Sierra Club Says Ozone Data Indicate Texas Air Has Been Getting Dirtier

Agency Data Show Peak Ozone Exceedances Have Gotten Worse

The Lone Star Chapter of the Sierra Club today released government data that indicates that air quality in Texas cities got worse in the late 1990s, as judged by the measurement of ozone – the indicator of urban smog.

“The air quality trends in Texas for 1996-1998 reveal that Texans are breathing dirtier air, especially in the last two years,” said Neil Carman, clean air program director for the Lone Star Chapter.  “Statewide peak ozone levels and exceedances of the one-hour federal ozone standard show that the air deteriorated in quality in 1997-1998, compared to 1996.  For example, the average peak one-hour ozone exceedance in Texas urban areas increased from 1996 to 1997 and again from 1997 to 1998.”

“Citizens in Texas urban areas, including Dallas-Fort Worth and Houston, are being exposed to higher air pollution levels,” continued Carman.  “The situation demands that Texas state officials take more aggressive steps to clean up  regional and urban air pollution.”

Carman reviewed data from the Texas Natural Resource Conservation Commission (TNRCC) on the exceedances of the one-hour ozone standard and the peak levels of those exceedances during the period 1996-1998 in thirteen Texas urban areas.  He found that the average peak one-hour ozone exceedance in these Texas urban areas increased from 115 ppb in 1996 to 126 ppb in 1997 and 129 ppb in 1998.  [“Ppb” refers to “parts per billion.”]  The maximum one-hour ozone reading increased in eleven of the thirteen Texas urban areas and decreased in only two areas during that time.

Carman noted that the EPA ambient air quality standard for ozone on a one-hour basis is 124 ppb.  The average peak exceedance for the thirteen Texas cities during this three year period thus increased to a point above what EPA considers adequate to protect human health.  Carman also noted that peak ozone levels are the most dangerous to public health, affecting children and those people with breathing problems.

Using the EPA AIRS* data summary for Texas,  Carman compiled six years of Texas one-hour ozone exceedances from 1993-98.  That data indicates that the number of exceedances in 1997 and 1998 were higher on average than the six-year average of 134 exceedances per year.  The number of exceedances for 1997 was 158.  For 1998 the comparable number was 148.  That equals 18% more in 1997 and 11% more in 1998, compared to the six-year average.

In fact, 1997-98 was the worst two-year period even though 1995 was an
exceptionally bad year for ozone exceedances in Texas and throughout the United States. Attached is the table constructed from the AIRS data. The table indicates that the air did not get cleaner in Texas, at least for ozone concentrations in 1997-98,  said Carman.

The rising trend of ozone exceedances can not be explained away by the increase in ozone monitoring sites, which did rise, Carman said.  He noted that the average number of ozone exceedances per site per year increased as well.

“We have recently heard assertions that air quality in Texas is improving – that the air is getting cleaner,” said Ken Kramer, state director for the Sierra Club.  “The data from ozone monitoring around the state during the late 1990s indicate that -- in terms of urban smog -- the air has gotten dirtier, not cleaner.  Whether dirtier or cleaner, the air in many Texas cities is still too dirty to breathe.  There is still much to be done to clean up the air in Texas.”

* Source: EPA Office of Air Quality Planning and Standards, AIRS Data, Monitor
Trends Report, Texas Air Quality Monitors for Ozone: