Proposal for Converting “Total” Dust Limits to Inhalable and Thoracic Dust Limits

Abstract

One step in the implementation of new particle size-selective sampling definitions of inhalable, thoracic, and respirable dust that are becoming internationally accepted is the establishment of appropriate limits on the concentrations of airborne dusts. The preferable approach is to analyze toxicological and epidemiological studies that incorporate sufficient particle size information to obtain particle size-selective dust limits directly. In the absence of such information but with sufficient information about the collection efficiency of the current “total” dust sampler and about the range of workplace aerosol size distributions for the material being considered, there is a rational approach to converting current “total” dust limits to approximately equivalent inhalable or thoracic dust limits, which is described briefly. Currently, there is very little information about the collection efficiency of the “total” dust personal sampler that is used most commonly in the United States. Because of this, there is insufficient information to take even the second approach outlined above. However, recommendations can be developed for converting current “total” dust limits to tentative inhalable or thoracic dust limits using guidelines presented here. Side-by-side sampling comparisons are strongly recommended to discover discrepancies. To illustrate this approach, formulas are proposed for converting current “total” dust limits established in the United States to tentative inhalable or thoracic dust limits (inhalable particulate matter [IPM]- and thoracic particulate matter [TPM] - threshold limit values [TLVs]), whichever is appropriate for the material under consideration: