MADISON, Wis. (02/14/01) – University of Wisconsin scientists have found high levels of a common chemical flame retardant in Lake Michigan salmon, according to a report published today by the online science journal Environmental Science and Technology.

“The concentrations are among the highest reported in the world for salmon in open waters,” said Jon Manchester, co-author of the report and a researcher in the UW-Madison Water Chemistry Program. The study was funded by the UW Sea Grant Institute and the American Chemical Society.

All 21 of the salmon examined for the study contained chemical compounds called polybrominated diphenyl ethers, or PBDEs, which are chemically similar to PCBs (polychlorinated biphenyls) and dioxins. Like PCBs, PBDEs resist breaking down in the environment and accumulate in animal tissues. Their health risks to humans and wildlife have not been fully assessed, although several studies indicate the risks may be similar to those of PCBs.

The lake's salmon are not harvested commercially for human consumption, but they are the centerpiece of the lake's recreational fishery, valued at $250 million annually.

The Lake Michigan salmon, collected in 1996, had an average PBDE concentration of 80 parts per billion. While information on world-wide levels of PBDEs is relatively scant, the levels in Lake Michigan salmon are about six times higher than the levels reported in 1999 for salmon from the Baltic Sea, the world’s most-studied area for PBDEs, Manchester said.

The Wisconsin scientists were prompted to look for PBDEs in Lake Michigan salmon by a 1996 report by the Wisconsin State Laboratory of Hygiene stating that blood samples from people who ate Lake Michigan fish contained PBDEs.

The concentrations of PBDEs in the salmon were, on average, only about 6 percent as high as the concentrations of PCBs.

“It’s important to note that our study did not address how toxic those amounts of PBDEs might be to the salmon,” Manchester said. “Those amounts could be more or less toxic than the much higher levels of PCBs we found.”

The salmon were taken from the Kewaunee River and from Strawberry Creek in Door County, Wis. Results of the study suggest that PBDEs probably have been spread throughout the lake for at least the lifetime of the salmon, or eight to ten years, Manchester said.

This preliminary study did not address the concentrations of PBDEs in the lake’s water or sediments, Manchester said. Studies of Baltic Sea sediments indicate PBDE concentrations began to accumulate only about 20 years ago, but they are accumulating at a much more rapid rate than PCBs ever did, he said.

Starting in March, UW Sea Grant will support a three-year study to determine where the PBDEs in Lake Michigan come from, whether the concentrations are increasing, and how much is accumulating in the lake’s plankton and fish. Manchester will participate in the study with William Sonzogni, professor of environmental chemistry at UW-Madison and director of the Environmental Health Division of the Wisconsin State Laboratory of Hygiene.

Sonzogni and Karlis Valters, an environmental chemistry researcher at Stockholm University, co-authored the Environmental Science and Technology report with Manchester.

PBDEs and other brominated compounds are among the most effective and economical flame retardants available, especially for plastics. As of the mid-1990s, brominated compounds accounted for a quarter of the 600,000 tons of all flame retardant compounds produced worldwide each year, which includes 50,000 tons of PBDEs.

PBDEs are widely used as flame retardants in plastics for electronic circuit boards and housings for personal computers and television sets. PBDEs are also used as flame retardants in clothing and other textiles, home appliances and business machines, upholstered furniture, carpets and wall coverings, and automobiles. It is believed that PBDEs enter the environment via gradual emission from these products, but the process is not fully understood.

Like PCBs, PBDEs have spread throughout the global environment. Studies in Scandinavia, Europe, Canada, and Japan have found PBDEs in sediments, meat, fish, sperm whale blubber, office air, and human blood, particularly among workers in electronics recycling plants. A recent Swedish study found a 50-fold increase in PBDEs in women’s breast milk during 1972-97.

Relatively few studies of PBDEs in the environment have been conducted in the United States, particularly in the Great Lakes region, Manchester said.

Compared with PCBs, little is known about the possible health effects of PBDE exposure. Early studies suggest that human health effects of long-term exposure may include cancer, liver damage, and thyroid gland dysfunction. Recent research on young mice showed an adverse affect on neurodevelopment, learning, memory, and behavior. Some brominated flame retardants may have hormone-mimicking properties that could cause reproductive problems in wildlife.

“The discovery of yet another chemical contaminant in these salmon is another reason to observe the U.S.-Canadian International Joint Commission’s recent recommendation that children and women of child-bearing age should avoid eating Great Lakes sport fish,” said UW Sea Grant Director Anders W. Andren, a member of the IJC’s Science Advisory Board.

According to the Wisconsin Division of Health, the state's current Lake Michigan fish consumption advisory, based on PCBs, is also adequate for fish containing PBDEs at the levels cited in Manchester's study.

Like PCBs, PBDEs are a group of related compounds, and some forms are more prevalent and bioavailable than others. The tetra- and penta-brominated diphenyl ethers used in polyurethane, for example, have high bioconcentration rates, while the no significant bioaccumulation has been found for the octa- and deca-BDEs often used in electronics.

Chemical structure of decabromodiphenyl oxide (C₁₂OBr₁₀)

The Swedish National Chemicals Inspectorate in 1999 called for a ban on all PBDEs, and the European Union has proposed stringent regulations on the disposal of waste electrical and electronic equipment. According to the Bromine Science and Environmental Forum, preliminary EU risk assessments indicate that octa-BDE and deca-BDE, the two most commonly used PBDEs, pose no risk to the public.

The use of PBDE has increased steadily since the 1970s, ironically, as a direct result of the phase-out of leaded gasoline to reduce lead pollution. Declining production of ethylene dibromide - a key ingredient in leaded gas and itself an extremely hazardous chemical - created a large excess in bromine production capacity that prompted the oil industry and chemical companies to find new uses for it.  The shift  to brominated flame retardants was also partly due to increasingly severe flammability standards imposed on plastic products, which are difficult to meet with the chlorinated flame retardants used previously.

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For more information, contact:

• Jon Manchester, associate researcher, UW-Madison Water Chemistry Program, (608) 265-4182

• William Sonzogni, professor, UW-Madison Department of Environmental Chemistry & Technology, (608) 262-4554, and director, Environmental Health Division, Wisconsin State Laboratory of Hygiene, (608) 224-6200

NOTE: The research article discussed here has been released on the Web to subscribers of the online journals of the American Chemical Society, which includes most university libraries. It was published in Environmental Science and Technology in the spring of 2001:

“Comparison of Polybrominated Diphenyl Ethers (PBDEs) and Polychlorinated Biphenyls (PCBs) in Lake Michigan Salmonids,” by Jon B. Manchester-Neesvig, Karlis Valters, and William C. Sonzogni, Environmental Science and Technology 35:1072-77.

"...one of the most cited recent papers in the field,"
according to the Institute for Scientific Information's Essential Science Indicators.
See Dr. Manchester's comments for ISI's Fast-Breaking Papers for August 2002.