In response to a court order, the U.S. Environmental Protection Agency (EPA) today proposed updates to its national air quality standards for harmful fine particle pollution, including soot (known as PM2.5). A federal court ruling required EPA to update the standard based on best available science. Today’s proposal meets that requirement and 99 percent of U.S. counties are projected to meet the proposed standard without any additional action.

EPA will accept public comment for 63 days after the proposed standards are published in the Federal Register. The agency will hold two public hearings; one in Sacramento, CA. and one in Philadelphia, PA. EPA will issue the final standards by December 14, 2012.

EPA says their proposal would strengthen the annual health standard for harmful fine particle pollution (PM2.5) to a level within a range of 13 micrograms per cubic meter to 12 micrograms per cubic meter, compared to the current annual standard is 15 micrograms per cubic meter. By proposing a range, the agency will collect input from the public as well as a number of stakeholders, including industry and public health groups, to help determine the most appropriate final standard to protect public health.

The proposal has zero effect on the existing daily standard for fine particles or the existing daily standard for coarse particles (PM10), both of which would remain unchanged.

EPA says that depending on the final level of the standard, estimated benefits will range from $88 million a year, with estimated costs of implementation as low as $2.9 million, to $5.9 billion in annual benefits with a cost of $69 million – a return ranging from $30 to $86 for every dollar invested in pollution control. While EPA cannot consider costs in selecting a standard under the Clean Air Act, those costs are estimated as part of the analysis undertaken for all significant regulations, as required by Executive Order 13563 issued by President Obama in January 2011.

The Clean Air Act requires EPA to review its standards for particle pollution every five years to determine whether the standards should be revised. The law requires the agency to ensure the standards are “requisite to protect public health with an adequate margin of safety” and “requisite to protect the public welfare.” A federal court ordered EPA sign the proposed particle pollution standards by June 14, 2012, because the agency did not meet its five-year legal deadline for reviewing the standards.