ATS member and Chair of the ATS Environmental Health Policy Committee, Mary Rice, MD, presented the comments before the EPA Clean Air Scientific Advisory Committee (CASAC) regarding the agency review of the National Ambient Air Quality Standard for fine particulate matter. In her comments, Dr. Rice expressed continued concern with the EPA’s decision to dismiss its particulate matter advisory committee and noted that the current seven-member CASAC panel does not have the breadth of expertise to analyze and understand the current research database of particulate matter-related studies. In her comments, Dr. Rice also cited a number of published studies that document why the current EPA PM annual standard of 12 ug/m3 and 24-hour standard of 35 ug/m3 are not sufficiently protective of the public health. Dr. Rice cited several high-quality studies that show both mortality and morbidity effects at exposure levels below 10 ug/m3, and further, that the research data continue to show linear effects even at lower exposure levels. Dr. Rice urged CASAC to consider supporting a National Ambient Air Quality Standard for particulate matter of 8 ug/m3 for the annual standard and 25 ug/m3 for the 24-hour standard.