With the industrialization of the region, much of the lake's shoreline was developed; domestic and industrial waste, due to industry and urbanization, led to the severe degradation of the lake. Unsafe levels of pollution led to the banning of ice harvesting as early as 1901. In 1940, swimming was banned, and in 1970 fishing was banned due to mercury contamination. Mercury pollution is still a problem for the lake today. Despite the passage of the Clean Water Act in 1973 and the closing of the major industrial polluter in 1986, Onondaga Lake remained one of the most polluted lakes in the United States until several initiatives, including a 15-year multi-stage program completed in late 2017, allowed the lake to reach criteria required by the New York State Department of Environmental Conservation and the United States Environmental Protection Agency. This includes implementing a long-term operation, maintenance, and monitoring program to ensure the effectiveness of the remedy.