Estimating factors to convert Chinese 'total dust' measurements to ACGIH respirable concentrations in metal mines and pottery industries

Historical data on the dust exposures of Chinese workers in metal mines (ir on/copper, tin, tungsten) and pottery industries are being used in an ongoi ng joint Chinese/United States epidemiological study to investigate the exp osure-response relationship for the development of silicosis, lung cancer, and other diseases. The historical data include 'total dust' concentrations determined by a Chinese method. Information about particle size distributi on and the chemical and mineralogical content of airborne particles is gene rally not available. In addition, the historical Chinese sampling strategy is different from a typical American eight-hour time-weighted average (TWA) sampling strategy, because the Chinese samples were collected for approxim ately 15 minutes during production so the sample could be compared to their maximum allowable concentration (MAC) standard. Therefore, in order to ass ess American respirable dust exposure standards in light of the Chinese exp erience, factors are needed to convert historical Chinese total dust concen trations to respirable dust concentrations. As a part of the joint study to estimate the conversion factors, airborne dust samples were collected in 2 0 metal mines and 9 pottery factories in China during 1988 and 1989 using t hree different samplers: 10 mm nylon cyclones, multi-stage 'cassette' impac tors, and the traditional Chinese total dust samplers. More than 100 sample s were collected and analysed for each of the three samplers. The study yie lded two different estimates of the conversion factor from the Chinese tota l dust concentrations (measured during production processes) to respirable dust concentrations. The multivariate analysis of variance (MANOVA) reveals that, with a fixed sampling/analysis method, conversion factors were not s tatistically different among the different job titles within each industry. It also indicates that conversion factors among the industries were not st atistically different. However, the two estimates consistently showed that conversion factors were the lowest in the pottery industry. Average convers ion factors were then calculated for each of the estimates across the indus tries studied. A pooled mean conversion factor, 0.25 +/- 0.04, was then der ived for all the job titles and industries. Respirable dust levels were est imated from the historical 'total dust' concentrations collected between 19 52 and 1992 by adopting the American standard. (C) 2000 British Occupationa l Hygiene Society. Published by Elsevier Science Ltd. All rights reserved.