of the iron may liberate formaldehyde from the permanent press fabric finish).
Because there are so many sources of formaldehyde emissions in the home, the presence of urea-formaldehyde foam insulation 20 years after installation should not significantly affect the overall quality of the home. In fact, the alternative, fiberglass insulation, may have health risks of its own.
