tems: remedial actions may have unforeseen consequences. In the 1950s and 1960s, for example, regulators addressed the problem of pollution from coal-fired electrical power plants by mandating the construction of tall stacks—chimneys that soared hundreds of feet into the air to disperse the pollutants from the plants over a wide area. The "tall stacks solution" was counted a success because pollution near the power plants was dramatically reduced. Unfortunately, the sulfur-containing smoke from these plants, many of which were built in the American Midwest near high-sulfur coal deposits, traveled with the prevailing winds to New England and southeastern Canada. The material in the plumes then underwent chemical reactions and resulted in acid rain falling over large areas.

Thus, requiring tall stacks did not solve the pollution problem. Regulators were more successful, however, in responding to the problems of lead, which "is known to cause neurological malfunctioning, learning disabilities, and increased blood pressure. Almost all regulatory efforts in the past have been based on the simple notion that controlling the release of pollutant emissions will result in improved air quality. Regulatory activity designed to phase out the use of lead compounds as an antiknock additive in gasoline has been quite successful and has resulted in drastic reduction of ambient concentration levels" of lead in our air, said McRae. And so far the sign seems to be right: no significant or problematic unintended consequences have surfaced after the removal of lead from gasoline. Smog, however, is a larger, more complex problem.


McRae and his colleagues have drawn some conclusions from their latest model that might influence regulators to redirect a current, major control strategy: the reduction of reactive organic gases. As with the tall stacks strategy, McRae wants to be sure "we aren't getting the sign wrong" and actually mandating a control strategy with unforeseen consequences that could be avoided. The environmental awareness that blossomed in the 1960s helped to establish the U.S. Environmental Protection Agency (EPA) in 1970. Atmospheric pollution was evident even before the dawn of the environmental movement: many cities were cloaked in a brown shroud of smog. Studies were sanctioned and conducted, and a series of regulatory guidelines developed to—again, logically—attack pollution at its source. With urban pollution, one major source appears to be the hydrocarbons that come from automobile engine combustion and from the use

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