Today’s media are filled with concerns about air pollution. But few people know which energy source has produced the greatest modern reduction in air pollution. The answer isn’t wind or solar energy.

During the 1950s, my grandfather had a coal furnace in his basement, like many homes in Chicago. Five days after a winter snowfall, the snow was covered with a visible black film of dust from coal furnaces. Our younger generation does not know the original reason for “spring cleaning.” Every spring, homeowners would wash their inside walls to remove coal dust.