Reconstruction of thirty years of free silica dust exposure in the taconite industry.
NIOSH 1990 Nov; :1001-1106
Longterm data on exposure levels to free silica (7631869) containing dust in the taconite (12249262) mining industry were examined. Quantitative exposure levels were determined for four taconite mines in Minnesota by analyzing respirable mass sampling data collected for the last 15 years and impinger sample results collected from 1957 to 1975. The establishment of current and past exposures consisted of two major tasks: compilation and summary statistics for a large amount of environmental sampling data by facility, job classification, and time period; and development of a model for converting the historical environmental measurement data into a form consistent with the current respirable mass sampling method. A matrix of respirable silica dust sample results was prepared. Descriptive statistics consisted of the number of samples, geometric mean, log of the geometric standard error, and minimum and maximum concentration. Sample data revealed the potential for high crystalline (71636) silica exposure. Average quartz (14808607) levels were 18 to 34% in the mine, 28 to 37% in the crushers, 14 to 37% in the concentrators, and 5% or less in the pellet facility. Mean exposure levels did not take into account changes in exposures, such as those due to improved control technology over time.
NIOSH-Author; Silica-dusts; Dust-exposure; Mining-industry; Exposure-levels; Respirable-dust; Occupational-exposure; Air-sampling; Analytical-methods; Statistical-analysis
7631-86-9; 12249-26-2; 71-63-6; 14808-60-7
Proceedings of the VIIth International Pneumoconioses Conference