The life-saving impact of the Six Cities Study

The Harvard Six Cities Study had a profound impact on efforts to curb air pollution in the U.S. and is estimated to have saved hundreds of thousands of lives.

Published in 1993, the study found just how harmful air pollution is. Researchers looked at pollution levels and deaths in six cities across the U.S. “People in the dirtier cities were dying faster than people in the clean cities,” said Harvard T.H. Chan School of Public Health’s Douglas Dockery, John L. Loeb and Frances Lehman Loeb Professor of Environmental Epidemiology, Emeritus, who led the study. “The differences we found in life expectancy—two to three years shorter—were remarkable.” The findings led to stricter air pollution limits in the U.S.

Today, environmental health experts at Harvard Chan School continue to study the risks of air pollution and propose solutions.