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.

In-depth survey report: spray polyurethane foam chemical exposures during spray application, All About Kids, Crestwood, KY.

“…A correlation coefficient value of 0.83 was determined, meaning there is a correlation between the two sampling methods. Similar findings were seen by Schaeffer et al [12] . The mean percent difference between the impinger results and the filter results is 54% indicating that the impingers collection efficiency is 54% higher than that for the filters.…”

In-depth survey report: spray polyurethane foam chemical exposures during spray application, Priority 1, Cincinnati, Ohio.

“…Impinger samples have better collection efficiencies than the glass fiber filters because they prevent loss of isocyanates to curing reactions by trapping, dissolving, and derivatizing the isocyanate aerosol. [14] Listed in Table 4 are the results of the impinger samples. 3 .…”

Isocyanates and work‐related asthma: Findings from California, Massachusetts, Michigan, and New Jersey, 1993–2008

“…Isocyanate use may be intermittent (e.g., spill cleanup), product‐specific, related to infrequent maintenance, or exposure may be indirect [Petsonk et al, ; Reeb‐Whitaker et al, ]. In addition, accurate air sampling for isocyanates is difficult, imprecise, and dependent on whether isocyanates are in gas or aerosol form, the size of the particles, the extraction and laboratory analysis methods used and the effectiveness in capturing monomers and polymers [Streicher et al, ; Bello et al, ; Lesage et al, ; Henneken et al, ; Booth et al, ; Thomasen et al, ; Reeb‐Whitaker et al, ; Schaeffer et al, ; Lockey et al, ]. For example, Thomasen et al [] found differential capture of monomer and polymer of HDI and variation depending on whether autobody paint was fast‐drying or slow‐drying; Lesage et al [] found that filter sampling method results were up to 40% lower than results from impinger methods.…”