A Comparison of Worker Exposure to Inhalable and Total Dust, Inorganic Arsenic, and Borates in a Borate Mining and Processing Facility.

The Phylmar Group, Inc.

This study describes a comparison of worker exposure to total and inhalable dust, inorganic arsenic, and borates as part of a comprehensive industrial hygiene evaluation in a borate mining and processing facility. Employees were segmented into similar exposure groups (SEG) based on work location within the facility, job category and agent. At least 10 percent of the employees in each SEG for total dust (n=197), inorganic arsenic (n=140), and borates (n=194) wore two personal dust samplers simultaneously to collect total (closed face, 37-mm mixed cellulose matched-weight filters (MMW)) and inhalable (Institute of Occupational Medicine type (IOM)) particulates. IOM concentrations were consistently higher than the corresponding MMW concentrations for all three agents. Analysis of the log transformed data revealed correlation coefficient values of 0.72, 0.82 and 0.84 for total dust, inorganic arsenic, and borates, respectively. These high correlation coefficients indicate that the IOM and MMW measurements are consistent with each other, and can be used for predicting exposure levels. Further, the spread of IOM/MMW ratios can be expressed for total dust, inorganic arsenic, and borates as 5.28±8.19, 1.27±0.91, and 3.36±2.50, respectively. The relatively low spread of the inorganic arsenic results, in comparison with total dust and borates, may be because approximately 78 percent of the IOM-MMW paired samples were below the detection limit. The total dust and borate large mean ratios should be considered in developing inhalable fraction-based regulatory standards.