NEWSSCIENCE EPA to release mercury report, reversing earlier decision A long-awaited EPA report to Congress on sources of mercury emissions to air and their human health and ecological effects will be released this month, according to agency officials. The report will be issued as a draft for comment, and EPA intends to finalize it by year's end, agency sources said in late February. The announcement reverses EPA's decision last December to put off the mercury report for a year until results from three toxicity studies were available. Complete results were still unavailable in late February, but preliminary data from one of the studies were published in Neurotoxicology on Feb. 7. That study of people on the Seychelles Islands, north of Madagascar, found no adverse effects to childhood development from fetal exposure to mercury at levels currently considered harmful by many organizations including the World Health Organization and EPA. Despite the differences, EPA officials interpret the new data as consistent with their own health standards, and those standards will be reflected in the upcoming mercury report. The comprehensive "Mercury Study Report to Congress" is required under the 1990 Clean Air Act Amendments. It provides estimates of the largest sources of mercury emissions, examines the human and ecological health effects of mercury, and surveys existing pollution control technologies. The report is required under a section of the Air Act that postponed regulation of toxic air emissions from electric utilities until the report is completed. The report was to be wrapped up by November 1994, and EPA was under a court-ordered deadline to issue it by Dec. 15, 1995. The report is likely to alarm officials in industries that emit mercury as well as in industries that market foods that may contain mercury. The report says fossil-fuel-burning power plants are the largest U.S. mercury emissions source, contributing more than 20%. In determining mercu-
ry's effects, EPA uses a new health standard it has developed that is three times more stringent than its previous standard. In a move independent of the report, EPA recently toughened its standards for mercury as part of its Integrated Risk Information System (IRIS). Under IRIS, EPA established in 1989 a reference dose (RfD) for methylmercury of .03 micrograms/kilogram body weight/day with an order-of-magnitude uncertainty. The RfD is an
"EPA should not release a mercury study that is not based on the best available science." — Edison Electric Institute spokesperson estimate of daily exposure to a human population that will not result in appreciable health risk. In December 1995, EPA tightened the RfD by a factor of three to .01 ug/kg body weight/day. The change was not contentious at the time, according to Terry Harvey, director of EPA's National Center for Environmental Assessment, Cincinnati, Ohio, which did much of the work on the mercury study. "We felt that, considering the universe of avail-
able data, this reduction was justified. We made it clear that there was an order-of-magnitude uncertainty in this estimate associated with the data and the process of establishing a reference dose." Harvey stands by the estimate in the face of the Seychelles study. Further complicating this issue, the National Institute of Environmental Health Sciences (NIEHS) also is required under the Air Act to investigate mercury and to determine a safe threshold level of exposure. In 1993, NIEHS published a report expressing a lack of confidence in then-existing recommendations for tolerable exposures to methylmercury through fish consumption. It heralded the Seychelles study and a similar Faeroe Islands (Denmark) study, both funded by NIEHS, as important advances that would considerably improve safety estimates. But the 1993 report concluded that further understanding of methylmercury toxicity and mercury biokinetics was needed before a safe threshold for mercury could be established. In July 1995, Secretary of Health and Human Services Donna Shalala estimated that, based on the 1993 NIEHS report, the information necessary to establish a threshold would not be available until 1998. EPA's approach to mercury was criticized by industry officials last September, even when formal
FUNDING DOE cleanup office to fund long-term basic research The Department of Energy's cleanup office for the first time will fund longterm fundamental environmental research to aid the department's cleanup efforts, DOE officials announced. The program marks a significant departure for the Environmental Management Office (EM), which has been criticized for its overreliance on applied research in seeking solutions for the DOE's environmental problems, DOE officials said. EM will allocate $50 million this year for multiyear research grants targeted toward department priorities. DOE will fund proposals in three categories: universities; DOE's national and energy laboratories; and collaborations with other federal agencies. DOE issued a request for proposals Feb. 9 {Federal Register 1996, 61(28), 4975-78). —DANIEL SHANNON
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release of the report seemed stalled. In a letter to EPA Administrator Carol Browner and Shalala, the National Fisheries Institute castigated EPA, saying, "This report will unnecessarily raise public fears about consuming fish and seafood." The institute's criticism was joined by several senators. Then in late February when EPA decided to formally issue the report as a draft, a spokesperson with the Edison Electric Institute, a utility-funded trade association, said, "The Seychelles study is not showing a toxic effect from fish consumption, and this important new data should be included in the report. EPA should not release a mercury study that is not based on the best available science." The Seychelles' study follows mother-infant pairs whose fish
consumption averages 12 meals a week. The average level of mercury in the mothers' hair was about 10 ppm but, according to an NIEHS statement, the study found no impairment in children whose mothers' hair contained as much as 36 ppm of mercury, three times EPA's safe level of 11 ppm. Harvey defended EPA's decision to release the report without the Seychelles data: "First, it is only partly available. The full results from the Seychelles study will follow the children's development to age five. What we have now is a partial analysis of the data to age two, and we don't know when the full results will be available." Meanwhile, for mothers with mercury levels comparable to EPA's recommended level, there would be no observable de-
velopmental effect, which is what the preliminary data show, he added. Shalala's recommendation to put off a decision until 1998 is based on NIEHS's view of how to handle the uncertainty in previous epidemiological studies, Harvey said. "We have used an existing EPA methodology to account for this uncertainty, and we are comfortable with it. NIEHS is not." EPA's report charts a clear path back from ingestion of methylmercury, a powerful neurotoxin, by fish to power plant emissions, added Steve Page, EPA Office of Air and Radiation communications director. It will have significant ramifications for utility industry regulation and advice concerning fish consumption. —REBECCA RENNER
Toxicity of aquatic mixtures yielding to new theoretical approach Researchers in the United States and the Netherlands are developing tests to predict the toxicity of complex chemical mixtures in the aquatic environment. Building on new research on the classification of chemical compounds by their "mode" of toxic action and a recently developed analytical procedure that estimates total bioconcentration, such tests could provide more information than do current empirical methods that determine toxicity by placing living organisms directly into effluent. Determining the toxicity of a complex chemical mixture is not straightforward because the toxicities of individual chemicals are not simply additive when combined. The total toxicity of a mixture may be less or more than the sum of its parts, depending on the chemicals in the mix. Toxicologists have long known that chemicals that influence an organism in the same way—have the same "mode of action"—are additive. But until recently they have not known which chemicals shared the same mode of action, or even how many different modes of action there are. Quantitative structure-activity relationship (QSAR) studies are providing that information by classifying chemicals with similar structural features and similar
modes of action, according to toxicologist Steve Bradbury of the EPA Environmental Research Laboratory in Duluth, Minn. Research at Duluth indicates that, in the aquatic environment, "a large range of chemical structures and classes can be classified into some five or six mode-of-action groups," he said. By first identifying the mode of action for each group, aquatic toxicologists hope to construct a framework of knowledge that will allow them to predict the toxicity of mixtures containing many groups. Although tests to predict the toxicity of mixtures still require
Additive toxicity A new analytical method estimates the toxicity of chemical mixtures in the aqueous phase by simulating bioconcentration in aquatic organisms. The "baseline toxicity" is the cumulative concentration of all compounds (three in this example) when the chemicals have the same toxic effect, or mode of action.
Source: Environ. Sci. Techno!., 1995,29,728.
considerable work, recent research is probing mixtures dominated by one mode-of-action group: narcotic chemicals. The toxicity of narcotic chemicals, often termed baseline or nonspecific toxicity, acts as a reversible general anesthetic. This group often dominates the toxicity of aquatic mixtures because it includes many industrial chemicals that were not designed to be biologically active, including chlorinated benzenes, toluenes, and alkanes. In standard biological toxicity tests of aquatic species, the effects of mixtures of narcotic chemicals are completely additive for endpoints such as mortality, inhibition of reproduction, and growth, according to Joop Hermens at the Research Institute of Toxicology, Utrecht University, the Netherlands. However, moving from the toxicity of mixtures in the lab to the toxicity of mixtures in the environment is a difficult step because from the moment a mixture enters the environment, its composition changes. No single rule or factor can be applied to convert the mixture toxicity determined in the lab to effects in the environment. Toxicologists at the Research Institute of Toxicology, Utrecht University, have devised an ana-
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