When Congress passed the National Park Service Organic Act in 1916, the stated purpose of setting aside nature's wonders was to "conserve the scenery and the natural and historic objects and the wildlife therein and to provide for the enjoyment of the same in such manner and by such means as will leave them unimpaired for the enjoyment of future generations."

There are now 58 national parks in the United States. The National Park Service attempts to carry out that original mandate through policy and practices that protect land, water, air, wildlife and plant life. By and large, Park Service employees do an admirable job preserving these resources and others under their purview with a limited budget.

Despite their best efforts, new research shows that many national parks are rife with pesticides, heavy metals and other airborne contaminants such as mercury. The six-year study, released Tuesday, found 70 contaminants in 20 national parks and monuments, including Glacier in Montana, Denali in Alaska, Big Bend in Texas and Yosemite in California. Contaminants in fish found in the eight most-studied parks exceeded human consumption thresholds.

The study, the Western Airborne Contaminants Assessment Project, found that much of the contamination is believed to have come from overseas, drifting on air currents from Europe and Asia. The United States must do what it can to protect the environment, but these findings are further evidence of the global impacts of nations that refuse or have not yet implemented strict environmental standards to protect air, water and land. Congress and the next president must insist upon more stringent environmental standards when entering trade agreements.

Domestically, more needs to be done to reduce other sources of contamination such as pesticides, which also move substantial distances, as well as emissions from coal-fired power plants such as mercury.

The national parks in this study could well be considered the canary in the coal mine, a warning to other nations who don't require proper environmental protections. There is cause for considerable concern and a clear need for action on the part of policymakers.