Environmental ▼ News Atmospheric processes may create perchlorate
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races of perchlorate are found Dasgupta’s group embarked on Jackson. “They go from levels too in rain and snow and can be low for us to detect to parts per bilthe new study, which they funded created in lab experiments lion, but we don’t know why.” themselves, in an attempt to exsimulating tropospheric processes, plain vast swaths of perchlorateThe group also passed a sodium according to research published in contaminated groundwater in chloride aerosol through an electhis issue of ES&T (pp 1569–1575). the southern high plains desert of tric discharge, which simulated These observations suggest that the Texas panhandle. Although lightning, and detected perchlorate there is a natural flux of atmospherthere is no evidence of anthropoeach time, with a ratio of perchloic perchlorate to the earth rate to chloride that was and a natural perchlorate two orders of magnitude background level, says greater than the control. corresponding author Perchlorate even formed Purnendu Dasgupta from when salt solutions were Texas Tech University. exposed to ozone and UV Facilities that manlight, simulating desert ufacture or use perchloconditions. Chemist Glen rate-containing rocket Miller at the University of fuel appear to be the Nevada, Reno, has found source of most contamithat photochemical oxination plumes. For sevdation on soil can also eral years, controversy generate perchlorate. has swirled around estiThe combination of mates of the health risks a desert area and recent posed by perchlorate in intensive irrigation may drinking water. The U.S. be what it takes to put New research showing that natural processes such as lighting can EPA and environmental natural perchlorate into generate perchlorate may help explain why the compound is being groups contend that only groundwater. In West found in drinking water. very low concentrations Texas and the Chilean genic sources in this region, water are safe, while the U.S. Atacama Desert, which is the perchlorate values of 20–60 parts Department of Defense and its source of perchlorate-containper billion (ppb) were measured contractors support higher levels. ing nitrate fertilizer, the harsh enA National Academy of Sciences (Environ. Sci. Technol. 2003, 37, vironment may well concentrate committee concluded in January 376A–377A). Instead, they find that the low-level flux, says Dasgupta. that perchlorate is about 23 times groundwater levels of perchlorate Then, activity—mining in Chile or less hazardous than EPA had estibest correlate with levels of iodate, the recent onset of water-intensive mated (Environ. Sci. Technol. 2005, which is known to be of atmospherfarming in West Texas—mobilizes 39, 96A–97A). ic origin. the perchlorate quickly. A natural However, as analytical methods In their newest study, the resource may also explain perchloimprove, researchers are finding searchers analyzed 21 rain and 4 rate contamination in part of eastlow levels of perchlorate everysnow samples collected mostly in ern Oregon, where arid land has where, which suggests a natural Lubbock, Texas, in 2003 and 2004. recently moved to intensive crop flux, says Dasgupta. His lab was the They found perchlorate in 70% production, says Kevin Mayer with first to publish a study of perchloof the samples at concentrations EPA Region 9. rate in milk (Environ. Sci. Technol. ranging from 0.02 to 1.6 ppb. Rain The Texas group is collaborating 2003, 37, 4979–4981), but Dasgupta collected at Cocoa Beach, Fla., from with the U.S. Geological Survey to hastens to add that finding a natuHurricane Frances contained 0.6 look for perchlorate in rain samples ral source of perchlorate should not ppb. The researchers don’t have taken across the country and planlessen concerns about anthropoenough information yet to quantify ning further lab experiments to pin genic contamination, which can the flux. “The data are highly varidown atmospheric mechanisms. range up to parts-per-million levels. able,” explains co-author Andrew —REBECCA RENNER 120A ■ ENVIRONMENTAL SCIENCE & TECHNOLOGY / MARCH 15, 2005
© 2005 American Chemical Society
News Briefs
GARY BAÑUELOS
For many years, scientists have used plants along with bulldozers and earthmovers to clean up toxic waste sites. New research published in this issue of ES&T (pp 1771–1777) reports the first field trial of a genetically modified (GM) plant used to remediate contaminated soils. “People have known about phytoremediation and how to genetically modify plants, but this is the first time anyone has brought these two together,” says study author Norman Terry, a professor of plant and microbial biology with the University of California, Berkeley. Lena Q. Ma, a professor of biogeochemistry of trace metals at the University of Florida, says that this paper pushes the boundaries of phytoremediation research. Her lab discovered a fern that naturally hyperaccumulates arsenic (Nature 2001, 409, 579), and she adds that genetic modification of wild plants is the next logical step. “This is better than getting into some long, drawn-out breeding pro-
These GM mustard plants were much larger and healthier than wild-type plants grown in selenium-contaminated soil.
gram that might not work,” adds Clayton Rugh, an assistant professor of phytoremediation at Michigan State University. Transgenic mustard plants (Brassica juncea) were field-tested in California by Gary Bañuelos, a plant soil scientist with the U.S. Department of Agriculture; he says that this technology is not ready for widespread application. Because of federal restrictions on transgenic plants, the mustards had to be harvested once they started to flower, which only allowed six weeks of growth. Although the study showed that the plants took in a large amount of selenium, he was unable to evaluate improvements to the field. “The plants weren’t in the field for a long enough period [for us] to evaluate the soils,” says Bañuelos. Selenium contamination is a serious problem in California’s Central Valley and other arid farmlands where irrigation water evaporates and leaves behind dissolved salts and other substances. In the Central Valley alone, decades of farming have left more than 100,000 cubic meters (m3) of soil with toxic levels of selenium and various salts. Removal and transportation of this sediment are estimated to cost $11–34 per m3, and experts say that phytoremediation is the only technology that is sufficiently cost-effective to clean up this contaminated farmland. For the study, the researchers created three lines of transgenic mustard plants that overexpress an enzyme, each involved in a very different pathway. Of the three lines, the most successful overexpressed adenosine triphosphate sulfurylase, which is a metabolic protein that converts selenate to organic forms of selenium. This
GHGs accelerating river flows
Rising greenhouse gas (GHG) emissions are boosting water flows in Arctic rivers, according to a study published in Geophysical Research Letters (2005, 32, L02703). Peili Wu and colleagues at Britain’s Hadley Centre for Climate Prediction and Research ran a river discharge model with both anthropogenic and natural external variables. The simulation agreed well with observations that precipitation and melting ice have swelled river flows to the Arctic Ocean by 8.73 cubic kilometers per year since the 1960s. When the model was run with natural solar and volcanic variables only, river discharges did not increase. With inputs of anthropogenic GHGs, sulfate aerosols, and ozone only, the modeled trend in discharges exceeded the observed trend by 50%.
What the world needs now
Investments in the protection of ecological systems and sustainable sources of energy are among the best options to make the world more secure, according to the Worldwatch Institute’s annual report, State of the World 2005: Redefining Global Security. “Poverty, disease, and environmental decline are the true axis of evil,” says Worldwatch president Christopher Flavin. The report claims that acts of terror and the dangerous relations they provoke are symptomatic of underlying sources of global insecurity. It urges governments to build on the growing array of joint environmental initiatives, including peace parks, shared river basin management plans, and joint environmental monitoring programs. To purchase the book, go to www.worldwatch. org/pubs/sow/2005.
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GM plant field-tested for enhanced soil remediation
Environmental▼ News GM plant captured 4.3 times more selenium than the wild-type mustard. Another GM line produced excess glutamyl-cysteine synthetase, a small protein that binds and detoxifies the metals, helping the mustard snag 2.8 times more selenium than the wild-type plant. The third line took up 2.3 times
more selenium than the wild type by producing excess glutathione synthetase, which allows the plant to tolerate adverse environmental conditions such as cold, drought, or high salinity. Banuelos says that the ES&T paper is proof of concept and that his group is aiming to engineer plants
Common arsenical pesticide under scrutiny weeks, almost 20% of the arsenic in the MSMA percolated below the root zone of sandy soils in the form of inorganic arsenic, Cai says. The more clay there is in the soil, the more arsenic is retained, he notes. The study has been submitted to a peerreviewed journal. Some industry scientists have criticized Cai’s study, saying that the apparatus used to collect leachate promotes the growth of bacteria, which boost the transformation of MSMA beyond what would be expected in the soil. However, Cai and Snyder’s findings are corroborated by a Florida Department of Environmental Protection (FDEP) study that found contamination after examining 65 groundwater samples from 7 different golf courses where MSMA was legally applied (http://fdep.ifas.ufl.edu/msma. htm). Shallow monitoring wells re-
vealed that 86% of the samples contained more than 10 micrograms of total arsenic per liter, which is the new groundwater standard in Florida. In areas with high water tables, just a single application of MSMA is likely to render the underlying groundwater out of compliance with the new standard, the study says. FDEP has recommended restricting the use of MSMA in vulnerable areas with sandy soils and high water tables. Florida’s Department of Agriculture and Consumer Services (FDACS) has asked companies that sell MSMA in the state to conduct further field tests, says Dennis Howard, chief of the bureau of pesticides at FDACS. Representatives from these companies have maintained that MSMA is quickly adsorbed into soil and not easily released, he says. Meanwhile, in Canada, the permit to inject pine trees with MSMA to curb outbreaks of mountain pine beetles has expired, and the manGRADIENT CORP.
Golfers can thank monosodium methanearsonate (MSMA) for flawless, weed-free fairways, but experts are questioning whether the arsenic-containing pesticide is safe for the environment and human health. New research reveals that, despite industry claims, MSMA applied to golf courses with certain types of soil degrades to toxic inorganic arsenic, which leaches into groundwater. A separate study has documented that MSMA can move through wildlife food chains. The news comes as Canada and the United States are re-evaluating registrations for MSMA. According to the U.S. EPA, MSMA “can reasonably be anticipated to cause cancer in humans” and is converted in the environment to inorganic arsenic, a known human carcinogen. About 4 million pounds of MSMA is applied every year to golf courses and cotton fields in the United States to control weeds. The pesticide has been banned in India and Indonesia. Concerns about the fate and transport of MSMA led to a collaborative study among Yong Cai and his colleagues at Florida International University and George Snyder, John Cisar, and their colleagues at the University of Florida. They dosed an experimental golf green at the University of Florida with MSMA and monitored the soil and the water percolating through the soil. “Presumably due to microbial activity in the soil, MSMA was transformed to As(V), As(III), monomethylarsonic acid, and dimethylarsinic acid, with As(V) being the major form,” Snyder says. After 14
that can accumulate even higher selenium levels. He adds that once the technology becomes commercial, farmers could process the harvested plants as cattle feed. California has a large dairy industry, and the cattle lack sufficient selenium in their diet, he points out. —PAUL D. THACKER
As this image shows, how the human body metabolizes arsenic depends on its form.
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chronic toxicity of methylated arsenicals, including the trivalent and pentavalent forms,” Styblo says. “If [Snyder and Cai] have really shown that MSMA is demethylated, that is very important because it means that arsenic could end up in drinking water,” he warns. MSMA does not cause cancer in animal studies and is safe if used properly, says Barbara Beck, director of health sciences at Gradient Corp., a consulting firm. If it is ingested, 95% is converted in the gut to monomethylarsonic acid, which is rapidly excreted, and the remainder is metabolized to dimethylarsinic acid, she adds. The EPA is currently reviewing MSMA for re-registration, says Enesta Jones, a press officer with the agency. The re-evaluation will include consideration of new research on the carcinogenic potential of the organic arsenic herbicides and their degradation in the environment, she says. The re-registration eligibility decision is due July 2006. —JANET PELLEY
Experiments show how polluted air may cause allergies An innovative molecular explanation of how air pollution may trigger allergies is described in this issue of ES&T (pp 1673–1678). Scientists from the Technical University of Munich (Germany) showed that a combination of NOx and ozone can nitrate tyrosine, an amino acid present in all proteins, which may then go on to trigger an allergic response. Increased urban air pollution is one of several explanations for the rise in allergies and life-threatening asthma, according to Ulrich Pöschl, the corresponding author of the paper. “There are epidemiological studies which have shown that air pollution and, in particular, trafficrelated air pollution is statistically connected with enhanced allergies in the population,” explains Pöschl. Roadside dust and airborne particulate matter (PM10 and PM2.5), including pollen, contain signifi-
cant amounts of proteins (Environ. Sci. Technol. 1999, 33, 4159–4168). Research from as far back as the 1930s points to nitro derivatives, particularly those of proteins, as strong immune stimulators, according to Pöschl. The authors theorized that high concentrations of NOx and ozone under “summer smog” conditions—heavily polluted, hot, humid air—could nitrate the tyrosine residues in proteins. These modified proteins might then induce inflammation and allergy after inhalation. “It was a surprise to us that apparently nobody had thought of this potential link from environmental pollution and NOx-rich pollution into the immune system,” says Pöschl. The researchers exposed a reference protein, BSA, and a birch pollen extract containing the prominent allergen Bet v 1, to parts-per-
News Briefs No soap needed
Time to toss out those bottles of laundry and dish detergent? New research suggests that clothes and china could be cleaned with water alone! Eliminating the dissolved nitrogen and oxygen bubbles in water lets the oil separate, according to a study published on January 27 in the Journal of Physical Chemistry B (2005, 109, 1231–1238). “Complete degassing of water improves its ability to disperse and, hence, remove hydrophobic dirt,” write Pashley et al. The researchers shook tubes of oil and either distilled water or degassed water. The tubes with degassed water were turbid after several seconds of shaking. Detergents help remove oily dirt from dishes and clothing, but in the environment, detergents can promote algal growth and destroy habitats.
U.S. coastal conditions still “fair”
U.S. coastal waters show few signs of improvement, according to the second federal assessment of conditions in coastal seas, estuaries, and the Great Lakes. Overall, waters received a “fair” grade, essentially the same ranking issued four years ago by the first National Coastal Condition Report, compiled by the U.S. EPA, National Oceanic and Atmospheric Administration, U.S. Geological Survey, U.S. Fish and Wildlife Service, and coastal states. Nationally, 25% of coastal waters are rated “impaired” for swimming, 22% are impaired for fishing, and 28% cannot fully support aquatic life, according to the latest report. Regionally, coastal conditions varied from good in the Southeast to fair in the Gulf of Mexico and the West, fair to poor in the Great Lakes, and poor in the Northeast and Puerto Rico. To access the National Coastal Condition Report II, go to www.epa. gov/owow/oceans/nccr.
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ufacturer, United Agri Products Canada, Inc., has withdrawn MSMA from the Canadian market. Agencies are also evaluating work from the Canadian Wildlife Service, which shows that woodpeckers feeding on bark beetles in treated trees had 4–7 times the level of arsenic in their blood than species that don’t feed on the beetles. Although organic forms of arsenic were once thought to be less toxic than inorganic arsenic, new research on the metabolism and toxicity of both organic and inorganic arsenic has changed that view, says Mirek Styblo, biochemical toxicologist at the University of North Carolina, Chapel Hill. He says that human cells metabolize As(V) to As(III) and trivalent methylated forms—monomethylarsonous acid and dimethylarsinous acid. He and others have shown that all the trivalent forms, including methylated ones, are genotoxic and more toxic than the corresponding pentavalent forms. “But we’re lacking data on the
Environmental▼ News billion (ppb) concentrations of NO2 and ozone mixtures. Both the BSA and Bet v 1 proteins were substantially nitrated after 30 hours at 100 ppb, a level found under low-smog conditions, and more affected after 30 hours at 200 ppb, which is reached during severe summer smog alerts. Tyrosine was also nitrated when the proteins were exposed to ambient air collected
from Munich’s heavily trafficked intersections. Moreover, environmental samples—dust collected from urban windows and from the roadside at a major urban traffic junction—also contained nitrated proteins. “It’s a reasonable theory,” says David Diaz-Sanchez, who studies pollution-related allergies at the University of California, Los
Angeles. “Any studies that look at how pollution affects the allergic response are welcome; it’s a very important area,” he adds. The missing link in these studies, however, is the demonstration of increased allergenic potential of these environmentally nitrated proteins, says Diaz-Sanchez. Pöschl says that these studies are under way. —BARBARA BOOTH
Thawing permafrost poses hurdles for development there is a risk that the pipe will be either cold or warm enough to freeze or thaw the soil. The resulting subsidence or frost heave could bend the pipe, requiring engineers to cut gas flow to prevent ruptures or institute costly repairs. Therefore, the ANTONI LEWKOWICZ
New data from the Global Terrestrial Network for Permafrost (GTNP) reveal that a warming climate is accelerating thawing of the permafrost—the concrete-like frozen ground found mostly in the far Northern Hemisphere. The rising ground temperature could spell trouble for the vast new energy developments proposed for the high northern latitudes, experts say. Tracking trends in the permafrost—soil that remains frozen for more than two years—is important because it is a sensitive record keeper of climate change, says Frederick Nelson, a physical geographer at the University of Delaware. New data from the Circumpolar Active Layer Monitoring Program, GTNP, and other monitoring programs, presented on December 13 at the American Geophysical Union meeting in San Francisco, clearly show that the permafrost is warming in response to rising air temperatures in the Arctic, he says. The changes in the permafrost have important implications for the natural gas pipeline planned in Canada’s Mackenzie River Valley in the Northwest Territories, says Chris Burn, Natural Sciences and Engineering Research Council of Canada Northern Research Chair at Carleton University in Ottawa. The buried pipeline will carry pressurized gas, chilled to match the surrounding ground temperature. Because the pipe will travel through areas with and without permafrost,
These shallow landslides on the Fosheim Peninsula of Canada’s Ellesmere Island resulted from a rapid thaw during a period of warm, sunny weather.
project’s engineers need to predict how permafrost responds to climate change so that they can minimize any thermal disturbance caused by the pipeline. But some experts worry that the pipeline’s proponents don’t consider climate change a serious challenge to the project’s overall design, says Stephen Hazell, Mackenzie WILD campaign director for the Sierra Club of Canada. The team of government scientists reviewing the environmental impact statement for the Mackenzie River project, which was released October 7, say that it is devoid of field data on ground temperatures and ignores
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most of the substantial literature on ground ice, according to Hazell. Scientists are not available for comment until public hearings on the pipeline commence late this spring. Meanwhile, measurements taken from boreholes in the permafrost at Svalbard, Norway, suggest that ground temperatures have increased by an average of 0.4 °C in the past decade, which is roughly 4 times faster than in the previous century, says Charlie Harris, a permafrost scientist at the Cardiff University (U.K.). Climate warming has boosted soil temperatures in northern Russia by 1 °C over the past 60 years and has increased the thickness of the active layer—the upper surface of the permafrost that thaws in summer—by 20–30 centimeters since the 1950s, according to Tingjun Zhang, a geophysicist at the University of Colorado at Boulder. Since the late 1960s, the average temperature of permafrost in Canada’s Mackenzie River delta has warmed from –8 to –6.5 °C, Burn says. At the same time, the rising frequency of 10-day intense events of continuous sunshine combined with warm summer temperatures is triggering landslides in parts of Canada’s Arctic, explains Antoni Lewkowicz, a geomorphologist at the University of Ottawa. Meltwater at the bottom of the active layer buoys up ice slabs nearly 650 meters long that slide off the lubricated surface. Landslides, some on slopes as gentle as 5°, have more than doubled on Ellesmere Island, from 6 per year before 1975 to about 14 per year for the past 25 years, he adds. —JANET PELLEY
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Environmental News PERSPECTIVE Proposed selenium standard under attack rigate fields over much of the U.S. Southwest. The metal also leaches out of piles of coal ash at power plants. The 2003 discovery of high selenium concentrations in West Virginia rivers downstream of mountaintop mining operations temporarily jeopardized this controversial activity. However, adverse effects in the field are hard to find, contends Peter Chapman with EVS Environment Consultants in Vancouver, Canada, which advises coal mining interests. “There is nothing catastrophic happening to fish populations, even in the areas most affected by coal mining,” he says. It is difficult to apply laboratory findings to wild populations when many are limited by habitat competition rather than by selenium-mediated effects, Chapman adds. Like mercury, selenium has a complex aquatic cycle, and diet is thought to be the main exposure route, according to aquatic toxicologists. Consequently, EPA’s current chronic criterion for selenium, 5 ppb in water, is often not closely related to the amount of selenium in fish. To improve the standard’s toxicological basis and sidestep the
VIVIAN STOCKMAN
The U.S. EPA’s proposed standard for selenium discharges to rivers and streams has come under attack by aquatic biologists and U.S. Department of the Interior (DOI) experts, including the author of a key study that is the basis of the new regulation. But EPA officials contend that the proposals—which were welcomed by power companies, mining officials, and California farmers—adequately reflect the study’s conclusions and will give selenium regulations a firmer scientific basis to protect sensitive fish. The current controversy is the latest in more than a decade of arguments over selenium that have pitted DOI scientists against industry scientists and EPA. The dispute began shortly after EPA set a chronic water quality standard of 5 parts per billion (ppb) in 1987. Biologists from the U.S. Fish and Wildlife Service (FWS) and the U.S. Geological Survey (USGS) argued that this standard should be cut in half to protect fish and birds. However, industries that discharge selenium said that the standard was overprotective and burdened operators with excessive compliance costs (Environ. Sci. Technol. 1998, 32, 350A; 2003, 37, 274A–275A). Selenium is a naturally occurring element and an essential micronutrient, but it can accumulate to harmful levels in fish and birds at the top of the food chain. The effects of extreme selenium poisoning were vividly demonstrated in the 1980s, when the metal deformed and killed hundreds of fish and birds at California’s Kesterson National Wildlife Refuge. In most cases, it is chronic exposure to relatively low doses in adults that leads to developmental effects in bird and fish embryos. Some studies show that dietary selenium levels only a few times higher than normal may cause such developmental problems. The toxic element concentrates in waters as a byproduct of mining. And it is in the water used to ir-
controversy, EPA contractors finished a draft guidance in March 2002 that expressed the chronic criterion as a whole-body fish tissue concentration of 7.9 ppm dry weight. The 2002 draft value pleased industry but infuriated DOI scientists. Aquatic toxicologists agree with the approach but not the value. FWS used its powers under the Endangered Species Act to block publication of the draft, which remained in limbo until February 2004, when the White House Council on Environmental Quality became concerned about the delay. As a result, FWS dropped its publication block. Meanwhile, 5 DOI scientists submitted a detailed critique of the 2002 7.9-ppm draft regulation to EPA in June. Nevertheless, the new draft released in December is quite similar to its 2002 predecessor. Both identify the most sensitive species as bluegill (Lepomis macrochirus), a staple of recreational warm-water fishing. EPA’s value was derived from a study by U.S. Forest Service aquatic toxicologist Dennis Lemley that combined selenium exposure with a temperature drop to simulate the natural stress on fish during the winter (Aquat. Toxicol. 2003, 27, 133–158).
Selenium concentrations that exceed current standards have been reported in West Virginia rivers downstream of mountaintop mining operations. MARCH 15, 2005 / ENVIRONMENTAL SCIENCE & TECHNOLOGY ■ 125A
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Environmental News PERSPECTIVE Lemley originally supported a 7.9-ppm standard, but he changed his mind and joined the June 2004 critique of the proposal. At a residue level of 7.9 ppm, 40% of the fish died, he warned. A more appropriate residue level would be 5.85 ppm, he wrote. Charles Delos, EPA’s selenium proposal manager, says that the 2004 proposal accounts for this by identifying 7.9 ppm as the critical value that protects fish but calls for additional monitoring if tissue concentrations reach 5.85 ppm in the fall. DOI scientists stopped talking to the press after EPA released its proposal, but FWS Division of Environmental Quality chief Everett Wilson says that his agency is still considering whether the researchers’ concerns have been adequately addressed by the December draft.
“Using 7.9 as a blanket approach is wrong and will not protect species,” argues fish biologist Vincent Palace with the Canadian Office of Fisheries and Oceans in Winnipeg. Palace’s three-year study of the impacts of selenium from coal mining in Alberta, currently in press in Environmental Toxicology and Chemistry, finds that rainbow trout appear to be very sensitive to developmental effects at levels below 7.9 ppm. Others take an opposite view. “The Lemley study is well done, but it’s difficult to interpret the mortality results, and it’s not the kind of study previously used,” says aquatic toxicologist William Adams with international mining giant Rio Tinto in Murray, Utah. “The overwintering stress doesn’t apply in the south. How should Florida, Louisiana, or any of those states interpret it?”
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ES&T could not verify that overwintering stress is an issue in southern states, but one state scientist spoke out strongly against the December proposal. “This 5.85 monitoring requirement is just confusing,” says the scientist, who requested anonymity. “If we get a 5.85 and then see levels going up, do we do something or do we have to wait until 7.9? We should use 5.85 because that’s protective,” he says. Delos does say that in principle action could be taken before fish tissue levels reach 7.9 ppm, but he says the details have not yet been worked out. EPA is taking comments on the proposal until April 18. Meanwhile, the agency is funding USGS to develop a separate aquatic standard for California that would protect wildlife as well as fish. —REBECCA RENNER
