Environmental▼News surrounding perchlorate has centered on contamination from rocket fuel, natural sources of it appear to be fairly common. “Here in west Texas, there are contaminated wells that are so far away from any possible source of munitions or munitions manufacturing that it certainly cannot be that,” Dasgupta says. Some evidence shows that it is generated atmospherically through the reaction of chloride aerosols with
ultraviolet radiation, ozone, or lightning, he says. Regardless of whether perchlorate is anthropogenic or naturally generated, it is beginning to show up in the food supply. Researchers speculate that crops like alfalfa, which is fed to dairy cows, may be one route for contaminating milk. Once thought to be essentially safe because of its low reactivity, perchlorate is now considered a cumulative
toxin because it interferes with the transport of iodide, which is critical for proper thyroid function. As a result, researchers are calling for more studies to look at the general occurrence of perchlorate in drinking water and in food crops, so that regulatory agencies such as EPA and the U.S. Department of Agriculture can set allowable perchlorate limits based on good science. —BRITT E. ERICKSON
Newly developed bacterial biosensors may offer a cheap and simple way to detect arsenic contamination in potable water, according to research in the October 15 issue of ES&T (pp 4743–4750). The sensors could help people living in areas like Bangladesh and Vietnam, where arsenic contamination is endemic and a way is needed to quickly determine if water is safe to drink. Although the health of millions of people is threatened by high arsenic concentrations in the groundwater they drink, the chemical field test kits currently used to detect arsenic are unreliable (Environ. Sci. Technol. 2003, 37, 35A–38A). Jan Roelof van der Meer and colleagues at the Swiss Federal Institute for Environmental Science and Technology (EAWAG), the Swiss Federal Institute of Technology, the German Collection of Microorganisms and Cell Cultures, and the University of Kentucky set out to address this issue by constructing three different biosensors based on nonpathogenic, genetically engineered E. coli. The sensors could potentially be used for routine field applications, the researchers claim. In the presence of arsenic, the genetically engineered bacteria in the sensors produce a “reporter” protein—bacterial luciferase, -galactosidase, or green fluorescent protein—that can be detected through bioluminescence or colorimetry. The -galactosidase biosensor is the simplest of the three because it directly gives a visible
JAN ROELOF VAN DER MEER, EAWAG
Biosensors for quickly detecting arsenic in drinking water
Arsenic contamination in water can be detected by paper strip tests with immobilized sensor bacteria. Upon detection of arsenic, the bacteria produce a blue color whose intensity correlates with the sample’s arsenic concentration.
color response and does not require sophisticated detection. For this sensor, bacterial cells immobilized on paper strips can be dipped in the water sample and visually read after about 30 minutes, making the system especially suitable for semiquantitative field tests. The luciferase sensor, in which the bacteria are placed in microtiter plates, requires a luminometer for detection but is more quantitative than the paper strip system. “Practice has to show which method people in the field prefer,” van der Meer says, and he stresses that field-portable luminometers are available.
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The biosensors are living organisms, and continued incubation with the sample leads to an increasing response, so that the output values need to be compared to a simultaneously run standard series, van der Meer says. This also means that the biosensors can be disturbed by toxic compounds; however, corrections can be made by spiking the samples with a known amount of arsenic, he adds. The sensors were constructed to give optimal results in the important concentration range for arsenic between 8 and 80 micrograms per liter. The paper strip sensors can be stored for two months without loss of activity, and frozen cell batches for the luciferase system can be stored for several years, van der Meer says. The luciferase biosensor is now being field-tested in Vietnam by EAWAG chemist Michael Berg and the Research Center for Environmental Technology and Sustainable Development in Hanoi. Berg says that the biosensors have promise as fast screening devices for large amounts of samples. “I could envision a system where water samples are screened for high arsenic concentrations on a community level and positive samples subsequently sent to the laboratory for more sophisticated chemical analysis,” Berg says. Another use for the method could be for local quality control in hospitals and water treatment, van der Meer suggests. The material costs for the paper strip biosensors are less than 10 cents per strip, according to van der Meer. EAWAG has applied for a patent for the new system. “The arsenic biosensors have an excellent potential for routine field
are two of the main problems in his eyes, but they should easily be overcome by more research, he thinks. “I believe that these sensors could make a significant contribution to society,” Sayler says. —ANKE SCHAEFER
EPA’s Science Advisory Board plans realignment grown considerably to keep up with an ever-increasing workload and technical areas. Changes must accompany this growth, she says. Likewise, SAB’s mission has expanded its scope by adding other sciences such as economics and social sciences, and better integration is needed among these different disciplines, Vu asserts. U.S. EPA
The U.S. EPA’s Science Advisory Board (SAB) is proposing to restructure the way it does business in an effort, planners say, to strengthen its peer review process and better focus on emerging environmental issues. The plan includes increasing the number of board members, expanding the peer review system, and forming committees to tackle specific issues. Environmentalists and industry representatives see the plan as a step in the right direction but voice concerns about how it might be implemented. SAB was established in 1978 to provide EPA’s administrators and Congress with independent advice on the scientific and technical aspects of environmental problems. The current SAB is composed of a 19-member executive committee, which oversees the work of 8 standing committees and ad hoc panels. Under the plan, a group of up to 30 individuals would serve on what would be called the science advisory board, which would replace the executive committee. Over the years, SAB has devoted most of its time to peer reviewing and approving committee reports and recommendations. At the same time, there has been a general perception that SAB may not be providing EPA with enough forwardlooking advice, says Bill Glaze, chair of the SAB’s executive committee and a professor at the OGI School of Science and Engineering in Oregon. In particular, Glaze says that the board doesn’t always help agency regulators anticipate emerging problems, such as endocrine disrupters, or develop appropriate science agendas for addressing them. Part of the problem, according to Vanessa Vu, director of the SAB staff office, is that the board has
News Briefs MTBE contamination widespread, low The first national survey of the gasoline additive methyl tert-butyl ether (MTBE) finds that about 9% of community water systems in the United States are contaminated, according to the U.S. Geological Survey. The random survey of nearly 1000 wells, rivers, and lakes measured MTBE concentrations ranging from 0.2 to 20 micrograms per liter, which is below U.S. EPA recommendations. Detection of MTBE was significantly greater in areas where more than 60% of the land is urbanized. Survey results also linked the concentration of MTBE to watercraft use. The reports and data from the survey may be downloaded at http://sd. water.usgs.gov/nawqa/vocns/ nat_survey.html.
Environmental lending rising again Vanessa Vu
The new structure adds another layer of reviewers in the form of executive review committees, says Vu, which would ensure that committee reports have met the peer review charge. Standing and ad hoc committees, as well as peer review panels established for specific reviews, would have their reports subjected to executive committee review before receiving final board approval. The hope is that the “right” experts, according to Vu, will approve reports. The new process also creates somewhat of a firewall between the board members, who are providing EPA with more strategic, forward-looking advice, and the peer review process. “We believe that a two-tier system of review is the best way to assure EPA, the Office of Management and Budget, and others that our efforts will meet the highest standards, particularly on highly
In 2004, the World Bank projects that it will lend $2.1 billion for environmentally oriented projects, the largest amount since 1998. In part, this rise is related to the growing suite of environmental problems faced by developing countries, says Kirk Hamilton, lead environmental economist for the World Bank’s Environment department. He also attributes the increase to the bank’s decision to include environmental components in loans aimed at other sectors, such as energy. But the number of projects earmarked for environmental policy and institutions is up sharply, too, he says. The bank’s “environmental loan” category includes funds for environmental biodiversity; climate change; and the management of land, pollution, environmental health, water resources, and other natural and environmental resources, according to a bank spokesperson. For more information, go to www.worldbank.org.
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application,” agrees Gary Sayler of the University of Knoxville–Tennessee, one of the pioneers in the development of bacterial biosensors. The adequate immobilization of the cells on the paper strips and the long-term survivability of the cells
