Forty years ago today, the United States Environmental Protection Agency (EPA) banned commercially manufactured polychlorinated biphenyls (PCBs), acting on evidence of their extreme environmental persistence and toxicity.

Five years before the April 19, 1979, ban, New Scientist published “US losing fight against PCBs – a new cancer risk?”, referencing its 1973 article by Allen and Norback (Vol. 57, p. 289) about changes in nonhuman primates at the Wisconsin Regional Primate Research Center exposed to PCBs.

“As far as the monkeys are concerned, the potential of PCB carcinogenicity is there,” senior author James Allen of the center’s experimental pathology unit stated in the article.

These early research findings were also described in the Summer 1973 issue of Primate Record, the Wisconsin center’s newsletter at the time. The narrative describes how three months of exposure to PCBs at 300 parts per million (ppm) in the animals’ diets resulted in liver enlargement, facial swelling, hair loss and gastritis of the type associated with cancer.

By that time, industrial accidents had at least twice contaminated human food supplies with up to 3,000 parts per million of PCBs. Levels of 28 ppm in milk and 35 ppm in certain fish had also been reported. In previous PCB studies with rats, liver enlargement was the only major reaction.

Quoting Allen, the final paragraph of the newsletter reads, “The discrepancy in clinical findings between the rat and monkey subjects in PCB tests again points to the inadequacy of testing drugs and chemicals only on organisms distantly related to man before certifying them as safe for humans…”

In 1975, the EPA cited the Wisconsin Primate Center team’s findings at its National Conference on Polychlorinated Biphenyls in Chicago. And in 1978, a paper by James Allen et al, published in Pharmacology Biochemistry and Behavior, fully described the toxic effects of PCBs on nonhuman primate health and pregnancy.

While no single study led to the landmark ban, several peer-reviewed studies like the monkey study contributed to the building body of evidence that PCBs cause cancer and other serious health problems. Today, these harmful chemicals are no longer produced in the United States.

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Pictured above are PCB cleanup operations on Wisconsin’s Fox River circa 1989.

Photo credit: Wisconsin Department of Natural Resources