Thank you for the opportunity to testify today about weather related events and their effect on ozone nonattainment under the Clean Air Act. Recurring natural events in the United States and foreign countries often influence air quality in Texas. Southwestern dust storms, Saharan dust, agricultural fires, and forest fires are just a few of the influences that we face. Today, I'd like to discuss one case in particular - the agricultural fires that occurred in 1998 in Mexico and Central America, the effect of the smoke on air quality in Texas, and the need for consistent policy and guidance at the national level on exceptional events like this one. Agricultural Fires in Mexico and Central America
During the period from April 1, 1998 through June 20, 1998, large amounts of smoke were transported into Texas from fires in Mexico and Central America. Even though agricultural burning is conducted every year in Central America, the smoke's intensity was unprecedented in recent history. The fires were unusually intense and widespread because of severe drought conditions in Mexico and Central America. The smoke also produced high levels of ozone and carbon monoxide. These pollutants accompanied the smoke into Texas.
By May, 1998, smoke intensity climbed to levels that threatened public health. Concerned by this threat, the Texas Natural Resource Conservation Commission stepped up it's air quality monitoring activities and worked with the news media and other governmental agencies to make the public aware of dangers posed by these smoke levels. When our agency became aware of unusual air quality monitor readings, we shifted additional ground monitors into the Rio Grande Valley and made numerous flights with an airborne sampling platform operated by Baylor University. In addition, our agency posted information and warnings on our Web site, established a toll-free information hotline, and issued public health alerts through the news media. Analysis of the Smoke
After the conclusion of this event, we undertook an analysis of the association of high ozone and carbon monoxide levels with smoke transported from Central America. Evidence of this relationship came from aircraft data and from a comparison of the peak smoke day with a non-smoke day. Numerous aircraft flights during the smoke period found layers of smoke aloft that contained greatly increased ozone levels. Ozone levels aloft as high as 100 to 140 parts per billion were found in association with smoke layers.
The comparison of the peak smoke day at Brownsville on May 8, 1998, with a non-smoke day, October 3, 1998, showed that ozone, carbon monoxide, and particulate levels were much higher on the smoke day - even though the wind speed, wind direction, and temperatures were almost identical on both days. Ozone levels on the peak smoke day reached peak 1-hour values near 100 parts per billion, whereas on the non-smoke day the ozone peaked at only 20 parts per billion.
Satellite imagery and air trajectories were used to show the origin of the smoke and its transport into Texas. Numerous large fires in Mexico and Central America produced large clouds of smoke that were visible in satellite imagery from March through June, 1998. The heaviest smoke production occurred in early to mid-May. Whenever winds were from the south to southeast in the southwestern portion of the Gulf of Mexico, the smoke was transported across the Gulf and into Texas.
Airport visibility measurements from National Weather Service automated stations were used to supplement particulate measurements for determining smoke intensities at various locations in Texas. A strong correlation between visibility and particulate levels was shown in measurements from both Brownsville and Austin. The combination of visibility and particulate measurements was then used to estimate the smoke impact on high ozone days during the smoke period. This investigation showed that 14 high ozone days in Texas also had moderate to high smoke levels and were therefore likely to have been influenced significantly by the ozone associated with the smoke. Consultation with EPA
As early as May of 1998, our agency began consultations with the U.S. Environmental Protection Agency (EPA). We provided significant amounts of data to the U.S. EPA's technical working group for the Central American forest fires through the Region 6 office. We also presented the U.S. EPA with the results of our own analysis of the fire's air quality impacts on Texas as part of our request to have ozone exceedance days during the period of April 1, 1998 through June 20, 1998, declared as exceptional events. As of this hearing date, the U.S. EPA has declined to grant an exceptional event status for all of the days that Texas has identified as being influenced by Central American smoke.
The Texas Natural Resource Conservation Commission believes that there exists a need for the U.S. EPA, at a national level, to increase its awareness of these exceptional natural events and their impact on ambient measurements of pollutants and pollutant precursors. In addition, there is a need for a coherent, flexible policy that provides guidance not only for one-time exceptional events, but also recurring or long term exceptional events that are beyond the control of air quality agencies. We look forward to working with Congress and the U.S. EPA on the development of such a policy.