A new study of 60 million Americans is strengthening the link between air pollution and premature death. Harvard T.H. Chan School of Public Health researchers found that long-term exposure to airborne fine particulate matter (PM2.5) and ozone increases the risk of premature death, even when that exposure is at levels below the National Ambient Air Quality Standards (NAAQS) currently established by the U.S. Environmental Protection Agency. In this week's episode we speak with two of the study's authors, Francesca Dominici, professor of biostatistics at Harvard Chan School and co-director of the Harvard Data Science Initiative, and doctoral student Qian Di about why the U.S. needs stricter standards to keep the air clean.