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By Rachel Leven
Engineer Jim Southerland was hired by the U.S. Environmental Protection Agency (EPA) in 1971 to join the nascent war on air pollution. He came to relish the task, investigating orange clouds from an ammunition plant in Tennessee and taking air samples from strip mines in Wyoming. Among his proudest accomplishments: helping the agency develop a set of numbers called emission factors—values that enable regulators to estimate atmospheric discharges from power plants, oil refineries, chemical plants and other industrial operations.