Annals of Occupational Hygiene Advance Access originally published online on July 27, 2009
Annals of Occupational Hygiene 2009 53(7):691-702; doi:10.1093/annhyg/mep048
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Quantification and Statistical Modeling—Part II: Dermal Concentrations of Monomeric and Polymeric 1,6-Hexamethylene Diisocyanate
1 Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
2 Department of Biostatistics and Carolina Population Center, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
3 Safety and Health Assessment and Research for Prevention Program, Washington State Department of Labor and Industries, Olympia, WA, USA
* Author to whom correspondence should be addressed. Tel: +1-919-966-3826; fax: +1-919-966-7911; e-mail: leena_french{at}unc.edu
We conducted a quantitative dermal and inhalation exposure assessment of monomeric and polymeric 1,6-hexamethylene diisocyanates (HDI) in 47 automotive spray painters from North Carolina and Washington State. We report here the use of linear mixed modeling (LMM) to identify the primary determinants of dermal exposure. Dermal concentrations of HDI, uretidone, biuret, and isocyanurate were significantly higher in 15 painters who did not wear coveralls or gloves (N = 51 paint tasks) than in 32 painters who did wear coveralls and gloves (N = 192 paint tasks) during spray painting. Regardless of whether protective clothing was worn, isocyanurate was the predominant species measured in the skin [geometric mean (GM) = 33.8 ng mm–3], with a 95% detection rate. Other polyisocyanates (GM 
0.17 ng mm–3) were detected in skin during <23% of the paint tasks. According to marginal R2 statistics, mixed models generated in this study described no <36% of the variability in dermal concentrations of the different polyisocyanates measured in painters who did not wear protective clothing. These models also described 55% of the variability in dermal concentrations of isocyanurate measured in all painters (N = 288 paint tasks). The product of analyte-specific breathing-zone concentration (BZC) and paint time was the most significant variable in all the models. Through LMM, a better understanding of the exposure pathways governing individual polyisocyanate exposures may be achieved. In particular, we were able to establish a link between BZC and dermal concentration, which may be useful for exposure reconstruction and quantitatively characterizing the protective effect of coveralls and gloves. This information can be used to reduce dermal exposures and better protect automotive spray painters from potential adverse health effects.
Keywords: dermal exposure • exposure determinants • hexamethylene diisocyanate • isocyanate • statistical modeling
Received April 11, 2008; in final form April 26, 2009