A study of sulfur-dioxide (7446095) exposures at a copper smelter was conducted. The smelter located at Garfield, Utah employed about 1,250 workers and processed 2,100 metric tons of copper-sulfide concentrate a day. Personal and area air samples were collected in the furnace charging deck, matte tapping area, and slag tapping area in the reverberatory furnace area, anode facility, acid factory, and diesel ore truck repair shop in 1973 and 1974. Workers in the diesel truck repair shop were selected as the control group as their sulfur-dioxide exposures were presumed to be low. The samples were analyzed for sulfur-dioxide, nitrogen-dioxide (10102440), acrolein (107028), formaldehyde (50000), sulfites, and total and respirable dusts. The sulfur-dioxide data were compared with data obtained in industrial hygiene surveys in 1940, 1959 to 1969, 1971, and 1972. Sulfur-dioxide exposures measured in 1940 varied from 0.5 to 2.3mg/m3 in the acid factory to 29.4mg/m3 in the furnace charging deck and matte and slag tapping areas. Sulfur-dioxide exposures measured in the furnace charging deck and matte and slag tapping areas from 1959 to 1969, in 1971, and in 1972 varied from 4.4 to 75.4, 8.6 to 25.0, and 2.0 to 16.8mg/m3, respectively. Personal air sulfur-dioxide exposures measured in 1973 and 1974 varied from 1.7 to 4.2mg/m3, the highest occurring in workers in the acid factory and the lowest in maintenance workers in the reverberatory furnace and converter areas. Total dust exposures varied only from 0.61 to 1.05mg/m3. Sulfite exposures averaged 0.020mg/m3. Average area air sulfur-dioxide exposures measured in 1973 and 1974 varied from 1.1mg/m3 at a point midway between the slag and matte tapping areas to 31.6mg/m3 in the matte tapping area. Area air sulfur-dioxide, acrolein, nitrogen-dioxide, formaldehyde, and total dust exposures in the truck shop averaged 0.3mg/m3, 0.002 part per million (ppm), 0.014ppm, 0.012ppm, and 0.61mg/m3, respectively. Personal air nitrogen-dioxide, sulfite, and respirable dust concentrations in the truck repair shop averaged 0.067ppm, 0.003mg/m3, and 2.2mg/m3, respectively. The authors conclude that sulfur-dioxide exposures in the smelter work areas can be quite high. Historical data show that they have changed very little over the years.