Common
house dust may be an important source of a potentially dangerous
class of chemicals called polybrominated diphenyl ethers (PBDEs),
according to an exploratory study* by researchers at the National
Institute of Standards and Technology (NIST) and the Environmental
Protection Agency (EPA). Recent studies by others have found
that PBDEs have been accumulating in human blood, fat tissue
and breast milk.
PBDEs
have been widely used in consumer products for years because
they are effective flame retardants, greatly increasing the
fire safety of products ranging from carpeting and cushions
to televisions, computers and coffee makers. In recent years,
however, concerns have grown with evidence that PBDE concentrations
are increasing rapidly both in the environment and in human
tissues and body fluids. Toxicological data on PBDEs is still
limited, but the compounds have been implicated in developmental,
reproductive, neurotoxicity and thyroid effects in rats, mice
and fish, and may be carcinogenic. Researchers in Europe and
the United States found concentrations of PBDEs higher in
Americans than in Europeans, although it is not known if these
levels affect human health.
Some
studies have suggested that people accumulate PBDEs through
diet (similar to polychlorinated biphyenyls or PCBs), however,
diet alone does not seem to explain the high levels of PBDEs
that have been measured in human breast milk and serum. According
to the new NIST/EPA study, house dust and the home environment
are likely candidates for other sources of exposure.
A survey
of 17 homes in the Washington, D.C., and Charleston, S.C.,
areas found high concentrations of PBDEs in household dust,
ranging from 700 to 30,100 nanograms per gram. Researchers
analyzed both dust from floors and clothes dryer lint for
22 variants of commercial PBDEs and found PBDEs in every sample.
Interestingly, there was little correlation between PBDE levels
and the age of the dwelling or the number of foam cushions
or appliances, but smaller dwellings tended towards higher
concentrations of the PBDEs commonly used in high-impact polystyrene
for TV and computer casings.
Although the new
study is limited, say researchers, it highlights the need
to study house dust as the primary source of PBDE exposure.
In particular, the authors note that small children are more
at risk than adults to dust exposures since they are more
prone to putting dusty hands and toys in their mouths.
*H. Stapleton,
N. Dodder, J. Offenberg, M. Schantz, and S.Wise. “Polybrominated
Diphenyl Ethers in House Dust and Clothes Dryer Lint.”
Environmental Science and Technology, published online
Dec. 29, 2004.
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