Environmental▼News this approach is separating the three components, and allowing different organizations to manage each piece on different scales. A basinwide agency could issue shares involving many states. A State Department of Water Resources or a water supply company could manage allocations, and an environmental protection authority could manage licenses. The approach could operate across the whole country, with trading between regions if they were linked hydraulically, for example, between the Murray River system and the Snowy River. An important advantage of the system is that the managing organizations could control trade and extractions as climatic, economic, and technical circumstances vary, says Young.
The most unusual aspect of the proposal is the license, which could help protect the environment, says Jim Boyd of Resources for the Future, a think tank in Washington, D.C. Water trading involving entitlements and allocations does occur in the United States in California, Colorado, Nevada, and Arizona, where water can be scarce. However, he says, water transfers can have significant environmental consequences, affecting wildlife, salinity of aquifers, and dilution of pollutants. If the license safeguards against these environmental concerns, then Boyd believes that a market-based approach has many benefits. “The price will effectively signal the resource’s scarcity, so higher prices should result in reduced use and more conservation.”
However, environmentalists are cautious. Tim Fisher of the Australian Conservation Foundation points out that on the Murray Basin, for example, increasing trade in water from upstream to downstream locations will further disrupt natural flow patterns already altered by dams. However, he does acknowledge that trading would bring some environmental benefits, such as taking water away from areas with high water tables and big salinity problems to areas where it could be used more efficiently. Copies of the report Robust Separation: A Search for a Generic Framework To Simplify Registration and Trading of Interests in Natural Resources can be downloaded from www.clw.csiro.au/ research/agriculture/economic/ publications.html. —MARIA BURKE
New concerns about arsenosugars in seaweed and shellfish senosugar metabolism. “That means that the accumulation of arsenic in sheep that we see may also appear in humans,” says Feldmann. JÖRG FELDMANN, UNIVERSITY OF ABERDEEN
Naturally occurring arsenosugars in seaweed and some shellfish may be more toxic than previously thought, according to new research conducted on sheep living on an island north of Scotland whose major food source is seaweed. The findings, which are reported in this issue of ES&T (pp 845–851), show that sheep metabolize arsenosugars very rapidly into pentavalent dimethylarsinic acid, (CH3)2AsO(OH) or DMA(V), which is considered a potential co-carcinogen. Although the implications for human consumption of seaweed and shellfish containing arsenosugars are still unclear, studies have shown that humans also metabolize arsenosugars to DMA(V). “We observed no toxic effects in the sheep,” says lead author Jörg Feldmann of the University of Aberdeen in the United Kingdom. “However, they are slaughtered when they are young, on average when they are four years old. So you can’t actually say whether they will get cancer when they are older.” What is surprising is that the sheep model is very similar to human metabolism in terms of ar-
Sheep that live on one island north of Scotland consume large amounts of seaweed that contains high levels of naturally occurring arsenosugars. New research suggests that these arsenosugars may not be as safe as previously thought.
There have been only limited studies on human exposure to arsenosugars, despite their prevalence in seaweed and edible bivalves, such as clams, oysters, and mussels. In one short-term study conducted by co-author Kevin Francesconi and colleagues at KarlFranzens-Universität Graz in Austria, a pure arsenosugar com-
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pound was chemically synthesized and ingested by a human. In that study, the quantity ingested by this one person was comparable to what a Japanese person eats in one day, says Francesconi. “The main metabolite was DMA(V), but there were several others that we identified and some we could not identify. The metabolites were excreted rapidly. After four days we had accounted for about 80% of what was ingested,” he says. Although, in one sense, no one has looked at the long-term effects of eating arsenosugars, in another sense, they have, “because the Japanese eat vast quantities of these edible algae and have been doing so for many years,” adds Francesconi. “There is no evidence to suggest that their incidence of certain cancers is higher than nonalgal eating groups,” he says. Still, there is only one animal study in the literature showing that there is not very high toxicity of arsenosugars to rodents, says X. Chris Le, a professor in the environmental health sciences program at the University of Alberta–Edmonton in Canada. “That doesn’t mean there are no health effects from arsenosugars in seaweed,” he says. DMA(V) is about 100 times less acutely toxic than inorganic ar-
sorption of arsenosugars by sheep and humans, and the similarities they share with inorganic arsenic in terms of metabolism to DMA(V), the researchers believe further studies on arsenosugar metabolism are warranted. In addition, the researchers are concerned about the growing use of seaweed as a fertilizer in Scotland. In a second paper, also reported in this issue of ES&T (pp 951–957), Feldmann and colleagues show that soils amended with seaweed fertilizer accumulate arsenic compounds. “In the soil, arsenosugars break down fairly quickly into DMA and then over time, they are demethylated to inorganic arsenic. We also see it happening the other way around, depending on what kinds of microorganisms are living in the soil. We see methylation from inorganic arsenic to DMA,” says Feldmann. Within a month, all of the arsenosugars had been transformed into DMA and inorganic arsenic, he says. “That means if you plant potatoes or other crops there, they will be exposed to these arsenic compounds.” It is unclear whether crops will take up DMA directly. “The uptake seems to be mostly inorganic arsenic,” says Le. However, according to Francesconi, it depends on the crop. DMA is not readily taken up, but you do see it in some plant species, he says. “Our studies showed that DMA(V) can be taken up by rice plants, but not as efficiently as inorganic arsenic species,” adds Feldmann. —BRITT E. ERICKSON
Sulfur-free fuels mandated European Union (EU) ministers and the European Parliament agreed last December to further lower sulfur in fuels by requiring refiners to phase in gasoline and diesel with less than 10 parts per million (ppm) of sulfur by 2005. The new legislation is designed to lower emissions of various pollutants and improve vehicles’ fuel efficiency. These “sulfur-free fuels” should be fully available by 2009, including for nonroad mobile machinery and
agricultural tractors. The EU had already set limits of 150 ppm for gasoline and diesel by 2005; present limits are 350 ppm for diesel and 150 ppm for gasoline. This compares with the U.S. EPA’s gasoline limits of 120 ppm for 2004 and 30 ppm by 2006, and 15 ppm by 2007 for diesel. As well as lowering emissions of conventional pollutants such as particulate matter and nitrogen oxides (NOx) from existing vehicles, sulfur-free fuels will improve the
News Briefs More gas, less oil The Powder River Basin of Wyoming and Montana contains 14 times more coal bed methane than previously thought, according to new estimates of oil and gas reserves in five Rocky Mountain basins. The U.S. Geological Survey now finds 14.3 trillion cubic feet of technically recoverable coal bed gas in the Powder River Basin. The significantly higher assessment is based on exploration and drilling records and studies of source and reservoir rocks that were not available when the last estimate was made in 1995. Meanwhile, better data and analysis from the five Rocky Mountain basins lowered estimates of technically recoverable oil by 30%, down to 1.9 billion barrels of crude oil. The report New (2002) Energy Policy and Conservation Act (EPCA) Results is available at http://energy. cr.usgs.gov/oilgas/noga.
Expanding environmental research and education The future of environmental research will require bridging the divides between engineering, natural science, and social science, says Stephanie Pfirman, past chair of the National Science Foundation (NSF) Advisory Committee on Environmental Research and Education (AC-ERE) upon release of its 10-year outlook on environmental research and education. Integrating the efforts of the public, educators, social and natural scientists, industrial managers, economists, and policy makers is necessary to synthesize environmental research and expand the capacity of electronic data networks and observing systems on a global scale, according to the report. Complex Environmental Systems: Synthesis for Earth, Life, and Society in the 21st Century is available at www.nsf. gov/ere.
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senic, but it can undergo a reduction to DMA(III), which is as toxic or even more toxic than inorganic arsenic compounds, he adds. Although Le and colleagues have not seen DMA(III) in urine samples from people who eat seaweed, they have seen it in the urine of people who are highly exposed to arsenic from their drinking water, such as individuals from Bangladesh, India, Inner Mongolia China, and Romania. “We haven’t seen DMA(III) with seaweed ingestion, partly because we haven’t really looked carefully for it. Analytical methods for DMA(III) have only been available for two years now.” In the past two years, Le and colleagues have spent most of their time analyzing the urine of people who have been exposed to arsenic in drinking water and the urine of rodents that have been fed arsenic. Most experts believe that it is probably safe to eat seaweed and shellfish that contain arsenosugars in moderation. The major form of arsenic in these foods is arsenobetaine, which is not metabolized by humans and has been shown to be essentially nontoxic, says Le. Shellfish, such as shrimp, crab, and lobsters, contain significant amounts of arsenobetaine, but they do not contain arsenosugars. Bivalves, on the other hand, contain both arsenobetaine and arsenosugars, he says. Feldmann and colleagues point out that currently there is no evidence that arsenosugars are toxic. However, because of the high ab-
