High Exposure to Respirable Dust and Quartz in a Labour-intensive Coal Mine in Tanzania

Labour-intensive mines are numerous in several developing countries, but dust exposure in such mines has not been adequately characterized. The aim of this study was to identify and quantify the determinants of respirable dust and quartz exposure among underground coal mine workers in Tanzania. Personal respirable dust samples (n = 134) were collected from 90 underground workers in June–August 2003 and July–August 2004. The development team had higher exposure to respirable dust and quartz (geometric means 1.80 and 0.073 mg m3, respectively) than the mining team (0.47 and 0.013 mg m3), the underground transport team (0.14 and 0.006 mg m3) and the underground maintenance team (0.58 and 0.016 mg m3). The percentages of samples above the threshold limit values (TLVs) of 0.9 mg m3 for respirable bituminous coal dust and 0.05 mg m3 for respirable quartz, respectively, were higher in the development team (55 and 47%) than in the mining team (20 and 9%). No sample for the underground transport team exceeded the TLV. Drilling in the development was the work task associated with the highest exposure to respirable dust and quartz (17.37 and 0.611 mg m3, respectively). Exposure models were constructed using multiple regression model analysis, with log-transformed data on either respirable dust or quartz as the dependent variable and task