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.

今天禁止制造这些化学品，因为它们属于一类称为持久性有机污染物（POPS）的化合物。

"'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."

Rifai说，PCB和其他POP是“我们要处理的令人讨厌的21世纪的现实，”她称他们为“复杂挑战”，因为它们可以存在于空气，土壤和水中。

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.

作为对PCB的科学知识增长，政府的关注也是如此。1976年，由于PCB健康问题，纽约州环境保护部禁止哈德森河禁区，并于1979年，EPA禁止PCB生产。

哈德森河几乎不是唯一污染了化学品的水道。由于这些化合物如此广泛使用，因此在德克萨斯州加尔维斯顿湾（PCB和Dioxins）的德克萨斯州的其他高度毒性副产品的Rifai（所有工业化国家）都发现了各种水平的PCB和所有工业化国家。新利18备用许多工业过程。

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