Interactive: Areas Exceeding EPA Ozone Air Quality Levels

Communities across Texas experienced a spike in ozone pollution this year, amid the hot weather and drought. Nonetheless, ozone pollution in Texas cities has fallen dramatically over the last decade.

Use the map below to understand how the number of bad ozone days in different Texas metropolitan areas has changed over time. The map shows violations of the 2008 eight-hour ozone standards, set by the Environmental Protection Agency at 75 parts per billion. Click the color-coded area to see the number of days in violation, and use the drop-down menu at the top left to change the year.

Some of the areas measured for ozone may soon expand: On Friday, the EPA sent a letter to Gov. Rick Perry recommending the addition of Hood and Wise Counties to the Dallas-Fort Worth area (as measured for ozone violations), and of Matagorda County to the Houston ozone area.

* The 2011 exceedances are as of Sept. 20, 2011 and are subject to change.

Number of days each MSA exceeded EPA eight-hour national ambient air quality standards for ozone
Not measured
0 to 10 days
10 to 25 days
25 to 50 days
50 to 90 days
Metropolitan statistical area
Day(s) exceeding EPA 8-hour measures