Source: US EPA
PCBs, polychlorinated biphenyls, are colorless and odorless chemicals that were widely used in electrical equipment and other industrial applications before they were banned in 1976. These man-made chemicals are considered toxic because exposure to small doses is suspected of contributing to a variety of health problems. PCBs do not quickly decompose into less harmful chemicals, so they are extremely persistent in the environment.
Of the 1.4 billion pounds of PCBs produced in this country before 1976, about half has entered the environment via discharges to air, land, and water. Products that contain PCBs are also still being disposed of. The problem is, PCBs remain mobile in the environment, leaching out of landfills into rivers and lakes, and evaporating into the air. Scientific studies have shown that atmospheric fallout accounts for a substantial amount of the PCBs entering the Great Lakes today.
Most PCBs in the environment end up in rivers, streams, lakes and, ultimately, the oceans. Once there, PCBs enter the food chain and become progressively concentrated from small organisms to large fish and, finally, in people who eat the fish. Many large, fatty fish like lake trout, carp, and chinook salmon have been found to contain PCB concentrations 100,000 to 1 million times greater than the concentrations in surrounding waters. As a result, some fish contain high enough PCB levels that they are considered unsafe for human consumption.
After completing this investigation, students should be able to:
Identify ways in which dangerous materials can enter the environment.
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Making Activities for the Great Lakes, Toxins in Fish: How Should the
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