Study: high levels of toxic chemicals in younger orcas

Young Puget Sound orcas have more potentially toxic flame-retardant chemicals in their bodies than their elders, adding to evidence that the controversial chemicals could be hurting the endangered animals, according to a new report by Canadian and U.S. researchers.

In one case, a 3-year-old male orca had roughly twice as much flame retardants as his elders in his pod.

The findings, released today in the journal Marine Pollution Bulletin, surprised some researchers because they defy a notion that orcas become more contaminated as they age because they accumulate chemicals from their food.

The report is especially troubling because the young whales are the future of the Southern Resident orcas — three pods that spend much of the year in Puget Sound. In 2006 the mammals were listed as endangered under the federal Endangered Species Act. Their total population numbers in the 80s.

"We don't really know what sort of impacts these contaminants might have on the population in the future," said Brad Hanson, a wildlife biologist at the federal Northwest Fisheries Science Center in Seattle, and one of the study's authors. "That's what we're concerned about is we're beginning to see these relatively high levels."

The results from the 3-year-old orca mentioned in this study don't appear to be an anomaly, because tests this year of another young orca in the same pod found similar fire-retardant levels, said Hanson.

It's been a worry for years that industrial chemicals such as PCBs and the pesticide DDT are collecting in the blubber of whales.

The flame retardants, called polybrominated diphenyl ethers, or PBDEs, have emerged as a concern recently because they turn up in everything from house dust to women's breast milk.

At high enough levels, PBDEs have been shown to impair the thyroids of marine mammals and harm the brains of other animals. Scientists suspect the chemicals could be worse for fetuses and young animals as they develop.

The high levels in the young orca probably stem from its mother's milk, Hanson said. It's thought the female orcas flush the PBDEs through their milk when nursing.

At the same time, the study also helped supply clues to a mystery about the Southern Resident pods: where they go in the winter.

Tests on tissues taken from L pod whales found higher amounts of DDT, which is consistent with pollution levels off the coast of California. The J pod by comparison had higher PCB levels, which is more consistent with Puget Sound. That corresponds with recent sightings of the L and K pods — but not J pod — off the California coast in recent years.

Warren Cornwall: 206-464-2311 or wcornwall@seattletimes.com