A soon-to-be released study shows tundra swans get sick from eating lead-laden soils at concentrations as low as 500 parts per million, say biologists with the tribe, which is pressing for ambitious cleanup of the Silver Valley mining pollution and has sued mining companies blamed for it. We know at 500- to 1,800-parts-per-million lead, birds are dying, biologist Phillip Cernera said. Theyll have to eliminate that risk. Federal officials have a new roster of plants, fish and animals whose well-being will help steer the cleanup. The U.S. Environmental Protection Agency list is part of a sweeping study of metals pollution in the Coeur dAlene River basin. The list represents species called receptors because they are exposed to and potentially harmed by mining waste. It relies on input from agencies and the public. Officials point out any cleanup will have to consider impacts on people and deciding what cleanup goal is an acceptable risk. Dolly Hartman of St. Maries is leery of wild rice as an indicator of the basins historic health. The plant was introduced to Lake Coeur dAlene in the 1930s. If it isnt native, there isnt any historic impact.