Concentrations of a flame retardant banned by many European countries have been found in Lake Michigan and are increasing, adding to concerns over previous findings that the chemicals were showing up in supermarket foods and women’s breast milk.
In the latest study, sponsored by the National Oceanic and Atmospheric Administration, University of Wisconsin scientists found PBDEs, or polybrominated diphenyl ethers, in sediment hundreds of feet down in Lake Michigan.
Fish and other animals absorb chemicals and pollutants through the environment, storing them in fat that people then eat. Studies in rats and mice suggest high levels can cause liver and thyroid damage, NOAA said.
“They’re really showing up all over the world,” Bill Sonzogni, a University of Wisconsin professor, said Wednesday. “And the Great Lakes — because of the food chain for bioconcentrating contaminants — has sometimes served as a sentinel for other parts of the world.”
Air a possible route
The three-year study found PBDEs of up to one part per billion in the lake sediment — the equivalent of one drop of water in a 10,000 gallon swimming pool. By dating the samples of PBDEs, Sonzogni and scientist Jon Manchester also found that the concentrations were increasing, and that they mirror levels of PBDEs and other flame retardants used since the 1970s.
How the PBDEs and other chemicals get into Lake Michigan is still not entirely clear, but the air appears the mostly likely way.
“We use a large number of synthetic chemicals and we do not have a good understanding of where these chemicals move to,” Manchester said.
PBDEs are added to plastics used in computers, televisions, furniture and carpets. Some computer makers stopped using PBDEs in 2002, but a flame retardant related to PBDEs is still used in some circuit boards.
No direct correlation has been shown between PBDEs and specific diseases or developmental impairment, and the government has not set any level of use that is considered safe in food.
California to ban
Starting in 2008, California will become the first state to ban two forms of the PBDEs because they accumulate in the blood of mothers and nursing babies. The ban was approved last year but delayed to give manufacturers time to find alternatives.
California researchers found that San Francisco Bay area women have three to 10 times greater amounts in their breast tissue than either European or Japanese women, while Indiana University researchers found levels in Indiana and California women and infants 20 times higher than in Sweden and Norway.
The European Union moved to restrict the chemicals’ use in February 2003. In the United States, the Bush administration has expressed concern that traces of the chemicals, part of a broader class known as brominated flame retardants, have been showing up in people and wildlife. The administration is still gathering information while working with industry on alternatives.
Last year, the Environmental Protection Agency won an agreement from an Indiana company to voluntarily stop producing two widely used forms. The action came after a study by the Environmental Working Group, an advocacy group, found the chemicals in the breast milk of each of 20 women it tested nationally.
The flame retardant chemicals, like PCBs that were banned decades ago in the United States, persist in the environment for years.
In 2001, scientists Sonzogni and Manchester also found that Lake Michigan’s top predator fish — coho and chinook salmon — had PBDEs at concentrations exceeding 100 ppb, among the highest measured in open water fish anywhere in the world.
Now, they say that the concentrations of PBDEs, if unabated, might eventually eclipse PCBs, or polychlorinated biphenyls, as the lake’s main contaminant.
“They’re small but they’re still important,” Sonzogni said. “Because what happens is they tend to concentrate at higher levels in the food chain in the fish, and then we eat the fish.”