The Bureau of Mines evaluated the emission control methods, including the capital investments and operating cost, necessary for further reducing lead levels in ambient air at the Glover, Herculaneum, and Buick Smelter-Refineries in Missouri and the East Helena, Montana, smelter. The U.S. Environmental Protection Agency has proposed more stringent lead in ambient air standards than those currently in effect. Lead emission inventories theoretically can be reduced from 1985 levels by 2,421 lb/d at the three Missouri operations by containing and filtering fugitive emissions within structural enclosures and baghouses. The aggregated capital and operating costs in 1986 dollars using conventional environmental and workplace technologies are estimated to be $250,014,100 and $18,507,800, respectively. Estimated total incremental cost is $0.063/Lb as refined lead. Additional regulatory costs attributable to Occupational Safety and Health Administration (OSHA) workplace standards are included since proposed environmental controls may otherwise degrade workplace conditions as an alternative to conventional osha controls. Substituting continuous drossing results in estimated aggregated capital and operating costs of $258,344,800 and $15,719,600, respectively. Estimated total incremental cost is $0.062/Lb as refined lead. For comparison, the average open market price of refined lead during the first quarter of 1986 was $0.184/Lb.