Groundbreaking air pollution study marks 30 years


January 4, 2024 – The Harvard Six Cities Study, which had a profound impact on efforts to curb air pollution in the U.S., turned 30 in December. The study found that fine particulate pollution was linked with mortality at much lower levels than previously thought.

A December 29 article in The Guardian quoted Douglas Dockery, John L. Loeb and Frances Lehman Loeb Professor of Environmental Epidemiology, Emeritus, and lead author of the study, about how the study was designed and what it found.

Harvard researchers followed more than 8,000 adults from six U.S. cities with different concentrations of air pollution. They sent a postcard annually to each participant, asking if the named person had died. They also collected air pollution data from each city.

Even after considering a range of factors that could contribute to mortality—such as age, diet, occupation, and smoking history—the researchers found there was a 26% difference in survival between the participants in the least-polluted cities and the most-polluted. Pollution from fine particulate matter, known as PM2.5, was the most dangerous to health, the study found.

“We showed that long-term exposure to air pollution had much more significant effects on mortality risk than previously believed,” Dockery said. “It changed the dynamics of the debate.”

In spite of pushback from various industries that relied on fossil fuels, the study’s findings were confirmed by many subsequent studies, and have led to stricter air pollution guidelines that are estimated to save many thousands of lives each year.

Read The Guardian article: Lasting legacy of the Six Cities study into harms of air pollution

Learn more

Major Harvard Chan studies concur: Air pollution boosts U.S. death rates (Harvard Chan School news)

Photo: Dori