Epidemiologist Dr. Ralph Delfino and his UC Irvine colleagues provide some of the first evidence that air-pollution particles, especially unregulated ultrafine particles, may be involved in deactivating antioxidant enzymes in red blood cells. The associated oxidative stress, they say, can trigger inflammation in arteries and veins and can activate platelets that cause blood clots in people with a history of coronary heart disease, thus elevating heart attack and stroke risk. The study, which currently appears in the online version of Environmental Health Perspectives, followed 60 elderly persons with coronary artery disease living in Southern California retirement communities.