Environmental Myth No. 2- PCBs cause human cancers

By Kennedy Maize

In 1979, researcher Renate Kimbrough of the Centers for Disease Control, part of the Department of Health Education and Welfare (now Health and Human Services), shocked the electrical world with an epidemiological study. She found that GE employees from the transformer works at Schenectady, N.Y., exposed to high levels of polychlorinated biphenyls for years, had high incidences of cancer.

The chemical was used as a insulator in transformers. PCBs were valuable because they meant that transformers were unlikely to catch on fire when they failed.

Earlier work with rats, done by Kimbrough had suggested that the chemical could cause cancer. She then took her laboratory research into the field to see whether rat exposures were relevant.

As a result of the in-vivo experiments and Kimbrough’s later epidemiological research, funded by GE, Kimbrough concluded that there was a likely, but slight, positive link between PCB exposure and cancer. The Environmental Protection Agency moved rapidly and unilaterally to ban the use of PCBs. That ban that stands today.

In making the regulatory decision to kill PCBs, EPA convened no scientific process to evaluate the evidence. There was no required adversarial process. The agency simply acted on its own.

As a result of the EPA action, without any litigation or evidentiary process, the electricity business has spent billions of dollars replacing PCBs, remediating sites, and the like. GE caved in after many years of contention and agreed to a Hudson River dredging process that, if PCBs are dangerous, increases the danger, by releasing them from sediments and entraining them in the water. It’s a classic example of misguided regulation.

Today, almost every article or news story about PCBs in the non-technical media describes them as “cancer causing.” That’s simply not true. There is no evidence that PCBs cause human cancers. Indeed, Kimbrough 20 years later – with a lot more epidemiological data – concluded that her earlier research was wrong. PCBs were not linked to cancers in workers that had massive exposures to the chemical.

Few media outlets covered Kimbrough’s disclaimer. One was my friend and former colleague Jack Cushman, who wrote in the New York Times in 1999, “The largest ever study of occupational exposure to toxic PCB chemicals has found no significant increase in cancer deaths among workers who were exposed on the job.”

That’s fine reporting, but note the use of the presumptive word “toxic” in the sentence. There is nothing “toxic” about PCBs.

Similarly, a few years ago, Gregg Easterbrook wrote an interesting article about the environmental cleanup for the New York Times magazine. His argument was that the focus on controlling PCBs, Radon, and Alar was misguided. His article referred to “cancer-causing PCBs.” He wrote a far better and more interesting article for the New Republic in 2004, downplaying the hysteria about PCBs in the Hudson River.

I called Gregg out about the claim of carcinogenesis in the Times, and he agreed with me, replying that an overwrought copy editor inserted the offending “cancer-causing” phrase. I believe him, as science writers for major media outlets have often complained to me that they hype their stories to the very edge of credibility, in order to get them played in the paper or on the broadcast, and then the editors hype them over the top.