Water Quality

Chemicals and other toxins dumped in the Great Lakes today will affect water quality for decades to come. PCBs and DDT, both banned in the 1970s, still linger in the sand, clay, silt and organic matter found at the bottom of the lakes and other regional water bodies, with newer substances such as mercury and PBDEs emerging every day.

Bottom feeders, such as tiny crustaceans and insect larvae, absorb these chemicals and pass them on to fishes, waterfowl and eventually to humans through a process known as “biomagnification.” For fishes that spend a lifetime eating contaminated bottom feeders, mercury and PCB levels accumulate and can become dangerously high. Contaminated fishes end up on our tables, harming our health and, in extreme cases, potentially leading to birth defects and brain damage.

The majority of mercury contamination in the Great Lakes area is caused by air pollution. Mercury is a by-product of burning coal from coal-fired power plants. The mercury in the air eventually falls back to earth, landing in Great Lakes waters and becoming part of the sediment.

Bacterial contamination from untreated sewage and runoff poses another dangerous threat to our health and our ecosystem. Fecal coliform and E. coli bacteria from animal feces, dirty diapers, failing septic systems and sewer overflows can contribute to higher levels of bacteria. The results are swimming bans and illness for those entering Great Lakes water.

Great Lakes water quality is crucial to sustaining all life in the region, not only because the lakes are a source of drinking water, but also because they are at the heart of our entire ecosystem.

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