One of the challenges of microbial source tracking is developing a complete library of bacterial strains that is specific to each locale. George Simmons, professor at Virginia Tech, said that the geographic distribution of strains is unknown. For instance, "we don't know if bacterial strains from raccoons on Virginia's Eastern Shore are the same as strains from raccoons in North Carolina
or California," he noted. Samadpour concurred that the diversity of bacterial strains increases as the geographic range of the library is expanded. His library now contains more than 23,000 fingerprints. He hopes someday to make a source-specific database of 150,000-200,000 fingerprints generally available. Meanwhile, his work has caught the attention of the Amer-
ican Water Works Association Research Foundation, which is funding a bicoastal study of drinking water sources. The $150,000 project will "demonstrate the utility of the microbial source tracking method as a way to pinpoint [potential contaminant] sources and treat or prevent the problem," said Misha Hasan, project manager with the foundation. JANET PELLEY
Worldwide effort underway to reduce SF6 greenhouse gas emissions This October, EPA began promoting voluntary pollution prevention agreements to reduce sulfur hexafluoride (SF6) emissions from two key industries. The effort is part of a worldwide effort to decrease emissions of the compound, which is one of the six greenhouse gases on the negotiating table at last year's international climate change conference in Kyoto Japan. Although total emissions of SF6 are far lower than those of the other greenhouse gases discussed in Kyoto, its longevity makes it an important target for reductions. With a large global warming potential (GWP)—23,900 times greater than mat of C0 2 —and an atmospheric lifetime of 3200 years, it is "the most potent greenhouse gas known," according to researchers from Germany's Max-PlanckInstitute for Chemistry (Environ. Sci. Technol. 1998 32(20) 30773086). Their ES&T report correlates sales of SF with the observed global burden "The lifetime of this comDound is as long as civilizations " noted A R Ravishankara senior scientist at Oceanic spheric Administration's omy Lahnratory in Rnnlder Colo Because of its large GWP it is much easier for nations to reduce greenhouse gas emissions by decreasing their use of SF6, explained Manfred Maiss, coauthor of the ES&T paper. The fact that the compound's price more than tripled in 1995 has added to industry's impetus to reduce its use, said Philip Bolin, product manager at Mitsubishi Electric Power Products Inc. in Warrendale Pa. a manufacturer of equipment that uses die gas. "Sixty
to seventy percent of SF6 emissions could be abated cost efficientiy if a trade system for greenhouse gas emission rights existed," said Jochen Harnisch of the Massachusetts Institute of Technology's Joint Program on die Science and Policy of Global Change, in Cambridge, Mass. To aid scientists in using models to evaluate the effects of emissions reductions, scientists working on the Global Emission Inventory Activity hope to be releasing maps showing SF6 emissions on a 1 ° by 1 ° grid, said Jos Olivier, senior scientist at the National Institute of Public Health and the Environment in Bilthoven The Netherlands. The maps are being created as part of the International GeosphereBiosphere project. The reduction efforts that are being undertaken by EPA's Atmo-
Sales of sulfur hexafluoride have grown dramatically over the past 40 years and correlate strongly with its atmospheric burden, which has experienced a similar growth trend. Source: Environ. Sci. Technol. 1998, 32(20), 3077-3086.
spheric Pollution Prevention division target industries associated with some of the largest emissions of SF6: electric utilities, magnesium casters, and electronics manufacturers. Companies signing an EPA memorandum of understanding aimed at electric utilities would pledge to annually report their emissions of the compound, as well as commit to establish a corporate policy to properly handle it, explained Eric Dolin a program manager with the division It is estimated that electric utilities directly or indirectly purchase 80% of all SF6 produced, although the assumptions behind this estimate are debated, explained Eric Campbell, general manager for Dilo Company, a German business with U.S. headquarters in Odessa, Fla., which manufactures equipment for recycling SF6. Dolin said that EPA's goal was to convince each of die nation's 3000 utilities and cogeneration facilities that has equipment requiring the use of SF to join the partnership The SF6 used by electric utilities is encased inside switchgear, where it serves as an insulating gas. The compound is similarly encapsulated inside linear accelerators used in the semiconductor industry and some research facilities. Before the price of the gas skyrocketed, utilities found it more economic to simply release SFfi during routine maintenance said Bolin. Now it is only vented into the atmosphere unintentionally. Equipment like that made by Dilo allows SF6 to be recycled during maintenance by capturing
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it and transferring it to a storage vessel, then later refilling the equipment after the maintenance has been completed. "With the technology and the equipment that's available on the market for SF6 recycling, there's absolutely no reason why a user of SF6 wouldn't have the ability to recover every bit," said Campbell. Manufacturers of electric switchgear have also made continual strides in rendering their equipment more leak-resistant according to Bolin of Mitsubishi Electric Power Products Inc Cigre an international organization associ-
ated with power production, has published a brochure on recycling SF6, and the National Electrical Manufacturers Association has created a working group on issues related to SF6. The magnesium industry is finding that it makes economic sense to reduce its SF6 use. Some of the incentive is coming from other industries that purchase their products. According to Maiss, Mercedes Benz has put pressure on European magnesium manufacturers, who use SF6 in magnesium processing, to discontinue using the compound
because it adds too many C0 2 equivalents to their automobiles. In the United States, Chrysler is working with Hydro Magnesium, a major magnesium producer, to find an SF6 alternative, according to Scott Bartos, a program manager with an EPA Atmospheric Pollution Prevention project aimed at magnesium casters. Other efforts are underway in the magnesium industry. Two SF6 applications in Germany its use in filling tires and sound-proofing windows—have already been discontinued according to Maiss KELLYN S. BETTS
Models gauge pollution in environmental justice disputes EPA's Science Advisory Board is expected this fall to approve three modeling techniques designed to investigate environmental justice complaints, one of several tools being crafted to respond to an increasing number of petitions filed under Title VI of the Civil Rights Act. After a September public meeting, the Science Advisory Board's (SAB) Integrated Human Exposure Committee appeared ready to support the techniques, two of which are standard air emission models. But they criticized the limits of using Toxics Release Inventory (TRI) data and the models' weighting technique. "They told us they were scientifically defensible," said Ann Goode, chief of EPA's Office of Civil Rights. "Which is not to say perfect." EPA staff has begun altering the models said Goode. However the models do enable an ment of cumulative air pollution exposure something few models are designed to do EPA officials and outside agency observers said Citizen complaints alleging discrimination through the approval of permits are filed against state regulators; EPA must then investigate the complaint. Fifteen investigations are underway, and an additional 12 await processing, according to an August 13 Federal Register notice describing the models. Title IV prohibits the recipients of federal funds from discriminating on the basis of race color or national origin.
The techniques can determine whether emissions from a new facility will create a disparate pollution impact on a community. The agency employed two of the techniques, known as relative burden analyses, in its investigation of a much-publicized complaint filed against the Louisiana Department of Environmental Quality over a polyvinyl chloride plant planned for construction by Shintech Inc in 3. predominantly African American neighborhood in Louisiana The company with-
"Part of the problem is that [EPA] doesn't really have a policy yet" —Henry Anderson, chief medical officer, Wisconsin Department of Public Health drew its permit on Sept. 17, and plans to build a scaled-down facility closer to Baton Rouge, La. Under a 1994 executive order, all federal agencies must take steps to ensure their programs do not violate Title VI. Another EPA project, a Title VI guidance document designed for EPA, but released in February, was roundly criticized by state regulators who said it will radically affect their permitting and cleanup programs. Several state officials pect the same about the models
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Some environmentalists have criticized the models saying they are complicating a straightforward decision. "What EPA ought to follow is what we call the precautionary principle. If you see a situation that is already badly polluted, then don't issue a permit for a new facility that is going to pollute," said Damu Smith, the Greenpeace activist who spearheaded the national effort to prevent approval of Shintech's permit. The simple Basic Relative Burden Analysis calculates the average pollution burden for two population subgroups, usually African American and non-African American, that reside in proximity to the permitted facilities, according to an EPA staff paper. This basic analysis is easy to carry out—a plus considering the legally imposed sixmonth timetable for an investigation. The Enhanced Relative Burden Analysis can incorporate meteorological information and stack parameters and measures pollution in smaller units EPA staff did not use the third, more complicated and costly analysis, known as the Cumulative Outdoor Air Toxics Concentration and Exposure Methodology, during the Shintech investigation. But this technique, which analyzes outdoor emissions from many sources including nonpoint and mobile sources over large areas, would allow the agency to get to the heart of the complaints filed under Title VI said an EPA staffer who asked not to be named The citizen com-
