Technology Transfer Network / NAAQS
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 ------------------------------------------------------------------------------------------------------ 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.