Long-Living Sharks Full of Pollutants

Aug. 3, 2007 — Greenland sharks, which inhabit some of the least populated regions on Earth in seemingly pristine Arctic waters, contain high amounts of human-manufactured industrial waste in their bodies, according to a new study.

Since the main source of the chemicals — polychlorinated biphenyls, or PCB's — was banned in the 1970's, the findings show how persistent such compounds are in the environment and how long-lived, top predator species may carry them for decades.

Co-author Ake Bergman, an environmental chemist at Stockholm University, told Discovery News that he and his team decided to focus on Greenland sharks, since their normal lifespan may exceed 100 years, based on an annual estimated growth rate of just a fraction of an inch.

"I noticed that quite a few recently captured sharks appeared to be older than when PCB's were first manufactured in bulk in 1929," Bergman said.

The chemicals were used in a variety of industrial applications, including electrical-related fluids for capacitors and transformers, heat transfer fluids, lubricating oils, pesticides, paints, carbonless copy paper, adhesives, sealants, plastics, and even in surgical implants.

Bergman and his team measured concentrations of PCB's, as well as the industry-related compounds dioxins and furans, in Greenland shark livers and muscle tissue. Dioxins and furans may occur naturally, such as during lengthy forest fires, but not in the amounts seen in today's environment.

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The shark samples came from 10 females that were accidentally caught in trawl or long-line fisheries around Iceland in the North Atlantic.

According to the study, which has been accepted for publication in the Marine Pollution Bulletin, the highest measured concentration was for the world's most toxic dioxin, TCDD, a compound found in the herbicide Agent Orange, which the U.S. military used during the Vietnam War. The herbicide had other applications from 1961 to 1971.