A report released Monday finds that two power plants in Arkansas are partly responsible for poor air quality in St. Louis.
Scientists from California-based Sonoma Technologies Inc. analyzed nitrogen oxide emissions, a component of ozone pollution, detected by air monitors in the St. Louis region in 2011. Their measurements revealed that Entergy's Independence and White Bluffs plants, located about 210 and 300 miles southwest of St. Louis, contributed emissions well above the federal standard for several days that year. The Sierra Club commissioned the study.
Ozone pollution, also known as smog, can cause chest pain and breathing problems, and can worsen conditions such as asthma and bronchitis. The Environmental Protection Agency has considered ozone levels in St. Louis to be unsafe since 2012.
"These Arkansas plants are pretty far away but what the research shows is that ozone moves regionally and moves a far distance," said John Hickey, director of the Sierra Club's Missouri chapter.
The air that travels to St. Louis tends to flow northeast from the Gulf of Mexico, said Benjamin de Foy, an earth and atmospheric science professor at Saint Louis University. De Foy was not an author on the report.
"What goes around comes around," de Foy said. "We all live in the same atmosphere and the impacts just go where the wind goes."
Entergy and the Missouri Department of Natural Resources are reviewing the data.
Hickey said Ameren Missouri's four plants contribute more to St. Louis' ozone pollution than the Entergy plants and that this report, "does not take Ameren off the hook." He and other environmentalists are using the data to demand that regional coal-fired power plants install technologies, called selective catalytic reduction, to clean up nitrogen oxide emissions. Ameren's Sioux Energy Center is the only power plant where such technology is installed.
"To solve the ozone problem in St. Louis, we need not only the participation of St. Louis groups like Ameren but we also need participation of groups like the Arkansas state government," Hickey said.
Follow Eli on Twitter: @StoriesByEli