In spite of their large size, the Great Lakes are sensitive to the effects of a wide range of pollutants. Fortunately, significant efforts to improve wastewater treatment plants have reduced the amount of many pollutants reaching the lakes. Since the 1970s, technology, governmental regulation, and public and private funds have been directed at limiting inputs of phosphorus, PCBs and other specific chemicals.
New laws make it more difficult for polluters to put wastes into the water, air and the ground.
Water quality has visibly improved, and some biological communities have been restored to viability. Much of these efforts focused on pollution coming from point sources, such as waste outlets and discharge pipes. Scientists have begun to document that many toxic substances persist in the environment and food chain for very long periods, accumulate in organisms, and injure the functioning of aquatic and other life. Eating fish is the greatest potential for exposure of humans to toxic substances found in the Great Lakes when compared with other activities such as drinking tap water or swimming. As a result, fish consumption advisories for select species are in place to limit exposure and protect health.