iments involve the solution that is applied during processing, not what might exist on products in people’s homes or discarded products in the environment. The authors assert that this represents the worst case, but there is no evidence for that,” he says. Perhaps more importantly, the scientists should examine a more relevant environment, such as activated-sludge systems used for wastewater treatment, instead of soil, says Criddle. “Hydrolysis rates will likely be greater, resulting in more rapid release of the alcohols, and stripping of the alcohols to the
atmosphere would be expected,” he adds. Scientists are still learning how to conduct these studies, says Fehrenbacker, but EPA has already started to list characteristics of a definitive study. First, scientists need to fully describe the polymer and any residuals present—using a radiolabeled polymer would be ideal but is expensive. Next, scientists need to maintain the mass balance; use of aggressive extraction methods should help meet this goal. “The DuPont study is useful but by no means definitive,” and lacks these
The technology sounds simple: fire a ceramic pot, perhaps coat it with a fine layer of silver, and let the water percolate through. In regions where water carries millions of microbes, this relatively inexpensive treatment method has its attractions. For about a decade, the nonprofit organization Potters for Peace has been teaching communities to manufacture their ceramic water filters, which retail for $5–15. Although they have been used widely from Nicaragua to Thailand, no scientific data have been published to prove their efficacy or to show how these ceramic filters work. Now, in ES&T (pp 927–933), researchers from the University of Virginia report that clay water filters from Mexico and the U.S. can remove more than 98% of the test organism E. coli. With an added layer of silver, the filters remove all E. coli. “Without the silver— just the ceramic filter—it seems like it works well, but adding the silver further improves the performance,” says coauthor James Smith. “Until this report, there have been very little data on how [the filters] work and what the specific mechanisms are,” says Kara Nelson, an environmental engineer
ceramic filter materials in the lab and found that commercial pottery material from the U.S. was the most successful at removing E. coli. The authors hypothesize that the industrial material has many more and much smaller pores than the coarser clays from Mexico. In addition, the pathways between the pores where water flows are more interconnected, allowing water to speed through more quickly, whereas the smaller pore sizes block E. coli from getting through. Added silver—purchased by local pottery manufacturers as a relatively inexpensive slurry, facilitated by Potters for Peace—could actually be killing the remaining E. coli through direct toxic contact, the authors posit. The results suggest that more sieving at on-the-ground manufacturing sites could lead to finer-grained ceramic filters and more effective water treatment. Although the filters’ $5–15 cost may be insurmountable for some households, it is a worthwhile investment for several years’ worth of filtration, the authors argue. The next step is to test how these filters “behave under real-world, longterm use,” Smith says. James Smith (lef t), Vink a Oyanedel-Cr aver (right)
Ceramic filter makes water treatment easy
characteristics, Fehrenbacker adds. The study has sparked vigorous debate on how and under what conditions to study biodegradation of fluoropolymers. Says Mackay, “I think that we are really trying to find out how to use fluorochemicals without suffering environmental harm. Obviously, applying the polymer to soil is different from what happens during the lifetime of dirty carpets or what happens in a wastewater treatment plant. This should be the first in a series of studies that will figure this out.” —REBECCA RENNER
Clay pots, made in a press such as the one shown here (left) in a Guatemalan factory, fit inside plastic buckets for filtering water.
who studies a variety of low-cost point-of-use water treatments at the University of California Berkeley. “Without an understanding of the fundamental mechanisms behind [a technology], we have to take a black-box approach,” she says. “That’s not efficient. There are so many different pathogens, so many environmental conditions, so many different things that could be in water.” Lead author Vinka OyanedelCraver and Smith examined the
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A major push on the household treatment front came last year from the Bill and Melinda Gates Foundation, which stepped in with $17 million and resources to further study simple point-of-use water treatments. Their end goal: determine which devices to mass produce and
how best to promote them. But researchers and policy makers alike emphasize that household water treatments may be appropriate only under certain circumstances. “There’s no single answer to the water supply and sanitation prob-
Ocean fertilization—time to regulate? set their carbon footprints. In October 2007, Australianbased Ocean Nourishment Corp. began a series of experimental releases of nitrogen-containing urea into the Sulu Sea near the Philippines to trigger plankton blooms. NASA
With global carbon emissions exceeding 8 gigatons annually and the effects of climate change looming ever larger, scientists and commercial interests have warmed to geoengineering schemes for mitigation that once were dismissed as science fiction. At the same time, the global market for carbon credits is ballooning, and canny entrepreneurs are jumping at opportunities to exploit it. One possible contender for lowering the atmosphere’s greenhouse gas burden, at least among entrepreneurs, is the “fertilization” of CO2-absorbing ocean phytoplankton with micronutrients such as iron or nitrogen. The concept is leapfrogging from small-scale scientific demonstrations to potentially large-scale commercial activities, with a virtual absence of government oversight and research into potential ecological effects. Scientists, environmentalists, and policy makers are calling for a clear regulatory framework in an effort to slow down the race to commercialization and allow the science to catch up. From 1993 to 2005, publicly funded researchers conducted about a dozen experiments that released iron over relatively small areas of open ocean. Accurately measuring the effects in moving water was problematic, and overall the outcomes were mixed. But the results were promising enough to encourage several companies to launch plans for marketing ocean fertilization (OF) carbon credits to the growing numbers of individuals and corporations looking to off-
Phytoplankton blooms, such as this one in Atlantic waters off the coast of Namibia, Africa, absorb large amounts of CO 2 .
The experiments were conducted without permission from the Philippines government, which has since protested the event. Such schemes raise the specter of a “Wild West” atmosphere that many scientists find disturbing. Kenneth Coale, a chief scientist on three “iron expeditions”, says, “It behooves us to find out what role the oceans could play to ameliorate climate change, but it’s alarming that market demands for carbon credits could end up driving this
lem,” says Peter Gleick, director of the nonprofit Pacific Institute. “Point-of-use systems can be effective, and can be a critical component, but they must not be allowed to derail the larger efforts to get cheap water for everyone.” —NAOMI LUBICK
process.” Coale emphasizes that previous demonstrations were designed specifically to investigate questions on climate history. “None addressed the ecological consequences of much larger scale or frequent fertilization efforts for climate mitigation,” he stresses. Researchers recently gathered at Woods Hole Oceanographic Institution to discuss thorny questions, such as whether broadscale nutrient seeding could produce greenhouse gases, generate harmful algal blooms, turn ocean midwaters eutrophic, or otherwise fundamentally alter marine ecosystems. Oceanographer John Cullen of Dalhousie University (Canada) warned that the collective impacts on the oceans could be not only catastrophic but also impossible to trace to any single liable party. Because OF would occur on the high seas, jurisdiction logically falls into the realm of international law. At a November meeting of the contracting parties of the Convention on the Prevention of Marine Pollution by Dumping of Waste and Other Matter, a voluntary agreement that has been ratified by 81 nations, delegates issued a statement of concern on OF. According to the statement, largescale OF isn’t yet justified because of gaps in scientific knowledge, and signatory countries should “use the utmost caution when considering [such] proposals.” Convention representatives agreed to address legal and scientific issues and decide on regulations at their next meeting in 2008. Because the convention has no enforcement powers, the ultimate responsibility for implementation
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