BILLINGS, Mont. - Pesticides, heavy metals and other airborne contaminants are raining down on national parks across the West and Alaska, turning up at sometimes dangerously high levels in lakes, plants and fish.

The substances detected ranged from mercury produced by power plants and industrial chemicals such as PCBs to the banned insecticides dieldrin and DDT. Those can cause health problems in humans including nervous system damage, dampened immune system responses and lowered reproductive success.

Contaminants that accumulated in fish exceeded human consumption thresholds at the eight parks that researchers focussed on most: Sequoia and Kings Canyon, Mount Rainier, Olympic, Glacier, Rocky Mountain, Gates of the Arctic and Denali national parks and Alaska's Noatak National Preserve.

Western Airborne Contaminants Assessment Project: http://www.nature.nps.gov/air/Studies/air_toxics/wacap.cfm