Twin Cities had less air pollution this summer than winter

The Twin Cities experienced less air pollution this summer than over the winter, according to Minnesota air quality experts.

Cassie McMahon, a Minnesota Pollution Control Agency air quality specialist, said the Twin Cities summertime temperatures were warm but not hot enough to create high levels of ozone and other pollutants that harm human health.

"We didn't have any days that reached the unhealthy, sensitive group level of our air quality index," McMahon said. "That's the level where those that have respiratory or perhaps cardiovascular conditions might experience some symptoms of their conditions due to air pollution levels."

McMahon said compared to peer cities around the country, the Twin Cities have relatively clean air. This summer, for example, she said there have been fewer episodes of atmospheric stagnation and inversion of air which can trap pollutants. Instead, McMahon said, there's been adequate mixing of the air with winds to blow away many of the pollutants.

McMahon said the Twin Cities air benefited from freshening winds from the Dakotas and Canada. McMahon said last winter from November to March by contrast had more than 20 days where alerts were issued because of high air pollution levels.