Analyses of six different organic pollutants highly resistant to breakdown, (known as POPs - Persistent Organic Pollutants), were undertaken for Greenpeace on fish out of lake Schwarzsee ob Soelden which is located 9183 feet high up in the Oeztal Alps in Austria. This lake is the highest mountain lake in Europe in which fish are found. It is far away from local sources of pollutant and draws its water solely from the neighbouring mountain tops. The pollutants found in the water enter almost entirely from the atmosphere.
Study: http://www.greenpeace.at/umweltwissen/chemie/pdf_files/neue_dauergifte_alpen_2002.pdf (pdf, 240 kb, de/en)