Technology Transfer Network / NAAQS
Ozone Implementation
Ozone and Carbon Monoxide
Air Quality Data Update Fact Sheet
Note: EPA no longer updates this information, but it may be useful as a reference or resource.
Following is a brief summary of EPA's 1991 air quality update for ozone
and carbon monoxide nonattainment areas.
Ozone (O3): As required by the Clean Air Act Amendments (CAAA)
of 1990, EPA designated 98 areas in 1991 that did not meet the National
Ambient Air Quality Standard (NAAQS) for ozone as ozone nonattainment
areas. Since that listing, Kansas City was the first ozone nonattainment area to
be redesignated to attainment. The NAAQS for ozone is 0.12 parts per million
(ppm) daily maximum 1-hour average concentration not to be exceeded more
than once per year on average. Compliance with the ozone NAAQS is judged
on the basis of the most recent three years with complete monitoring data. The
ozone standard is met when the average estimated exceedances of the ozone
NAAQS is less than or equal to 1.0. Today's list updates air quality monitoring
data for the three year period, 1989-91. During this current three year period,
41 of the remaining 97 nonattainment areas had average estimated exceedance
rates less than or equal to 1.0. These 41 areas meeting the NAAQS include 29
of the 42 Marginal areas and 12 of the 33 Moderate areas. An additional 12
areas were originally classified as ozone transitional areas, and all 12 of these
areas met the ozone NAAQS during 1989-91 as required by Section 185A of the
CAAA of 1990.
Carbon Monoxide (CO): There are 42 areas that have been designated
as nonattainment for carbon monoxide. The carbon monoxide NAAQS is 9 parts
per million (ppm) 8-hour nonoverlapping average concentration not to be
exceeded more than once per year. The CO standard is met at a site when there
are fewer than two exceedances for the two most recent calendar years with
complete air quality monitoring data.
Today's listing does not mean that those areas meeting the NAAQS during
the last three years will automatically be redesignated to attainment. The Clean
Air Act Amendments of 1990 state that an area can be redesignated to
attainment if the following conditions are met:
(1) the area has air quality data meeting the national air quality
standards,
(2) the area has an approved State Implementation Plan (SIP) meeting
Clean Air Act requirements, and
(3) the area has an approved maintenance plan showing attainment for
10 years.
OZONE FINDINGS (97 Nonattainment Areas)
12 of 33 Moderate Ozone Nonattainment Areas have ozone air quality
data meeting the Ozone National Ambient Air Quality Standard
during the period 1989-91.
Charleston, WV Lewiston, ME Raleigh, NC
Dayton, OH Miami, FL Reading, PA
Greensboro, NC Monterey, CA Richmond, VA
Kewaunee Co., WI Parkersburg, WV Toledo, OH
29 of 42 Marginal Ozone Nonattainment Areas have ozone air quality
data meeting the Ozone National Ambient Air Quality Standard during the
period 1989-91.
Albany, NY Greenbrier, WV Memphis, TN
Allentown, PA Harrisburg, PA Norfolk, VA
Altoona, PA Indianapolis, IN Owensboro, KY
Buffalo, NY Jefferson Co., NY Paducah, KY
Canton, OH Jersey Co., IL South Bend, IN
Cherokee Co., SC Johnstown, PA Tampa, FL
Columbus, OH Knoxville, TN Walworth Co., WI
Edmonson Co., KY Lancaster, PA York, PA
Erie, PA Lexington, KY Youngstown, OH
Evansville, IN Manchester, NH
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CARBON MONOXIDE FINDINGS (42 Nonattainment Areas)
13 of 42 Carbon Monoxide (CO) Nonattainment Areas have CO air
quality data meeting the Carbon Monoxide National Ambient Air Quality
Standard during the period 1990-91.
Baltimore, MD Memphis, TN
Chico, CA Philadelphia, PA
Colorado Springs, CO San Diego, CA
Duluth, MN Syracuse, NY
Grants Pass, OR Washington, DC
Klamath Falls, OR Winston-Salem, NC
Longmont, CO.