PCBs: Banned Since 1979, Still in the Sediment

PCBs were banned in the United States in 1979, but they have not gone away. These industrial chemicals — polychlorinated biphenyls — spread so widely before the ban that traces turned up in people and animals around the world, and they still sit in the sediments of waterways today.

PCB contamination is high in the Housatonic River and New Bedford Harbor in Massachusetts. Credit: U.S. Fish and Wildlife Service.

What PCBs are

According to the EPA, PCBs belong to a broad family of human-made organic chemicals called chlorinated hydrocarbons. They vary in toxicity, and in consistency from thin, light-colored liquids to yellow or black waxy solids. They were made domestically from 1929 until manufacturing was banned in 1979.

How they were used

An estimated 1.5 billion pounds of PCBs were made between the 1920s and the ban, for products such as microscope oils, electrical insulators, capacitors and appliances like television sets and refrigerators. Before their consequences were understood, they were even sprayed on dirt roads to keep down the dust.

How they got into the environment

Before 1979, PCBs entered the air, water and soil as they were made and used. Manufacturing wastes containing PCBs often went to dumps and landfills, and occasional spills, leaks and transformer fires released more.

Everywhere, even the Arctic

When the first research results came out in the 1960s, traces of PCBs could be found in people and animals worldwide — not only in crowded places like New York City, but in places as remote as the Arctic. That evidence of widespread, persistent contamination helped bring about the 1979 ban.

How they break down — slowly

PCBs can break down in the environment, but how depends on their chemistry and on where they are. Sunlight breaks them down in the air, shallow water and surface soils; bacteria, algae and fungi biodegrade them in soil and sediments.

The cleanup dilemma

Because PCBs remain in sediments, scientists have to decide whether to dredge the contaminated sediment out of a waterway, or leave it in place and cover it with clean sediment so it can biodegrade naturally. A cap or barrier can also be laid over it to keep it from spreading. Every option carries environmental, human health and financial concerns.

Sources

Based on "What are PCBs?" from NOAA's National Ocean Service, a work of the United States government in the public domain.