Environmental ▼ News A new record for PBDEs in people ple are taking up increasing concentrations of PBDEs for seven years, particularly in North America (Environ. Sci. Technol. 2001, 35, 274A–275A), but these data are higher than what extrapolating from previous trends would predict, Birnbaum says. Most PBDE MYRTO PE TRE AS
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he newest data on polybrominated diphenyl ether (PBDE) flame retardants in U.S. residents, which are published in this issue of ES&T (pp 5177–5182), include the highest concentrations yet reported in humans. The data reveal some disturbing trends, experts agree. Kurunthachalam Kannan of the New York State Department of Health and his colleagues collected data that set records on two fronts, says Linda Birnbaum, director of experimental toxicology for the U.S. EPA’s National Health and Environmental Effects Research Laboratory. The group of 52 people whose tissue Kannan collected and analyzed harbors the highest individual PBDE concentrations yet reported—9630 nanograms of PBDEs per gram of lipid (ng/g) in a 32-year-old man and 4060 ng/g in a 23-year-old woman. Taken as a whole, the group also has the highest median (77.3 ng/g, which equals 77.3 parts per billion [ppb]) and mean (399 ppb) levels, she says. The research is noteworthy for using human adipose tissue, which was donated by David Rapaport, a New York City-based cosmetic surgeon who performs liposuction. Kannan and his colleagues argue that adipose tissue is more representative than the human blood or breast milk that are the basis of most reports of PBDEs in humans to date. “The levels of lipids in blood and breast milk can vary every day, depending upon what you eat,” Kannan says. The study includes 12 samples from men, which is important because most PBDE studies in the United States have focused on samples from women. Kannan and his colleagues say that they found no significant difference between the PBDE levels in the men and women. Scientists have known that peo-
Researchers are finding high levels of PBDEs in discarded electronics (ewaste) and auto shredder waste, which may become a source for the chemicals to enter the environment.
researchers “are seeing levels between 4 and 400 ppb in [human] blood and milk,” explains Arnold Schecter, a public-health physician at the University of Texas Health Science Center in Dallas. Although researchers have not seen human health effects associated with high PBDE body burdens, animal studies have shown that the chemicals can cause liver toxicity, disrupt thyroid hormone levels, and lead to developmental neurotoxicity and reproductive toxicity (Environ. Sci. Technol. 2004, 38, 386A–387A). The PBDE levels in the two people with exceedingly high concentrations in Kannan’s study are on a par with levels that have been shown to cause effects in animals in some of these studies, Birnbaum says. “There really is no margin [of safety] for some of these highly exposed people,” she says.
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Scientists suspect that infants and toddlers are the most vulnerable population (Environ. Sci. Technol. 2005, 39, 79A–80A). Another research article in this issue of ES&T (pp 5121–5130) suggests that house dust is a major source of PBDE exposure for young children. More than half of the people in Kannan’s study also had higher amounts of PBDEs than PCBs in their fat, a U.S. trend that many scientists have noted as both significant and troubling. The PBDE concentrations in the two people with the highest overall levels were more than 100 times higher than their PCB concentrations. Most of the people in the new study had uptake patterns for individual PBDE compounds that match what researchers have come to expect. But 14% of the individuals in the study, including those with the highest overall PBDE levels, had dominant concentrations of brominated diphenyl ether–153 (BDE–153), according to Kannan and his colleagues. This is noteworthy because BDE–153 makes up only about 4% of the commercial Penta and Octa PBDE formulations. This pattern has previously been seen in electronics recycling workers. Kannan and his colleagues suggest that occupational exposure may account for some of the high BDE– 153 levels, but the manuscript musters little evidence to support this contention. Myrto Petreas, an environmental scientist whose California EPA lab has looked for the compounds in breast milk and adipose tissue from breast biopsies, debates the hypothesis and suggests that environmental exposures are a better explanation. Petreas predicts that BDE–153 may ultimately become the dominant compound in people worldwide. —KELLYN S. BETTS © 2005 American Chemical Society
Normal or not? Oocytes—immature female egg cells—have been found in the testes of male X. laevis frogs that lived in outdoor tanks in South Africa.
LOUIS DU PREEZ, POTCHEFSTROOM UNIVERSIT Y
The controversy over whether the herbicide atrazine affects sexual differentiation in frogs is hopping again. A study in this issue of ES&T (pp 5255–5261) reports that gonadal abnormalities—in particular the presence of immature female egg cells, or oocytes, in the testes of male frogs—are common in Xenopus laevis, the “lab rat” of amphibian species. The research, funded by atrazine manufacturer Syngenta, suggests that such abnormalities may be a normal part of development, according to the authors. But other amphibian experts describe the results as “amazing” or “surprising” and say that they have never seen such abnormalities in laboratory studies. Atrazine is one of the most commonly used herbicides in the world, although it is banned in the EU. In 2002, University of California, Berkeley, amphibian endocrinologist Tyrone Hayes reported that atrazine exposure as low as 0.1 parts per billion induced gonadal abnormalities—multiple gonads or multiple testes and ovaries—in male X. laevis (Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 5476–5480). The paper set off a heated and acrimonious debate between Hayes and Syngentafunded scientists over atrazine’s effects on frogs. In October 2003, U.S. EPA experts and a special pes-
ticide scientific advisory panel concluded that studies supporting and refuting the finding all suffered from confounding effects (Environ. Sci. Technol. 2004, 38, 107A–108A). Despite the controversy, atrazine was re-registered for another three years by EPA in October 2003. The new paper describes microcosm experiments conducted in 12 big outdoor tanks in X. laevis’s native land, South Africa. The researchers report that more than 50% of newly metamorphosed X. laevis frogs had testicular oocytes, regardless of whether they were exposed to atrazine. The incidence of oocytes was much lower in 10month-old males, which suggests that oocytes in the young frogs may be a “normal” part of development that resolves itself as the frogs age, say the authors. “Most researchers do spot-check sections and, in doing so, would miss the oocytes,” says corresponding author Louis du Preez, a biologist with Potchefstroom University (South Africa). “We sectioned the complete testis and examined each and every one of the sections,” he adds. But Columbia University biologist Darcy Kelley says that she has never seen such oocytes in control frogs in her lab. “We have run extensive studies on the effects of hormones on gonadal sex for these studies. We section every gonad . . . and we do not observe testicular oocytes,” she states. All the amphibian experts contacted for this story echoed her views. Hayes also questions the paper, noting that he has never seen testicular oocytes in atrazine-free or atrazine-exposed Xenopus and did not report them in a 2001 paper that focused on other gonadal abnormalities. A likely explanation, Hayes suggests, may be that the tad-
News Briefs POPs treaty targets further chemicals
A key outcome of the latest UN treaty negotiations on persistent, bioaccumulative, and toxic pollutants is a new review committee for evaluating which additional chemicals should be placed on the treaty’s list of banned substances. The Stockholm Convention on Persistent Organic Pollutants (POPs), which entered into force last year, currently has 12 hazardous pesticides and industrial chemicals slated for worldwide phaseouts. Participating governments agreed at the May meeting, however, to further exempt the pesticide DDT from elimination until safe, affordable, and effective alternatives can be developed for combating malaria. Further chemicals nominated for inclusion on the POPs list include two flame retardants, pentabromodiphenyl ether and hexabromobiphenyl, and two pesticides, lindane and chlordecone. For more information, go to www.pops.int.
Are low levels of lead in water risky?
Because little information is available on the health effects of drinking water contaminated with low levels of lead, the U.S. EPA should coordinate with the U.S. Centers for Disease Control and Prevention in pursuing research into this risk, according to a U.S. Government Accountability Office (GAO) report. Lead levels in Washington, D.C.’s drinking water appear to be dropping in response to the addition of orthophosphate, an anticorrosion agent, according to District of Columbia’s Drinking Water: Agencies Have Improved Coordination, but Key Challenges Remain in Protecting the Public from Elevated Lead Levels. To view the report, go www.gao.gov/ new.items/d05344.pdf.
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RHONDA SAUNDERS
Do male frogs naturally have female traits?
Environmental▼ News poles were reared at low temperatures. Temperature can affect the ratio of males to females in amphibians, and salamanders raised at low temperatures develop such oocysts, he says. Du Preez and his colleagues do report that the water temperatures in the tanks were initially 10 °C and rose to 20 °C by week 10. The tadpoles began metamorphosing to
frogs at week 10. Du Preez says that he, too, was surprised by the large number of frogs with testicular oocytes. However, he rules out temperature as the cause because it was not significantly lower than in local natural ponds and his group has found some oocytes in mature frogs from another area. “My feeling is that this is a natural phenomenon, but I
still have to prove this,” he admits. Meanwhile, to comply with EPA data requirements, Syngenta is funding two independent labs to conduct parallel dosing experiments on X. laevis to see whether they can obtain reproducible results. The frogs will then be sent to a different lab for examination. The results could be made public in 2006. —REBECCA RENNER
Environmental▼ News PERSPECTIVE Canada’s research funding system works Canada produces far more toprated environmental science than would be expected, given its size, experts say. They credit Canada’s grant system, which gives researchers more freedom than the U.S. approach does. A 2002 profile of Canadian environmental science from the Observatoire des Sciences et des Technologies, a nongovernmental measurement organization, reveals that from 1980 to 1998, Canadian scientists overall published 21,503 articles in 317 journals, compared with 137,692 articles by U.S. scientists in the same journals. However, on a per capita basis, Canadian scientists are publishing 60% more environmental science than their U.S. colleagues. In addition, Canadian researchers dedicate 4.6% of all their scientific publications to environmental sciences, outstripping the United States’ 3.7% rate, says Frederic Bertrand, a coauthor of the report and a project director at Science-Metrix, a science measurement company. More important, the quality of Canadian papers has been steadily gaining, say observers. By 1998, the last year for which data are available, Canada ranked second internationally in terms of “expected citations”—the average number of citations received by the journals in which papers are published—and
just 3% behind the U.S., says Bertrand. Although figures for environmental science alone are not available, Canada’s funding for all science programs combined is thrifty, with per capita funding levels about 39% lower than those in the U.S., he adds. A pillar of Canada’s funding system is the Natural Sciences and Engineering Research Council (NSERC) discovery grant, fiveyear awards averaging $33,000 per year that allow scientists to follow any research track. “It’s a perfect fit to how science is done,” says John Smol, an aquatic ecologist at Queen’s University and the 2004 winner of the Herzberg Medal, Canada’s highest science award. “I did not anticipate any of my top 10 [cited] contributions, and the idea for them probably came in year two or three of the funding cycle after attending a meeting or hearing a talk,” he adds. Discovery grants are guaranteed, as long as applicants maintain a good record over the previous five years. In contrast, the U.S. National Science Foundation (NSF) grants for core research projects provide more money over a 3–4-year period but are much more competitive, says Dave Schindler, an aquatic ecologist at the University of Alberta and a winner of the Stockholm Water Prize. The win big–lose big
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cycles of the NSF system discourage continuity in research programs, says Schindler, a veteran of both U.S. and Canadian universities. “If you run into a minor screwup in your research program, you lose your funding after just getting a program started,” he reports. “The funding stability you get under the NSERC system is a good factor.” The NSF proposals also comprise 15 pages, compared with NSERC’s 5, and have stringent reporting requirements. The larger NSF grants provide more money for the postdoctoral researchers and graduate students who are the engines of cutting-edge labs, counters Alan Tessier, the environmental biology program director at NSF. Although NSF also offers smaller, less-competitive grants, they are not as popular as the core research grants, for which proposals have doubled over the past couple of years, he says. Canada’s environmental research capacity and success get a big boost from star scientists at government labs, which have hired the best people and given them the freedom to explore, says Scott Mabury, an environmental chemist at the University of Toronto. However, Tom McElroy, a senior research scientist with the Meteorological Service of Canada, warns that drastic cuts to the government lab system since the mid-1990s are endangering crucial long-term monitoring and research projects. —JANET PELLEY
