Flame retardants morph into dioxins

From Hamburg, Germany, at a meeting of the Society of Environmental Toxicology and Chemistry–Europe

Polybrominated diphenyl ethers (PBDEs) make up a family of common flame retardants for plastics, foams, and fabrics. Nearly ubiquitous in air and water, these pollutants have gained notoriety for accumulating not only in wildlife but also in human blood and breast milk (SN: 10/13/01, p. 238: Burned by Flame Retardants?). Now, German chemists report evidence that sunlight can degrade these chemicals. The bad news: Their breakdown products include brominated analogs of chemicals that belong to the infamous dioxin family.

Wolf-Ulrich Palm of Lüneburg University and his colleagues set out to study dissolved PBDEs. Because these compounds are only slightly soluble in water, the scientists used an organic solvent and irradiated the solution with ultraviolet wavelengths found in sunlight.

In a surprisingly strong effect, about half the light’s energy went into driving the PBDEs’ breakdown. Palm’s group tested types of PBDEs common in either Europe or the United States. Among the breakdown products, “we have definitely found tetrabrominated dibenzofurans,” which are dioxinlike molecules, Palm told Science News.

Conventional dioxins and furans, toxic compounds that are usually the product of incomplete combustion, have chlorine atoms at up to eight sites per molecule. The most toxic are those with four chlorines. The big question, Palm concedes, is whether their brominated counterparts are comparably toxic.


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Janet Raloff is the Editor, Digital of Science News Explores, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer, specializing in toxicology. To her never-ending surprise, her daughter became a toxicologist.

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