Assessment of occupational exposure in a granite quarry and processing factory

Workers in the granite industry face an occupational hazard: silicosis due to the crystalline silica present in inhalable dust. As granite can also present a variable, and occasionally significant, content of naturally occurring radionuclides, they may also face a radiological hazard. In order to assess the risk, a granite industry with a quarry and processing factory was selected to assess the occupational exposure. Three main potential pathways were observed: external irradiation, inhalation of granite dust, and radon exposure. The external dose rate was similar to that in a nearby farming area. A slight increment (0.016-0.076 mSv yr^-1) was observed in the quarry and stockpile, due to quarry faces and granite blocks. The effective dose due to granite dust inhalation was 0.182  ±  0.009 mSv yr^-1 in the worst case scenario (3 mg m^-3 dust load in air and no use of filter masks). Thus, the mean value of the effective dose from these two pathways was 0.26 mSv yr^-1, lower than the reference level of 1 mSv yr^-1 for the general population. The annual mean value of radon concentration in the indoor air was 33 Bq m^-3. However, during granite processing works the radon concentration can increase up to 216 Bq m^-3, due to mechanical operations (sawing, polishing, sanding, etc). This radon concentration was below the 600 Bq m^-3 reference level for action in working places. Therefore, workers in this granite factory face no significant additional radiological exposure, and no-one needs to be designated as occupationally exposed and subject to individual dosimetry.