SAN FRANCISCO -- The mystery surrounding unhatched eggs and a dead chick produced by George and Gracie, San Francsico’s popular peregrine falcons, has led state researchers to the discovery of high levels of flame retardant in their eggs.

Scientists have found that falcons throughout the state are ingesting PBDEs, a flame retardant used in consumer products, which travels up the food chain via smaller prey such as pigeons.

The chemical leaches out of furniture foam, plastic TV casings, consumer electronics, wire insulation, draperies, upholstery and other plastics, and ends up in sewage, landfills, and runoff, where pigeons and other small birds are thought to ingest it.

Much like the proverbial canary in the coal mine, scientists believe that the health of peregrine falcons can serve as a harbinger of dangers posed to humans.

Kim Hooper, a research scientists with the California Environmental Protection Agency’s Environmental Chemistry Laboratory, told the San Francisco Chronicle that the birds are “sentinel species.”

Information from these species, she said, “can be useful to us in protecting the sensitive members of our population like infants, children and pregnant women.”

The study is being presented Thursday at the annual meeting of the Northern California Society of Environmental Toxicology and Chemistry at UC Berkeley.