adverse effects on the reproductive potential of several bird species and decreases in their populations. Using large sample sizes to follow the reproductive progress of 500-1000 eggs of each species during 1994 and 1995, the researchers were able to resolve subtle reproductive effects. Blackfooted albatrosses hatched about 2.5% fewer eggs than did the Laysans each year because of eggshell thinning. The probability of obtaining these results at random is less than 0.002, suggesting that this was a real biological difference between the species, according to Giesy. Albatrosses were chosen as a suitable species to study because they mate for life, return to the same nests year after year, and do not fear humans. The group compared the concentration of contaminants found within the eggs and blood to the range of dose-response information available for other birds. The black-footed albatross, with a total equivalent toxicity burden two times greater than that of the Laysan albatross, fell within the effect range; the lower Laysan burden indicated that no adverse reproductive effects should be expected. The researchers hypothesize that the difference in exposure was caused by diet. "Although these birds are very similar," said Giesy, "Laysans eat squid, while the black-footed eat squid and flying fish and flying fish eggs, which are about half a trophic level higher [in the food chain] than squid. With each trophic level, you get enrichment, and that seems to be enough of a difference to explain the greater exposure." The birds' high exposure to contaminants came as a surprise, according to Rolland, a WWF conservation scientist. "We chose the Midway albatross as representative of a relatively pristine environment," she said. Albatrosses feed from the open ocean surface far away from the usual continental sources of organochlorine pollutants. So in spite of their positions near the top of the food web, they were expected to be only minimally contaminated. —REBECCA RENNER
Chiral compounds show promise as environmental tracers According to new studies, chiral compounds show promise as environmental tracers and as tools for understanding chemical toxicity. Research presented in November at the Society of Environmental Toxicology and Chemistry (SETAC) meeting in Vancouver, Canada, included an international array of research on soils, surface waters, and wildlife. Many agrochemicals are chiral compounds—distinctive compounds with two mirror-image structures called enantiomers— and the list of environmental chiral compounds is growing as improved analytical techniques have been developed. Researchers expect that the different enantiomers of the parent compound will exhibit significant differences in toxicity and persistence because of small structural differences in the molecules. Enantiomers of biologically active compounds have different physiological properties in an organism, a finding that has led to the development of single-enantiomer drugs with improved effectiveness. When chiral pesticides are metabolized by an organism, the ratio of the two enantiomers, 1:1 when synthesized, is changed, reflecting the enhanced biological
activity or toxicity of one of the enantiomers. Researchers have found, however, that this selective metabolism of chiral compounds results in different enantiomer ratios in different species, suggesting that the toxicity of these compounds varies by species. "Different animals may fractionate different enantiomers of the same compound," reported Renee Falconer of Youngstown (Ohio) State University. "We know that two different species of invertebrates fractionate the same chiral compound differently. One of these enantiomers is probably toxicologically more significant than the other, but we don't know which one. Nor do we know the mechanism for differentiation." An analysis of chiral pollutants in the tissue of seals and herring from the Baltic Sea by Karin Wilberg from the University of Umea, Sweden, indicated that both animals show selective accumulation of one enantiomer of transchlordane. In the case of herring, variation among individuals was small, with neither sex nor geographical location playing a role. The seal samples, however, showed significantly different enantiomer ratios between sexes. Research on chiral compounds
Evidence for preferential biological uptake The chiral insecticide alpha-HCH was the first to be found to demonstrate selective differentiation of the mirror-image isomers in the environment. New gas chromatography results for alpha-HCH samples taken in the Arctic Ocean show a decrease in the (+) alphaHCH peak, with increased depth reflecting selective loss of this enantiomer in the deeper waters. (Courtesy of Liisa Jantunen and Terry Bidleman, Atmospheric Environment Service, Ontario, Canada.) Q| c,
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in the environment is still in its early stage, according to Terry Bidleman, with the Canadian Atmospheric Environment Service. "We are at the stage of identifying chiral compounds, seeing different distributions of the different enantiomers, and observing the selective metabolism of the enantiomers by microbes, fish, birds, and mammals." Enantioselective metabolism was first demonstrated in 1991 with the insecticide alpha-hexachlorocyclohexane (alpha-HCH) in marine waters. Several analytical laboratories continue to refine separation techniques developed in Germany and Switzerland. The selective metabolism of chiral compounds also makes them valuable as environmental tracers because they can signal the effects of biological transformation processes. Falconer and Clifford Rice of the U.S. Department of Agriculture are applying this idea to pesticide residues in soils. Selective breakdown of one enantiomer of o,p'-DDT has been found in Maryland soils that were formerly treated with DDT. Soils from the Fraser Valley in British Columbia contain residues of organochlorine pesticides that were applied more than two decades ago. Some of these soils are depleted by up to 30-40% in one enantiomer of alpha-HCH and heptachlor epoxide, according to Falconer. The enantiomeric signatures of these pesticides in the soil can also be seen in the airspace over the field, she said. "Since these pesticides are persistent," Bidleman says, "releases from contaminated soils will continue to recycle them into the ecosystem, even after these chemicals are no longer in use. We think that enantiomers can be employed to distinguish the emission of soil-metabolized pesticides from the atmospheric transport of freshly applied chemicals." The researchers reported, however, that considerable work remains. Unknowns include the kinetics of enantiomer degradation in the environment, the biological mechanisms of enantiomer differentiation, and the toxicological significance of the selective accumulation of pollutant enantiomers. —REBECCA RENNER
NEWS TECHNOLOGY Life-cycle analysis stirs continued debate on impact of electric cars Life-cycle analysis is growing rapidly as an internal tool manufacturers use to make environmentally sound product design decisions. But attempts to broaden the use of life-cycle analysis methodology to compare environmental impacts of consumer products have generated considerable debate. Now, one of the first life-cycle analyses of environmental policy in the United States has again raised questions about the role and utility of life-cycle analysis. This spring a group of economists and engineers at Carnegie Mellon University published its analysis of life-cycle implications of laws passed in California and other states that require introduction of "zero emissions" or electric vehicles to reduce air pollution {Science, May 19, 1995). The researchers argued that the indirect effect of increased use of battery-powered vehicles would be dramatically increased total lead discharges to the environment, because these cars would require large lead-acid batteries. Tom Graedel, an environmental designer at AT&T Bell Laboratories, believes that the Carnegie Mellon study opens new ground. "Used to inform policy decisions, life-cycle analysis raises significant issues and forces people to think about them. Of course, whatever assumptions are made must be clearly spelled out, or this kind of work can be subject to misinterpretation." According to the Carnegie Mellon study, an electric car would release 5-60 times more lead to the environment than a new Geo Metro burning the type of leaded gasoline that is banned in the United States. This analysis only examined the Metro's air emissions and compared them with the electric car's gaseous and solid waste discharges, a misleading comparison according to the study's critics and one that points out the drawbacks of life-cycle analysis.
In November, members of the International Center for Technology Assessment, a Washington, D.C., policy group, and David Goldstein, co-founder of the Electric Vehicle Industry Association, issued a lengthy rebuttal claiming that the Carnegie Mellon study had misrepresented data for lead emissions rates at smelting facilities, the capabilities of current and future battery technologies, and the number of electric cars expected to be in use in the near future. But according to Chris Hendrickson, a Carnegie Mellon en-
"As a new way of looking at things, life-cycle analysis is bound to solve some easy problems. But to be useful, it must be quantitative." —Lester Lave, Carnegie Mellon University gineer, a revised analysis incorporating more recent data and taking into consideration emissions to air substantiates the original conclusions. In a paper presented at the Future of the Electric Vehicle Conference in November in Frankfurt, Germany, the Carnegie Mellon group presented new calculations that reduce the estimated total lead discharges to 15-34 times more than those of the Geo Metro, and estimate lead emissions to air to be 0.5-391% of the Geo Metro's. More important, life cycle work in progress on the impact of electric cars in California indicates that the benefits for ozone reduction are small, said Carnegie Mellon economist Lester Lave, because current emissions standards have dramatically reduced new car emissions. The new work concludes that a fleet of half-amillion lead-acid battery-powered vehicles in Los Angeles in
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