Air quality | Bacterial infection and beach closings | Chlorination by-products
Contaminated soils and sediments | Industrial and agricultural use of water
Persistent Organic Pollutants (POPs) | Radiation | Wildlife populations

Persistent Organic Pollutants (POPs)
In 1972, the United States and Canada signed the Great Lakes Water Quality Agreement to initiate remedial actions to improve the quality of Great Lakes waters, focusing on the issue of excessive loadings of nutrients. In 1978, the two countries signed a revised Agreement to "restore and maintain the chemical, physical and biological integrity of the waters of the Great Lakes ecosystems," with an emphasis on reducing toxic contaminants. The Agreement was amended again in 1987, expanding many of the programs and recognizing that an ecosystem approach was required to truly restore and protect the Great Lakes ecosystems.

The presence of toxic substances in the Great Lakes continues to be a significant concern in the 1990s. In the U.S., some 70,000 commercial and industrial compounds are now in use. More than 30,000 chemicals are produced and used in the Great Lakes region. There have been 362 contaminants identified in the Great Lakes system; of these 362, approximately one-third have been evaluated for their potential toxic effects on aquatic life, wildlife, and human health, according to the International Joint Commission (IJC). In 1985, eleven of the most persistent and widespread toxic substances were identified as "critical Great Lakes pollutants" by the IJC. These critical pollutants are the following:

Alkylated lead Benzo[a]pyrene (a member of a class of substances known as PAHs) Dichlorodiphenyl trichloroethane (DDT) and metabolites Dieldrin Dioxins

Furans Hexachlorobenzene Methylmercury Mirex Polychlorinated biphenyls (PCBs) Toxaphene

All eleven of the persistent toxic substances tend to bioaccumulate in organisms, biomagnify in food webs, and persist at high levels in some areas of the ecosystem of the Great Lakes. In the Great Lakes basin, 43 geographical locations in the U.S. and Canada have been identified as Areas of Concern (AOCs) because of high concentrations of these toxic pollutants. Of these 43 locations, 26 are located within the boundaries of the U.S. and five are shared with Canada, (i.e., connecting channels).

Eight of these pollutants are organochlorine compounds and are potentially harmful because of their persistence, ubiquity, and associated toxicity. Both alkylated lead and methylmercury are heavy metals that are potentially harmful because of their chemical characteristics and demonstrated toxicity. Eight of the eleven IJC critical pollutants are lipophilic and biomagnify within the aquatic food chain, thereby making them available to higher forms of life including humans. PAHs, methylmercury, and alkylated lead also bioaccumulate in human tissues.

Demonstrating health effects in humans from chronic, low level exposure to persistent organic pollutants typically encountered in the Great Lakes region is a challenge for researchers. Human epidemiological studies are limited in their ability to separate health effects attributable to contaminant exposures from those related to other known health factores like smoking, alcohol intake, and general health status. In addition, exposure to contaminants from Great Lakes fish is dependent upon the amount eaten and species consumed. For many parts of the Great Lakes basin, there is little information available on exposure levels, body burdens, and health effects.

Human Health and the Great Lakes design and maintenance provided by
the Great Lakes Commission

Photos: Great Lakes National Program Office of the U.S. EPA
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