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Missouri Air Conservation Commission approves plan to show EPA that Jefferson County air is cleaner

An illustration of pollution, 2017
Rici Hoffarth | St. Louis Public Radio
It's now up to the Environmental Protection Agency to decide if sulfur dioxide levels in Jefferson County have improved since 2013.

Jefferson County is one step closer to attaining the federal clean air standard for sulfur dioxide, a noxious gas that can cause asthma and respiratory illness.

The Missouri Air Conservation Commission on Thursday approved the state's recommendation to the Environmental Protection Agency that the county's sulfur dioxide levels are within the federal limit of 75 parts per billion.

The county exceeded the limit in 2013, largely due to the high amount of emissions from the Doe Run lead smelter in Herculaneum. This prompted the EPA to designate the county as "nonattainment" for sulfur dioxide. But the smelter has closed since, which caused emissions to drop significantly. That led state officials to ask the EPA to change the county's air status to "attainment."

The Missouri Department of Natural Resources' data also measures emissions from prominent sources of sulfur dioxide emissions, including Ameren Missouri's Rush Island Energy Center. The data indicated that levels were well below the limit. 

"We're interested in ensuring that the air quality is safe to breathe for our coworkers as well as the citizens of Missouri," said Steve Whitworth, senior director of environmental services at Ameren Missouri. "We'll continue to do our part to make sure that the air quality stays good in the area."

Environmentalists are opposed to the recommendation to change the county's air quality designation. Researchers from Washington University's Interdisciplinary Environmental Law Clinic havepresented modeling data that indicates the air monitors near the Rush Island plant are not in locations where emissions are expected to be highest. Therefore, they say, the state's data does not accurately portray Jefferson County's sulfur dioxide levels. 

Ken Miller, an environmental scientist at the clinic, also is concerned that the MDNR's plan to change the county's air-quality status to meeting federal standards does little to address emissions coming from the Rush Island Energy Center.

"There's basically nothing in the plan that will ensure that sulfur dioxide levels are safe for people to breathe," Miller said. "If Ameren were to operate at their permitted limit or close to it, you'd probably get widespread nonattainment through the area." 

It's now up to the EPA to accept or reject the MDNR's proposal. The agency's final decision may not come for some time, since its recommendation for the county will also involve a public comment period. 

Follow Eli on Twitter: @StoriesByEli

Eli is the science and environment reporter at St. Louis Public Radio.