treated wells, most of which are shallow, poorly constructed, and used by low-income families, may be in question. The state Department of Public Health did caution private well owners to have their water tested if the well had been flooded. But it is unclear whether well owners struggling to move back into their flooded homes will have the water tested, the officials said. Lab tests of water collected from a small number of rural wells conducted by the University of North Carolina School of Public Health revealed a small amount of viral pathogens and protozoan parasites. State water officials do not usually test for these contaminants. But those at the meeting suggested that monitoring should be considered, because of the looming, potential long-term risk. A virus transported by the flood might move into the shallow aquifer and con-
taminate a family well, speculated Alex Cardinell, senior hydrologist with the U.S. Geological Survey. And under the right conditions, animal feed antibiotics could cause existing bacteria to develop a new resistance, or perhaps create an entirely new bacteria strain. The potential for future disease is compounded by the characteristics of the population living in the flooded areas. A large percentage of the population affected by the flood and by any long-term environmental consequences are low-income individuals, many of whom "already have diminished health status," said Suk. This complicates the potential for conducting a risk assessment aimed at teasing out any flood-related diseases. But it also adds to the urgency of trying to determine what the contamination is Children in the flooded region who play in the water-
ways, roll around on the sediment deposits left on land by the flood, and drink potentially contaminated well water, are at a higher risk than adults. "In general, we are talking about populations who are more susceptible to a particular level of exposure, such as children, who could develop long-term problems such as lower I.Q.s or maybe a reproductive problem," Suk said. "I don't really think we will see the consequences of the exposures that took place in the population 'out east,' as we say here, for maybe another 5, 10, or maybe 20 years, because we just don't know what is in the environment," said Suk. "Wouldn't it be nice," Suk added in an interview, "that if in say, seven years from now if we saw a disease cluster appear that we could look back" and relate it to exposures associated with Hurricane Floyd? CATHERINE M. COONEY
Researchers point toward chiral chemistry as pollution cure Changes in climate, land use, or even a change from inorganic to organic fertilizer, could affect the toxicity of many persistent pollutants, according to research led by David Lewis, an EPA microbiologist at the University of Georgia in Athens. To eliminate these uncertainties, manufacturers should intentionally design chemicals that are chirally pure, Lewis's team concluded. In work published in the October issue of Nature, the team of scientists found that the toxicity of persistent pollutants can be enhanced following a change in the environmental fate of chiral pollutants in soil. Chiral compounds are those that have mirror-image structures, called enantiomers. These include many agrochemicals, accounting for one-quarter of all commercial pesticides. It is already well known that the enantiomers of biologically active compounds have different
physiological properties in biological environments. Half of the top 100 best-selling drugs, including barbiturates, Ritalin, and ibuprofen, are marketed as single enantiomers to avoid adverse side effects. Pheromones, flavor, and fragrance compounds also exhibit similar effects.
Scientists are still debating whether conversion of one enantiomer into the other could occur in the environment or in the human body. But the study and the idea have received mixed reviews from other researchers who study chiral compounds in the environment. The
research is important, said Terry Bidleman, an atmospheric chemist wim Canadian Atmospheric Environment Service, because it is the first to look at environmental factors that might influence enantioselective degradation of pollutants in soils. The authors showed clearly mat manipulation of environmental factors can change the preference for which enantiomer is degraded, he said. Other researchers criticize the study's approach as too simple. "The article describes very complex interrelations in a very simple way," said Walter Vetter at the Friedrich-Schiller University in Jena, Germany. Throughout this decade, researchers have been uncovering evidence showing that the environmental fate of chiral compounds depends on very complex interactions, but this knowledge base is not reflected in the study Vetter said.
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Environmental News One of the most surprising discoveries concerns the insecticide alpha-hexachlorocyclohexane (a-HCH). Only one enantiomer can permeate the bloodbrain barrier, suggesting a world of unexpected effects, according to research by Heinrich Hiihnerfuss at Hamburg University in Germany. This observation holds true for all of the animals investigated so far, which include ducks, dear, seals, sheep, and humans.
University of Georgia microbiologist David Lewis holds (right hand) weeds treated with the active (+ enantiomer) form of the herbicide dichlorprop) and the inactive mirror-image molecule of the chemical (left hand).
Lewis and his colleagues sampled soils from three sites of longrunning studies. At long-term research sites in Norway and the United States, scientists have heated soils for many years to model global warming. In Brazil, scientists are studying the effects of deforestation. In the laboratory, Lewis's team applied one of three pesticides to each soil sample. They also added organic fertilizer to half of the samples. The researchers found that different soils and their associated microorganisms reacted in differ-
ent ways. For example, organic fertilizers caused a strong shift in which the enantiomer was preferred by microorganisms in samples from the United States and Brazil, but not from Norway. Soils from the warmed sites showed a preference for one pesticide enantiomer, while those from nearby unheated sites preferred the other. This probably happens because the changes in environmental factors cause changes in die population of microbes in the soil the scientists state This complex behavior accords with the results of other studies, said Bidleman. "Currently, it is difficult, if not impossible, to predict how a given chiral pollutant will behave in a particular soil," he said. That is because research into chiral compounds is still in the preliminary stage, asserted Michael Oehme, whose research at the University of Basel, Switzerland, is directed at improving the reliability of chiral analysis. Until recently, researchers have been looking for the range of environmental fates, he said. But now they are beginning to try to optimize parameters in an effort to uncover correlations, and ultimately, to look for causes. In Switzerland, regulations require that new pesticides and herbicides contain only the enantiomer that is biologically active, Oehme said. This reduces the load on the environment, because the inactive form, which may also have some deleterious effects, is no longer released. For example, a farmer would apply 0.5 kg/hectare of chirally pure mecoprop herbicide, and that dosage would be as effective as 1.0 kg/hectare of mecoprop containing equal amounts of both enantiomers This represents an improvement, but not a pollution cure, because transformations that can occur in the environment at any stage of degradation can produce molecules with undesirable characteristics, Vetter said. For example, microbes can covert the enantiomerically pure form of the herbi-
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cide mecoprop into its mirror-image. In addition, some compounds that are not chiral may have chiral breakdown products. Thalidomide, one of the most infamous drugs, illustrates how complex the chiral world can be, according to Bidleman. In this chiral drug, one enantiomer is beneficial and the otiier is highly toxic. The drug that caused the horrible birth defects in the 1960s contained both enantiomers. The bad enantiomer was responsible for the problems. Now there are proposals to remanufacture the beneficial enantiomer in pure form. Controversy exists, however, about whether conversion of one enantiomer into the other could occur in the environment or in the human body. For chiral compounds in the environment, such complexities abound. "I think that one has to be very careful and not let the profit motive shortcut the cautious deliberation of science that is needed to ensure that these things are truly safe," Bidleman said. REBECCA RENNER
DidYouKnow? Whale alert: Since ship strikes account for 50% of known right whale deaths, the International Maritime Organization is aiding approximately 300 endangered Atlantic right whales with a system that alerts large ships to the presence of these animals. Source: Water Environment & Technology, April 1999.
