Polybrominated 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. Now 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.
UC Riverside scientists have done research using rat
tissue that shows that PBDEs disrupt mechanisms that are
responsible for releasing hormones in the body. Moreover,
their work has shown that like polychlorinated biphenyls
(PCBs), whose manufacture in the U.S. 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 neuroscience
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. 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,
mattress 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. When people
ingest food contaminated with PBDEs, it adds to their
body burden over their lifetime.
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 U.S. Environmental
Protection Agency as well as internationally by other
In a paper to be published in a forthcoming issue of
Neurochemical Research, Curras-Collazo and Coburn, in
collaboration with Prasada Rao S. Kodavanti, a senior
research toxicologist at the U.S. Environmental Protection
Agency, 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
"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.
"Due in part to our lifestyles -- electronic equipment,
car and airplane travel, computers -- PBDEs bioaccumulate,
increasing their concentration in human and animal tissues
over time," she said. "They are difficult to
get rid of, persisting in the environment and in our bodies."
In the United States, 80-90 percent of industrial chemicals
destined for use in commercial products are sold without
any legally required premarket testing.
"We need a different legal strategy," said
Carl Cranor, a professor of philosophy at UCR who researches
legal philosophy, regulatory policy and philosophic issues
in science and the law. "Unauthorized chemical invasions
usurp important decisions over which, at a minimum, citizens
should have considerable collective control. Invasions
that also pose risks or harm are additional wrongs."
With the help of funding from the University of California
Toxic Substances Research and Teaching Program and the
University of California Institute for Mexico and the
United States (UC MEXUS), Curras-Collazo and Coburn now
are studying other mechanisms, such as nitric oxide signaling,
through which PBDEs act to cause neurotoxic effects. They
also are researching the potential effect of the chemicals
on blood pressure regulation, especially as a consequence
of perinatal exposure such as that experienced by infants
"While we plan to increase and continue our focus
on the mechanisms of PBDE toxicity, our long-term goal
is to investigate the neurodevelopmental effects of PBDEs,"