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DENVER — A study published this month mapped the parts of the country that have strong connections between traffic-related air pollution and childhood asthma. The interactive map shows Denver and the surrounding counties with a high percentage.

That’s no surprise to Dr. Kristin Woodward.

“Certain chemicals in the pollution — like nitrogen dioxide and ozone, and certain particulates — can increase the risk of asthma. And it can increase symptoms of asthma,” she said.

University of Colorado Boulder researchers conducted a similar study in the Denver area.

“We  found the association was stronger for asthma-like symptoms in homes that were closer to major roadways,” said Dr. Shelly Miller, a professor at CU Boulder.

Miller says the information is important to consider when deciding where to build homes and how to protect the ones we already have. Homeowners can weatherize the windows and doors, and use air filters or purifiers.

Here is a look at the study and the interactive map.