�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 toxicologists.�
In a paper to be published in a forthcoming issue of Neurochemical
Research (the paper is available online), 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 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.
�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 and children.
�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,� Curras-Collazo said.
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