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Technology Transfer Network / NAAQS
Ozone Implementation

October 20, 1999

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


EPA Proposes to Reinstate the 1-Hour Ground-Level Ozone (Smog) Standard

Today's Action

  • EPA is proposing to reinstate its 1-hour standard for ground-level ozone (smog) in nearly 3,000 counties where the standard had been revoked since 1998.
  • The reinstatement is intended to ensure public health protection in light of the limits of a recent court ruling that prevents EPA from enforcing the new, more protective, ozone standard.
  • The reinstatement will affect some areas that had been designated as "attainment" for EPA's 1-hour ozone standard and some that formerly were designated as "non-attainment" but where monitors showed clean air for three consecutive years. (Attainment and nonattainment are legal designations; they do not indicate whether an area's air currently is clean or dirty.)
  • Affected areas would have to continue monitoring for ozone, and some areas would be subject to requirements intended to limit ozone formation. Those requirements include implementation of maintenance plans, transportation conformity and new source review requirements.

Why EPA Previously Revoked the 1-Hour Standard

  • EPA revoked the 1-hour standard in nearly 3,000 counties in an effort to smooth the transition to the new, more stringent 8-hour standard that would better protect public health. The revocation was designed to allow areas where the 1-hour standard had been attained to redirect their focus toward meeting the 8-hour standard.
  • EPA revoked the 1-hour standard only in areas that had clean air for three consecutive years.
  • EPA did NOT revoke the standard in areas that continue to violate the 1-hour standard.

What Reinstatement Will Mean

  • Most of the affected counties have never had an ozone problem and continue to meet the 1-hour ozone standard. Reinstatement will not trigger any new requirements for those areas.
  • Fifty-three areas comprising 114 counties (both non-attainment and attainment) could be required to take some action to further reduce ozone pollution or to prevent future ozone increases. The areas would have the same designations (attainment or nonattainment) that they had when EPA revoked the standard.
    • Seven of the 53 areas affected by today's proposed reinstatement would have to implement contingency measures in their existing maintenance plans, because the areas violated the 1-hour standard based on 1996-1998 data.

- A maintenance plan is required for areas that once were designated as non-attainment areas but were reclassified as attainment after monitors showed clean air for at least three years. The plans outline strategies to ensure that an area will continue to comply with ozone standards.

- Contingency measures are invoked when an area records a new violation of the standard.

  • Forty-six of the 53 areas formerly designated non-attainment had the 1-hour ozone standard revoked. These areas continue to have clean air based on 1996-1998 data; however, reinstatement will mean these areas will have to meet transportation conformity and New Source Review requirements. If the areas want to be redesignated as attainment, they would need to develop maintenance plans and meet other redesignation requirements.

- Conformity refers to requirements under the Clean Air Act that federally funded transportation projects not aggravate air quality problems.

- New Source Review requirements set out the levels of emission control required for new and modified industrial facilities to prevent air quality from declining. New Source Review requires newly built or modified facilities 1) to install state-of-the-art emission controls and 2) to purchase emission offsets from existing sources to compensate for the new pollution.

- Note: many Northeastern states continued implementing New Source Review requirements as part of their participation in the Ozone Transport Region.

  • Four additional counties have always been designated attainment, but data show they violated the 1-hour standard between 1996 and 1998. These areas would not have to take any immediate action upon reinstatement of the 1-hour standard. However, if EPA later decides to designate them as non-attainment areas, the areas would be subject to conformity, New Source Review and other nonattainment area planning requirements.

Background & Chronology

  • In July 1997, EPA announced a new national ambient air quality standard for ground-level ozone (the first revision in 18 years), the primary constituent of smog.
  • The new, more stringent standard was developed following a lengthy scientific review process. The new standard, based on 8-hour ozone readings, would better protect health and the environment than the 1-hour standard.
  • EPA subsequently revoked the 1-hour standard in nearly 3,000 counties, beginning in June 1998.
  • On May 14, 1999, the U.S. Court of Appeals for the District of Columbia Circuit blocked EPA's authority to implement the new 8-hour standard. That action left nearly 3,000 U.S. counties without any federal public health standard for ozone.
  • EPA and the Department of Justice have appealed the court's decision and are seeking to have it overturned. EPA anticipates resolution of this issue could take as much as two years.

Ozone & Health

  • Ground-level ozone is formed when emissions of nitrogen oxides and volatile organic compounds react with sunlight. Sources for these pollutants include power plants, factories, motor vehicles, chemical solvents and consumer products.
    • When inhaled - even at very low levels - ground-level ozone can: cause acute respiratory problems; aggravate asthma; reduce lung capacity; inflame lung tissue; and impair the body's immune system.
  • Children - especially those with asthma - are at greatest risk from ozone pollution. During the summer, when concentrations of ground-level ozone are highest, children playing outside may suffer from coughing and decreased lung function, and may have trouble catching their breath.
  • People with asthma are much more likely to have attacks - or more severe attacks - when ozone levels in the air are high. Studies show that ozone can aggravate asthma, causing an increase in asthma attacks and leading to increases in medication use, medical treatment and hospital emergency room visits.
  • Repeated exposures to ozone can damage lung tissue, which may result in a reduced quality of life as people age.
  • Ground-level ozone also makes plants more susceptible to disease, insect attack and other pollutants. Ground-level ozone has been shown to reduce agricultural yields for many economically important crops, such as soybeans, corn, peanuts, wheat and cotton.
  • Nitrogen oxides also contribute to airborne particulate matter, regional haze (visibility) problems, global warming, and eutrophication in sensitive lakes and rivers.

For more information

  • For further information about this proposal call, Tom Helms (919) 541-5527 or Jeff Clark (919) 541-5557. For technical questions, call Annie Nikbakht (919) 541-5246 (ozone policy) or Barry Gilbert (919) 541-5238 (air quality data).

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