Air Quality in Texas Compared to Other States
Air quality in Texas, as compared to other parts of the U.S., shows favorable trends.
Eight-Hour Ozone State-by-State Comparison
- In 2000, the eight-hour ozone three-year average for Texas was near 0.12 ppm, well above all but one state in the nation. Between 2000 and 2010, Texas has made significant progress relative to the rest of the nation, decreasing ozone levels by 27% statewide. Overall, the citizens of Texas are experiencing healthier air compared to 2000.
- In 2000, the Houston-Galveston-Brazoria (HGB) and Dallas–Fort Worth (DFW) areas had some of the highest eight-hour ozone design values.
- In 2010, the HGB area was tied for seventh lowest design value out of the 13 major areas, and the DFW area was eighth.
- The HGB area had the second largest decrease in eight-hour ozone design values from 2000 to 2010, with Atlanta having the largest.
Trends in Ozone Concentrations
- As of 2007, the areas with the highest ozone concentrations were located in California, Connecticut, Georgia, Massachusetts, North Carolina, and Pennsylvania.
- While Texas does have sites measuring above the 1997 eight-hour ozone NAAQS, no sites in the state are measuring in the highest range of 0.096–0.126 ppm.
- Nationally, eight-hour ozone concentrations were 5 percent lower in 2007 than in 2001.
- A comparison of two three-year periods, 2001–03 and 2005–07, shows that most sites in Texas reduced ozone concentration.
- One of the four sites in the country showing the greatest improvement was the Houston area.
Trends in the Air Quality Index
The EPA has provided a scale called the Air Quality Index (AQI) for rating air quality.
- In both HGB and DFW the number of AQI “Good” air days has increased since 2000 and the number of “Unhealthy” and “Unhealthy for Sensitive Groups” air days has decreased.
- For Houston and Dallas, the number of Unhealthy days has been trending down since 2005. In 2007, both cities achieved their lowest number of Unhealthy days in 7 years, with 14 in Dallas and 38 in Houston.
- In many eastern states, the number of Unhealthy days is comparable to those in Houston and Dallas. However, many of the Eastern cities are trending up, while Houston and Dallas are trending down.
- Cities in California are also trending down, but remain much higher in the overall number of Unhealthy days. For example, Los Angeles totaled 100 unhealthy days in 2007.
Trends in Particulate Matter
- All areas in Texas meet NAAQS and most areas have shown decreases in both design values since 2002.
- In 2010, the El Paso area is the only area in Texas to not meet the PM10 NAAQS with 2.0 expected exceedances.
Comparison of Los Angeles to Houston
- A comparison of fourth highest ozone concentrations for Houston and Los Angeles reveals a downward linear trend for Houston and Los Angeles for 2000-2010.
- In 2010, L.A.'s ozone annual fourth high is 0.021 ppm higher than Houston's fourth high.
- An AQI comparison shows that, for the categories "unhealthy for sensitive groups" and "unhealthy" for everyone, Houston has a lower percentage of unhealthy days than L.A., and shows either a flat or small downward trend for both.
- The number of less harmful "moderate" days in Houston has increased, surpassing the number in L.A. in 2005. Also, while the number of "good" days in L.A. has increased since 2004, the overall percentage of "good" days remains lower than in Houston.
DFW Clean-Air Plan First Approved
In February 2009, the Dallas–Fort Worth clean-air plan became the first in the country to be approved by the EPA. Texas' remains the only approved State Implementation Plan for this standard.
