Carbon Monoxide 1996-98 Air Quality Data Update

The following is a brief summary of EPA's 1998 air quality update for carbon monoxide nonattainment areas.

Today's list updates CO air quality data for the two year period, 1997-98. During this two year period,

• 3 of the original 42 areas designated nonattainment for the 8-hour CO NAAQS in 1991 failed to meet the CO NAAQS in 1997-98 (Table 4).
• 3 additional areas failed to meet the CO NAAQS in 1997-98 (Table 4).

EPA's National Ambient Air Quality Standard for carbon monoxide is 9 parts per million (ppm) nonoverlapping 8-hour average concentration not to be exceeded more than once per year. The CO standard is not met at a monitoring site if there are two or more exceedances of the level of the CO NAAQS in either of the two most recent calendar years of monitoring data.

Areas not meeting the 8-hour Carbon Monoxide National Ambient Air Quality Standard, 1997-98

Notes:

1. The level of the 8-hour National Ambient Air Quality Standard for carbon monoxide is 9 parts per million (ppm) not to be exceeded more than once per year. The design value for the 8-hour CO NAAQS is the highest annual second maximum nonoverlapping 8-hour concentration during the most recent two years.

2. Annual second highest nonoverlapping 8-hour average CO concentration.

3. Number of nonoverlapping exceedances of the 8-hour CO NAAQS.

SOURCE: U.S. EPA's Aerometric Information Retrieval System (AIRS)