A prolific and potentially toxic fire retardant is showing up in Puget Sound marine life ranging from tiny herring to massive killer whales, raising alarms among scientists who warn it could become the next big toxic threat to underwater animals.

"We've got fireproof killer whales," said Peter Ross, a research scientist with the Institute of Ocean Sciences in Canada and an expert in toxic chemicals in marine animals. "We're concerned about this."

The problem appears greatest in south and central Puget Sound — where fish, seals and whales had higher levels of chemicals called polybrominated diphenyl ethers, or PBDEs.

Since the early 1980s, levels of those chemicals in southern Puget Sound harbor seals have soared, a sign of an emerging threat to local killer whales that also feed on fish, Ross said. The whales are on the verge of being listed as a threatened species under the federal Endangered Species Act.

"I'm surprised at the rate of increase [of contamination]," said Sandie O'Neill, a research scientist with the state Department of Fish and Wildlife. "This is definitely an increasing concern, and that's what's getting everybody's attention."

Scientists are unsure how the chemicals are affecting marine life, or what threat is posed to people who eat contaminated fish. The state Department of Health hasn't established safety thresholds for food containing PBDEs.

A bromine-industry spokesman questioned whether the presence of PBDEs was cause for concern.

Production of some versions of the chemicals ended in 2004 because of health concerns. The most widespread version now is considered far less toxic, or not toxic at all, said John Kyte, executive director of the industry-backed Bromine Science and Environmental Forum.

"To simply say, 'We've found PBDEs' ... it's hard to make any meaningful judgment about whether this means anything."

But marine biologists worry the chemicals, used to fireproof everything from computers to mattresses, could interfere with neurological development or throw off an animal's hormones or immune system. PBDEs can linger in the environment for years, increasing the risk they will travel up the food chain as one animal eats another.

New research suggests those orcas may absorb much of the chemicals through the chinook salmon they eat. Puget Sound chinook had between three and five times higher levels of PBDEs and PCBs, a longstanding contaminant, compared with chinook from elsewhere, O'Neill said. This Puget Sound hot spot affects a number of marine creatures, according to studies by state, federal and Canadian agencies discussed yesterday at the Puget Sound Georgia Basin Research Conference, a Seattle meeting of scientists studying the waters shared by Washington and British Columbia.

The fire retardant may wind up in Puget Sound through storm-water runoff; or after floating into the air and then falling into the water, where they can be absorbed by animals scouring the sediment for food; or by plankton, O'Neill said. PBDEs also have been found in house dust and in women's breast milk.

The state Department of Ecology last year called for a ban on PBDEs, except in cases where no replacement flame retardant is available. But the ban proposal has stalled in the state Legislature this year.

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