This chapter highlights well-known and widely studied environmental issues associated with persistent, long-banned contaminants lingering in the Great Lakes and describes how environmental policies instituted in the 1970s have contributed to water quality improvements. It evaluates the most recent challenges there, namely contaminants of emerging concern (CECs). CECs include pharmaceuticals, fragrances, flame retardants, and pesticides. In 1997, United States and Canada adopted the Great Lakes Binational Toxics Strategy intended to "virtually eliminate" 12 chemicals in the Basin over a 10-year period. Contaminant research and monitoring efforts were reinvigorated in 2010 by a major investment from the White House through the Great Lakes Restoration Initiative (GLRI). The goal was to protect and restore the integrity of the Basin's ecosystem. The GLRI Action Plan identified toxic substances as one of five major focus areas. It also identified CECs as ecosystem threats and called for identification of significant sources of new contaminants.