WASHINGTON, May 31, (AP): Air quality in some parts of the United States is worsening as smoke from dozens of wildfires in Canada travels south, pushed by winds high in the atmosphere. Through parts of Minnesota and into Wisconsin, the air quality is deemed unhealthy for people and animals sensitive to pollution and other airborne particles, according to the Environmental Protection Agency's AirNow page.

As of Friday afternoon, the interactive air quality map showed a strip of orange moving northwest to southeast across Wisconsin. Most of the state showed moderate air quality as did all of Michigan’s Upper Peninsula. Eastern Iowa and northwestern Illinois also showed moderate air quality on the AirNow map. Over the next day or so, particulates from the burning trees, leaves and other vegetation could reach further south into Oklahoma, Tennessee and Arkansas, said Patrick Ayd, a meteorologist with the National Weather Service in Duluth, Minnesota.

Murray Kinsey, owner of a houseboat company just outside of Babbitt, Minnesota, said Friday afternoon the sky was "hazy," but anglers still were fishing on nearby Birch Lake. "It's getting a little hard to breathe,” Kinsey said. "But it's not terrible. We've had it before, but it's been way worse.” The Air Quality Index - AQI - measures how clean or polluted the air we breathe is on a daily basis.

The index focuses on the health effects that might be experienced within a few hours or days after breathing polluted air. AQI is calculated based on ground-level ozone, particle pollution or particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide. Ground-level ozone and airborne particles are the two pollutants that pose the greatest threat to human health in this country. The index ranges from green, where the air quality is satisfactory and air pollution poses little or no risk, to maroon, which is considered hazardous. That level comes with health warnings of emergency conditions where everyone is more likely to be affected, according to AirNow.