Agustin J. Colussi, senior research associate in environmental science and engineering, and colleagues have found that airborne particulates impair the lungs' naturaldefenses against ozone. Their research focused on what happens when air meets the thin layer of antioxidant-rich fluid that covers our lungs, protecting them from ozone, an air pollutant that pervades major cities. "We found new chemistry at the interfaces separating gases from liquids using a technique that continuously monitors the composition of these interfaces," Colussi says. Under normal physiological conditions, ascorbic acid instantly scavenges ozone, generating innocuous byproducts. However, the researchers discovered that when the fluid is acidic, a pathological condition found in asthmatics, ascorbic acid instead reacts with ozone to form potentially harmful compounds called ozonides.