Cincinnati, OH Air Quality Index (AQI) Today

Relief is what separates Cincinnati’s air from a flat city’s. The Ohio River runs at the bottom of the bowl, the hills stand several hundred feet above the water, and the Mill Creek valley cuts north from downtown as a second, narrower trench. Two neighborhoods a mile apart, one on a hilltop and one on the valley floor, are not breathing the same air on a still night, because the cold layer that forms in the low ground never reaches the ridge.

What collects down in that trench is largely combustion. I-75 carries the region’s freight up the Mill Creek corridor, where a University of Cincinnati air pollution study measured roughly 159,000 vehicles a day past its sites with about 11 percent of them diesel. Add the Queensgate rail yard, barge traffic on the river, and the sulfate the wider Ohio Valley airshed has long carried from coal burned upwind, much reduced from its peak but not gone.

Winter stagnation and midsummer regional haze are the two worst stretches, and they arrive by different routes. One citywide figure averages the ridge and the trench into a single number, which is why a local nonprofit, Groundwork Ohio River Valley, built a neighborhood-level monitoring dashboard rather than work from the official one.