Fresh horizons.

• Position: Pollution control in Mexico

Mexico City, the shining City of Palaces, has become the City of Darkness, a thick veil of smog covering what was once a clean, picturesque metropolis. In the years since World War II, this ancient Aztec capital has undergone prodigious growth. Today its wide and colorful avenues are jammed with automobiles and buses while its luxury hotels, restaurants and clubs have become a mecca for international tourism and business conventions. At the same time, emissions from thousands of new automobiles and the wastes and contaminants from the scores of industrial plants on the city's outskirts have created an urban nightmare of untold proportions for city planners and the central government.

Facing a barrage of international criticism, city officials with the strong support of the central government are attempting "to clean up their act."

They are motivated by a deep concern for the health of the city's residents as well as the imperative need to protect the hub of the nation's political, industrial and intellectual life.

In one of the most publicized efforts to reduce pollution, the government recently closed the March 18 oil refinery located in Azcapotzalco, a suburb of Mexico City. According to the Ecology and Urban Development Secretariat (SEDUE), this refinery emitted 280 tons of contaminant daily. Officials estimate that it would cost $3 billion to replace the facility. Since this closure, SEDUE has announced that it will permanently close 38 firms, principally metal foundries, for violating long-standing environmental laws. Furthermore, another 140 companies may be either temporarily or permanently closed within a period of time.

"Our commitment is real," said President Carlos Salinas de Gortari, "because there is a real demand from society." One 70-year-old foreign resident...