Science: The Acid Threat

They were measures that all ecologically minded citizens could applaud. By the 1950s, more and more communities in the industrial U.S. Northeast were switching from burning dusty, high-sulfur coal in their furnaces to extremely clean natural gas. Along with the fuel changeover, factories raised the height of smokestacks to help disperse smoke over a wider area and added sophisticated devices called particle precipitators to collect soot before it escaped. Yet for all of the good intentions, those anti-pollution efforts may have created a new headache: a marked rise in the acidity of rainfall,...