Recent efforts by the Environmental Protection Agency (EPA) to implement a new air quality standard for fine particulate matter have come under attack. The shaky scientific underpinnings and potential high cost of the proposed standard have caused many observers, including the Department of Transportation and other federal agencies, to show concern that there may be no justification for spending billions of dollars for a new PM2.5 standard. To refute these claims, the EPA cites its own Clean Air Science Advisory Committee (CASAC) staff report as evidence of scientific consensus on the need for a PM2.5 standard. The staff report, as well as a majority of CASAC's members, supported a new standard in a 19-2 vote, but a close look at CASAC's May 16th and 17th discussion of the PM2.5 standard shows that no consensus was reached on the issue of health benefits resulting from a new standard. In fact, only two CASAC members voted for a standard as low as that imposed by EPA Administrator Carol Browner.
During its regular review of the National Ambient Air Quality Standards (NAAQS), the EPA decided to propose a new air quality standard for particulate matter 2.5 microns and less in diameter (PM2.5). The standard would implement an annual and daily standard for PM2.5 at 50 and 15 micrograms per cubic meter, respectively. The daily standard would take an average of the 98th percentile of daily PM2.5 levels over three years, which would effectively allow a community to exceed the standard about six times a year. The annual standard would be based on a three-year average of annual PM2.5 concentrations, allowing only 15 micrograms per cubic meter.