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.

Keywords:

• drywall
• exposure modeling
• joint compound
• respirable dust
• sanding

ACKNOWLEDGMENTS

All authors are employees of ENVIRON International Corporation, and we acknowledge the contributions of our colleagues in the implementation of this work. Workers in Study A were performing routine work activities under direction of their employer. This research was funded by Georgia-Pacific (Atlanta, Ga.). Georgia-Pacific did not participate in the design of the study, analysis of the data, or preparation of the manuscript. We gratefully acknowledge the constructive comments from the reviewers.

[Supplementary materials are available for this article. Go to the publisher's online edition of the Journal of Occupational and Environmental Hygiene for the following free supplemental resources: a PDF containing Appendix I (Model Sensitivity) and Appendix II (Model Spreadsheet and Example) and an Excel file containing worksheets.]

Notes

^A C_R,1h-twa,PBZ is a respirable dust concentration.

^A Measured in isolation chamber testing events (see Table I for probability distributions).

^B Chosen based on exposure scenario to be modeled, and informed by literature and general knowledge.

^A f_emit = 1 indicates continuous emission.

^B W, worker.

^A f_emit = 1 indicates continuous emission.

^B W, worker.