Development and Evaluation of a Semi-Empirical Two-Zone Dust Exposure Model for a Dusty Construction Trade

Abstract

Drywall finishing is a dusty construction activity. We describe a mathematical model that predicts the time-weighted average concentration of respirable and total dusts in the personal breathing zone of the sander, and in the area surrounding joint compound sanding activities. The model represents spatial variation in dust concentrations using two-zones, and temporal variation using an exponential function. Interzone flux and the relationships between respirable and total dusts are described using empirical factors. For model evaluation, we measured dust concentrations in two field studies, including three workers from a commercial contracting crew, and one unskilled worker. Data from the field studies confirm that the model assumptions and parameterization are reasonable and thus validate the modeling approach. Predicted dust C(twa) were in concordance with measured values for the contracting crew, but under estimated measured values for the unskilled worker. Further characterization of skill-related exposure factors is indicated.

Comparative Risks of Cancer from Drywall Finishing Based on Stochastic Modeling of Cumulative Exposures to Respirable Dusts and Chrysotile Asbestos Fibers

“…Workers had dedicated tasks (bifurcated crew), and the finishing worker was a union member. Site 2 (Study A in Jones et al …”

“…Here we integrate previous work to characterize cumulative exposures to dusts and asbestos fibers resulting from the sanding of joint compound during drywall finishing. Specifically, we apply a semi‐empirical mathematical model to predict 8‐h TWA respirable dust concentrations from joint compound sanding activities . These predictions are coupled with an empirical factor that relates chrysotile asbestos fiber to respirable dust concentrations to predict 8‐h TWA asbestos fiber concentrations .…”

Exposures from Chrysotile‐Containing Joint Compound: Evaluation of New Model Relating Respirable Dust to Fiber Concentrations

“…One study has been published using the same JCN as tested in the bench‐scale chamber that provides personal breathing‐zone respirable dust mass concentrations, C M‐rd , during sanding. ( 13 ) Due to the number of data points available ( N = 5) for the tested JCN, four additional published studies ( 2,12,14‐16 ) were identified that report C M‐rd values during sanding of other modern‐day joint compounds (Table I). To apply the new procedure to respirable dust data from these five published studies, we have assumed minimal variation in the characteristics (including emission rates) of the tested JCN and other modern‐day joint compounds in the other four studies.…”

“…Because respirable dust samples used in the new procedure are also task‐ or shift‐duration TWAs, ( 2 , 12‐16 ) it would be ideal if the short‐term or peak PCM fiber concentration distributions from F79VM80 were adjusted to “shift‐TWA” equivalent values before fiber concentration estimates based on historical data were compared to those based on the new procedure. Although there are no historical studies that report both peak and shift‐TWA fiber concentrations for workers sanding joint compound, Epling et al .…”

“…( 3,4 ) In contrast, virtually all of the respirable dust measurements (used to derive fiber concentration estimates using the new procedure) were from long‐term time‐weighted average (TWA) measurements. ( 2 , 12‐16 ) Therefore, a further adjustment was made to the historical fiber concentration distributions to correct for peak versus TWA sample concentration differences. To assess the effects of collection time, the distributions of estimated and measured fiber concentrations were compared both with and without this time adjustment.…”