Environmental t News Fertilizer from Chile puts perchlorate on the table
R
U.S. import of Chilean nitrate (NaNO3), teragrams (billion kilograms)
esearchers recognize three but it’s not enough. Most people, with the advent of synthetic fermajor sources of perchlorate including myself, have focused on tilizers. But military and agriculin the food chain: military– military–industrial sources of pertural activities no longer lead to industrial activities, agricultural chlorate,” he says. “But the numperchlorate contamination. Rockuse of Chilean nitrate fertilizer, bers don’t support it. Stepping back, et fuel washout is now properly and natural atmospheric sources. the best way to get something into contained, and in 2000, Chilean The relative magnitude of each the food chain is fertilizer.” nitrate producers instituted prosource has long cessing changes been subject to that removed per2 speculation. New chlorate from their research published product. Atmoin this issue of ES&T spheric reactions (pp 6608–6614) generate small 1.6 shows that the hisamounts that fall torical use of Chilto earth when it ean nitrate fertilizer rains. is as large a source Production and of perchlorate in use estimates of 1.2 food as military–inperchlorate are dustrial activities hard to come by: are, with natural atthe military conmospheric sources siders the numbers 0.8 coming in far besecret, and ferhind. tilizer producers The paper is the won’t share them, first to quantitasaying they are tively assess the proprietary infor0.4 magnitude of these mation. Dasgupta’s sources, and it turns team engaged in current assumptions document detecabout the past oritive work to check 0 gins of perchlorate and cross-check 1910 1930 1950 1970 1990 contamination on estimates for each 1920 1940 1960 1980 their head. military–indusYear Perchlorate is as trial and agriculWide-ranging data: to track historic imports of Chilean nitrate fertilizers, controversial as it is tural source. The researchers combined information generated from the U.S. Department ubiquitous. The poresearchers used of Agriculture (orange), congressional testimony (purple), and the U.S. tential health risks their own analyses Bureau of Mines (green). from this thyroid of rainwater and disrupter and the huge potential In the past, perchlorate conothers’ analyses of ancient groundcosts of cleaning it up have made tamination from military activities water to estimate atmospheric the issue one of the most highly occurred during manufacture, or sources. politicized scientific debates of the when rocket fuel past its prime was To rank the sources, Dasgupdecade. washed out of missiles and other ta’s team estimated the historical “We wanted to address the gendevices onto the ground and evensources of perchlorate that could eral pervasive presence of pertually into groundwater. Chilean account for the current legacy of chlorate,” says Purnendu “Sandy” nitrate fertilizers, produced from water pollution. In terms of proDasgupta of Texas Tech University, rock deposits, are naturally conduction or importation, over the who led the team that wrote the pataminated with perchlorate, but past 60 years, the military–indusper. “Precipitation was attractive, their use diminished in the 1950s trial estimate dwarfs the others:
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© 2006 american chemical Society
ignore studies on the current impacts to food crops of irrigation water contaminated by military– industrial sources. The estimates for these sources also appear low and are based on sketchy data, he says. In addition, Herz questions the detailed calculations that Dasgupta’s team used. Other scientists welcome the work. “The relative contribution of different perchlorate pollution streams has been a hot topic of debate for years,” says Renee Sharp of the Environmental Working Group, an advocacy organization. “It is good to see a quantitative treatment of the subject, rather than one that relies on guesses or conjecture,” adds Sharp, whose comments reflect those of most other scientists contacted for this article. “The scientific community’s understanding of perchlorate in the environment, while incomplete, continues to grow, and this paper makes an important contribution,” says U.S. Air Force scientist Greg Harvey. “I think additional studies in areas like Orange County, Calif., and others that went through intensive agricultural development in the first half of the 20th century should be illuminating,” he adds. —REBECCA RENNER
Hormesis gets massive data support Humble yeast cells may be shedding new light on the controversial theory of hormesis. Cancer researchers collected data on 13 strains of yeast, generating a large database of their responses to different chemicals. For low doses, those reactions are best explained by hormesis—a nonintuitive dose–response theory—and not by theories currently used in risk assessment, according to a new analysis by University of Mas-
sachusetts toxicologist Edward Calabrese and colleagues, published in Toxicological Sciences (2006, doi 10.1093/toxsci/kfl098). Hormesis explains that low doses can have the opposite effect of high doses, such that chemicals that can have harmful biological effects in relatively large amounts can have beneficial effects in small quantities. Calabrese and colleagues have found in scores of recent papers signs that such be-
News Briefs Bringing back a killer pesticide
The World Health Organization (WHO) will actively encourage broader reintroduction of DDT to fight malaria in Africa, according to an announcement made on September 15. WHO will be promoting the pesticide for use indoors to kill disease-bearing mosquitoes at times when they threaten humans most. The balance between protecting the environment from a persistent organic compound and using it to save lives has long made DDT controversial as a way to kill mosquitoes. The pesticide gets credit for eradicating malaria in the U.S. and Europe in the 1950s and 1960s as well as for protecting ground troops during World War II and other conflicts. But DDT’s harmful effects on bird reproduction led to a ban on its use in the U.S. in 1972. Researchers also have argued in the past that DDT lost its impact as mosquitoes adapted to the pesticide. WHO considered about a dozen other possible compounds before endorsing DDT, which has continued to be used in a limited fashion for indoor applications in certain African regions. But Arata Kochi, director of WHO’s malaria department, announced in September that the organization would now back DDT for expanded use. “After this reevaluation, the World Health Organization is announcing that indoor residual spraying with DDT and other insecticides will again play a major role in its efforts to fight the disease,” Kochi said. “WHO is now recommending the use of indoor spraying not only in epidemic areas but also in areas with constant and high malaria transmission, including throughout Africa.”
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USGS
10,600 metric tons (t) per year (yr) compared with 750 t/yr for Chilean nitrate fertilizer and 130–640 t/yr for precipitation. But not all of the perchlorate produced for military and industrial use was washed out to become a water contaminant. Some was used to propel missiles and for outer-space exploration, and some still resides in existing devices. As a result, no one knows how much of the military–industrial perchlorate contributed to water pollution. “This is a big uncertainty,” says Dasgupta. The Chilean nitrate, however, was used exclusively on agricultural land. This increases the impact of that perchlorate by 5.5 times, to 4200 t/yr, the paper shows. For military–industrial dumping to equal fertilizer as a source, some 40% of the military–industrial perchlorate had to have been dumped. This seems unlikely, the authors note. Dasgupta hastens to add that pockets of high levels of perchlorate pollution may still exist for which the military–industrial complex is solely responsible. William Herz, vice president of scientific programs at the Fertilizer Institute, a trade group, says that he is skeptical of the paper’s conclusions because the estimates
JULIAN SIMON
Environmentalt News
At high doses, potential anticancer drugs inhibit yeast growth (right), but at low doses, the same chemicals enhance growth (left), according to new research.
havior may be ubiquitous. But risk assessments and environmental regulations throughout the world operate on one of two assumptions: either doses below a toxicological threshold have no adverse effects, or all doses have similar effects. This means that hormesis has the potential to overturn some environmental regulations, and its relevance to such policies has engendered lively debate. “The proper understanding and utilization of hormesis will do a much better job of both protecting and promoting public health than the policy-based defaults that are currently in use,” Ralph Cook, a physician with RRC Consulting, and Calabrese wrote this summer (Environ. Health Perspect. 2006, 114, 1631–1635. Not so, argued Kristina Thayer, a toxicologist with the National Institute of Environmental Health Sciences (NEIHS), and colleagues last year. “If hormesis were used in the decision-making process to allow higher exposures to toxic and carcinogenic agents, this would substantially increase health risks for many, if not most, segments of the general population,” they wrote (Environ. Health Perspect. 2005, 113, 1271–1276). The new analysis is the first to
use a single large database to put hormesis to the test against the threshold model, says Calabrese. “In this single, detailed data set, we again find that the threshold model fails to predict the low-dose responses and the hormesis model does,” he says. Calabrese and colleagues analyzed 2189 dose–response curves generated by a National Cancer Institute investigation that was looking for chemicals that might make good antitumor drugs (Cancer Res. 2000, 60, 328–333). The chemicals include many synthetic and natural organic compounds as well as inorganic and organometallic chemicals. Few, if any, industrial compounds appear in the set. The cancer researchers exposed the 13 different strains of yeast to 5 doses of each of the chemicals. They looked for compounds that blocked growth in mutant yeast cells at high doses because these chemicals might also be able to kill human cancer cells, says Julian Simon, who is a cancer researcher at the Fred Hutchinson Cancer Research Center and who organized the study. If hormesis were valid, then these chemicals would make the yeasts grow better at low doses, the researchers thought. To test
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this, Calabrese and colleagues determined the amount that did not affect growth, known as the benchmark dose. If hormesis applied, then doses lower than the benchmark dose would be more likely to enhance growth. If the threshold model held, then these lower doses would have an equal chance of enhancing, inhibiting, or not perturbing growth. When the researchers compared responses below the benchmark dose, they found that growth was enhanced. Indeed, they found that this occurred in most of the responses. Several toxicologists and statisticians say that Calabrese’s team modified standard procedures for identifying the benchmark dose in their analysis. Some of these scientists add that the modifications were needed to study such low doses, whereas others question the statistical methods used in the new study. “I know that they are trying to find out if this data on aggregate supports hormesis, but there are ways of doing this that have already been evaluated in the literature, and this is not one of them,” says Christopher Portier, associate director for risk management at NEIHS. Others, including Tony Cox, a biomathematical modeler with research consultants Cox Associates, describe the work as “important, suggestive, and provocative.” The new paper makes an important contribution to this debate, notes Cox, who adds, “I believe everyone would benefit from further analysis of this data set. This would show whether the authors’ conclusions are robust to changes in modeling assumptions.” Calabrese is more certain. “There is little justification to continue to accept and use the threshold model, and growing evidence to support the hormesis model,” he says. “How often can the threshold model be wrong before it is questioned and set aside? Reasonable people who care about public health or even the concept of truth must ask that question.” —REBECCA RENNER
News Briefs
Tracking buried CO2
Researchers have found that perchlorate, a component of rocket fuel, interferes with the endocrine systems of fish. A study published in Environmental Toxicology and Chemistry (2006, 25, 2087–2096) reports that the chemical affected the sexual development of the threespine stickleback, a common lab fish. The female fish exposed to perchlorate produced both male and female sexual organs and began behaving like their brethren. The females’ male organs even produced sperm that were capable of fertilization, although the embryos later died. The doses used in the study were well above what has been found in the environment. Earlier studies have shown that perchlorate interferes with thyroid hormone production. For more than a decade, the U.S. EPA has been studying safe exposure standards for perchlorate.
EPA to monitor air from animal feedlots
This well at Canada’s Weyburn oil field is one of many sites where researchers are injecting CO 2 into geologic formations.
Animal feedlots can emit large volumes of methane and other air pollutants. Citing the Clean Air Act, the U.S. EPA recently asked such operations, known as concentrated animal feedlot operations (CAFOs), to voluntarily report their pollutant emissions. By late August, more than 2500 operations, which often include multiple farms, had signed on to the industry-led monitoring survey. The CAFOs that are cooperating include cattle, poultry, and swine businesses. Voluntary reporting will take place over 2 years, after which EPA will have 18 months to evaluate the data. The results will help set emissions estimates for possible compliance standards. Critics of the program have noted that large feedlots will continue to operate without emissions controls potentially until 2010.
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U.S. COAST GUARD
Rocket fuel masculinizes fish
the source of CO2, whatever industrial source you choose, is more often than not distinct from what’s in the reservoirs already,” says Raistrick, adding that the carbon isotope ratios serve as a fingerprint for tracking CO2. At depths of 1000 meters, CO2 behaves as a supercritical fluid, mixes with oil and water, and dissolves into bicarbonate. The researchers followed bicarbonate levels and carbon isotope ratios before and after large-scale CO2 injection started in the fall of 2000. They measured a decrease in the carbon isotope ratios, indicating that the industrially fingerprinted carbon entering the system was dissolving into the brine and converting into HCO 3–. The concentration of bicarbonate climbed over the 3-plus years of monitoring, and the carbon dioxide increased by about 10-fold. The new research, says Susan Hovorka, who is the principal investigator of the carbon sequestration project at Frio, confirms that scientists can make reasonable predictions of what will happen when CO2 is injected into brine and oil reservoirs in rock beds. “That’s really important because what people want to know is what’s going to happen 10 years from now.” —NAOMI LUBICK PE TROLEUM TECHNOLOGY RESE ARCH CENTRE
Pumping CO2 underground is one of the most promising solutions for limiting the greenhouse gas in the atmosphere, but doubts have lingered over the permanence of this storage method. A new technique for tracking sequestered CO2, published in this issue of ES&T (pp 6744–6749), confirms that the gas stays put when deposited in depleted oil fields. Drilling operators have been injecting CO2 and other fluids back into the earth over the past few decades to improve recovery from oil reservoirs. But few monitoring systems track what happens to the gas. Many projects are under way in such places as the Norwegian Sleipner field in the North Sea and a small-scale experiment in the Frio Formation in Texas. But the best plumbed in the world is the Weyburn field in Canada. Weyburn’s oil sits in saline water enclosed in carbonate rocks. The oil field’s operators inject about 1.8 million tonnes of CO2 a year, monitored by the International Energy Agency Weyburn CO2 Monitoring and Storage Project. Over a 40-month period, Mark Raistrick of the University of Calgary (Alberta, Canada) and his coworkers measured carbon isotopes in the fluids of numerous wells. “A fortunate side effect [is] that
Environmentalt News Can you catch radiation sickness? logical effects in cells that have received signals from cells that were exposed to radiation. The science on this phenomenon, called the bystander effect, was ignored for decades, says Mothersill, until more studies reached a cumulative mass in the mid-1990s. USDA
Call it startling and counterintuitive, but researchers report that a trout hit with X-rays can make other fish come down with radiation sickness. The results, published in this issue of ES&T (pp 6859–6864), may help regulators identify leaks from nuclear power plants. For the study, researchers set a tank holding a single rainbow trout in front of an X-ray machine and gave the fish a nonfatal dose of radiation. This fish was then placed in a tank for 2 hours with another trout that had not been X-rayed. But when the apparently healthy fish was later examined, some cells in its organs had died, and others began to express proteins as if the fish had been irradiated. Carmel Mothersill, a professor of radiation biology at McMaster University (Canada) and the lead author of the study, says that the results are not that surprising. Since 1921, researchers have detected bio-
Bystander effects from radiation have been found in multiple animals, including rainbow trout.
“The weight of evidence is now shifting,” says Mothersill. She points out that her study was heavily funded by the nuclear industry, which is interested in understanding the effects of low-dose
Northern fires feed southern smog high aerosol levels, “some of the highest we saw all summer,” says Gary Morris of Valparaiso University. Morris and his co-workers traced the wind patterns for those days. The wind path led them back to eastern Alaska on July 12 and 13, when forest fires were pumping thick smoke into the air. Using satellite data, the team mapped carbon monoxide levels carried by winds from Alaska and Canada, down the Mississippi River to DalNASA
Millions of acres of Alaskan and Canadian forests burned during the summer of 2004. That July, ozone pollution levels in Houston, Texas, skyrocketed. New research published September 26 in the Journal of Geophysical Research—Atmospheres (2006, 111, doi 10.1029/2006JD007090) connects the two distant events. Measurements of optical depth of the air column above Houston on July 19 and 20, 2004, showed
Winds carried plumes of smoke from fires in Alaska and Canada to the southern U.S. and with them, ozone that made Houston’s smog worse. 6528 n Environmental Science & Technology / november 1, 2006
radiation in order to plan for any potential regulations in the future. The study sought to mimic what might happen if a nuclear power plant had a small leak. Bill Morgan, director of the Radiation Oncology Research Laboratory at the University of Maryland, says that he finds the study both fascinating and puzzling. But he finds it counterintuitive and does not understand how a healthy animal can become sick when it was never exposed to radiation. He has tried and failed to replicate an earlier study by Mothersill, with irradiated cells placed in a dish with healthy cells. In Mothersill’s experiment, the healthy cells began to show effects of radiation and die. Still, Morgan adds, “There are enough studies to show that this effect is real.” Mothersill says that she is now finishing up some other studies with the trout to identify the chemical signals that are passing between irradiated and healthy fish. —PAUL D. THACKER
las, Texas, and finally to Houston, where the clouds got stuck. The large dose of ozone magnified Houston’s air pollution. “A number of factors that make Houston ripe for ozone production—static meteorology, nitrogen oxides, and sulfur oxides—[mean a] starting point that’s not zero.” The new research “reinforces what we see here in the Northeast,” where the plume comes from fossil-fuel-burning power plants in the west, says Paul Miller, deputy director of NESCAUM, a nonprofit association of air-quality agencies in the Northeast U.S. “Those sources are under our control”, Miller continues, noting that Houston’s chemical industries and car culture are also controllable factors. Although natural events might push Houston over regulatory limits, such episodic events should not be used “as excuses for not doing anything.” —NAOMI LUBICK
News Briefs
Underground heat gives light
CHENA HOT SPRINGS RESORT
Fresh produce year-round in Alaska: Gwen Holdmann holds tomatoes that grow in a greenhouse powered by geothermal electricity.
Cleanup hazards of 9/11
So, currently there’s a tremendous amount of resource that’s not being used,” amounting to billions of gallons. Biederman expects to have demonstration projects running at oil and gas wells in Texas and Nevada by early next year. The power plant is essentially a cooling system that runs in reverse: instead of using energy to cause a temperature difference, like a refrigerator does, it converts that difference into energy. In this case, the refrigerator compressor becomes a turbine that is driven as heat vaporizes a refrigerant. Although this reverse-refrigeration concept has been around for a long time, costs to build a power plant based on it have remained a stumbling block, according to Gwen Holdmann, a mechanical engineer who is the vice president of new development at the Chena resort. But UTC has kept prices low by using commercially available parts from its sister company, Carrier Refrigeration. “At the same time, the cost of fuel is going up,” Holdmann says. “Those are the two main driving factors” that are making the technology more attractive. At Chena, the power plant eliminates diesel generators, cutting expenses and emissions. “We’d been burning diesel fuel at the cost of about $1000 a day to keep the lights on here,” Holdmann says. The resort invested $2.2 million in the UTC plant, which should pay for itself in 5 years or less. Moreover, because the plant’s capacity is 400 kilowatts (kW)—in the form of 2 standard 200-kW modules—and the resort needs about 250 kW to operate, Chena will have surplus energy. “Right now, our resort is basically operating off close to 100% renewable energy,” Holdmann says, with plans to apply geothermal power to other uses as well. The resort already uses it for heating lamps at a new 5000-squarefoot greenhouse. —PRACHI PATEL-PREDD
Evidence is mounting that toxic dust from the collapse of the World Trade Center (WTC) is causing longterm health problems. In the largest study yet, published in Environmental Health Perspectives (2006, doi 10.1289/ehp.9592), researchers suggest that the impacts are widespread and persistent. Doctors examined 9442 rescue workers between July 2002 and April 2004 and found that nearly 70% in this group experienced new or worsened respiratory symptoms after their exposure to the 9/11 wreckage. These symptoms, which include an ailment dubbed “WTC cough”, persisted more than 2.5 years after the tragedy. Dust from the WTC contained benzene, metals, PAHs, asbestos, lead, and pesticides. Research has shown that first responders not wearing breathing masks could have inhaled sufficient quantities of particulate matter to cause significant respiratory effects.
Insurer fights climate change
With annual revenues approaching $5 billion, Marsh, Inc., recently joined the Pew Center on Climate Change’s Business Environmental Leadership Council (BELC). Marsh is one of the world’s largest insurance companies and is now attempting to protect itself against economic consequences that might arise from global warming. Established in 1998, BELC has 41 members, mainly Fortune 500 companies representing industries such as chemical and pharmaceutical producers along with mining and energy firms. Each company has committed to take steps that address global warming while remaining competitive and profitable, according to BELC. In April, Marsh published Climate Change: Business Risk and Solutions, a 32-page report that describes the potential impact of global warming on businesses.
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U.S. EPA
A new geothermal power plant at an Alaskan hot springs resort harnesses the lowest-temperature underground heat source ever used to generate electricity. The plant, which went on-line this summer, could make geothermal power more common across the U.S. and lead to the use of low-temperature waste heat to produce electricity. Typically, geothermal sources at temperatures greater than 300 F (177 C) are used to generate electricity on a large scale, powering whole cities in a few cases, whereas lower-temperature sources provide heat, but not electricity, to single buildings. But the system created by the United Technologies Corp. (UTC) extracts electricity from the 165 F (74 C) water at the Chena Hot Springs Resort, 60 miles northeast of Fairbanks. “That’s amazing, because that beats the record for lowest temperature for a geothermal power plant,” says Roger Hill, a geothermal power researcher at Sandia National Laboratories. Hill, who was not involved in the project, says that naturally occurring low-temperature geothermal sources crop up across the U.S. and that the new technology will make them accessible for electricity generation. The system also paves the way for using a byproduct from drilling oil and gas wells. “Ninety-five to 98% of what they pump out of the ground in Texas is hot water,” says Bruce Biederman, who leads the UTC project. “They either reinject that hot water or discard it.
