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Salmon Tales: Polychlorinated Biphenyls (PCBs)

1.) What are PCBs anyway?      PCB stands for Polychlorinated Biphenyls. The Environmental Protection Agency (EPA) defines them as such: “PCBs belong to a broad family of man-made organic chemicals known as chlorinated hydrocarbons. PCBs were domestically manufactured from 1929 until their manufacture was banned in 1979. They have a range of toxicity and vary in consistency from thin, light-colored liquids to yellow or black waxy solids. Due to their non-flammability, chemical stability, high boiling point, and electrical insulating properties, PCBs were used in hundreds of industrial and commercial applications including electrical, heat transfer, and hydraulic equipment; as plasticizers in paints, plastics, and rubber products; in pigments, dyes, and carbonless copy paper; and many other industrial applications (EPA, 2008)." It turns out that large quantities of substances containing high concentrations of PCBs were dumped into public water sources, contaminating plant life, animal life, and eventually humans. PCBs also leak from old insulation equipment and make their way back to water sources. The main concern surrounding PCBs is the possibility that they may in fact cause cancer in humans. For a comprehensive history of PCBs, please click here.

2.) How are PCBs passed on to humans?      Similar to how mercury accumulates in some large fish, such as swordfish and tuna fish, PCBs accumulate in fish via the food chain. “As fish eat other smaller fish or bottom- dwelling organisms, they take on the *body burden of PCBs present in their prey...” This is a cyclical and exponential process. “...Fish are able to metabolize (break down) some PCBs; those that are not metabolized or excreted accumulate in the fish’s fatty tissues. The result is bioaccumulation of PCBs (Kucewicz, pg. 29, 2005)." The fish are then caught in the wild, or harvested on farms, and consumed by the human population. *To read more on body burden, please click here.

3.) Do PCBs really cause cancer?      In lab animals, administered at unnaturally high doses for the equivalent of 70 human years, yes. The first study conducted on the carcinogenic properties of PCBs was in 1972 by Nagasaki et al. PCBs were found to cause tumors in mice. A series of follow up studies found similar results in rats (Kimbrough et al., 1975; Schaeffer et al., 1984; Norback and Weltman, 1985; National Cancer Institute, 1978). To recreate these results in humans (which is obviously restricted by ethical implications), a human would have to consume 1000x as many PCBs as would ever be found under normal circumstances daily over the course of 70 years! And even at this rate, there is no regard to the differences in physiologic and metabolic processes between lab animals and humans.      The American Council on Science and Health (ACSH) released a publication known as the "ACSH Holiday Dinner Menu." This menu gives a long list of rodent carcinogens that are found in everyday food items - such as celery, carrots, nuts, and bread. This is not to say that we should stop eating these foods. What is important to remember, however, is that the poison (or toxicant, as the ACSH calls them) is in the dose. The following graphic illustrates this point: This example shows how important it is to consider the dose received, even before considering the obvious physiologic and metabolic differences between the lab animals and humans. For your own copy of the ACSH Dinner menu, please click Here.

4.) So what do we know about PCBs and HUMANS?!      There has been no definitive scientific proof linking PCBs with cancer in humans. Most studies that focus on human contamination are those done on the people who worked in the manufacturing of electrical equipment while PCBs were still in-use. These people were exposed to incredible amounts of PCBs by way of mouth (contaminated food and cigarettes), direct contact, and through the lungs. Cancer is thought to have a 10-30 year latency period, and it has been 50 years since these workers were first heavily exposed to PCBs. Despite the fact that these workers have high serum and fat concentrations of PCBs (where PCB’s are stored in the body), there have been no acute or chronic health effects definitively attributed to their exposure to PCBs. The only noted effects are localized and temporary skin and eye irritation related to direct contact (Rosenman, 1992 and Kucewicz, pgs. 15-16, 2005).

5.) Are PCBs found in all foods?      In many foods, yes. PCBs can be found in trace amounts in many of the foods that we consume on a day to day basis. The following graph was compiled by Salmon of the Americas, and represents the total per capita intake of PCBs from consuming various foods as indicated by the Environmental Working Group Report, July 30, 2003. Please visit Salmon of the Americas and SalmonFacts.org It can be clearly seen that there are many other sources of PCBs in our diet, with salmon making up a meager 6%.  Please keep in mind that all of these foods are still well within government-sanctioned consumer guidelines. [REFERENCES]

I want to learn more about... PCB findings in Wild and Farm-Raised Salmon Flawed Science and Misinformation What the experts are saying (Scientific Findings) Organic-Farmed Salmon Conclusions Salmon Tales Home These are some available online resources: Salmon Nutritional Information http://www.farmfreshsalmon.org Title: Farmed salmon, PCBs, Activists, and the Media Title: Who Says PCBs Cause Cancer? The complete, unabridged, definitive source for all PCB information.

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