Science News - November 26, 2003

Peregrine falcons take up Deca

The eggs of Swedish peregrine falcons contain brominated flame retardants associated with the Deca formulation, according to research posted to ES&T’s Research ASAP website this week (10.1021/es034614q). Falcons are top predators, and they inhabit the highest trophic level in which brominated diphenyl ether (BDE) 209, a Deca molecule, has been found, says the paper’s corresponding author, Cynthia de Wit of Stockholm University in Sweden.

The research also represents one of the first times that Deca has been detected in a terrestrial predator, and it provides further evidence that the compound may be more of a concern in terrestrial ecosystems than previously believed (see earlier Online News story on issues with the Deca flame retardant for more information). Polybrominated diphenyl ethers (PBDEs) may be similar to the heavier dioxins in that they are more likely to biaccumulate in the terrestrial environment, de Wit says. The heavier PBDE compounds may be less of a factor in aquatic environments because they are strongly bound to the sediments, she explains.

The research also shows that, despite its relatively large molecular size, Deca can cross intracellular membranes, or it would not be getting into the eggs, deWit explains. Because the large BDE-209 molecules in the Deca formulation are so hydrophobic that the body has a difficult time removing them from fat, the BDE-209 burdens may be significantly higher in the females that laid the eggs, which were collected by the Swedish Society for Nature Conservation, she says. Because other studies have shown how efficiently animals can break down Deca, the levels de Wit observed imply that falcons must be continually exposed to the flame retardant.

The overall levels of PBDEs in the eggs were up to 39,000 nanograms per gram of fat, which are some of the highest yet reported in wildlife, de Wit adds. Although the PBDEs are not associated with the eggshell thinning that made falcons’ uptake of DDT so problematic, the neurobehavioral problems associated with neonatal exposure to PBDEs could prove problematic for a bird that relies on surprising its prey and diving on it, she says.

"PBDEs are a concern for falcons," says Michael Green, the national coordinator of the American peregrine falcon monitoring program for the U.S. Fish and Wildlife Service (FWS). Although the peregrine was removed from the U.S. endangered species list in 1999, the FWS expects to announce a 13-year monitoring program next month that will include the collection of tissue samples to allow scientists to analyze the levels of contaminants they contain.

Levels of PBDEs are known to be higher in North America than in Europe, and the possibility that they could become more of an issue for falcons "is precisely why we've included a contaminant monitoring program," Green says.

The diet of peregrine falcons consists solely of other birds, and de Wit posits two potential sources for the Deca compounds. Shorebirds, such as wading ducks, are the main prey of falcons living in the northern part of Sweden. Such birds may be taking up PBDEs by filtering contaminated sediments or eating the invertebrates that live in the sediments. And songbirds, such as thrushes and doves, which are more favored by falcons living in southern Sweden, may be taking up PBDEs through worms exposed to soil contaminated via atmospheric deposition or through sewage sludge applied as fertilizer. The falcons may also be exposed to the PBDEs when they overwinter in central European sites with known PBDE releases, she says. —KELLYN S. BETTS