It's summer, and the national parks beckon. But they're far from the pristine refuges that many perceive them to be.
Both polycyclic aromatic hydrocarbons (PAHs, which come primarily from combustion sources) and pesticides are pervasive in 8 diverse US national parks, according to two Environmental Science & Technology studies by international teams of university and government agency researchers.
- "Sources and Deposition of Polycyclic Aromatic Hydrocarbons to Western U.S. National Parks,"  online May 14, 2010.
- "Variability in Pesticide Deposition and Source Contributions to Snowpack in Western U.S. National Parks,"  online May 26, 2010.
The parks studied were Sequoia, RockyMountain, Glacier, Olympic, Mt.Rainier, Denali, Gates of the Arctic, and Noatak.
Pesticide contamination tended to come primarily from the local region. Both currently-used and historically-used pesticides were readily found. Sequoia, RockyMountain, and Glacier were the most contaminated.
PAH contamination tends to come more from human sources, rather than ones such as forest fires. For example, an aluminum smelter near Glacier contributed to a PAH concentration that was about 60,000 times higher than most other samples.
These findings add to a number of previous studies conducted as part of the National Park Service's Western Airborne Contaminants Assessment Project. Participants have included the Environmental Protection Agency, the US Geological Survey, the US Forest Service, OregonStateUniversity, the University of Washington, and others.
- Western Airborne Contaminants Assessment Project.  Sample analysis data for the entire WACAP are downloadable in MS Access format,  which may help reporters develop stories customized to their areas.
Among the cumulative findings:
- 70 of the 100+ toxic substances tested for were found in the parks.
- Many fish in the parks have contaminant concentrations so high that they threaten people and other animals that eat them.
- Hormone disruption, similar to that seen below wastewater treatment plants, is evident in fish in some of the parks.
- Contamination tends to be worse at higher altitude.
- The occurrence of flame retardants is increasing in the parks.
- In some parks, the dominant pollution sources tend to be nearby land uses, such as agriculture or industry. In other parks, pollutants drifting in from as far away as Asia and Europe are more prevalent.