Comparison of health of occupants and characteristics of houses among control homes and homes insulated with urea formaldehyde foam. I. Methodology.

The methodology of a study in which a comparison is made of the health and house characteristics of the occupants of 231 control homes and 571 houses containing urea formaldehyde foam insulation (UFFI) is described. All homes and occupants were examined on two occasions separated by an interval of 12 months, during which two-thirds of the UFFI houses performed remedial work. The occupants were examined using a health questionnaire and a series of objective tests including pulmonary function, nasal airway resistance, sense of smell, nasal surface cytology, and patch tests. The houses were assessed using a questionnaire and measurements of indoor formaldehyde and carbon dioxide levels. No obvious bias has been identified in this survey with respect to the representativeness of the population studied, the classification of the UFFI and control groups, and the input from both the respondents and observers. The symptom responses made by individuals within the same households were not correlated. Quality control assessment of the objective health tests and formaldehyde sampling and assays demonstrated that these procedures remained stable over the two phases of the study, with the exception of the expected decrease in the pulmonary flow rates over 1 year and a small unexpected increase in the forced vital capacity and the forced expiratory volume in 1 s.