Airborne Methylene Diphenyl Diisocyanate (MDI) Concentrations Associated with the Application of Polyurethane Spray Foam in Residential Construction

Abstract

The primary objectives of this study were (a) to measure potential exposures of applicators and assistants to airborne methylene diphenyl diisocyanate (MDI), (b) to measure airborne concentrations of MDI at various distances from the spray foam application, and (c) to measure airborne MDI concentrations as a function of time elapsed since application. Other study objectives were, (a) to compare the results from filter and impinger samples; (b) to determine the particle size distribution in the spray foam aerosol; (c) to determine potential exposures to dichlorofluoroethane; and (d) to measure any off-gassing of MDI after the foam had fully cured. This study was conducted during application of spray polyurethane foam inside five single-family homes under construction in the United States and Canada.

Spray foam applicators and assistants may be exposed to airborne MDI concentrations above the OSHA permissible exposure limit. At these concentrations, OSHA recommends appropriate respiratory protection during spray foam application to prevent airborne MDI exposures above established limits and to protect against exposure to dichlorofluoroethane (HCFC-141b). Airborne MDI concentrations decrease rapidly after foam application ceases. The highest airborne concentrations measured after 15 min and 45 min were 0.019 mg/m³ and 0.003 mg/m³, respectively. After 45 min, airborne concentrations were below the limit of quantitation (LOQ) of 0.036-μ g per sample. For samples taken 24 hours after completion of foaming, results were also below the LOQ. Approximately two-thirds of the total mass of the airborne particles in the spray foam aerosol was greater than 3.5 microns in diameter. Airborne MDI concentrations determined by filter sampling methods were 6% to 40% lower than those determined by impinger methods.

Keywords:

• dichlorofluoroethane
• HCFC-141b
• methylene bisphenyl isocyanate
• methylenediphenyl diisocyanate
• polymeric MDI
• polyurethane spray foam

ACKNOWLEDGMENTS

The authors would like to thank the Alliance for the Polyurethanes Industry (API, part of the American Chemistry council) for funding the study, and the Canadian Urethane Foam Contractors Association (CUFCA) and the Spray Polyurethane Foam Alliance (SPFA) for finding contractors to participate in the surveys and for educating their members on its importance.

The authors also would like to thank Karroll Booth (consultant to Bayer MaterialScience), Barbara Cummings (Bayer MaterialScience), and Lucille Richard (IRSST) for their assistance in conducting the surveys.

The authors express their appreciation to Cambria Glass and Insulation Inc. and Isolation Rolland Belisle Inc. and their employees for their participation in the surveys.

Notes

*indicates pump failed.

^A Foam applicator.

^B Spray foam assistant.