Field Comparison of Air Sampling Methods for Monomeric and Polymeric 1,6-Hexamethylene Diisocyanate

Abstract

This study was to critically compared 13 different air samplers for their ability to monitor air exposures to monomeric and polymeric 1,6-hexamethylene diisocyanate (HDI) in the automotive refinishing industry. Using both fast- and slow-drying clearcoat, we tested the following types of samplers: single- and dual-stage 37-mm polypropylene (PP) and polystyrene (PS) samplers (open- and closed-face), IOM (with plastic and stainless steel inserts), OSHA42, IsoChek, and WA-DOSH samplers. Midget impingers with frit were used as reference samplers. We observed the PP, PS, and IOM samplers to measure greater levels of HDI monomer and biuret when a fast-drying clearcoat was applied compared with a slow-drying clearcoat. When a slow-drying clearcoat was applied, the open-face PP and PS samplers measured significantly more monomeric and polymeric HDI (2-fold; p < 0.003) than the closed-face PP and PS samplers. We determined that significantly more monomeric and polymeric HDI were measured by impingers (1.3–1.9-fold) compared with single-stage PP/PS (N = 59), dual-stage PP/PS (N = 59), or IOM (N = 24) samplers. However, when stratified by cassette characteristics, the open-face single-stage PP and PS samplers performed equally to the impingers for HDI monomer when a fast-drying clearcoat was applied, and for all analytes when a slow-drying clearcoat was applied. Significantly higher HDI monomer concentrations (1.2–3.1-fold; p = 0.001) were measured with OSHA42 compared with the impinger. The IsoChek did not detect HDI monomer, and of the three samplers analyzed by laboratories other than UNC (i.e., OSHA42, IsoChek, and WA-DOSH), the WA-DOSH was in the best agreement with the impingers. The influence of clearcoat drying time on the sampler's ability to measure monomeric and polymeric HDI emphasizes the importance of the speciation of diisocyanates in chemical analysis and the careful consideration for the selection of the air sampler to be used when measuring exposures during automotive spray painting.

Keywords:

• 1
• 6-hexamethylene diisocyanate (HDI)
• air sampling
• inhalation exposure
• polyisocyanate
• sampling method

Acknowledgments

This study was supported by grants from the National Institute for Occupational Safety and Health (T42 OH008673). The authors are grateful to South Seattle Community College for their help in collecting the samples in Washington State.

Notes

^A Instrumental limit of detection: μg per filter.

^B Based on limit of quantitation (reporting limit) provided by accredited laboratory.

^A For HDI, biuret, and isocyanurate, respectively.

^A Dual-stage filters results are the sum of both filters, however bottom filter (GFF) <LOD but top filter (PTFE) >LOQ. Numbers in parentheses represent the number of GFFs <LOD.

^B Dual-stage filter results are the sum of both filters, however top filter (PTFE) <LOD but bottom filter (GFF) >LOQ. Numbers in parentheses represent the number of PTFEs <LOD.

^A Sample size (N) = 6.

^B Impingers were analyzed using a different analytical method;⁽³¹⁾ N = 3.

^C Impingers converted to NCO using Eq. 1.

^D p-value not calculated because IsoChek data <LOQ.

^E p-value calculated using LOD/√2.