Missouri air quality today

Lead is one of the six criteria pollutants in the federal standards, and in very few places is it the one that binds. Missouri is one of them. EPA designated the Viburnum Trend, running through parts of Iron, Dent and Reynolds counties in the Ozarks, a nonattainment area for the 2008 lead standard in November 2010, with mining, milling and secondary lead smelting as the sources. That is an air problem in rural country with no metro attached to it, which means a metro-by-metro table has no row where it belongs.

St. Louis is the ozone case, and its geometry changes how a reading from it should be read. The nonattainment area crosses the river into Illinois, and the monitors that carried the area past the standard sit north of the city in St. Charles County, at West Alton and Orchard Farm, downwind on the summer days that actually produce the readings. The Missouri portion was reclassified from Moderate to Serious at the end of 2024 after missing its attainment deadline; in August 2026 EPA finalized a determination that the same area had reached clean data on 2023–2025 monitoring.

The Air Pollution Control Program within the Missouri Department of Natural Resources handles monitoring and permitting statewide. It also oversees the Gateway Vehicle Inspection Program, the emissions test required of vehicles in the St. Louis-area counties and nowhere else in Missouri.