The eggs of peregrine falcons living in California's big cities contain some of the highest levels ever found in wildlife of a flame retardant used in consumer products, a new study has found.

Studies of peregrine falcon eggs and chicks by state scientists reveal that the birds hunting in San Francisco, Long Beach, Los Angeles and San Diego are ingesting the flame retardant called PBDEs, believed to leach out of foam mattresses, synthetic fabrics, plastic casings of televisions, electronics and other products. The research shows that the indoor chemicals can contaminate the outdoors and even humans.

The predator birds - which can fly 200 mph - feed on pigeons and other birds, which probably pick up the chemicals in the environment from sewage, landfills and runoff, scientists say. Humans can be exposed by inhaling household dust and absorbing the chemicals through the skin.

"Urban wildlife are the sentinel species that can tell us about chemicals of emerging concern that are coming from city exposures. Information from these species can be useful to us in protecting the sensitive members of our population like infants, children and pregnant women," said Kim Hooper, one of the leading research scientists with the California Environmental Protection Agency's Environmental Chemistry Laboratory.

The work, which Hooper will present today at the annual meeting of the Northern California Society of Environmental Toxicology and Chemistry at UC Berkeley, is part of the state's Wildlife Early Warning System supported by the California Department of Toxic Substances Control.

Included in the study are unhatched eggs and a dead chick from nests of San Francisco's celebrity pair of peregrine falcons, George and Gracie, and in the future might include an unhatched egg from Carlos and Clara, who are raising young at San Jose City Hall.

The prevalence of PBDEs, or polybrominated diphenyl ethers, is raising concern among research scientists. The flame retardants are known as endocrine disrupters because they interfere with the function of the thyroid hormone, which is critical to the proper development of the brain and nervous system. Hooper is concerned that the levels of PBDEs in peregrine falcons are close to levels damaging developing neurological systems in lab rats and mice.

Compared to PCBs

Scientists compare the flame retardants to the notorious PCBs, or polychlorinated biphenyls, because of their potential for harming wildlife and humans, the persistence in the environment and the enormous amounts in commercial use. Three decades after PCBs were banned as insulators in transformers and capacitors, they are still found in San Francisco Bay, although their concentrations in birds and fish are diminishing as levels of PBDEs rise.

Two years ago, California was the first state to ban two of the commercial mixtures of PBDEs - octa and penta. State chemists Hooper and Myrto Petreas and their teams had found that women in Northern California had some of the world's highest PBDE levels in breast milk and tissue. Researchers also found that the flame retardants were contaminating the bay's harbor seals and seabirds, which feed on fish.

A third mixture, called deca, is still in use and represents 70 percent of the PBDEs put into consumer products. Assemblyman Mark Leno, D-San Francisco, has introduced a bill (AB706) to ban all brominated and chlorinated flame retardants, a measure supported by environmental groups.

The four major manufacturers of flame retardants - Albemarle Corp. and Chemtura in the United States, Tosoh in Japan and Israeli Chemicals Ltd. - oppose the legislation, as does the trade group Bromine Science and Environmental Forum.

John Kyte, a spokesman in Washington, D.C., said the group maintains that deca is one of the most studied and effective chemical flame retardants available for electrical and electronic equipment and contributes to saving thousands of lives a year.

One of the concerns over deca is that the amount in the environment is under-reported and might be more prevalent than is measured in the environment because it is unstable and breaks down to other forms of PBDEs.

But the trade group's literature says the deca mixture is not a significant source of the wide array of PBDEs found in the environment.

The state findings that will be released today appear to contradict that argument.

The state chemists found high deca levels when they measured the concentrations in peregrine falcons that live in California's big cities. Overall, the eggs from the birds in urban areas contained higher levels of PBDEs than eggs from coastal or inland regions.

They also found what could be the breakdown products of the deca in the peregrine falcons. These and other data are consistent with the breakdown of the deca to the banned PBDEs, they say.

State scientists decided to study the predatory birds, although there are only seven known nesting pairs in the Bay Area. Along with other raptors and brown pelicans, their numbers plummeted when DDT and other chlorinated compounds caused thinning and breakage of eggshells. Scientists fear the PBDEs will do the same.

The UC Santa Cruz Predatory Bird Research Group at the Long Marine Lab in Moss Landing had 131 eggs on hand for the study, including 95 from California. Researchers had been saving and freezing unviable eggs since the mid-1970s when the scientists started trying to repopulate the species. Most were found as unhatched eggs in wild birds' nests.

"We certainly weren't thinking about flame retardants, but when you have a biological sample, you don't just throw it away," said biologist Janet Linthicum, a research associate at the bird research group.

George and Gracie

In the study, two eggs and one dead chick produced by San Francisco's George and Gracie were among the samples containing high levels of PBDEs, including deca, Hooper said.

The high-flying pair gained fame as Market Street observers watched them hunt birds on the wing downtown. In 2005, they set up a nest on the 33rd floor ledge of PG&E headquarters, where a video camera recorded their intimate personal life for the Web. The next year, they moved to a skyscraper across the street at 201 Mission St. Last year, the Santa Cruz lab removed the eggs from their nest on the west span of the Bay Bridge, saying it was necessary to safeguard the babies when they fledged. The mating pair returned briefly to the PG&E nest box to produce an egg that was incubated by the bird lab. Since then, the birds have disappeared from public life.

George and Gracie haven't been seen at all this nesting season.

"We don't know what happened to George and Gracie," said Linthicum. "We're hoping they'll show up someplace else."