Dust and gas exposure in tunnel construction work

Personal exposures to dust and gases were measured among 189 underground co nstruction workers who were divided into seven occupational groups performi ng similar tasks in similar working conditions: drill and blast crew; shaft -drilling crew; tunnel-boring machine crew; shotcreting operators; support workers; concrete workers; and electricians. Outdoor tunnel workers were in cluded as a low-exposed reference group. The highest geometric mean (GM) ex posures to total dust (6-7 mg/m(3)) and respirable dust (2-3 mg/m(3)) were found for the shotcreters, shaft drillers, and tunnel-boring machine worker s. Shaft drillers and tunnel-boring machine workers also had the highest GM exposures to respirable a-quartz (0.3-0.4 mg/m(3)), which exceeded the Nor wegian occupational exposure limit (OEL) of 0.1 mg/m(3). Shaft drillers had the highest exposure to oil mists (GM=1.4 mg/m(3)), which was generated ma inly from pneumatic drilling. For other groups, exposure to oil mist from d iesel exhaust and spraying of oil onto concrete forms resulted in exposures of 0.1-0.5 mg/m(3). Exposure to nitrogen dioxide was similar across all gr oups (GM=0.4-0.9 ppm), except for shaft drillers and tunnel-boring machine workers, who had lower exposures. High short-term exposures (> 10 ppm), how ever, occurred when workers were passing through the blasting cloud.