Environmental ▼ News High levels of perchlorate found in U.S. mothers’ milk tee member and thyroidologist David Copper of Johns Hopkins University. Other chemicals, such as nitrates and thiocyanates found in cigarette smoke and some vegetables, can also inhibit iodide uptake, but they are less potent than perchlorate. Suppression of iodide is of concern because the thyroid uses it in
of a person’s body weight per day, an estimated value that is 23 times more than EPA’s draft proposal (Environ. Sci. Technol. 2005, 38, 96A–97A). Although the committee based its recommendations on adult human studies, the report does cite a single, industry-funded study of nursing mothers and their children in Chile who live in an PURNENDU DASGUPTA , TE X AS TECH UNIVERSIT Y
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he first sampling of perchlorate in breast milk from nursing mothers in the United States reveals levels as high as 92 parts per billion (ppb), which expose infants to concentrations of the contaminant that are 20 times higher than the safe dose recently recommended by a National Academy of Sciences (NAS) committee. A potentially more disturbing finding is that some of the milk samples are so low in iodide—possibly because of the presence of perchlorate—that infants are receiving much less of this important trace nutrient than the international health experts recommend. This first-ever U.S. survey of perchlorate in breast milk, conducted by researchers at Texas Tech University in Lubbock, is reported in this issue of ES&T (pp 2011–2017) and adds to the growing number of studies that suggest the contaminant is pervasive. “Our findings are very surprising because we found that perchlorate in breast milk is widespread, doesn’t appear to come from drinking water, appears to suppress iodide in breast milk, and in some cases, the levels are really high,” says first author, Ph.D. student Andrea Kirk. The survey analyzed 36 samples from 17 states, drawing from participants contacted through Internet listserv groups for nursing mothers. According to corresponding author Purnendu “Sandy” Dasgupta, the scientists found measurable levels of perchlorate in every sample they analyzed. Perchlorate, whose presence has been linked to both anthropogenic and natural sources, can competitively inhibit iodide uptake to the thyroid gland. Breast tissue concentrates iodide in the same way, so perchlorate may also inhibit iodide uptake to breast milk, says commit-
Andrea Kirk (left) and Kalyani Martinelango make adjustments on a mass spectrometer used to analyze samples for perchlorate. They also found low iodide levels in breast milk, possibly due to the presence of perchlorate.
the production of hormones that are essential to proper brain development. The Texas Tech scientists report that in 6 samples with 10 ppb or higher of perchlorate, iodide levels dropped as perchlorate concentrations increased. This supports the idea that perchlorate is blocking iodide uptake and possibly exacerbating already low levels of the nutrient in nursing moms. These findings come a month after an NAS committee recommended a perchlorate reference dose of 0.7 micrograms (µg) per kilogram
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area with high levels of naturally occurring perchlorate. This study found that “perchlorate in breast milk is high, but maternal thyroid hormones are normal and the newborns are normal and have normal thyroid hormones,” said Harvard thyroidologist and NAS committee member Robert Utiger at the report’s unveiling. Those results seem to be at odds with the new research. However, Chilean mothers enjoy higher levels of iodide in their diet and, consequently, in their breast milk, © 2005 American Chemical Society
Cooper’s calculations. This is not necessarily harmful to infants, say many experts. The NAS reference dose is just an estimate and is accompanied by a great degree of uncertainty. But the experts say that the study raises a warning flag and should be repeated. The other unanswered mystery is the source of the perchlorate. “We think this means that the perchlorate is coming from food,” says Kirk. Perchlorate has already been found in lettuce and milk at partsper-billion levels in a nationwide Food and Drug Administration survey. Recently, Texas Tech investigator Andrew Jackson found perchlorate in commercially grown wheat and alfalfa samples at concentrations that ranged into parts per million fresh weight ( J. Agric. Food Chem. 2005, 53, 369–373). —REBECCA RENNER
Pesticide risks remain uncalculated
USDA
Recent research has reignited an old fuss about the environmental toxicity of pesticides (Proc. Nat. Acad. Sci. U.S.A. 2005, 102, 701– 706). In the paper, researchers point out that the active ingredients of many common pesticides consist of mirror-image structures. These isomers can have very differ-
Farmers might have to use less of many common pesticides if EPA regulations recognized the different properties of chiral active ingredients.
ent toxicities and degradation rates, and this fact is often missed by current U.S. EPA regulations. “In terms of regulations, nobody considers this,” says study author Jay Gan, a professor of environmental chemistry at the University of California, Riverside. “They regulate at the compound level.” About 25% of all currently sold pesticides are chiral chemicals, and Gan says that the resulting isomers function almost like two different compounds. He examined five common insecticides, including organophosphates and pyrethroids. In each of the pesticides, one of the isomers was at least 10 times more lethal than its mirror compound to Daphnia during 96-hour aquatic toxicity tests. He also found that the chiral pesticide isomers degrade at different rates. In the case of two pyrethroids commonly sold to household consumers, he found
News Briefs Revised 1,1,1-trichloroethane emissions
Annual emissions of 1,1,1-trichloroethane in Europe are almost 6 times lower than previous estimates, as reported by Reimann et al. in February in Nature (2005, 433, 506–508). 1,1,1Trichloroethane is an ozone-depleting substance that was phased out under the Montreal Protocol in the 1990s. Analyzing long-term data from Ireland (Mace Head) and Switzerland (Jungfraujoch), an international team of scientists report that recent annual emissions range between 300 and 3400 tons. These numbers revise published emission estimates of more than 20,000 tons per year that were made from short-term data and that had raised questions about the implementation of the Montreal Protocol and underreporting of emissions by EU member states.
Sustainable World Bank
“Economic development does not have to come at the expense of the natural environment—the two are intimately linked,” said Ian Johnson, World Bank Vice President for Sustainable Development, when his organization released its first sustainability report in February. The World Bank is the first multilateral development bank to release such a report, which is based on the popular guidelines drawn up by the Global Reporting Initiative. The report provides details on the bank’s Corporate Greening Program, exploring how the bank “walks the talk” by reducing energy consumption, using renewable energy, recycling, and supporting the local communities in which its 108 offices are located throughout the world. For an electronic copy of Focus on Sustainability 2004, go to www.worldbank.org/ess.
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and they may be less affected by perchlorate than U.S. moms, who appear to be deficient in iodide, Cooper points out. Chilean values were above 300 ppb, whereas breast-milk iodide values in the U.S. survey were as little as 4.5 ppb, averaging around 63 ppb. “These iodide values seem quite low,” says Cooper. The recommended adequate intake of iodide is 90–110 µg per day for infants up to 6 months of age, according to Boston University endocrinologist Elizabeth Pearce. Because infants consume 0.5–1 liter of breast milk per day, it must contain 110–220 ppb iodide to meet this target. The highest concentrations of perchlorate reported in the U.S. breast milk are 20 times higher than the NAS committee’s estimate of a safe dose, according to
Environmental▼ News that the more toxic isomers lingered much longer in the environment. In one case, when sediment samples contaminated with a pesticide were tested after one year, the more lethal isomer was found at twice the levels of the less toxic isomer. “That’s the case with these particular pesticides, but I don’t know if that’s always the case,” Gan says. “The people in the Office of Pesticides Programs are busy with so many regulations and new pesticides that they can’t worry about this,” says Wayne Garrison, a research chemist with EPA. Scientists recognized the importance of chiral pesticides back in the late 1980s, and the issue has become more relevant in recent years (Environ. Sci. Technol. 2000, 34, 9A–10A). “Some registrants have taken advantage of this by enriching or purifying the pesticidally active isomer to reduce the amount of active ingredient needed to achieve effective pest control,” says Ray McAllister, regulatory science and pol-
icy leader with CropLife America. Although more expensive to produce, these enriched pesticides require less application and create marketing opportunities. For instance, Syngenta Crop Protection, Inc., retooled a production plant in the late 1990s to produce S-metolachlor, a formula of the old metolachlor pesticide but with a greater percentage of the active ingredient’s more effective isomer. Syngenta claims that the enhanced isomer ratio reduces the herbicide’s application rates by 35% and lowers the pesticide load to the environment by about 20 million pounds annually. Because of disagreements over registration and marketing of other metolachlor products, Syngenta later sued EPA and another pesticide manufacturer. Garrison says that the Europeans seem to be more on top of this issue than Americans. In Switzerland, for instance, all new herbicides and pesticides can contain only the biologically active isomer.
European scientists have published the most compelling explanation to date for why a trace component of the popular hexabromocyclododecane (HBCD) flame retardant is bioaccumulating in North American and European wildlife. The new research by Jan Boon of the Royal Netherlands Institute for Sea Research (NIOZ) and his colleagues, which is published in this issue (pp 2095–2100), is raising questions about whether HBCD is a suitable replacement for the “Penta” and “Octa” polybrominated diphenyl ether (PBDE) flame retardant formulations that have been banned in Europe and are being phased out in North America (Environ. Sci. Technol. 2003, 37, 8A–9A). HBCD is the third most widely used brominated flame retardant in the world. Toxicological studies suggest that it can disrupt thyroid function and may have developmental neurotoxicity effects.
PHOTODISC
More clues to HBCD isomer mystery
Tests of common dolphins from European waters have found that they are taking up only the isomer of the widely used HBCD flame retardant.
HBCD’s unexpected behavior first came to light when researchers looked for the compound’s individual chemical isomers in wildlife (Environ. Sci. Technol. 2003, 37, 380A–381A). The isomer that often predominates in wildlife samples represents only about 6% of the commercial HBCD product. Boon and his colleagues from the
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Garrison adds that the degradation of the pesticides can be even more complicated than what Gan found. The environment itself can even change which isomer degrades more quickly. In a study of the fungicide metalaxyl, researchers found that one isomer broke down more rapidly in acidic soils, while the other isomer degraded more quickly when the pH of the soil rose above 5 (Environ. Sci. Technol. 2003, 37, 2668–2674). They concluded that the soil and the presence of bacteria that break chemicals down are important factors in determining which isomer might become more prominent over time. Steven Bradbury, the director of the environmental fate and effects division at EPA, says that isomeric mixtures of pesticides have been a well-known issue for some time and that Gan’s paper has captured some of these concepts. “As the research advances, there are things to learn in this field,” he says. —PAUL D. THACKER
University of Amsterdam and the Vrije Universiteit (both in The Netherlands) and the University of Aberdeen (U.K.) report that the isomer was the only form of HBCD found in blubber samples they tested from 10 harbor porpoises and 9 common dolphins from European seas. This new study represents the first instance in which only the isomer has been found in more than just a few wildlife samples, says Boon. Other researchers agree that this finding is attributable to the high trophic level at which cetaceans such as porpoises and dolphins operate. The complete predominance of the isomer is nonetheless surprising because it is different than what scientists have been seeing in the Arctic, says Gregg Tomy, a contaminant scientist at the Freshwater Institute in Winnipeg. He explains that although his tests of Arctic animals occupying higher trophic levels show that they are mainly bioaccumulating the isomer, these
it’s the parent compound or the metabolites which have the potential for adverse effects. There may be multiple mechanisms involved here,” she adds. “The results call for identification of metabolites being formed from HBCD, as well as new toxicological studies of the individual isomers,” agrees Åke Bergman of Stockholm University. For all the importance of the new discoveries, “there are a lot of holes in our knowledge still,” Boon stresses. One is whether the relative enrichment of the isomer is the result of another chemical transformation. Because the HBCD molecule is known to be isomerized by heating at temperatures above 160 °C, researchers recognize that any heating involved when the flame retardant is added to the products that it is meant to protect could shift the isomer ratio. However, this can’t fully explain what researchers are seeing in marine fish and mammals because most of the sediments that have been tested still resemble the technical mixture, Boon says. Additionally, Tomy says that he has found evidence that at least some fish species from the Great Lakes are biotransforming the and isomers into the isomer. In the meantime, research into the compound is revealing even more complexities. Scientists at the Norwegian Institute of Public Health report that enantiomers of the HBCD isomers may have different chemistries in the environment. In research published in this issue (pp 1987–1994), the researchers show that whiting and bib fish are more likely to bioaccumulate the (+) HBCD enantiomer. Other researchers have reported finding and isomers of the compound. “This compound frankly scares the heck out of me in terms of the fact that it clearly is persistent and it is bioaccumulative,” Birnbaum says. “Alpha clearly is hard to get rid of. Why we would [consider HBCD as an environmentally acceptable alternative to PBDEs] is confusing,” she adds. —KELLYN BETTS
News Briefs Fuel-efficient cars are safe
Most Americans have a simplistic understanding of automobile fuel economy: Increasing fuel efficiency leads to lighter automobiles, and lighter cars equal more traffic fatalities. But David L. Greene, a research fellow at the Oak Ridge National Laboratory’s National Transportation Research Center, says this equation is out of date. After examining national aggregates of traffic fatalities from 1966 to 2002, he found that greater fuel economy in the American fleet of cars and light trucks correlated with even fewer traffic fatalities. His study controlled for a host of other variables that changed during this period, such as seat belt use, driver demographics, and speed limit legislation. The research that originally linked lighter cars and increased mortality was published in 1989 and only looked at fatalities from 1978 to 1981. Greene concludes that inspecting traffic fatalities across a larger time span results in a more reliable analysis.
Rethinking electronics recycling
More than half of all U.S. households have electronics items in working condition that are no longer being used, according to a survey conducted by the A.C. Nielsen organization. The survey results were announced in tandem with the introduction of a nationwide initiative called Rethink, which is sponsored by some of the country’s largest electronics manufacturers in collaboration with the U.S. Post Office, the online auction website eBay, and the Silicon Valley Toxics Coalition, an environmental group. The goal is to make dealing with obsolete computing equipment easier for U.S. consumers. The effort is centered around a website: http:// ebay.com/rethink. The site provides a wealth of information about how to sell or donate old computers and gadgets or safely recycle them.
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animals are also taking up the and isomers, which are found in greater abundance in the commercial product. Studies of the Lake Ontario food web show that HBCD, and particularly the isomer, is more likely to bioaccumulate up the food chain than PCBs, PBDEs, or dichlorodiphenyldichloroethylene (DDE), the degradation product of the pesticide DDT, says Tomy. Boon and his colleagues also found persuasive evidence for why the isomer is so much more likely to bioaccumulate than the other two isomeric forms. Researchers had previously hypothesized that cytochrome P450 enzymes, which aid human and animal livers in breaking down toxic substances, might play a key role in biotransforming the isomers. Using liver tissue from laboratory rats and a freshly dead harbor seal, Boon and his group showed that the cytochrome P450 system readily metabolized the and isomers. In contrast, the isomer did not appear to be metabolized; researchers familiar with the study agree that this finding provides strong evidence for why the isomer is so much more likely to bioaccumulate. Perhaps just as importantly, Boon’s group showed that the mammalian cytochrome P450 system was producing hydroxylated metabolites from the and HBCD isomers. “The biotransformation makes these compounds more polar and therefore potentially more easily excretable. But you also add a reactive group, and there are many examples where such a compound binds to physiologically active endogenous compounds and becomes more toxic than the parent compound. This is the case for many of the PCBs and PBDEs,” Boon explains. He says that he has found that fish also produce HBCD metabolites, in as-yet-unpublished research. The hydroxylated metabolites are a potential concern, agrees Linda Birnbaum, director of the EPA’s experimental toxicology division. “We don’t know whether
