Final US standards for particulate matter and ozone
16 July 1997
The US Environmental Protection Agency (EPA) issued final air quality standards for particulate matter and ozone. The EPA expects the new standards will save 15,000 lives annually and will protect millions of children, asthmatics and the elderly from the adverse health impacts of smog and soot.
PM Standard. The EPA announced new standards for particulate matter (PM) under the national ambient air quality standards (NAAQS). EPA is revising the primary (health-based) PM standards by adding a new annual PM2.5 standard set at 15 micrograms per cubic meter (µg/m3) and a new 24-hour PM2.5 standard set at 65 µg/m3. EPA is retaining the current annual PM10 standard of 50 µg/m3 and adjusting the PM10 24-hour standard of 150 µg/m3 by changing the form of the standard. EPA is revising the secondary (welfare-based) standards by making them identical to the primary standards. EPA believes that the PM2.5 and PM10 standards, combined with the Clean Air Act-required regional haze program, will provide protection against the major PM-related welfare effects, including visibility impairment, soiling and materials damage.
EPA is issuing new rules related to PM monitoring requirements under the new standards. One rule addresses the monitoring network design needed for the new PM2.5 standards. Other rules establish a new federal reference and equivalent methods for monitoring PM2.5. Also, in a separate action, EPA is proposing rules to improve visibility by requiring states to develop programs to help reduce regional haze.
Ozone Standard. The EPA announced new national ambient air quality standards (NAAQS) for ground-level ozone, the primary constituent of smog. EPA is phasing out and replacing the previous 1-hour primary ozone standard (health-based) with a new 8-hour standard to protect against longer exposure periods. In establishing the 8-hour standard, EPA is setting the standard at 0.08 parts per million (ppm) and defines the new standard as a “concentration-based” form, specifically the 3-year average of the annual 4th-highest daily maximum 8-hour ozone concentrations. EPA also replaces the previous secondary standard (to protect the environment, including agricultural crops, national parks, and forests) with a standard identical to the new primary standard.
The 0.12 ppm 1-hour standard will not be revoked in a given area until that area has achieved 3 consecutive years of air quality data meeting the 1-hour standard. The purpose of retaining the current 1-hour standard is to ensure a smooth, legal, and practical transition to the new standard.
Health Concerns. EPA determined in a scientific review that the existing standards were not adequately protective of public health:
- For ozone—longer-term exposures at levels below the existing standard were found to cause significant health effects, including asthma attacks, breathing and respiratory problems, loss of lung function, and possible long-term lung damage and lowered immunity to disease.
- For particulate matter—exposures to particles smaller than those that were being regulated by EPA were found to lodge deeply in the lungs and cause premature deaths and respiratory problems.
Changes From EPA’s Earlier Proposal. The final standards include two significant changes from EPA’s November 1996 proposal:
- For ozone—the final standard would be set at the average 4th highest concentration instead of the 3rd, a point toward the upper-end of the range on which EPA took public comment. This should provide greater stability in the standard for businesses and communities by requiring more “bad air” days before an area is found to be out of attainment.
- For particulate matter—the final standard would set the 24-hour limit at 65 micrograms per cubic meter, instead of 50 micrograms (as proposed), in order to provide maximum flexibility for local areas and sources, while still retaining the public health protections of the proposal that are incorporated into the annual standard.
Source: US EPA