A Comparison of Two Sampling Methods for the Detection of Airborne Methylene Bisphenyl Diisocyanate

Abstract

The purpose of this study was to determine if there was a significant difference between two readily available sampling methodologies for airborne methylene bisphenyl diisocyanate (MDI), which is an essential precursor in the spray-on truck bed lining industry. Seventy-two personal airborne samples of MDI were collected and analyzed from nine spray-on truck bed liner businesses in northern Colorado. Wide ranges of exposure concentrations were encountered during the spray-on application, including concentrations that exceeded the OSHA permissible exposure limit. The highest airborne MDI concentration measured was 690 ppb. A statistically significant difference between field-desorbed and laboratory-desorbed methods was determined. The field-desorbed sampling methodology yielded consistently higher MDI concentrations than the laboratory-desorbed sampling methodology, which suggests that immediate desorption minimizes isocyanate loss and potential underestimations. Results from the analysis of variance also indicated that different facility factors and environmental conditions within each company, such as the use of ventilation or humidity level, affected the MDI concentrations, indicating the potential for better mitigation of exposures using the hierarchy of controls.

Keywords:

• field desorbed
• laboratory desorbed
• MDI
• spray-on truck bed liner

ACKNOWLEDGMENTS

The investigative team would like to acknowledge the CSU Occupational Safety and Health Consultation Program for providing the sampling equipment for this project. The authors are indebted to the WOHL for providing the sample analyses, and to Jim Zumbrunnen, faculty consultant at the CSU Franklin A. Graybill Statistical Laboratory, for consulting and advising on data analysis and interpretation of results. The investigative team is also thankful to Patty Jeffries with the CSU OSHA Consultation Program for providing information about northern Colorado STBL businesses.