on behalf of the British Occupational Hygiene Society doi:10.1093/annhyg/mep046 Quantification and Statistical Modeling—Part I: Breathing-Zone Concentrations of Monomeric and

We conducted a repeated exposure-assessment survey for task-based breathing-zone concen-trations (BZCs) of monomeric and polymeric 1,6-hexamethylene diisocyanate (HDI) during spray painting on 47 automotive spray painters from North Carolina and Washington State. We report here the use of linear mixed modeling to identify the primary determinants of the measured BZCs. Both one-stage (N 5 98 paint tasks) and two-stage (N 5 198 paint tasks) filter sampling was used to measure concentrations of HDI, uretidone, biuret, and isocyanurate. The geometric mean (GM) level of isocyanurate (1410 mg m23) was higher than all other analytes (i.e. GM < 7.85 mg m23). The mixed models were unique to each analyte and included factors such as analyte-specific paint concentration, airflow in the paint booth, and sampler type. The effect of sampler type was corroborated by side-by-side one- and two-stage personal air sam-pling (N 5 16 paint tasks). According to paired t-tests, significantly higher concentrations of HDI (P 5 0.0363) and isocyanurate (P 5 0.0035) were measured using one-stage samplers. Marginal R2 statistics were calculated for each model; significant fixed effects were able to describe 25, 52, 54, and 20 % of the variability in BZCs of HDI, uretidone, biuret, and isocya-nurate, respectively. Mixed models developed in this study characterize the processes govern