Jump to main content or area navigation.

Contact Us

EPA's 1997 Decision on Ozone and Particulate Matter Standards

Fact Sheet - EPA's 1997 Recommended Ozone and Particulate Matter Standards

Information provided for informational purposes onlyNote: EPA no longer updates this information, but it may be useful as a reference or resource.

Note: EPA no longer updates this information, but it may be useful as a reference or resource.


    Updated Air Quality Standards

    June 25, 1997

    EPA's recommended final standards for particulate matter and ozone (otherwise known as soot and smog) will be a major step forward in protecting the public from the health hazards of air pollution. These updated standards, the product of many years of intense scientific review, move us toward fulfilling the Clean Air Act's goal of ensuring Americans that their air is safe to breathe. The new standards will provide new health protections to 125 million Americans, including 35 million children.

    Particulate Matter

    The standard for coarse particles remains essentially unchanged, while a new standard for fine particles will be set at an annual limit of 15 micrograms per cubic meter, with a 24-hour limit of 65 micrograms per cubic meter.

    • This is the first time ever that the government has set a public health standard for fine particle pollution.

    • Scientists say that fine particles -- those measuring 2.5 micrometers in diameter and smaller -- are some of the most damaging to human health because they penetrate and remain in the deepest passages of the lungs.

    • This new standard, as revised from EPA's original proposal, will provide new protections to nearly 70 million Americans, and will prevent approximately 15,000 premature deaths each year.

    • By setting an annual limit of 15 micrograms per cubic meter, the new standard focuses on the most important issue -- controlling the amount of pollution and exposure to which Americans are subjected -- and therefore addresses the most significant health concerns.

    • A more flexible 24-hour standard of 65 micrograms per cubic meter, revised from the original EPA proposal, will give greater flexibility to individual sources of pollution, while still ensuring that the health of the American people is protected.


    For ozone, the recommended final standard will be updated from 0.12 parts per million of ozone measured over one hour to a standard of 0.08 parts per million measured over eight hours, with the average fourth highest concentration over a three-year period determining whether an area is out of compliance.

    • This is the first time in 20 years that the ozone standard will be updated.

    • The updated standard recognizes the current scientific view that exposure to ozone levels at and below the current standard causes significant adverse health effects in children and in healthy adults engaged in outdoor activities.

    • The new 0.08 standard is much stronger and more protective than the old standard of 0.12. It will extend new health protections to 35 million people, bringing to 113 million the number of Americans protected by the air quality standard for ozone.

    • For children, the new standard will reduce respiratory problems, such as asthma attacks. It will result in one million fewer incidences of decreased lung function in children each year.

    • By moving from a one-hour to an eight-hour measurement, the standard will better reflect the real-world effects of ozone on human health.

    • By focusing on concentration of ozone, the new standard will do more than merely designate high-pollution areas as out of compliance -- for the first time, it will also respond to health concerns based on how much an area is out of compliance.

    • Using the fourth maximum rather than the third (as originally proposed by EPA) -- will provide greater stability in the designation of areas, consistent with providing strong public health protections.

    Return to NAAQS Decision Information Page

Jump to main content.