Back in the 1970s the waters of Lake Vänern were heavily polluted. The lake was considered to be one of the world's most heavily polluted where mercury was concerned, and its fish had far too high levels of mercury in them to be safe to eat. First and foremost it was the pulp and paper industry and the chemicals industry that were responsible for major emissions of mercury and fibre.

The 1970s saw major changes within the pulp and paper industry. Many small mills were closed down. Those that remained in operation introduced extensive measures for purification of emissions. At the same time the local authorities around the shores of the lake improved the treatment of municipal wastewater. These changes led to the waters of the lake becoming much cleaner. Water transparency improved by almost two meters, levels of phosphorus and organic matter fell, and the levels of mercury in fish also fell. Today the water in Lake Vänern is so clean that, out in the lake itself, it can often be used for drinking purposes directly. Go to Current environmental issues for more information about the environmental problems we are facing today.