Environmental ▼News Salmon flame retardant research raises new questions armed salmon contain significantly higher levels of the polybrominated diphenyl ether (PBDE) compounds used as flame retardants than do wild salmon, according to research published in this issue of ES&T (pp 4945–4949). The research shows that the PBDEs follow the same trends as other contaminants that salmon take up, such as PCBs and dioxins, but it also raises some important new questions about the nature of these persistent organic pollutants.
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grams of total PBDEs per gram of fish tissue [ng/g, wet weight]). In turn, the levels of PBDEs in the farmed North American salmon (median 2.937 ng/g) were significantly higher than the levels in farmed salmon from Chile (median 0.803 ng/g), which were higher than the average levels in wild salmon. In both the farmed and wild salmon, approximately 50% of the total PBDEs that Hites and his colleagues found were in the form of one congener: brominated diphenyl ether
Contaminated fish mystery. Farmed salmon have higher levels of PBDEs than their wild counterparts, although the highest levels were measured in wild chinook salmon from British Columbia, Canada.
The study’s authors, Ronald Hites of Indiana University and colleagues, analyzed the same set of 700 farmed and wild salmon collected from around the world that was also the basis for highly publicized research published earlier this year (Science 2004, 303, 226 –229). As was the case with the 14 contaminants described in the earlier report—which included pesticides such as toxaphene and dieldrin— the researchers found the highest levels of PBDEs, on average, in farm-raised salmon from Europe (the median level was 3.095 nano-
(BDE) 47. This congener is associated with the Penta formulation used in polyurethane foam in furniture, which, together with a second formulation known as Octa, has been banned in Europe and is being discontinued in the United States. The PBDE uptake patterns in salmon do not correlate at all with the levels found in people; samples of fat and blood from North Americans contain levels 10 times higher, on average, than those of Europeans. Exactly how people are taking up PBDEs remains unclear, but some researchers thought that fish could
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be the primary source of exposure for PBDEs, says Tom McDonald of the Office of Environmental Health Hazard Assessment of California, the first state to ban PBDEs associated with the Penta formulation. Hites’ data raise significant questions about this theory, McDonald says. “I’m getting more and more convinced that the high U.S. levels [in people] are due to more of an inhalation route of exposure,” says Åke Bergman of Stockholm University’s department of environmental chemistry. “I don’t see why there should be such a difference between North America and Europe otherwise,” he says. The data, together with other new research investigating PBDEs in foods, raise questions about exposure pathways, agrees Linda Birnbaum, director of the experimental toxicology division of the U.S. EPA’s National Health and Environmental Effects Laboratory. Hites’ study also begs the question of how the farmed European salmon are being exposed to the PBDEs, Birnbaum says. “Why should the levels, especially of BDE-47, be higher in the European salmon than in the North American salmon, when there’s very little Penta in Europe?” she asks. Birnbaum speculates that the heavier brominated compounds associated with the Deca brominated flame-retardant formulation used more extensively in Europe may be breaking down, or debrominating, to produce lighter compounds such as BDE-47. There is already evidence that some fish can break down the Deca compounds in this way (Environ. Sci. Technol. 2004, 38, 9A–10A), as well as evidence that this can happen environmentally. Hites theorizes the fish food fed to the farmed European and North American salmon may come from the same, or similar, sources in the © 2004 American Chemical Society
wild chinook inhabit must also play a role, the scientists interviewed for this article agree. Compared with PBDE levels in other fish, the levels in salmon found in the Hites study are low, according to Salmon of the Americas, an industry group. They claim that the total intake of PBDEs from farmed salmon is only a fraction of that from other foods. Hites and his colleagues suggest that it is “prudent” to consume salmon to avoid the higher levels of contaminants found in salmon. They point out that PBDEs are endocrine disrupters that have been shown to have reproductive toxicity. —KELLYN BETTS
A nationwide census of airborne bacteria
CDC
Scientists at the U.S. Department of Energy’s Lawrence Berkeley National Lab (LBNL) are using microarrays to compile a national database of airborne bacteria, which could be a boon for environmental researchers. Immediately after the September 11 attacks, American security officials began planning for a possible chemical or biological attack, and the Department of Homeland Security set up detection systems in major cities. But the detectors have to be calibrated to ignore background noise or, in the case of a biological attack, ambient airborne bacteria.
Environmental scientists should benefit from an ongoing U.S. national survey of ambient airborne bacteria, which has measured background levels of Actinomyces and other microbes.
“The problem is that we really had to create the technology to do this,” says Gary Andersen of the Center for Environmental Biotechnology at LBNL in Berkeley, Ca. “Nobody else has ever done this before.” Created with the aid of gene-chip company Affymetrix, the current generation microarray chip now holds 500,000 probes for over 9000 taxa. “You end up with a table of what’s present and their relative abundance,” says LBNL research associate Todd DeSantis. “So you can see from the sample when a taxa is declining or if it’s on the rise.” This is the first work that shows microarrays can detect not just the presence but also the quantity of taxa. The findings will be published in the journal Environmental Microbiology. The microarray chips uses 25 DNA-base long probes to bind selected sections of 16s ribosomal DNA. The ribosomal DNA is probed because it has sufficient variability to serve as a marker of biological taxa. DeSantis says designing the first chip for broad environmental
News Briefs U.S. fish advisories increase The number of state-issued fish advisories is on the rise, according to the U.S. EPA’s 12th Annual National Listing of Fish Advisories. State agencies issue fish advisories for water bodies as a warning that elevated levels of toxic chemicals, such as mercury or dioxin, have been found in local fish. Since 2002, the number of lake acres under an advisory increased by 2%, river miles increased by 9%, and coastline by 4%. A large part of the increase in lake acres and river miles occurred because Montana and Washington issued statewide advisories for all of their lakes and rivers in 2003; Hawaii issued a statewide advisory for its entire coastline. EPA Administrator Mike Leavitt notes that advisories grew even as emissions for a number of pollutants dropped. For more on the fish advisories, go to www. epa.gov/waterscience/fish.
More bad air days Warmer temperatures caused by global climate change will speed the formation of ground-level smog and increase the number of “red alert” days when people with asthma, children, and older Americans are advised to stay indoors, a new report concludes. By mid-century, individuals living in 15 cities in the eastern United States will see a doubling of red alert days from 2 to 4 per summer. These conclusions are expressed in a report penned by the environmental group Natural Resources Defense Council and are supported by new, unpublished research conducted by Jonathan Patz of the University of Wisconsin–Madison and Johns Hopkins University, Patrick Kinney of Columbia University, and others. Heat Advisory: How Global Warming Causes More Bad Air Days is available at www.nrdc.org.
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North Atlantic, which are relatively contaminated. However, he acknowledges that this does not explain why the PBDE levels in farmed European salmon are higher. Researchers are also at a loss to explain why wild chinook salmon from British Columbia had the highest levels of contamination of any salmon Hites tested. They posit that it has to do with the adult chinook’s tendency to feed higher in the food web, eating mainly fish, unlike other salmon species that tend to consume more invertebrates and plankton. Because wild Alaskan chinook tested in the study contained significantly lower PBDE levels, the relative contamination of the waters that the
