Scripps Howard News Service, Joan Lowy Published May 10, 2004
Contamination from brominated flame retardants is so pervasive in American homes that people cannot avoid exposure to the toxic chemicals, two new studies of household dust found.
Studies by government scientists at the National Institute of Standards and Technology and by the Environmental Working Group, an advocacy group that researches toxic chemicals, found high levels of PBDEs (polybrominated diphenyl ethers) in dust from 27 homes.
The studies raise new concerns about potential health risks to young children because toddlers who crawl on the floor and put their hands in their mouths generally have greater exposure to household dust than adults and because their brain and organ systems are still developing.
The only study of PBDEs in children, done in Norway, found higher levels in 4-year-olds than in adults.
The new studies indicate household dust may be an important source of human exposure to PBDEs, said Environmental Protection Agency scientist Linda Birnbaum, an expert on brominated flame retardants.
Nevertheless, it is likely that food _ particularly fish _ is the chief source of the PBDEs that wind up in people's bodies, Birnbaum said. That's because PBDEs appear to act similarly to their chemical cousins, PCBs, which persist in the environment for very long periods, accumulating in animal fat and working their way up the food chain to top predators, she said.
PBDEs are a class of brominated flame retardants used in thousands of consumer products, from computers to televisions to textiles to foam cushions. Laboratory studies of mice and rats show that some of the most widely used PBDEs can interfere with brain development and thyroid function.
Used extensively since the 1970s, PBDEs did not attract much attention until 1999, when Swedish scientists detected them in breast milk. Further studies found that PBDE levels in women's blood and breast milk have been increasing rapidly over the past three decades, especially in American women.
About 5 percent of women tested have been found to have PBDE levels near or above the levels that have produced health effects in animal studies. Scientists do not know how much exposure is dangerous for people, especially the developing fetus, which is the most vulnerable.
The institute of standards study found high levels of PBDEs in dust samples taken from 17 houses in the Washington metropolitan area. The levels of the chemical components of deca, the most widely used of the PBDE mixtures, ranged from 160 parts per billion to 8,700 ppb. Levels of penta, the second-most widely used mixture, ranged from 200 to 25,000 ppb.
The working group's study found high PBDE levels in dust samples from 10 home around the country. The average combined levels of deca, penta and octa _ a third commercial mixture _ for nine of the homes was over 4,600 ppb.
All the homes in the working group's study belong to new mothers whose breast milk was tested for PBDEs in an earlier study by the organization.
"Exposure to brominated fire retardants is unavoidable," the working group study concluded. "(We) found them in the dust of every home and in the body of every participant tested. ... Even if these toxic fire retardants were phased out immediately, our exposures to them would continue through the foods we eat or from the products in our households."
Institute chemist Heather Stapleton said PBDEs are so pervasive in most indoor environments that she had trouble keeping her uncontaminated dust samples free of the flame retardants.
Peter O'Toole, a spokesman for the Bromine Science and Environmental Forum, a trade association for the brominated flame retardants industry, said the health risk from household dust is "infinitesimal."
"These levels mean that one needs to eat over 10 pounds of dust per day before seeing any effect," O'Toole said.