The birds' eggs contained some of the highest levels of BDEs (brominated diphenyl ethers) ever found in any kind of wildlife, and this was the first time that the deca formulation of BDE has been found in a living organism. The findings add to mounting concern among some scientists that deca-BDE -- the world's most widely used brominated flame-retardant -- is not as harmless as previously believed.
The report, which examined three peregrine falcon populations in Sweden -- two in the wild and one in captivity -- appears in the current edition (Jan. 1) of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, the world's largest scientific society.
Aerial predators that can power-dive on their prey at speeds up to 200 mph, peregrine falcons approached the brink of extinction after World War II. Their decline was blamed mostly on organochlorine pesticides like DDT, which were linked to thin-shelled eggs that broke during incubation.
While BDEs do not produce the eggshell thinning associated with DDT, there has been some evidence of neurobehavioral problems from exposure to the chemicals in laboratory animals, a potential concern for a bird that relies on surprising its prey and diving on it. Two BDE forms -- the penta and octa versions -- will be banned in member states of the European Union beginning later this year, and the main U.S. manufacturer of the products recently announced its plans to phase out production of penta- and octa-BDEs as part of a voluntary agreement with the U.S. EPA.
"We found high concentrations of all the different BDEs in both wild populations," says Cynthia de Wit, Ph.D., an associate professor at Stockholm University's Institute of Applied Environmental Research and lead author of the study. "The total concentrations of all the BDEs in the wild falcons are some of the highest seen in any wildlife globally."
Finding the deca form of BDE in the falcons was a surprise to the researchers since that formulation has long been considered too big a molecule to cross cell membranes and be taken up by wildlife or humans. "This is the first time anyone has found deca in wildlife," de Wit says.
"The fact that we have found [deca] in falcon eggs means that it is in their food, is taken up from the gut and is transferred to the eggs," de Wit says. "Thus, deca seems to cross cell membranes without too much trouble."
The new findings add to growing concern that the deca molecule might not be as harmless as previously believed, de Wit says.
Researchers from the University of Maryland, also reporting in the current issue of Environmental Science & Technology, recently found evidence that fish exposed to deca can metabolize it into the lighter and more harmful penta and octa forms.
The European Union recently conducted an environmental risk assessment on deca. In early December 2003 it concluded that deca poses an acceptably low risk and will not be banned.
Many scientists, however, advocate a more cautious approach. "We discovered the DDT problem because bird populations crashed," de Wit says. "They still haven't completely recovered from DDT, so new effects could be masked. Or the BDE concentrations haven't gotten high enough yet to cause a recognizable effect."
"The least that should be done is to reduce exposure, especially for humans," de Wit says. "Deca does not seem to be a very stable molecule and I am concerned that the release of huge amounts of deca over many years will lead to a buildup in the environment that will then slowly degrade to BDEs that are much more bioavailable."
There is a high probability that peregrine falcons in North America could face a similar risk from deca exposure, de Wit notes. "According to statistics from 1999, 24,300 tons of deca were used in the Americas, compared to only 7,500 tons in Europe," de Wit says.
The Swedish Society for Nature Conservation provided funding for this research.
-- Jason Gorss
The online version of the research paper cited above was initially published Nov. 25 on the journal's Web site. Journalists can arrange access to this site by sending an e-mail to firstname.lastname@example.org or calling the contact person for this release.
EDITOR'S NOTE: The U.S. Fish and Wildlife Service's Web site about the recovery of the peregrine falcon can be seen at: http://endangered.