Photo credit: Hadoram Shirihai and Brett Jarrett, Princton Press
Some records you just don't want to break. But killer whales now hold the dubious honor of being the most polluted European arctic mammal, says a new study published in the latest issue of Environmental Toxicology and Chemistry.
The levels of contaminants measured in whales near Norway were six to 20 times higher than those of other high-Arctic species, such as white whales. Researchers, who used a dart gun to take blubber samples from eight live, free-ranging whales, discovered very high levels of halogenated organic contaminants (HOCs), including polychlorinated biphenyls (PCBs) and chlorinated pesticides. Unsurprisingly, these chemicals are highly concentrated in herring, the whales' primary diet source.Although PCBs, toxphene, and DDT have been banned, these persistent chemicals continue to threaten the health of humans and marine organisms. And new HOCs, such as the polybrominated diphenyl ethers (PBDEs), which are used in flame retardants, are free to wreak havoc, especially in marine organisms that are particularly vulnerable.
These compounds manage to creep up the food chain until they achieve the highest concentrations in marine mammals. One unexpected finding was that the killer whales in this study had lower levels of certain PCBs, pesticides (chlordane, DD), toxpahene, and PBDEs than expected, suggesting a limited ability to metabolize these compounds.
This doesn't change the fact, however, that these whales still contain record-high levels of contamination. Several studies have already shown that these compounds can adversely effect the endocrine and immune systems of marine mammals.
One particular incident stands out: Concerned about the inordinate number of dead whales washing up on shore, a team of scientists from Montreal University, between 1983 and 1999, performed autopsies on 100 dead Beluga whales found next to the St. Lawrence River in Canada. They found that 27 percent of adult and 17 percent of juvenile belugas examined had died of cancer, likely due to exposure to carcinogenic polycyclic aromatic hydrocarbons (PAHs). The scientists also noticed that none of the females over 21 years old seemed capable of reproducing, while 36 percent of the females had lesions in their mammary glands. :: Newswise