The Health Effects of Polychlorinated Biphenyls

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Polychlorinated Biphenyls or “PCBs” are widely known to cause a number of serious health problems. Studies conducted on animals who have been exposed to PCBs have discovered elevated rates of cancer in animals with exposure to PCBs, as well as a number of non-cancer problems, including a depressed immune system, disrupted reproductive health and nervous system function, as well as an effected endocrine system.

Studies conducted on humans have provided similar results. The cancer and non-cancer results of exposure to PCB may be interconnected, as a depressed immune system and affected endocrine, reproductive, and nervous systems can contribute to cancer.


When it comes to classifying something as a carcinogen, the EPA relies on a “weight of proof” method. This means that the more cases there are, the better likelihood there will be that a substance will be classified as a carcinogen. Taking this approach, PCBs have been conclusively identified as a carcinogen in animals and as a “probable” carcinogen in humans.

This substance was first brought to the EPA’s attention in the 1980s, and the first studies were completed in 1987. Peer review of this study agreed that PCBs are likely to be human carcinogens, based on the fact that evidence supports PCBs causing cancer in animals and its potential to cause cancer in humans. While this first study did not take into account different kinds of PCB or how they are mixed, it still stands as one of the best studies into the harmfulness of these substances.

While there is not enough evidence yet to say that PCBs definitely cause cancer in humans, there is enough evidence to suggest it, especially based on the fact that it does cause cancer in animals.

Other Diseases

Because the immune system is vital to the protection of the body and fighting infections, having a depressed immune system is a serious problem. The most widely accepted studies about the effects of PCBs on the immune system were conducted on a number of animals, and show that after exposure to PCBs, across the board, the animals had a decrease resistance to viruses.

In the category of reproductive health, studies have shown that exposure to PCBs affects birth weight, gestational age, conception rates, and live birth rates, all negatively. In that same vein, test subjects that were exposed to PCB from the beginning of life had serious neurological and endocrine impediments, which made it difficult for those subjects to progress at the same rate as test subjects that were not exposed.

Both humans and animals who have been exposed to the substance have difficulty learning and have abnormal thyroid levels, which stunts the individual both mentally and physically.

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