Comparison of health of occupants and characteristics of houses among control homes and homes insulated with urea formaldehyde foam. III. Health and house variables following remedial work.

This report describes the second survey of a group of 762 control and urea formaldehyde foam insulated (UFFI) houses performed following an interval of 1 year, after about two-thirds of the UFFI households either had their UFFI removed or performed other UFFI-related remedial work. The UFFI subjects who lived in remedial houses showed a decline in indicators of impaired health status, to roughly equalize with those whose houses were not altered; they continued to show a small excess of adverse health indicators relative to the controls, but at a somewhat lower level than seen in the first survey. This improvement was not associated with changes in indoor levels of formaldehyde. Weak exposure-response relationships were observed between formaldehyde and upper and lower respiratory symptoms, but mainly in the combined UFFI and control populations; these are interpreted as representing the contribution of background levels of formaldehyde to the prevalence of respiratory complaints in the general population. The principal findings of this study were primarily based on subjective variables, but most could be directly validated by objective measurements in the UFFI and control subjects. The support for a causal relationship between impaired health and living in a UFFI house is considered to be moderately strong. However the demonstrated adverse effects are generally minor in nature.