Environmental t News Fingerprinting perchlorate sources chlorine isotopes in perchlorate (Environ. Sci. Technol. 2003, 37, 3859–3863). With both chlorine and oxygen isotopes, the team saw similar effects of biodegradation by two bacterial strains at different temperatures. “You can essentially ‘see Tom Mohr
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erchlorate, found nearly everywhere, has become a fiery topic over the past few years. The chemical, which occurs both naturally and as a residue from explosives and rocket fuel, interferes with thyroid function and is particularly dangerous to children. In research published in this issue of ES&T (pp 2796–2802), a team led by Neil Sturchio of the University of Illinois Chicago reports on advances in perchlorate fingerprinting that could help resolve some hot debates surrounding the chemical’s origin. Communities with perchlorate contamination want to know where it came from and who is responsible for cleaning it up, and isotopes can help answer those questions. But perchlorate can also linger from decades-old sources, such as cold war rocket-fuel production, or the historical use of nitrate fertilizers from Chile’s Ata cama Desert, which naturally contain perchlorate. “These change with degradation in the environment, and we need to know if those isotopic signatures are preserved. We need to know if the Atacama signature would degrade to look like man-made or vice versa,” says Andrew Jackson of Texas Tech University. “Millions of dollars are spent cleaning up perchlorate, and we need to understand what we’re cleaning up.” In the new study, Sturchio’s group used isotopes of chlorine and oxygen to determine how biodegradation affects perchlorate’s isotopic composition. They found large effects on isotopes and a strong correlation between effects on chlorine and oxygen. The new work goes beyond the team’s previous research, in which they studied biodegradation of
An ion exchange system removes perchlorate from a contaminated well in Morgan Hill, Calif.
through’ any dilution or dispersion of perchlorate, such as mixing with perchlorate-free water” in aquifers, using the combined isotope signatures, Sturchio says. By comparing the results with known signatures, “you can get some idea if perchlorate is biodegrading and [by] how much,” he continues. More important, “you can extrapolate backwards [to an undegraded signature] to get an idea of the perchlorate’s source.” The approach might help the town of Morgan Hill, Calif. Perchlorate contamination there became a complex mystery, after a national monitoring program
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turned up perchlorate in about 800 private wells in 2002. Because a former road-flare manufacturer is located in town, Morgan Hill officials thought at first that the issue of responsibility would be straightforward. But the area used to be covered in orchards and farms, which may have used Chilean fertilizer. And a maker of solid rocket fuel was located to the north. “It really became puzzling in Morgan Hill that we found perchlorate upgradient from the old flare plant,” says Tom Mohr, a hydrogeologist for the Santa Clara Valley Water District. Because water carrying perchlorate should not flow uphill, the road-flare maker, Olin Corp., is only willing to pay for downgradient cleanup. So residents are paying a 15% surcharge on water bills until the matter is resolved—possibly by Sturchio and co-workers’ tests. “Our goal is to see if we can distinguish perchlorate from the manufacture of flares from perchlorate in rocket fuel or fireworks,” Mohr says. Eventually, Sturchio’s team hopes to be able to pinpoint a particular manufacturer. The Morgan Hill case won’t be the first time the dual-isotope method has been put to work. On January 31, NASA’s Jet Propulsion Laboratory in Pasadena, Calif., released an analysis of perchlorate in Pasadena’s drinking water by Sturchio and others. “Imported Colorado River water may turn out to be much of the source,” Sturchio says. The team is also thinking beyond water supplies, because perchlorate has been found in the U.S. food supply and in human breast milk and urine. “It’s conceivable that by coupling our methods with studies of food grown in certain areas, we might be able to pinpoint sources of perchlorate in humans,” Sturchio says. —ERIKA ENGELHAUPT © 2007 American Chemical Society
News Briefs
Anna Leung
Discarded electrical and electronic equipment, often called e-waste, is becoming a major environmental concern, particularly in developing countries. In a report published in this issue of ES&T (pp 2730–2737), researchers from Hong Kong Baptist University have found elevated levels of polybrominated diphenyl ether (PBDE) flame retardants as well as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in surface soil samples and combustion residues in Guiyu in southeastern China, a region notorious for its intensive e-waste recycling centers.
Printer rollers were dumped beside a pond in Guiyu, China.
“Crude e-waste recycling activities, including the open burning of e-waste, are a hot spot for PBDEs and PCDD/Fs,” says the paper’s first author, Anna Leung. The researchers found that PBDE levels in combustion residues from open burning were some of the highest found in any environmental medium (33,000–97,400 nanograms per gram [ng/g]), more than 16,000 times higher than those found in soil samples in a distant reservoir that served as a control site. High levels of PBDEs were also found in soils from an acid-leaching site (2720–4250 ng/g), where workers use a mixture of nitric acid and hydrochloric acid to recover precious
metals from shredded printed circuit boards and from a printerroller dump site (593–2890 ng/g). BDE–209, a signature of Deca-BDE, was the dominant congener; however, signature congeners from Penta- and Octa-BDE were also found. Levels of PCDD/Fs at an acidleaching site were higher (12,500– 89,800 picograms per gram [pg/g]) than those in the combustion residues (13,500–25,300 pg/g). Bixian Mai from the Guangzhou Institute of Geochemistry (China) suggests that “the PCDD/Fs from combustion may be emitted to the atmosphere instead of depositing to the nearby soils,” whereas the “wastes from acid leaching are directly discharged to the surrounding surfaces.” The UN Environment Programme estimates that each year 20–50 million metric tons of ewaste are produced worldwide; this number is increasing rapidly. The U.S. EPA estimates that between 2000 and 2007, 500 million computers will become obsolete in the U.S. As an alternative to overpacking landfills or recycling domestically, some industrialized countries have found it cheaper to export e-waste to developing countries where labor costs are low, and occupational and environmental laws are lax or not well implemented. According to the environmental group Basel Action Network, 50–80% of e-waste collected in the U.S. for recycling is exported to developing countries. “This situation is exacerbated because the U.S. has not ratified the Basel Convention, which prohibits the shipment of hazardous waste [including ewaste] across countries,” says Oladele Ogunseitan of the University of California, Irvine. “Therefore, it
States seek to ban most common flame retardant
Washington may become the first state to ban the most common form of polybrominated diphenyl ether (PBDE) flame retardants, Deca-BDE, which the U.S. EPA lists as a carcinogen. Maine may not be far behind (see below). In Washington, proposed legislation would phase out DecaBDEs in computers and other products by 2011. The bill was introduced in January, marking the third year a ban has been suggested, according to Robert Duff, director of the state’s Office of Environmental Health Assessments. The law would make the state one of a handful that have banned Octa- and Penta-BDEs, also considered toxic. Deca-BDE replaced these and other discontinued PBDEs.
Deca PBDEs not needed in TVs, Maine claims
Maine should ban the Deca polybrominated diphenyl ether (PBDE) flame retardant in televisions beginning in 2012, recommends a report by the state’s Department of Environmental Protection (DEP). “Televisions account for the majority of the use of the Deca flame retardant in the U.S.,” explains John James of the Maine DEP. He notes that Sony, Panasonic, and Philips already offer TVs that use alternatives to Deca. In 2004, Maine passed legislation banning the more toxic Penta and Octa PBDEs and requiring that the heavier Deca formulation be banned in 2008 if safer alternatives were found. Maine’s DEP also recommends banning mattresses and upholstered furniture containing Deca, although the formulation is not now known to be used in these products.
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E-waste creates hot spots for POPs
Environmentalt News may not necessarily be illegal for the U.S. to export e-waste out of the country,” adds Leung. The interdisciplinary team, led by Minghung Wong, has been conducting research in Guiyu since 2003. Its studies provide evidence that pollutants, such as PCDD/Fs, PBDEs, PAHs, and heavy metals (Cd, Cu, Ni, Pb, and Zn), are found at higher levels at open-burning sites than at nonopen-burning sites. The work underscores the importance of e-waste processing activities.
Workers in the e-waste recycling industry are especially vulnerable. “Exposure to PBDEs and PCDD/Fs for the workers can come through industrial exposure by skin contact or inhalation,” says Minghu Zheng from the Research Center for EcoEnvironmental Sciences in Beijing. The research group and Ogunseitan recommend further studies to assess the impact of pollutants on the local wildlife and human population. “We are also [undertaking] a human-health risk assessment by conducting a food consumption
survey and analyzing fish tissues and human milk” for persistent organic pollutants, says Leung. She also hints that unpublished data reveal elevated levels of several heavy metals in dust inside recycling workshops and in road dust in the vicinity. She hopes that the results from their research can be used as a “case study to alert other e-waste processing regions of the adverse environmental and health impacts associated with unregulated and primitive e-waste practices.” —THANH WANG
Losing the scent of danger ter, so the nose would be the first part in contact with the contaminants,” says lead author Jason Sandahl, who completed the work as a graduate student at Oregon State University. “One thing that surprised me was how sensitive their CARL A STEHR
Fish are like swimming bloodhounds. Swirling water through their noses, they pick up minute chemical cues that can guide them thousands of miles to spawn in just the right spot, or can sound an alarm that tells them to hide from oncoming predators. But research published in this issue of ES&T (pp 2998–3004) shows that copper entering streams from urban and agricultural runoff can damage salmon’s fine sense of smell. The problem extends beyond copper, and even beyond fish. Greg Pyle of Nipissing University (Canada) says he and other toxicologists are starting to refer to the loss of animal sensory systems as “the hidden global change”. Pyle has studied animals at three levels of the aquatic food chain, from leeches that “live in the muck” to top predator fish. “With every organism we look at, and every metal we’ve considered, we see the same effects,” he says. “Very low concentrations of metals can knock out the chemosensory system.” Storm water rinses copper into streams from roadways and agricultural fields, where it accumulates from sources including pesticides, vehicle exhaust, and tiny particles ground off brake pads. “The neurons in a fish’s nose are in direct contact with the wa-
Coho salmon have an exquisite sense of smell, thanks to their layered noses, one of which is shown here in a scanning electron micrograph.
olfactory systems are—they’re much better than dogs’,” he says. The team studied coho salmon and found that they could detect pheromones emitted from a piece of fish skin 1 square millimeter in size—smaller than a grain of rice—in 100 liters of water. The study combined observations of fish behavior with physiological measurements of nerve signals measured by placing sensors in fish noses. The team demonstrated in earlier work that copper damages salmon’s delicate
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nose tissue and disrupts olfactory nerve signaling. “For the last 30 years, we’ve known that olfaction could be affected, but the question was, what does it mean when a fish can’t smell? This is the first study to link that to a specific behavior,” says Scott Hecht, an ecotoxicologist at the National Oceanic and Atmospheric Administration. In a video of the study, a young coho salmon darts madly around an aquarium filled with clean, copper-free water until a researcher drips in a solution made from a tiny piece of torn fish skin. Suddenly, the salmon sinks to the bottom of the tank and hovers in a fish version of a doggy paddle. Its nose is telling it that another fish has been injured, so a predator must be nearby. In the wild, bears and other fish-eaters look for movement, so this stop-and-drop technique helps salmon avoid notice. Meanwhile, a salmon in another tank has been swimming for 3 hours in water spiked with just 10 parts per billion copper, a level commonly found in streams after storms. When the skin solution hits the water, this fish seems oblivious. Instead of lying low, the salmon just keeps speeding along. In the real world, this can mean becoming someone else’s dinner. And that’s a real problem. Today, 26 different populations of salmon are listed as threatened or endangered under the U.S. Endan-
dissolved organic matter.” The coho were able to regain their sense of smell within hours after short exposures to low doses of copper, as receptor neurons recovered. However, other research has shown that these neurons can die at higher concentrations. “When neurons in the nose die, they can still regenerate, but it can take several weeks to a month to regrow,” Sandahl says, which could be too late for a fish that needs to hightail it to safety. —ERIKA ENGELHAUPT
Lipid coating increases uptake of nanotubes
The empty guts of starved daphnids (left) fill up with water-soluble carbon nanotubes (right).
Stephen Klaine et al .
As the rapidly expanding nanotechnology industry churns out newer and more complex nanomaterials, many worry about the potential environmental impacts of these materials.
A new study published in this issue of ES&T (pp 3025–3029) shows that when carbon nanotubes are made water-soluble with natural lipid layers, they are readily taken up and structurally modified by daphnids, or water fleas (Daphnia magna). The nanotubes are also toxic to the fleas at high concentrations. A previous study in ES&T (2007, 41, 6; 179–184) showed that increased solubility makes nanotubes persist longer in aqueous environments, but the researchers did not test their direct impact on living organisms. Carbon nanotubes are known for their insolubility. However, treatments with various materials, like surfactants and certain natural polymers, make them more
water-loving. To investigate the potential toxicity of water-soluble single-walled carbon nanotubes, environmental toxicologist Stephen Klaine of Clemson University and his colleagues placed different concentrations of lipid-coated nanotubes in cups of water containing starved daphnids. The researchers were surprised to find that as they increased the concentration of the nanotubes, more of the fleas survived. Without nanotubes, 20% survived, whereas with 0.5 milligrams of nanotubes per liter (mg/ L), about 90% survived. Beyond 0.5 mg/L, the fleas began to die and fall to the bottom of the cups. “It was good for a while,” says Klaine. “And then it became toxic.” Klaine repeated the experiment with algae in the cups containing the nanotubes and water fleas. In the presence of algae, nearly 100% of the fleas survived at all concentrations of nanotubes up to 5 mg/L. The numbers fell to a little less than 80% at 10 mg/L. The results suggest that the toxicity of the tubes was from ingestion and that when algae were present, the daphnids ate more algae and fewer nanotubes. They also observed the daphnids under the microscope and found that their guts fill up with nanotubes within 45 minutes to an hour of exposing them
News Briefs Olive cakes help contain herbicides
Researchers have found a new use for olive cakes, a major waste product of the olive-oil industry: preventing herbicides from polluting water. A team of researchers in Spain applied olive cakes, either raw or composted, to herbicide-containing soil samples and found them to help retain herbicides in soil, thus reducing the amount leaching into groundwater. The effect was limited to two waterhating herbicides— terbuthylazine and prometryn. Treatment with raw cakes halved the amounts of prometryn leaving soil particles, from 40% to 20%. The results, published in the Journal of Agricultural and Food Chemistry (2007, 55, 836–843), suggest that olive-oil industry wastes could be used to prevent some groundwater contamination.
DuPont cuts PFOA levels
DuPont has taken a big step toward eliminating perfluorooctanoic acid (PFOA) by 2015, introducing a new manufacturing process that slashes emissions of the chemical by 97%. PFOA is used as a processing aid in making fluoropolymers, which in turn are used in products such as Teflon, rain gear, and the grease repellents in food-wrapper coatings. The U.S. EPA lists the chemical as a “likely carcinogen”. Research has also documented trace levels in the blood of Americans. Although DuPont disputed the conclusions of a 2004 study on the carcinogenic effects of PFOA, in 2006 the company agreed to slowly eliminate the chemical’s emissions. According to DuPont’s website, “there are no known human health effects caused by PFOA,” but the company reiterates its commitment to achieve the 2015 goal.
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gered Species Act. Coho are particularly vulnerable to copper in streams, because they spend the first year of life in freshwater. “It’s possible that the risk is underestimated, because this is just one of many chemicals that could influence behavior,” says Richard Di Giulio, an ecotoxicologist at Duke University. However, he adds that “the largest uncertainty would be how this would play out in realworld surface waters with materials that could potentially reduce the bioavailability of metals, like
Environmentalt News to the material. As the fleas gorged on the soluble nanotubes, the researchers also observed a dark precipitate accumulating at the bottom of the cups, just like the kind that forms when the uncoated, insoluble nanotubes are put in water. Klaine suspected that the daphnids were swallowing the tubes, stripping the lipid layer, using it for food, and spitting out the naked nanotubes, thus making them insoluble once again. The researchers confirmed that suspicion with a spectrophotometry technique that showed that the black precipitate did indeed have identical spectral properties to the original, unmodified nanotubes. Taken together, this meant that not only were
daphnids feeding on these tubes but they were also “drastically modifying” them, says Klaine. The study also illustrates the significance of evaluating the environmental impacts of both coated and uncoated nanomaterials, especially since they have different solubilities, says Klaine. “The implications are that [a soluble nanoparticle] is moving downstream,” he points out. This will affect organisms in the water even far away from the site of release of the nanoparticles. On the other hand, an insoluble nanoparticle “remains in the sediments. So, entirely different organisms get affected,” he says. However, the study does not elucidate the mechanism by which
these particles kill water fleas or how the daphnids use the lipid layer for food, he adds. “This is a nice piece of meat,” says Ron Turco, a soil microbiologist at Purdue University. Until now, the few studies on ecotoxicity of nanoparticles have focused on the materials themselves. This study “shows that the coating matters,” says Turco. “We do have to be careful of what we put on the outside more than [what is] inside.” However, this is not the final word on the environmental impact of such soluble nanomaterials, warn Klaine and Turco. It is only the beginning of evaluating their environmental effects. —RHITU CHATTERJEE
Natural settings may diminish the high toxicity of fullerenes or C60 nanoparticles to soil-dwelling microbes, according to new results published in this issue of ES&T (pp 2985–2991). The findings contradict previous studies, which have shown that the nanoparticles are lethal in more unsoiled settings. The new experiments, conducted under some of the most realistic conditions yet with microbes in soil, come from a team led by Ron Turco of Purdue University. The researchers exposed soil microbes to relatively high concentrations of C60 (1000 parts per million) both in dry form and in an aqueous suspension with tetrahydrofuran. They also exposed the microbes to tetrahydrofuran alone. This solvent is typically used in lab experiments to suspend C60 because the particles are not soluble in water at room temperature. The team incubated their C60 concoctions in real soil samples taken from corn plots northwest of the Purdue campus. While exposing soil to the C60 nanoparticles over several months, Turco and co-workers measured the presence and activity of mi-
Courtesy of Wikipedia
Microbes survive in soil with fullerenes
Buckyballs may not be as toxic to microbes in soil as predicted.
crobial populations. To see how the bugs were faring, the researchers assessed glucose respiration, microbial biomass, enzymatic activities, and DNA extracts, among other measures of the populations’ health. Overall, the team found little effect on the structure or function of the soil microbial community. Because microbes are at the bottom of the food chain, Turco points out, effects on them have the potential to work their way up to higher tro-
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phic levels. But so far, “there is no effect on that key part of the food chain,” he says. “Is there a possible effect that we don’t see?” he asks. Those effects could come from dosing effects or different possible arrangements of the fullerenes themselves, such as various outer coatings that manufacturers apply to obtain certain functions. Coated nanomaterials will interact with more complex environments differently, with regard to both exposure and potential for mobility. Organic matter, for example, might make some nanomaterials move farther while sequestering others, depending on their chemistry. Also, “you cannot extend this [new research] to other types of nanomaterials,” such as titanium nanoparticles, says Mark Wiesner of Duke University. However, “this is a really important study because there has been, based on really preliminary and methodologically young studies, a lot of very strong reaction to the potential for nanomaterial toxicity,” he adds. The new research includes factors missing from previous studies, with a soil matrix that “resembles much more closely a real exposure setting,” Wiesner continues. “That there is not a significant impact
maybe in a lake,” stream, or other open water system, she says, “lower fullerene concentrations might be relevant.” “I don’t know of any other study to date [regarding potential nanomaterial impacts] that has taken such a holistic approach with quantitative outcomes,” agrees John Fortner, who is a postdoctoral researcher at the Georgia Institute of Technology, where he focuses on the fate and transport of nanomaterials. Soil biology is complicated, he notes. With billions of bacteria living in 1 gram of soil, studying bioavailability is complex. “But you have to start somewhere,” he says. —NAOMI LUBICK
Nanosized C 60 particles known as fullerenes or buckyballs have the potential to serve as direct drug-delivery messengers or be used for other beneficial purposes, but they can be toxic to cells. How the tiny particles do damage depends on where they end up. For the first time, researchers have found a way to observe the uptake of C 60 into the cytoplasm and nuclei of human macrophage cells, in research published in this issue of ES&T (pp 3012–3017) that relies on the use of energy-filtered transmission electron microscopy (TEM). A team of researchers led by Alexandra Porter of the Nanoscience Centre at the University of Cambridge (U.K.) produced TEM images that provide cloudlike tomographic maps, as shown in this image (top) of the material inside cells. Interpreting these images from in vitro experiments, the team confirms that human macrophages take up C 60 and then sequester the particles mainly in the cytoplasm and lysosomes. But sometimes the C 60 ends up inside the cells’ nuclei, as shown in the image (bottom). “If you can’t visualize where things are, being able to interpret the biochemistry is nearly impossible,” says Trevor Douglas of Montana State University. “What they’re doing is so incredible: to pull out a signal for buckyballs and carbon that’s different from the carbon in the cell,” he says. “They’re not manipulating the system at all; they’re looking at it directly.” Now that the method works for in vitro samples, the team can move on to experiments in vivo, Porter says, to look for functional consequences of exposure. Even though the researchers can map nanoparticles inside cells, Porter continues, “we now have to back this up with toxicity assays, and that’s when it becomes important.” —NAOMI LUBICK
Ale x andr a Porter E T AL .
Seeing buckyballs inside human cells
News Briefs Pesticides threaten coral reefs
As coral reefs contend with acidity and rapidly warming seas because of climate change, scientists have measured an additional threat: fungicides and insecticides at very low concentrations. A new paper by researchers in Australia shows that chlorpyrifos, endosulfan, permethrin, and other pesticides can affect corals during fertilization and metamorphosis, and in some cases even harm adult corals. Profenofos, for example, caused bleaching after several days’ exposure at concentrations of 10 micrograms per liter. The finding “highlights the critical need to assess toxicity against all life-history stages of keystone organisms: to focus on mature individuals may underestimate species sensitivity,” the authors write in the study, published January 25 in Marine Ecology Progress Series (2007, 330, 127–137).
Mercury still rising
Environment ministers from around the world agreed to study mercury reduction options but did not commit to legally binding goals at a meeting of the UN Environment Pro gramme (UNEP) governing council. At the February meeting in Nairobi (Kenya), the council established an ad hoc working group that will spend 2 years considering future international actions, which could include a treaty. In 2002, UNEP’s Global Mercury Assessment report found mercury to be a growing and worldwide problem. Since then, UNEP has established its mercury program to help countries understand and reduce mercury pollution levels. As at previous UNEP meetings, the EU called for a legally binding treaty, but the U.S. and India objected to any mandatory limits. Instead, both favor continuing voluntary partnerships.
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on the microbial community is a very different result than has been found in these more pristine systems studied.” Delina Lyon, a graduate student who studies fullerenes and bacteria at Rice University, notes that the field is young enough that researchers still “don’t know what a relevant concentration is to use” when testing antibacterial activity. In past studies, bacteria have been directly exposed to fullerenes, but that exposure can be mediated if organic matter causes the nanoparticles to cluster or adsorb to soil. “It depends also on what matrix you use—maybe in soil it’s not going to have an impact, but
Environmentalt News NIST standardizes household dust A bottle of Standard Reference Material 2585 consists of about 10 grams of dust. Collected from vacuum cleaner bags from urban homes, cleaning services, motels, and hotels in various U.S. states during 1993 and 1994, this material is the latest tool in the arsenal to analyze organic contaminants. Accurate assessments of everyday exposure to the wide range of potentially hazardous chemicals in household dust are difficult because of the complexity of the analyses and the small quantities involved, according to researchers with the U.S. National Institute of Standards and Technology (NIST).
To ensure more accurate analyses, NIST researchers developed the new reference sample, certifying the concentrations of more than 80 organic contaminants. The work is described in this issue of ES&T (pp 2861–2867). The motivation came from U.S. EPA scientists, says Michelle Schantz, a NIST research chemist. They were looking for a dust sample that different laboratories could use as a control sample to verify that their methods are valid and that data from different studies are comparable. “It’s really intended to ensure that the methods being used to make these state-
Analytical chemist Abul Hussam of George Mason University won the $1 million first prize in the Grainger Challenge for Sustainability. The challenge, organized by the U.S. National Academy of Engineering (NAE) in conjunction with the Grainger Foundation, was aimed at stimulating the development of ingenious arsenic-removal devices tailored for developing countries. Naturally occurring arsenic in groundwater is a worldwide problem, but the most severely affected areas are in Bangladesh and the neighboring West Bengal region of India. Estimates suggest that in Bangladesh alone, about 10 million tube wells are supplying 77–95 million people with arsenic-contaminated drinking water. Hussam was born in Kushtia (Bangladesh) where, in 1999, he first detected arsenic in drinking water in his own family’s tube wells. After he confirmed his findings in other parts of Bangladesh, Hussam decided to devote part of his research at George Mason University to developing a low-cost technology for arsenic filtration.
Courtesy of NAE
Chemist wins sustainability award
Analytical chemist Abul Hussam wins the Grainger Challenge for his arsenicremoval SONO filter.
Nine years later, he is the winner of the challenge, and his arsenic filter, called the SONO filter, is providing arsenic-free drinking water to 14 districts in Bangladesh. The SONO filter is a point-ofuse system that provides enough clean drinking water for one or two families. The simple design consists of three buckets piled one above the other. Water enters the top bucket and filters first through coarse river sand from local rivers and a composite iron matrix (CIM)
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ments [regarding potential health risks due to dust exposure] are valid methods,” Schantz explains. NIST researchers collected the vacuumed dust with EPA assistance. After sterilizing, filtering, homogenizing, and analyzing the resulting material, the NIST researchers certified each dust sample for concentrations of 33 selected PAHs, 30 PCBs, 4 chlorinated pesticides, and 15 polybrominated diphenyl ethers (PBDEs). They also provided reference values—measurements believed to be accurate but not meeting NIST criteria for a certified value—for an additional 33 PAHs, 12 PCBs, 10 chlorinated pesticides, and 3 PBDEs. —KRIS CHRISTEN
that took “years of upgrading and developing,” says Hussam. While the sand traps coarse particles, the CIM captures inorganic arsenic. The second bucket contains more of the coarse river sand, and wood charcoal that removes other inorganic contaminants. Finally, the bottom bucket, which contains fine river sand and wet brick chips, removes fine particles and stabilizes the water flow. A single SONO filter costs $35– 40 and lasts about 5 years. The only maintenance, if any, involves changing the coarse sand layers every 6 months. Hussam’s filter was exceptional because it had passed its test in the field, says Charles O’Melia, the chair of the panel of judges. The Grainger Challenge also acknowledged two runners-up for the award. Arup K. Sengupta, John E. Greenleaf, Lee M. Blaney, Owen E. Boyd, Arun K. Deb, and the nonprofit organization Water for People won the $200,000 second prize for a community water-treatment system in use in West Bengal. The Children’s Safe Drinking Water Program, run by Procter & Gamble, won the $100,000 third prize for its PUR water purification system. —RHITU CHATTERJEE
