A weekend trip to a national park would seem like the perfect opportunity to escape the dirty air of a congested city. Unfortunately, just as people migrate out of Seattle, so too do airborne pollutants. That’s the uncomfortable reality revealed by a study nearly eight years in the making, whose results have only come to light recently.Back in 2002, the National Parks Service was pushed into action after pollutants were found in remote ecosystems near the poles. The Western Airborne Contaminant Assessment Project (WACAP) is what came out of the operation, a multidisciplinary team charged with performing a kind of forensic ecology on eight Western parks, including Mt. Rainier and Olympic, in order to find out how polluted they were and where those pollutants came from.What WACAP found was disturbing. Of the 100 or more toxic substances tested for, 70 were found. Mercury levels in fish in both Olympia and Mt. Rainier exceeded EPA thresholds for human consumption. And the air was filled with pollutant run-off from local cities and agriculture.”The choices we make locally can affect these national parks when they’re downwind of these agricultural and urban areas,” says Staci Simonich, an associate professor in environmental and molecular toxicology at Oregon State University and one of the WACAP participants researchers. “That’s the study’s take home message.”It may seem like common sense; of course parks that are downwind of major cities are going to be choked with a little extra air grime. But the WACAP study is a first of its kind. And it’s already paying dividends.After WACAP data showed that the pesticide endosulfan was a particularly persistent bugger — able to live and lodge in the local environment for decades after being used — the EPA banned it this spring. Maybe not enough to make you completely trust that weekend escape into the supposed pristine landscape, but at least enough to help you breathe easier.