Researchers Call for More Funding to Study Heath Affects of Fire-retardant Chemicals
diphenyl ethers (PBDEs), chemicals used as fire retardants, can be
found in numerous items in the home, such as the television, computer,
toaster and the sofa. As reported in a KNBC (Los Angeles) story on Nov.
28, they are being found in alarming concentrations, in human blood and
breast milk -- a potentially major concern for human health.
In addition, these industrial chemicals have been associated with
cases of feline hyperthyroidism, a potentially fatal condition in cats.
University of California - Riverside (UC Riverside) scientists
interviewed for the KNBC story have conducted research using rat tissue
that found that PBDEs disrupt mechanisms that are responsible for
releasing hormones in the body. Moreover, their work indicated that
like polychlorinated biphenyls (PCBs), whose manufacture in the United
States was discontinued in 1977, PBDEs alter calcium signaling in the
brain -- a critical mechanism for transmitting information between and
within brain cells, for learning and memory, and for regulating the
release of hormones in the body.
"Long-term exposures to PBDEs may pose a human health risk,
especially to infants and toddlers who are more likely to ingest
household dust or acquire these chemicals through mother?s milk," said
Margarita Curras-Collazo, an associate professor of cell biology and
and one of the scientists interviewed for the KNBC story. "How much
PBDE in the body is considered safe is yet to be determined and will
require further federal and state research funding."
PBDEs, which have different forms based on the number and location
of bromine atoms they contain, closely resemble the molecular structure
of PCBs, the researchers said. Because they can slow the spread of a
fire, PBDEs currently are being produced for use as flame-retarding
compounds in a variety of consumer goods, including electrical
appliances, building materials, some foams and upholstery furnishings.
Because they are used as flame retardants, the volume of PBDEs in
household goods is higher in states, such as California, that have
enacted stringent flammability regulations for these products.
PBDEs mobilize into the indoor air and household dust from household
goods, resulting in humans and pets getting exposed continuously to
these toxicants. Over time, PBDEs, PCBs and similar organic toxicants
leach into the environment when household wastes decompose in landfills
or are incompletely incinerated. They are now found in air, water and
soil as well as in wildlife and supermarket foods, the researchers
Some forms of PBDEs are subject to a ban that will become effective
in California in January 2008. The form that is most commonly used in
plastics such as computer casings, is not subject to the ban, however,
but may deteriorate to the more detrimental forms (including those that
are banned) over time.
"It is clear that the environmental levels of PBDEs are increasing,"
said Cary Coburn, a student in the Environmental Toxicology Graduate
Program and a member of Curras-Collazo's laboratory, who also was
interviewed for the KNBC story. "The extent of their toxicity is
currently being investigated by the EPA as well as internationally by
In a paper to be published in a forthcoming issue of Neurochemical Research (the paper is available online in PDF format at http://www.springerlink.com/content/v47015p773863517/fulltext.pdf),
Curras-Collazo and Coburn, in collaboration with Prasada Rao S.
Kodavanti, a senior research toxicologist at EPA, show that the
regulation of calcium in neurons can be compromised by PBDEs and PCBs.
This summer, the three researchers reported in Toxicological Sciences
that PBDEs, like PCBs, can disrupt the neuroendocrine system, which
regulates the secretion of hormones such as those responsible for body
water regulation and cardiovascular function.
"At present, one more mass-produced chemical is finding its way into
our bodies -- one with features similar to a banned substance," Coburn
said. "This in itself should be cause for concern, given that low level
concentrations of hundreds of man-made compounds have been found in the
human body and may act cooperatively to produce harmful health effects."
Curras-Collazo is urging more research funding into the short- and long-term toxicity of PBDEs.