Bay Seabird Has Record Level of Toxic Chemical

A fish-eating seabird in San Francisco Bay has the highest concentration of toxic flame retardants found in any wildlife in the world, California scientists reported this week at an international conference.

The chemicals, brominated compounds called PBDEs used in furniture foam and plastic electronic parts, have been building up at an alarming pace in wildlife and human bodies around the world, particularly in the United States.

The extremely high reading in the egg of a Forster’s tern nesting in the bay has mystified and worried experts. It could explain why the birds are having problems breeding.

“Why this particular bird has this particularly high level is unknown,” said Arthur Holden of the state Department of Toxic Substances Control, one of the scientists who conducted the research on the birds.

“It certainly makes your ears perk up to see the highest level in the world.”

Large quantities of various pollutants wash into San Francisco Bay because it drains a sprawling area of Northern California and the Central Valley.

In 2002 and 2003, 118 tern eggs were collected from the bay. The highest concentration was found in a Forster’s tern egg from the East Bay, south of San Leandro, Holden said.

The maximum -- 63 parts per million -- was higher than the level found in peregrine falcons in Europe and carp in the southeastern U.S. -- animals previously found to have the highest concentrations. Levels in humans remain much lower than in wildlife, with the maximum found in U.S. women, approaching 1 ppm in their breast milk.

Throughout North America, concentrations of PBDEs in the bodies of people and wildlife are doubling every two to five years, the highest rate for any contaminant in almost half a century, according to various studies.

PBDEs, or polybrominated diphenyl ethers, were developed by chemical companies to reduce the flammability of upholstered furniture, building materials and electronics equipment.

California has banned two of the compounds, effective in 2008; but the most abundant one, deca, used in electronics, is unregulated and growing in volume. The toxicity of deca is less clear than that of the others.

Forster’s terns are fairly common in San Francisco Bay, with an estimated 2,000, most of them living there year-round.

The birds dive a few inches for their prey, eating small fish, including anchovies, smelt and guppies, in shallow areas where pollutants attach to the sediment.

Terry Adelsbach, a biologist specializing in contaminants at the U.S. Fish and Wildlife Service who worked on the study of PBDEs, said Forster’s terns have problems reproducing. Some colonies have a success rate as low as 7%, which could eventually cause their population to crash.

“It looks like contaminants could be playing a role,” he said.

Flame retardants aren’t the only contaminant plaguing the terns. They also have high levels of mercury and PCBs.