Summer vacation season is upon us, with camping, hiking and other outdoor activities. For some of us, that means visiting remote locations in the Great Lakes region, such as Isle Royale National Park, Sleeping Bear Dunes National Lakeshore and Pictured Rocks National Lakeshore.

Still others set their GPS for historic locales such River Raisin National Battlefield Park in Monroe and Keweenaw National Historic Park in the western Upper Peninsula.

Wherever you’re heading, there are air pollution problems, according to a new report by the National Parks Conservation Association, an advocacy group based in Washington, D.C.

The association examined air pollution at 417 National Park Service properties and concluded that that 96% of them “are plagued by significant air pollution problems in at least one of four categories”: unhealthy air, harm to nature, haze pollution and climate change.

“Many parks suffer from the negative effects of air pollution in more than one of these categories,” it said, adding that climate change and air pollution adversely affect almost all national parks, with “fossil fuels and industrial air pollution” as the primary contributors to the problem.

The report said, “While most air pollution doesn’t originate in national park, it can travel hundreds of miles from its source, thereby affecting all parks – even remote ones – and distant communities.”

Superintendent Scott Tucker at Sleeping Bear Dunes said air-borne nitrogen from Milwaukee and Green Bay along the western coast of Lake Michigan is part of the problem at his park.

Read more: Air quality casts pall over Michigan national parks