April 21, 2008 -- A flame retardant found in everything from consumer electronics to furniture is contaminating waters where sharks swim and winding up in fish oils sold as nutritional supplements, according to a new study published in the journal Food Chemistry.
Scientists led by Kensaku Kakimoto of the Osaka Prefectural Institute of Public Health in Japan analyzed fish oils purchased from Japanese markets for the presence of the potentially toxic chemical hexabromocyclododecane (HBCD).
The researchers first chemically separated the oils into their basic ingredients, and then used mass spectrometry, a process that looks at charged particles, to identify the presence of HBCD.
They found it in 15 of the 22 samples. While concentrations varied, some sardine and shark liver oils from fish captured near Japan contained "relatively high levels of HBCD, indicating that both the surface and deep seawaters around Japan may have been contaminated," the researchers wrote.
It's unknown how the chemical wound up in the water, but an event as simple as someone dumping a VCR into a landfill could contribute to the problem, since rainwater could wash the chemical into oceans or the chemical could vaporize and enter the atmosphere, according to Tim Fitzgerald, an Environmental Defense Fund marine scientist.
Shark liver oil manufacturers don't always state what species the oil came from, but it is commonly derived from deep-sea sharks, dogfish sharks and basking sharks. As the name suggests, the oil is extracted from the livers, which can make up about 25 percent of the shark's total body weight.
Although certain chemicals in shark liver oil have been studied as immune system stimulants, there is little medical evidence to support some of the oil's purported health benefits, which range from treating radiation sickness to pimple breakouts to cancer.
Shark liver oil does, however, serve as a lubricant in certain popular over-the-counter hemorrhoid creams.
Fitzgerald said chemically contaminated shark and other fish oils, such as cod liver oil, could be particularly toxic when consumed as supplements, since HBCD, PCB's, dioxins and other chemicals concentrate in shark organs, especially the liver.
According to the Netherlands Organization for Scientific Research, which also found HBCD in porpoise and dolphin blubber, the flame retardant "disrupts the thyroid function and the functioning of the nervous system in mammals."
Jan Boon and his team studied the bodies of marine mammals stranded off the coasts of Scotland, Ireland, the Netherlands, Belgium, France and northwest Spain. Together with the Japanese data and prior HBCD studies, the research suggests contamination from the chemical is extremely widespread -- possibly affecting waters, fish and marine mammals across the globe.
Sharks appear to be among the most susceptible to chemical contamination since they are high on the food chain, where chemicals can "bio-accumulate," gradually increasing in concentration as they are passed from the tiniest plankton to small fish and onward up the chain.
"Sharks are ocean apex predators," Fitzgerald explained. "A lot of animals in the ocean wind up in a shark."
He advises that if a consumer still wishes to purchase a fish oil, the individual should look for fish "body oils" instead of "liver oils," since they probably contain fewer contaminants and usually come from smaller fish. Such a purchase would also be better for fish populations, since sharks, which often produce few pups later in life, are "very vulnerable to fishing pressures," he said.
As for HBCD, several countries have initiated studies of the chemical, but thousands of tons of it continue to circulate in products worldwide.
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