stack right next to homes ana tne school, the possibility of scientists "fudging" risk assessment data, and ENVIRON. "ENVIRON is questionable because of its ties to industry. I would have thought [EPA] would get someone that is more evenhanded, rather than choosing someone right out of the gate that appears to be in a conflict of interest. It makes this all the more questionable. When dealing with something this critical, there shouldn't be a 'question.' We're talking about people's lives." In response, Croke said ENVIRON's role was a concern to EPA, too. But the Agency conducted an in-depth study, she said, and concluded that there was not a conflict, provided ENVIRON did not
Despite the study's scope, residents remain concerned about emissions, the credibility of risk assessment data, and the role of a key study contractor. supply toxicological data. "ENVIRON's role was to use EPA data and to perform calculations under our very close oversight." Currently, risk assessments are not mandatory for facilities that burn hazardous wastes, but most commercial incinerators have conducted them. A recent EPA policy encourages owners of industrial furnaces, cement kilns, and boilers that burn hazardous waste to do assessments, however. But these are less extensive than WTI's assessment, said Alex McBride, an EPA environmental protection specialist. In the future, EPA may rely less on risk assessments for burners, McBride added, and more on emissions standards, once new standards are set in December 1996. —JEFF JOHNSON
NEWS SCIENCE Researchers find unexpectedly high levels of contaminants in remote sea birds A three-year, EPA-sponsored study by the World Wildlife Fund (WWF) has found concentrations of persistent organic pollutants in sea birds living on Midway Island in the north Pacific that are almost as great as levels found in birds in the Great Lakes. These chemicals have previously been detected in high concentrations in organisms in the Northern Hemisphere, but this research is the first to indicate that high levels of contamination also occur in remote tropical regions. Adult black-footed albatrosses living on Midway were found to have concentrations of polychlorinated biphenyls (PCBs), dioxins, furans, and other dioxin-like chemicals in their eggs of 124 picograms per gram expressed as toxic equivalents. This level is within the range of concentrations where sensitive avian species show adverse reproductive effects. This toxic-equivalent measurement is the sum of the toxicity of all of the dioxin-like chemicals thought to affect an organism in the same way, converted to the effect of 2,3,7,8-TCDD, the most toxic member of this chemical family. "What our research indicates is that we are right at the threshold. There is no more assimilative capacity," said Michigan State University toxicologist John Giesy, who discussed the results at the November meeting of the Society of Toxicology and Environmental Chemistry in Vancouver, Canada. "Any TCDD-like pollutants that are added now will push us above the threshold and give an effect. This is especially true because the dose-response relationship for TCDD is so steep."
Reproductive effects from persistent organic pollutants were documented in new study of albatrosses on Midway Island in the north Pacific. (Photo courtesy of J. P. Giesy, Michigan State University.)
This new study adds to accumulating evidence based on ocean water samples and studies of marine mammals that persistent organic pollutants are dispersed by global atmospheric transport and cycling processes to create exposures in areas far from the sources. Using methods developed to study fish-eating birds in the Great Lakes (ES&T, March 1994, p. 128A), Giesy and colleagues Rosalind Rolland and James Ludwig studied two similar species that nest on Midway: Laysan and black-footed albatrosses. They measured concentrations of polychlorinated, diaromatic hydrocarbons including PCBs, dioxins, dibenzofurans, and pesticides in the birds' eggs, blood, and tissues. They also studied the albatross population and used historical population data. In the Great Lakes and other areas, high exposures have been correlated with
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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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