Rationale: Rising energy costs have prompted increased use of the known asthmogen methylene diphenyl diisocyanate (MDI), the cross-linking agent for generating sprayable polyurethane foam insulation. Sprayed polyurethane foam insulation is often considered "green" construction and labeled "environmentally-friendly"; however the health hazards associated with occupational exposure remain unclear. We performed a cross-sectional study to evaluate MDI exposure and its possible health effects among construction workers who spray polyurethane foam insulation. Methods: One hundred three workers were recruited from small construction companies that apply polyurethane products, including sprayable polyurethane foam insulation. Spirometry, questionnaire, air monitoring, and surface SWYPE tests were used to assess respiratory physiology, symptoms, and potential for MDI exposure. Serum levels of MDI-specific IgG and IgE were determined by ELISA. Results: Among the total study population, work-related asthma symptoms were reported by N=24 (23%) workers and MDI-specific immune responses (IgG) were observed in N=35 (35%) workers. Among those workers that regularly applied MDI-based polyurethane foam insulation, a significantly higher proportion of workers reported work-related asthma symptoms (N=11, 41%) and/or developed anti-MDI IgG responses (N=20, 77%). MDI-specific IgG serum levels were significantly (p < 0.05) associated with MDI usage, based on questionnaire data, which, in turn, was associated with significantly (p < 0.05) increased frequency of work-related respiratory (asthma), eye (irritation) and skin (rash) symptoms. Five of seven (71%) subjects with MDI-specific serum IgE were diagnosed with probable MDI asthma, based on further clinical assessment. Conclusions: Application of sprayable polyurethane foam insulation is significantly associated with MDI exposure, immune sensitization, and increased frequency of work-related asthma symptoms.
Bronchial-asthma; Respiratory-system-disorders; Pulmonary-system-disorders; Lung-disorders; Isocyanates; Immune-reaction; Immune-system; Insulation-materials; Insulation-workers; Sprays; Polyurethane-foams; Methyl-compounds; Phenyls; Environmental-factors; Environmental-health; Construction-materials; Construction-workers; Construction-industry; Spirometry; Respiratory-function-tests; Antibody-response; Sensitization
A. V. Wisnewski, Yale University, New Haven, CT