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Peregrine falcons were almost wiped out in some areas due the use of DDT which causes the egg shells to thin and break before the eyases hatch. Numbers have now recovered, and they are no longer considered to be in danger. They have adapted to modern city life, often to be found nesting on ledges of high buildings.
Once again, the law of unintended consequences has raised its ugly head. The Peregrines adapted to raising their families on the cliff-like towers of big city office buildings. The DDT contaminated places were not the cities. The cities were full of lots of great Peregrine food - millions of pigeons. Seemingly a good solution all around. But....
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California's peregrine falcons, once driven to the edge of extinction by the pesticide DDT, now are contaminated with record-high levels of other toxic chemicals that may threaten them again.
State scientists have found that peregrines in Long Beach, Los Angeles and San Francisco contain the highest levels of flame retardants found in any living organism worldwide.
The findings parallel studies that have detected high concentrations of the chemicals, known as polybrominated diphenyl ethers, or PBDEs, in human breast milk, particularly in California women.
The compounds, which mimic thyroid hormones and can damage developing nervous systems, have spread to wildlife and people worldwide, working their way up food webs.
The concentrations found in California's urban peregrines are similar to those that cause neurological damage in lab mice and rats, resulting in reduced motor skills and altered behavior.
Scientists said the peregrines, the fastest and most agile birds, are being contaminated with the industrial chemicals from eating urban pigeons that scavenge on city streets.
The chemicals are used as flame retardants on electronics and furniture cushions. They begin as indoor pollutants, building up in household dust, then migrate outdoors, where they pollute urban environments.
www.latimes.com
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Kim Hooper, a scientist with the state Department of Toxic Substances Control's environmental chemistry laboratory who led the study, said the PBDE levels in the peregrines have doubled every 10 years, and might still be increasing.
Hooper and his colleagues suspected that because household dust contains PBDEs, top predators in big cities would have the worst contamination, so they tested the eggs of peregrines in 42 locations, including Los Angeles, Long Beach, Newport Beach, Coronado and the San Francisco Bay Area.
Their hunch was right. The eggs in rural inland and coastal areas had only trace amounts of PBDEs, but the urban eggs contained up to 52 parts per million, and one dead chick contained 95 ppm. Scientists consider those concentrations extremely high -- substantially higher than nearly any chemical measured in any species worldwide in recent years.
"We think urban wildlife are sentinels for exposure to indoor pollutants in big cities," Hooper said.
Hooper said a PBDE compound called deca is largely responsible for the birds' contamination. Deca, used in electronics since the 1970s, is produced in large amounts in the United States -- about 80 million pounds a year.
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