Older children and infants, who may be more susceptible to the harmful effects of the chemicals, can have several times as much as adults, the research team reported Wednesday in the journal Environmental Science & Technology.
The chemicals, known as polybrominated diphenyl ethers, or PBDEs, have been shown in animals to cause thyroid hormone disruption and to interfere with developing reproductive and nervous systems.
Widespread use of the chemicals began with the passage of a California law 30 years ago requiring furniture and bedding to withstand 12 seconds of contact with an open flame without igniting. To meet the standard, foam and similar materials contain as much as 12% PBDEs by weight.
U.S. furniture manufacturers stopped using one form of PBDE -- thought to be the most hazardous -- in 2004, but it is still found in imported furniture. A state law that would have banned a second form of PBDE did not pass in August.
The chemical is released from furniture in dust produced by abrasion and normal wear. Children get larger doses because they come in contact with the fine dust on floors and frequently put their hands to their mouths.
"The health effects are of particular concern for babies, children and pregnant women," said environmental epidemiologist Ami Zota of the Silent Spring Institute in Newton, Mass., who led the study.
The research team, which also included scientists from UC Berkeley, Brown University in Rhode Island and Communities for a Better Environment, a California environmental activist group, collected samples from 49 homes in the San Francisco Bay Area cities of Richmond and Bolinas and 120 homes on Cape Cod and compared levels in those homes with published levels from Canada, Europe and several U.S. cities.
Levels in California homes were 10 times higher than those on Cape Cod, five times higher than those in Texas, six times higher than those in Washington, D.C., four times higher than those in Boston and 200 times higher than those in Europe, where the chemicals are used sparingly.
The researchers also analyzed levels in blood collected by the U.S. National Health and Nutrition Examination Survey.
They found levels were highest in California and the West, lower in the South, lower still in the Midwest and lowest of all in the Northeast.
Levels in children in California were three times those found in their mothers.