"The combination of our balloon-borne ozone data and observations by NASA satellites, aircraft, and a network of ground stations provided unprecedented insight into the origins of locally poor air quality in Houston on those two days," Morris said.
Houston frequently exceeds federal standards for ground-level ozone. On 52 days in 2005, Houston's air quality violated the eight-hour Environmental Protection Agency (EPA) standard for ozone, placing Houston among the worst urban areas in the U.S. for ozone pollution. Besides posing a health risk for people with respiratory problems, ground-level ozone has also been linked to increased rates of asthma among children, and it can destroy plants and reduce crop yields. Federal regulators have given the Houston-Galveston region until 2007 to comply with federal air-quality standards for ground-level ozone, under the threat of severe economic sanctions, including loss of federal highway dollars.
In the new study, Morris and colleagues relied on imagery from NASA's Moderate Resolution Imaging Spectroradiometer on the Terra satellite, aerosol data from the Total Ozone Mapping Spectrometer satellite, and carbon monoxide data from the Atmospheric Infrared Sounder on the Aqua spacecraft. They tracked an air mass from the region of forest fires in western Canada and eastern Alaska on July 12-13, 2004, and followed it as it traveled across Canada, through the mid-western United States and into the Houston area on July 19.
"We found that with the arrival of the pollutants associated with these forest fires, ozone levels increased between 50-100 percent in the first five kilometers over Houston," Morris said.
Meteorological conditions, the smoke from the distant forest fires, and the typical urban pollution generated in the Houston area provided a potent mix for increasing local ozone concentrations, he said.
Morris said it's likely that such