been unwilling to set consumption standards for PCB-contaminated fish because the type of PCB contamination had not been demonstrated to cause cancer. The new GE-supplied data, however, show that all PCB mixtures are potentially carcinogenic. EPA's acceptance of industrydirected research also breaks new ground. DeFur said the partnership worked because GE used an independent lab to conduct the studies, worked with federal researchers to design high-quality assays, agreed in advance to accept the tests' results, and used outside experts to evaluate the studies before they were given to
New industry data uphold the view that PCBs cause cancer, but they downgrade the potency of PCBs. EPA. The company is also satisfied with the reassessment process, according to company spokesperson David Warshaw. However, the debate over PCBs' toxicity is not settled with lower cancer potency estimates, said David Carpenter, dean of the University at Albany School of Public Health. "The effects of PCBs go way beyond cancer," he said, warning that "the ultimate pollution is that which reduces the IQ of a whole generation." Carpenter has studied PCB consumption by Mohawk Indians living along the St. Lawrence River in New York. Based on his ongoing research, Carpenter expects to continue to find health effects such as IQ loss, reduced memory, diminished physical growth, and depression from PCB exposure. Carpenter compared PCBs to lead. He predicted that, as lead researchers found a range of developmental, behavioral, and physical problems stemming from lead exposure, PCB researchers will find diverse PCBrelated health effects working through many biological mechanisms. —PAT PHIBBS
"Starved" bacteria investigated as bioremediation, biobarrier technology A physiological response of some bacteria to starvation is under study as a means of producing a "biobarrier" that can isolate subsurface contaminant plumes or function as a subsurface delivery system for organisms. The biobarrier technology, currently undergoing large-scale laboratory trials supervised by J. William Costerton, director of Montana State University's Center for Biofilm Engineering in Bozeman, exploits a common response of many strains of environmentally occurring non-spore-forming bacteria. Unlike spore formers that become dormant cells covered by a protein coat when stressed, these bacteria starve, becoming small, nonvegetative forms called ultramicrobacteria. To produce the ultramicrobacteria, Costerton and colleagues starve the bacteria in the laboratory, which prompts the physiological response that would occur in the natural environment. Once starved, the bacteria, which normally are about 1 micron (um) in length, decrease to about 0.3 um and become more spherical. They then can readily penetrate porous areas in the subsurface. In laboratory experiments, the ultramicrobacteria are brought back to normal size in less than two days. According to Frank Caccavo, Jr., of Costerton's laboratory, "Ultramicrobacteria of 'sticky'
bacteria can be injected downstream of a contaminant plume, resuscitated, and create a biobarrier that prevents the contaminant plume flow." This technology is now the subject of a study utilizing a 38 45 centimeter, three-dimensional physical simulator sandpack. The research is funded by the U.S. Department of Energy and MSE, Inc., an engineering and environmental consulting company in Butte, Mont. The basis for the biobarrier technology is work done by Costerton, formerly of the University of Calgary, Alberta, and a group headed by Hilary M. Lappin-Scott of the University of Exeter in the United Kingdom. The researchers use the ultramicrobacteria to penetrate porous matrices underground and then bring the bacteria back to normal size by feeding them, producing plugs of bacteria and the slimy polysaccharide the bacteria produce. Caccavo, who studies bacteria that reduce metal and can be used in bioremediation of heavy metal contamination, has shown that a Shewanella strain can change to the ultramicro form and then be resuscitated. This may allow its introduction into a chromium- or radionuclide-contaminated environment for bioremediation or for dehalogenation of organic contaminants. —MYRNA E. WATANABE
Ultramicrobacteria (white streaks), moving within a scintered-glass porous medium (dark areas), shrink when starved, allowing them to penetrate porous areas. Time-lapse scanning confocal laser micrograph by Guy Cook, courtesy Frank Caccavo, Jr. VOL. 30, NO. 8, 1996 /ENVIRONMENTAL SCIENCE & TECHNOLOGY/ N E W S " 3 3 3 A
