Chuck Bednar for redOrbit.com – Your Universe Online
Not really, but they are one of the most contaminated avian species on the planet, according to researchers from the University of Michigan in a recent edition of the Journal of Great Lakes Research.
Nil Basu, an associate professor at McGill University who conducted his research while at the Ann Arbor-based university, and his colleagues analyzed hepatic polybrominated diphenyl ether (PBDE) levels in Wisconsin river otters and Michigan bald eagles from 2009 to 2011.
According to PlanetExperts.com, the researchers examined 33 eagles, and found that all but two of them tested positive for at least four common types of PBDE, a type of flame retardant which were commonly used from 1970 through 2004, when they were banned and/or phased out.
In fact, one of the bald eagles tested measured at 1,538 parts per billion PBDEs in its liver, the website explained. In comparison, the median concentration in humans in the US is about 30 ppb, making it one of the highest concentration rates in the world.
Previous studies have linked exposure to the substance to liver, thyroid and brain damage in humans, and in birds, it has been associated with hormone disruption, reproductive issues and behavioral and developmental problems. While the population is stable, the eagles had PBDE concentrations that were “among the highest…in liver tissues of any wildlife.”
“While the sensitivity of eagles to PBDEs has yet to be determined, there is a possibility that the exposures reported here may be associated with sub-clinical effects,” Basu explained Monday in an interview with Scientific American. While the flame retardant is no longer used, it can still be found in air, dirt and residents all over the world, including in and around Michigan,
The chemicals “are everywhere. They build up in the food chains so that top predators – such as bald eagles – accumulate high levels,” Basu added. The compound seeps out of the products they were used in, he noted, and once it gets into the environment it can stay there a long time. Basu believes that the birds were exposed to the flame retardant by eating contaminated fish, but noted that they may also have inhaled it or licked tainted dust off of their feathers.
A history of PBDE
The four major PBDE compounds found in the bald eagles were components of a flame retardant that was sold commercially as penta-PBDE mixture, which was used in cars, wire insulation and plastics. In 2009, penta was added to the UN Stockholm Convention as a persistent pollutant that was to be phased out internationally. Yet, it has remain present in the environment.
PBDEs are “very persistent” once they get into the environment, explained Indiana University assistant scientist Marta Venier. “We can expect to see PBDEs in wildlife for a long time.” The new study also found PBDEs in the liver tissue of 100 percent of 35 dead river otters collected throughout Wisconsin in 2009 and 2010, Scientific American added.
Exposure to the flame retardants have also been linked to lower nest temperatures, smaller eggs with thinner shells, delayed egg laying, a reduced number of mating calls and loss of appetite in birds, the website added. However, the chemicals affect different species in different ways, so it is possible that the PBDE compounds impact the bald eagles in different ways.
“If there were health problems, it would be kind of under the radar and we wouldn’t necessarily notice in the [dead] birds we got in here,” Tom Cooley, a wildlife pathologist with the Michigan Department of Natural Resources, told Scientific American.
Furthermore, the eagles could have more flame-retardants on them that the research indicates, since Basu and his colleagues only looked for four specific types. While the lead author said that the PBDE levels of the eagles should eventually decrease, that could take “years or decades.”
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