Government Watch
Drought curbs this year's dead zone This summer's measurements of the low oxygen area off the Louisiana coast known as the dead zone recorded the smallest zone since the 1988 drought, according to Nancy Rabalais, a marine biologist at the Louisiana Universities Marine Consortium. Mapped at 4400 square kilometers, the zone is one-fifth the size of last year's record-breaking 20,000 square kilometers. The two components necessary for stripping the water of oxygen—high nutrient flow from the Mississippi River and a layer of fresh water overlying salty Gulf of Mexico water—were much less abundant this year, thanks to drought conditions in the Mississippi basin, Rabalais says. The drought resulted in lower than average freshwater discharges from the Mississippi River and a lower flow of nutrients in March, April, and May, which contributed to this year's smaller hypoxic zone. —J.P.
targets help to get people around the table to cooperate, then they are healthy," he adds. If the plan sets an aggressive goal, there is a risk that key players in the states and agricultural industry will not sign on, admits Dennis Keeney, a senior fellow at the nonprofit Institute for Agriculture and Trade Policy in Minneapolis, MN. Of the four states with the highest nitrogen re-
leases, only Wisconsin and Minnesota are supportive of the plan's goals, while Iowa and Illinois are strenuously objecting to them. "If we can get a commitment from the agricultural industry to improve their practices, then come back and have another summit after a few years and strengthen the plan, we will eventually reach the goal," he says. —JANET PELLEY
A new route for endocrine disrupters Most studies of endocrine disruption focus on interactions with hormone receptors, particularly the estrogen receptor. Now, Thomas Sanderson and colleagues from the Netherlands' University of Utrecht and scientists from Michigan State University (MSU) are demonstrating that endocrine disrupters can work in a different way by increasing production of aromatase, an enzyme that converts androgens to estrogens. Scientists have known that many other mechanisms of potential interference with endocrine function exist, and Sanderson and colleagues are among the first to prove that this happens. In in vitro experiments using the human H295R adrenocortical carcinoma cell line, the scientists found that 2-chloro-s-triazine herbicides, atrazine, simazine, and propazine dose-dependently induce aromatase activity. At a 30-pM concentration, an appar-
ent maximum induction of about 2- to 2.5-fold was observed after the cells were exposed to the triazines for 24 hours (see figure). These cells, which are like undifferentiated human fetal adrenal cells, can produce a range of steroid hormones. "This is the first documented case, to my knowledge, of aromatase enzyme disruption and a switch from androgen to estrogen," says Lynn Goldman, former chair of the U.S. EPA's Endocrine Disrupters Screening and Testing Advisory Committee (EDSTAC), which is overseeing the development of methods to evaluate chemicals for endocrine disruption. Sanderson and co-worker's results are in agreement with environmental toxicity studies. For example, Andrew Crain and coworkers at the University of Florida-Gainesville found that atrazine induced aromatase activ-
EPA's technology-based approach stands in contrast to California's Department of Agriculture standards, proposed in September, which are designed to ensure that heavy metals do not pose a risk to human health or the environment California's risk-based standards would allow higher levels of metals in fertilizers than technology-based standards, EPA officials say. But the Fertilizer Institute, an industry group supports risk-based standards because they are healthbased and reasonable for the industry to meet Environmental groups say California's standards will increase heaw metal levels in farm fields
EU harmonizes emissions monitoring A European Pollutant Emission Register (EPER), similar to the U.S. Toxics Release Inventory (TRI), is expected to enhance government monitoring of toxic emissions across the European Union (EU). The European Commission (EC) adopted plans for the register under the 1996 Integrated Pollution Prevention and Control directive in late July. The TRI covers more than 600 toxic compounds whereas EPER will cover only 50 pollutants—including greenhouse gases, metals, and organic and inorganic compounds, according to the EC. Contained in the EPER list, however, are a greater number of substance groups than in the TRI, which targets individual chemical species. Like the TRI, EPER's aim is public accessibility, but also emissions monitoring by governments, with governments reporting emissions directly to the EC. Most EU member states already have emissions inventories, but some are weaker than others, and they rely on different measurement methods, making communitywide comparisons difficult {Environ. Sci Technol. .999,33 (3), 61A-62A)
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Environmental News ity in male hatchling alligators {Environ. Heallh Perspect. 1997, 105, 528-533). This line of research is important because it raises the possibility that "a small exposure to atrazine at a critical developmental stage could have a lasting effect," says MSU zoologist John Giesy Sanderson's coauthor. This is because aromatase plays a key role in the sexual differentiation of the central ner-
researchers have found a similar, but less pronounced, effect using placental choriocarcinoma (JEG-3) cells, but not breast cancer cells (MCF-7). Such results do not rule out the significance of the triazine herbicides' effect on aromatase, because the lack of a response could reflect a peculiarity in the engineered cell line or be sex-specific or tissuespecific, according to EPA toxicologist Roger Hawks. Recenuy completed rat studies suggest that atrazine's effect on aroTriazine activates aromatase matase production may Dose-response curves for induction of aromatase not fully explain the activity by triazine herbicides after 24-hour expoeffects observed in the sure. Error bars represent standard deviations animal, according to of four tests at each concentration. Values on EPA toxicologist Ralph the y-axis should be multiplied by four for correct Cooper, whose research aromatase activities. has been crucial in determining how atrazine impacts the endocrine system by affecting the brain-pituitary system These studies showed a dose-dependent delay in the onset of puberty in male rats, and other indications that atrazine affects estrogenic hormones. "The results tend to say that we can see the mechanism in vivo, but it Source: Toxicol. Sci., 2000,54,121-127. appears to occur only at doses that are above those required to alter pubertal vous system during fetal develdevelopment. This indicates that opment in some animals, mechanisms other than just aro~ because aromatase controls the matase induction may be inamount of estrogen in the brain, volved " says Cooper he says. In the brain, which alIt has so far proven very difficult ways starts out female, aroto study the effect of prenatal matase converts androgens to atrazine exposure, Cooper adds, estrogens. Brains that will turn because atrazine alters the horout female are protected by monal support of normal animal other compounds from the efpregnancy and delivery. fects of the estrogen. Brains that will turn out male react to deAlthough many of the tests velop masculine traits, Giesy exEPA plans to use to screen chemiplains. Altering the hormone balcals for endocrine-disruptive efance at this critical time could fects look for binding to the espossibly interfere with the develtrogen receptor, some of the tests opment of masculine traits would detect aromatase induction, explains Gary Timm, one of But fleshing out the details of the EPA scientists managing the such a hypothesis and evaluating EDSTAC process. Two in vivo tests it are likely to prove difficult. The 4 1 6 A • OCTOBER 1, 2000 / ENVIRONMENTAL SCIENCE & TECHNOLOGY / NEWS
involving puberty in rats and one in vitro test under development would be able to pick up such effects, he says. The pubertal female assay detects aromatase induction. But the pubertal male assay is not sufficiently sensitive to detect this effect. The in vitro aromatase assay would be used in conjunction with the male pubertal assay to offset this weakness if the latter assay is used instead of the pubertal female assay. One assay under development, the in utero/lactation assay, would involve both males and females. It could replace either of the pubertal assays and would detect aromatase inhibition, Timm says. —REBECCA RENNER
Chemical Exposure Chemicals linked to developmental defects Mounting evidence correlates rising incidences of developmental, learning, and behavioral disabilities in U.S. children to toxic chemicals. A report released in September by environmental and physician groups offers a comprehensive look at where the chemical contaminants possibly contributing to these disabilities come from. Using U.S. Toxics Release Inventory data, this latest study finds that more than half of the 1.2 billion pounds of chemical emissions reported in 1998 are known or suspected developmental or neurological toxins. The chemical, paper, metal, and plastics industries, together with electric power companies, are the largest industrial sources of reported emissions. The rising incidence of lowbirthweight babies, babies born prematurely, physical birth defects, autism, attention deficient disorder, and other disabilities is leading a growing number of scientists to believe that exposure to toxic chemicals could be partly responsible. Polluting Our Future can be accessed on the Web at www. safekidsinfo.org.
