Carbon Monoxide

Description: These layers contains the nonattainment and maintenance areas (counties) in Texas. It was derived from the EPA’s Greenbook. A nonattainment designation means an area has not achieved compliance with the National Ambient Air Quality Standards (NAAQS). A maintenance designation means the area was formerly in nonattainment but has monitored attainment and is currently under a maintenance plan1. The U.S. Environmental Protection Agency (EPA) established the 8-Hour ozone NAAQS in 1997 and revised it with the 2008 and 2015 standards. The 1997 ozone NAAQS was revoked in April 6, 20152, along with the classifications, so the current maintenance designation is based on the approval of a maintenance plan by EPA for the region; rather than an official reclassification. These nonattainment counties were designated by the EPA based on their air quality monitoring data. Before it was revoked, there were 17 nonattainment counties for the 1997 ozone NAAQS: 8 counties in the Houston/ Galveston area (Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller); and 9 counties is the Dallas/Fort Worth area (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, and Tarrant). There are 3 maintenance counties for the 1997 ozone NAAQS in the Beaumont/Port Arthur area (Hardin, Orange, Jefferson)3. There are 18 nonattainment counties for the 2008 ozone NAAQS: 8 counties in the Houston/ Galveston area (Brazoria, Chambers, Fort Bend, Galveston, Harris, Liberty, Montgomery, and Waller); and 10 counties in the Dallas/Fort Worth area (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Rockwall, Tarrant, and Wise)4. There are 16 nonattainment counties for the 2015 ozone NAAQS: 1 county in the San Antonio area (Bexar); 6 counties in the Houston/ Galveston area (Brazoria, Chamber, Fort Bend, Galveston, Harris, and Montgomery); and 9 in the Dallas/Fort Worth area (Collin, Dallas, Denton, Ellis, Johnson, Kaufman, Parker, Tarrant, and Wise)5. The EPA established the NAAQS for particulate matter with a diameter of 10 micrometers or smaller (PM-10) in 1987. There is one nonattainment area for the 1987 PM-10 NAAQS: which is a portion of El Paso county6. The EPA established the NAAQS for carbon monoxide (CO) in 1971. There is one maintenance area for the 1971 CO NAAQS: which is a portion of El Paso county7. References: 1. United States Environmental Protection Agency, Frequent Questions about General Conformity; accessed 1 April 2021, <https://www.epa.gov/general-conformity/frequent-questions-about-general-conformity#86-523A-4466-AE04-09EAEF7C16F3%7D> 2. United States Environmental Protection Agency, Transportation Conformity Guidance for the South Coast II Court Decision, 2018 3. United States Environmental Protection Agency, Green Book 8-Hour Ozone (1997) Area Information - NAAQS Revoked; accessed 1 April 2021, <https://www.epa.gov/green-book/green-book-8-hour-ozone-1997-area-information-naaqs-revoked> 4. United States Environmental Protection Agency, Green Book 8-Hour Ozone (2008) Area Information, accessed 1 April 2021, <https://www.epa.gov/green-book/green-book-8-hour-ozone-2008-area-information> 5. United States Environmental Protection Agency, Green Book 8-Hour Ozone (2015) Area Information, accessed 1 April 2021, <https://www.epa.gov/green-book/green-book-8-hour-ozone-2015-area-information> 6. United States, Environmental Protection Agency, Green Book PM-10 (1987) Area Information, accessed 5 April 2021, <https://www.epa.gov/green-book/green-book-pm-10-1987-area-information> 7. United States, Environmental Protection Agency, Green Book Carbon Monoxide (1971) Area Information, accessed 6 April 2021, <https://www.epa.gov/green-book/green-book-carbon-monoxide-1971-area-information> Update Frequency: As needed. Source: Environmental Affairs Security Level: Public