Polychlorinated biphenyls (PCBs), a group of 209 chemicals that have very good thermal and electrical insulating properties, were widely used in industrial applications for decades beginning in 1929, when they were first commercially produced under the Aroclor trade name. Their popularity grew through the decades as they were used in numerous applications, including adhesives, cables, carbonless copy paper, caulking, floor finishes, plastics, oil-based paint, and transformers and capacitors.
Manufacture of these chemicals is banned today as they belong to a class of compounds known as persistent organic pollutants (POPs).
"'Persistent' means they stick around for a long time and don't break down," says Hanadi S. Rifai, an environmental engineering professor at the University of Houston whose expertise includes PCBs in the environment. "They also bio-accumulate and propagate through the food chain, accumulating in fatty tissue."
PCBs and other POPs are "nasty 21st-century realities that we have to deal with," Rifai says. She calls them a "complex challenge" because they can be present in air, soil and water.
The Environmental Protection Agency classifies PCBs as probable human carcinogens. They also have been shown to cause toxic health effects on the endocrine, immune, nervous and reproductive systems of animals.
But in the early years of widespread PCB use, no one fully realized that the properties that made these chemicals so useful in manufacturing also made them a menace to health and the environment, Rifai says. At least as far back as 1937, scientists began to question the chemical's health effects, and studies emerged in the following decades as PCBs were increasingly found in the environment and outside of manufacturing sites, she says.
"To see PCBs outside of manufacturing and use, for environmental engineers, is a concern," Rifai says.
As scientific knowledge about PCBs grew, so did government concerns. In 1976, the New York State Dept. of Environmental Conservation banned fishing in the upper Hudson River due to PCB health concerns, and, in 1979, EPA banned PCB production.
The Hudson River is hardly the only waterway contaminated with the chemical, though. Because the compound was so widely used, various levels of PCBs are found in a few hundred U.S. waterways and in those of all industrialized nations, says Rifai, who is studying Galveston Bay, Texas, for PCBs and dioxins, another highly toxic by-product of many industrial processes.
Back to Main ENR Cover Story: Lessons From the Hudson River PCB Cleanup Project