Comparison of Total Dust/Inhalable Dust Sampling Methods for the Evaluation of Airborne Wood Dust

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Abstract
This article describes a comparison of sampling results from air monitoring conducted using total dust and inhalable dust sampling methodologies for the evaluation of wood dust exposures in a carpenter shop. While it is recognized that the total dust sampling method underestimates the true total inhalable aerosol, and it is desirable to select a sampling method for wood dust that accurately measures inhalable particulate, the results presented in this article indicate that the currently available inhalable dust sampling method may not be reliable for the evaluation of wood dust exposures, particularly at low concentrations. Traditional personal total dust sampling was performed in accordance with National Institute for Occupational Safety and Health Method 0500, and side-by-side comparison sampling was performed with SKC[rgrave] brand inhalable particulate mass (IPM) samplers in accordance with American Conference of Governmental Industrial Hygienists criteria. A total of 25 sample pairs (17 personal, and 8 area) were collected utilizing both the total dust and IPM sampling methodologies. The results from this study, and data from two unpublished poster presentations, indicate that the IPM/total dust ratio for wood dust is generally in the range of 2 to 4 at relatively high wood dust concentrations (>0.5 mg/m3). However, when total dust concentrations were below 0.5 mg/m3, the corresponding inhalable ratio for personal samples was erratic (range of 2.1 to 71). Using only IPM sampling data in this concentration range could be misleading and may lead to substantial and unnecessary costs to control wood dust. Unpublished sampling data from industry wood dust monitoring have also shown similar results. Particulates larger than 100 μm in diameter were projected into the IPM sampler, causing an overestimate of the amount of wood dust particulate that was actually inhalable. The IPM method needs further research and development before it can be accurately applied in field industrial hygiene evaluations for wood dust, particularly at low concentrations.