The pesticide DDT, washing into the river and the fish the ospreys eat, nearly wiped the birds out by the 1970s -- thinning their eggshells to the breaking point. PCBs, industrial chemicals that gather in the bodies of wildlife, also rose to dangerous levels.

The good news is those pollutants are declining, and ospreys are rebounding.

The bad news is there's a new chemical appearing in ospreys, and, unlike PCBs, it's coming from our homes. It is a flame retardant called polybrominated diphenyl ether, or PBDE, and it's as common today as the computers, televisions and furniture that contain it.

PBDEs appear to be rinsing out of homes and businesses in sewage, through treatment plants and into rivers, where they end up in fish and the birds that eat them, scientists say.

That makes the birds a telling barometer not only of what's in the river, but also what is in us -- because we're exposed, too.

Young salmon from the Willamette River near the Morrison Bridge contain concentrations of the flame retardants known to cause neurological damage in laboratory rats, according to new studies by the National Marine Fisheries Service. The levels were twice as high as in salmon from Seattle Harbor, possibly because the Willamette funnels chemicals downstream.

U.S. Geological Survey scientists began tracking chemicals in Columbia River osprey more than 10 years ago. Now they're looking for this new threat.

Branden Johnson, a Corvallis-based biologist with the U.S. Geological Survey, climbs an extension ladder propped on the deck of a boat as two irritated ospreys circle overhead. She plucks an egg from their 3-foot-wide nest atop a weather-beaten piling west of St. Helens.

Taking the egg will scarcely dent the osprey population, since one chick in a nest often dies regardless. But its contents will give scientists a snapshot of toxins building in the birds.

The studies are a combination of painstaking data-crunching and on-the-water bravery. As wind whips up waves near the mouth of the Columbia estuary, biologist James Kaiser leaps from the ladder on a channel marker back to the bobbing boat -- egg nestled in a padded section of PVC pipe.

Biologists credit some of the osprey's resurgence to the U.S. Coast Guard, which gave up trying to keep the birds from nesting on channel markers. Instead, the Coast Guard began adding platforms so they could nest without blocking lights that guide ship traffic.

"The Coast Guard accommodated them instead of trying to do battle with them," Kaiser said.

Scientists keep careful notes on the number of eggs in each nest and how long the birds are off the nests as eggs are retrieved. A laboratory in coming months will check levels of PBDEs in the eggs.

The flame retardants are chemically similar to PCBs and on their way to becoming a modern-day version of PCBs. Although PBDEs have generally not yet reached levels that threaten bird reproduction, like PCBs, they build over time.

Other studies have found levels doubling in some wildlife every three to five years, said Barnett Rattner, a research scientist at the Geological Survey's Patuxent Wildlife Research Center.

"If it keeps doubling, in five or 10 years, we might" reach harmful levels, he said.

PBDEs have been found in household dust and breast milk of Northwest mothers, and levels are rising in people, too. But the compounds have gained attention so recently it's still not clear how much is too much.

Olympia acts

Washington state last month restricted flame retardants in certain new products, such as mattresses -- overriding intense lobbying by the chemical industry. Other states are considering similar moves. Oregon banned two types of retardants but not the third outlawed in Washington.

The problem is that even with the bans, a vast storehouse of the compounds remains in products, such as plastic television housings, already in use.

"This is something we come into contact with on a daily basis, in our homes and in our work," said Michael Ikonomou, a research scientist at Fisheries and Oceans Canada, who in 2003 found that flame-retardant levels in mountain whitefish near the Columbia River headwaters had doubled in less than two years.

Osprey wield tiny spines on their talons to help snatch fish from the water and depend on fish for almost all their food. An osprey pair consumes about 375 pounds of fish during the breeding season.

Osprey eggs along the lowest stretch of the Columbia River, from St. Helens west, and part of the Yakima River had the highest levels of PBDE in testing from 2002 to 2004. That may be connected to PBDE-laden wastewater entering the rivers nearby and to where in the river the compounds tend to settle out.

The same section of the Columbia is the only place the number of osprey young per nest declined from 1997 to 2004, even as the total number of nests increased. It's not clear why -- though eagles, which steal fish from osprey, may have a role.

Mate for life

PBDE levels were lowest in osprey eggs from the more remote headwaters of the Willamette River.

Ospreys mate for life, winter in Mexico and Central America, and return to the same nest each spring.

The emergence of PBDEs is a mirror opposite of the decline of DDT and PCBs, which were widely banned in the 1970s. They built up in wildlife and the environment and took decades to start declining.

Through the late 1990s some osprey eggs from the Columbia contained high levels of DDE, a byproduct of DDT. Their eggshells thinned by nearly 20 percent, and fewer hatchlings survived.

But the DDE levels dropped sharply by the time of repeat testing in 2004. Total PCB concentrations in eggs dropped roughly by half over the same period, according to Geological Survey studies led by Charles Henny, a research zoologist in Corvallis.

On the other hand, mercury levels rose about 50 percent, though they remain below levels known to be toxic to wildlife.

Osprey numbers responded to reduced loads of PCBs and DDE, zooming from 13 pairs on the Willamette between Portland and Eugene in the 1970s to more than 250 today. The number on the Columbia from Umatilla west jumped from 94 in 1997 to 225 in 2004.

"They've finally been released from the reproductive injury of those traditional chemicals," said Bob Grove, a scientist on Henny's team. "It's taken this long for the environment to clean it up."