Toxic chemicals found in Great Lakes salmon

University of Wisconsin (UW) researchers found that all 21 salmon examined contained polybrominated diphenyl ethers (PBDEs), which are chemically similar to PCBs (polychlorinated biphenyls) and dioxins. According to Jon Manchester, co-author of the report and a researcher in the UW-Madison Water Chemistry Program, the concentrations “are among the highest levels of flame retardant reported in the world for salmon in open waters”.

The Lake Michigan salmon had an average PBDE concentration of 80 parts per billion. While information on worldwide 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. 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 (see related story).

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 % 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, Wisconsin. 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 10 years, Manchester says.

This preliminary study did not address the concentrations of PBDEs in the lake’s water or sediments, Manchester says. 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 says.

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 many are accumulating in the lake’s plankton and fish.

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 flame retardant compounds produced worldwide each year. PBDEs are widely used in plastics for electronic circuit boards and housings for personal computers and television sets and 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.

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 behaviour. 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,” says UW Sea Grant Director Anders W. Andren, a member of the IJC’s Science Advisory Board.

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 (see related story). 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.

Like PCBs, PBDEs have spread throughout the globe. 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 but relatively few studies of PBDEs in the environment have been conducted in the United States, particularly in the Great Lakes region, Manchester says.