Researchers Call for More Funding to Study Heath Affects of Fire-retardant Chemicals

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. 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 neuroscience (http://cbns.ucr.edu) 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 said.

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 other toxicologists."

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.

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