Quantification and Statistical Modeling—Part I: Breathing-Zone Concentrations of Monomeric and Polymeric 1,6-Hexamethylene Diisocyanate

Abstract

We conducted a repeated exposure-assessment survey for task-based breathing-zone concentrations (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 = 98 paint tasks) and two-stage (N = 198 paint tasks) filter sampling was used to measure concentrations of HDI, uretidone, biuret, and isocyanurate. The geometric mean (GM) level of isocyanurate (1410 microg m(-3)) was higher than all other analytes (i.e. GM < 7.85 microg m(-3)). 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 sampling (N = 16 paint tasks). According to paired t-tests, significantly higher concentrations of HDI (P = 0.0363) and isocyanurate (P = 0.0035) were measured using one-stage samplers. Marginal R(2) 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 isocyanurate, respectively. Mixed models developed in this study characterize the processes governing individual polyisocyanate BZCs. In addition, the mixed models identify ways to reduce polyisocyanate BZCs and, hence, protect painters from potential adverse health effects.

Airborne Isocyanate Exposures in the Collision Repair Industry and a Comparison to Occupational Exposure Limits

“…While all seven of the semi-downdraft booths in this study met an average of 100 LFM exhaust velocity, only 52% of the downdraft booths and none of the four cross-draft booths met this target. The ventilation measurements presented here are discussed by co-authors in Fent et al (24) and shown to be correlated with polyisocyanate breathing zone concentrations. Increased airflow and downdraft booths (vs. cross- or semi-draft booths) were associated with reduced polyisocyanate breathing zone concentrations.…”

“…The greatest limitation to a comprehensive polyisocyanate NCO/m 3 OEL is that the differences in toxicity between the individual polyisocyanates are not accounted for. (24) While this is a significant limitation, the alternative of developing OELs for all possible individual polyisocyanates would be challenging. The need for a comprehensive polyisocyanate OEL has been suggested previously by Bello et al (23) and the results reported here demonstrate this necessity.…”

“…Painters were recruited as described previously. (24) Recruitment, sampling, and data handling procedures were approved by the Washington State Institutional Review Board (WSIRB) at the Washington State Department of Social and Health Services, and by the Institutional Review Board in the Office of Human Research Ethics at the University of North Carolina at Chapel Hill. The exposure assessments were conducted between August 2006 and February 2007.…”

Hemoglobin adducts in workers exposed to 1,6-hexamethylene diisocyanate

“…Breathing-zone and dermal exposure measurements among these occupationally exposed spray painters have been published elsewhere (Fent et al 2009a, 2009b). Briefly, a personal air sample in the worker’s breathingzone was collected during each spray painting operation of HDI-containing paint.…”

“…HDI on the skin was collected using three consecutive tape-strips (10 cm 2 ) applied to six different sites on the worker’s body (e.g., right and left forearms, hands, and neck) after each paint task. Air and skin samples were analyzed by LC-MS as previously described by Fent and colleagues (2009a, 2009b). Work diaries and questionnaires about workers’ physical characteristics (e.g., age, height, weight), PPE use (e.g., coveralls, respirator, gloves), and work environment (e.g., paint booth type, duration of paint tasks) were completed during each visit.…”