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from recently deposited mercury, then emissions controls could have a relatively rapid beneficial effect in reducing the amount of mercury that freshwater fish take up. EPA policy on mercury emissions is currently in a state of flux. In December 2000, EPA announced its intention to regulate coal-fired
if we cut emissions, we’ll see a positive result in the short term.” Gilmour and coauthors compared the results from three studies in which stable mercury isotopes were added to aquatic ecosystems. The mercury isotope addition studies, which were conducted in 2000 and 2001 in the Florida Everglades GEORGIA RIEDEL
ercury newly deposited on lakes and wetlands is more readily available for methylation than mercury that already exists in these ecosystems, according to preliminary results from three different mercury loading studies in the Florida Everglades and northwestern Ontario. The findings, which were presented at the American Chemical Society meeting in Orlando, Fla., in April, may shed light on the value of controversial proposals to control mercury emissions from coal-fired power plants. The researcher who presented the findings, Cynthia Gilmour, a microbiologist with the Academy of Natural Sciences Estuarine Research Center in St. Leonard, Md., says the findings offer the first signs of hope that mercury emissions controls could curb methylmercury production and bioaccumulation in the near term. Other scientists involved with the studies sound a note of caution, while agreeing that the initial results are promising. “Converting mercury to methylmercury is the first step on a long and twisted path that leads to accumulation in fish,” says U.S. Geological Survey scientist David Krabbenhoft, also a principle investigator for the studies. “We need to follow the path further before we can say what will happen and when it will happen.” Mercury, in the form of methylmercury, is the most common contaminant in U.S. and Canadian fish. Mercury enters most ecosystems through atmospheric deposition, much of it from coal-fired power plants and waste incinerators. But lake sediments are a vast reservoir of old mercury. If old mercury is responsible for the problem, then potentially costly emissions controls might not be effective for decades. If most methylmercury is formed
Gilmour samples the uppermost sediments where mercury methylation occurs. For the whole-lake experiment in northwestern Ontario, this involves diving to the bottom of the frigid waters.
power plants’ mercury emissions in 2004. The agency estimated the cost of these controls to be several billion dollars per year. That effort could be superceded by President Bush’s controversial Clear Skies Initiative, proposed on February 14. Proponents estimate that Clear Skies would cut mercury emissions by 69% by 2010. EPA science and policy advisers although cautious, called the results of the new studies, “very promising”. A senior policy adviser explained, “for emission controls the question is, how long before we see a positive result? If it takes too long then it may not be cost-beneficial. But these results suggest that
ENVIRONMENTAL SCIENCE & TECHNOLOGY / JUNE 1, 2002
and in the Canadian Experimental Lakes Area, were part of two large mercury cycling projects: the U.S. Geological Survey’s Aquatic Cycling of Mercury in the Everglades (ACME) project, and METAALICUS, or “Mercury Experiment To Assess Atmospheric Loading in Canada and the United States”, the first experiment to investigate the effects of adding mercury to an entire ecosystem (Environ. Sci. Technol. 2001, 35, 229A–230A). The experimental systems were 75 one-m-diameter enclosures in the Everglades, four 10-m enclosures in the shallow waters of a Canadian lake and the 8-hectare METAALICUS lake. © 2002 American Chemical Society
sites of methylation.” “We’re seeing different kinetics but the same processes in very different environments—the warm, hot wetlands of the Everglades and the cold, boreal lake in Canada. At previously identified sites of methylation, the new mercury gets methylated more efficiently than the old,” says Krabbenhoft. Maximum mercury isotope concentrations in sediments in the small warm Everglades enclosures occurred within hours to days after the spike, but mercury isotope concentrations in the Canadian enclosures continued to rise through both the first and second summers after spiking, Mercurystable isotopes were still being added to the whole lake in the fall of 2001, and methylation of the new isotopes was continuing at that time. Studies in the Florida Everglades are continuing in an effort to determine the complex interactions between mercury, sulfate, and dissolved organic matter, which control mercury methylation. In Canada, scientists are continuing to add different stable mercury isotopes directly to the lake and to the other parts of the ecosystem—the forested uplands and wetlands. Since most mercury is deposited on these other parts, these results are crucial for evaluating the efficacy of mercury emissions controls, says Gilmour. —REBECCA RENNER
Complexity behind biotech corn not addressed Amid the explosive growth of agricultural biotechnology, the discovery last year of escaped transgenes in corn’s Mexican birthplace intensified the debate over the environmental safety of genetically engineered corn (Environ. Sci. Technol. 2001, 35, 472A). Although the research behind that finding was challenged in early April, recent Mexican government studies confirm that the global center of corn biodiversity is contaminated. But researchers disagree as to whether the genetic pollution is worthy of concern. The controversy was ignited when Ignacio Chapela, a microbial ecologist at the University of Cali-
fornia, Berkeley, announced in the November 29, 2001 issue of Nature that he had discovered transgenes in native Mexican maize using the polymerase chain reaction (PCR), a technique that amplifies DNA sequences. He claimed that the transgenes were unstable, breaking into many sequences scattered throughout the maize genome. The second finding is likely inconclusive because of a poor choice of PCR primers and artifacts generated by the process itself, scientists charge in two letters published in the April 5 issue of Nature. On the basis of the criticism, the editors of Nature concluded that there was insufficient evidence to
Governm Case closed, for now, on PM and ozone standards The protracted legal challenge to the fine particulate matter (PM) and ozone standards set by the U.S. EPA in 1997 has ended, clearing the way for EPA staff to designate areas in the country that are out of compliance with the levels. A ruling in late March by the U.S. Court of Appeals found that the levels chosen for the National Ambient Air Quality Standards (NAAQS) for PM less than 2.5 micrometers in diameter (PM2.5) and ozone were not “arbitrary”, as three Midwestern states and industry groups had argued. The court also rejected the industry’s claims that the standards were not supported by the evidence, writing that the available science on PM was adequate to support EPA’s setting the standard where it did. The agency doesn’t need to establish “perfectly safe levels of pollutants” before setting levels, the court wrote in its March 28 decision. “EPA’s inability to guarantee the accuracy or increase the precision of the PM2.5 NAAQS in no way undermines the standards’ validity,” the court wrote. “Rather, these limitations indicate only that significant scientific uncertainty remains about the health effects of fine particulate matter at low atmospheric concentrations. As the exhaustive rulemaking process makes clear, ... EPA set the primary NAAQS notwithstanding that uncertainty, just as the [Clean Air Act] requires.” The litigation, led by the American Trucking Association, began shortly after EPA finalized the NAAQS and evolved into complex legal questions including whether the agency had the constitutional right to set the stan-
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The researchers added stable mercury isotopes, which can be traced, to each of the aquatic systems in amounts up to ~5 times greater than the annual wet atmospheric deposition. After adding these mercury spikes, Gilmour and her colleagues sampled the surface sediments to determine what proportion of the new mercury—the stable mercury isotope—had been methylated and what proportion of old mercury was methylated. In each system, methylation occurred predominantly in either surface sediments or in the communities of algae and other microscopic plants and animals that cover the underwater plants and rock surfaces, says Gilmour. Once the stable mercury isotopes reached the sediments, methylation began quickly, within hours to days, she says. In each case, when the researchers compared the amount of methylation of the new stable isotope spikes and existing mercury, they found that a larger fraction of the labeled spikes were methylated. The amount of the spike that made it to the sites of methylation was very different among the three experimental systems, Gilmour says. “The amount of methylmercury produced and the timing of production seem to be very dependent on the timing and magnitude of delivery of the ‘new’ mercury to
Continued on Page 229A
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justify publishing the original paper. Although Chapela’s initial finding of transgenes was not disputed in the letters, it could also be incorrect because of contamination with engineered genes from other plants, alleges Nick Kaplinsky, a developmental biologist at the University of California, Berkeley, and author of one of the critical Nature letters. Kaplinsky acknowledges that native Mexican corn is almost certainly contaminated with transgenes from Bt corn, which produces a bacterial toxin lethal to the European corn-borer, because of crosspollination with illegally planted Bt corn. Other scientists stand behind Chapela’s first finding, says David Andow, an insect ecologist at the University of Minnesota. The Mexican government has confirmed Chapela’s results, documenting 10–15% contamination of the crop in the states of Oaxaca and Puebla, announced Jorge Soberon, executive secretary of Mexico’s biodiversity commission, on April 18 at the Hague, Holland. The Bt genes have been present in native maize for about 5–6 years, speculates Wayne Parrot, a crop ge-
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EnvironmentalM News
neticist at the University of Georgia. Because the genes have gone unnoticed until now, they are probably not causing any problems, he says. Guenther Stotzky, a microbiologist at New York University, counters that biological complexity, from the level of the cell on up to ecosystems, dictates that more research needs to be done before scientists dismiss the finding. For
Methyl triclosan found in Swiss lakes While investigating the occurrence of lipophilic pesticides in Swiss lakes, a team of scientists unexpectedly detected a methylated form of the disinfectant triclosan. The findings, which are reported in this issue of ES&T (2002, 36, 2322–2329) by Thomas Poiger and colleagues at the Swiss Federal Research Station for Fruit-Growing, Horticulture, and Viticulture, and the Insititute of Enviornmental Chemistry at Umeå University in Sweden, show that under certain conditions triclosan can rapidly photodegrade, but methyl triclosan is relatively stable in the environment. Triclosan is a bactericide used in a growing number of consumer products, including antibacterial soaps, toothpaste, shampoo, lotions, deodorants, shoes, sportswear, carpets, and plastic trashcans. 228 A
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It is acutely toxic to some aquatic organisms, particularly certain algae species, at low microgram-per-liter levels. Little is known about the occurrence of triclosan in aquatic environments, although it has recently been found at low microgram-perliter levels in U.S. streams in less developed locations (Environ. Sci. Technol. 2002, 36, 1202–1211; 140A– 145A), suggesting that contamination is widespread. Poiger and colleagues report triclosan levels entering wastewater treatment plants in Switzerland in the 0.6–1.3 µg/L range. They found that some triclosan is removed during the treatment process, resulting in effluent concentrations in the 70–650 ng/L range. Although levels of methyl triclosan were much less than those of triclosan (about 2% of the amount of triclosan), methyl
ENVIRONMENTAL SCIENCE & TECHNOLOGY / JUNE 1, 2002
example, for unknown reasons, Bt corn plants contain more lignin, the glue that holds plant fibers together. No one knows what effect this may have on soil structure and soil communities. Nor has much work been done on nontarget insects, he says. Other studies suggest that the Bt corn may indeed be causing trouble. Green lacewings, which are beneficial insects, have a higher death rate when fed pests grown on Bt corn than when fed pests grown on conventional corn, according to Angelika Hilbeck, research scientist at the Swiss Federal Research Station for Agroecology and Agriculture in Zurich. A thorough investigation of the mortality of nontarget insects would require field experiments costing up to $100,000 per year, half the amount budgeted for environmental impact studies by the U.S. Department of Agriculture last year, says Stephen Malcolm, a chemical ecologist at the University of Western Michigan. Without adequate research, no conclusions can be drawn about whether Bt corn will be harmful, he says. —JANET PELLEY
triclosan was generally higher in the effluent than in the influent, suggesting that it is being formed in the wastewater treatment plants. In surface water samples from Swiss lakes and rivers, Poiger and colleagues found triclosan concentrations as high as 74 ng/L and methyl triclosan as high as 2 ng/L. Other researchers are also investigating the behavior of triclosan in wastewater treatment plants and the environment. In a recent study, which has yet to be published, Heinz Singer, Stephan Müller, and colleagues at the Swiss Federal Institute for Environmental Science and Technology (EAWAG) observed significant removal of triclosan during wastewater treatment. They estimate that 79% of triclosan entering a wastewater treatment plant is removed via biological degradation, 15% is adsorbed to sludge, and 6% remains in the effluent. In another unpublished study, Singer and
Cl
Cl pH > pKa
Cl
O
Cl
Cl
Cl
O
pH < pKa O
O–
H
triclosan, phenolate form (photodegradable)
triclosan, phenolic form (photostable) Cl Cl
O O
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The importance of methyl triclosan is not straightforward because at the pH of natural waters, nonmethylated triclosan exists in two different forms. Under acidic conditions, triclosan occurs primarily in the phenolic form, which does not readily photodegrade and is likely to bioaccumulate. In that case, the amount of methyl triclosan relative to triclosan is likely to be small. However, above pH 8, the phenolate form of triclosan predominates. The phenolate form rapidly photodegrades in the presence of sunlight and therefore does not bioaccumulate. The concentration of methyl triclosan relative to triclosan increases to 30% in summer in Swiss lakes, when the pH commonly rises above 8, says Poiger. The increase in pH combined with increased sunlight during summer provides the ideal conditions for triclosan to photodegrade, while methyl triclosan is unaffected. It is very difficult to give general information on the behavior of triclosan in the environment because it is site specific, Müller warns. “This is a special situation in the epilimnion [upper layer] of the lake. If you go to rivers or to the deeper layer of lakes, where the pH is 6–8, you have the protonated form of triclosan, which is bioaccumulative,” he says. The danger of these compounds for biota lies not only
Cl CH3
methyl triclosan (photostable)
Laboratory experiments have shown that the dissociated form of triclosan rapidly degrades in the presence of sunlight. Nondissociated and methylated forms of triclosan, however, are photostable. Because the acid dissociation constant of triclosan (pKa = 8.1) is close to the pH of natural waters, both the dissociated and nondissociated forms are likely to be present in the environment.
dards. In February 2001, the U.S. Supreme Court decided that EPA had constitutional authority. The agency is still on schedule for the PM2.5 rule, despite the complex litigation, staff says. EPA has collected three years of PM monitoring data from most of the states needed to determine the designations and will propose a partial list of states’ PM2.5 status later this summer. However, an earlier ruling from the Supreme Court requires EPA to rewrite the implementation plan for the 8-hour ozone standard, which will delay the designation list for that standard, EPA staff says. “It’s only logical that we let the states know what the process is going to be before we work with them on designations,” one staffer says. The legal challenges may not be over. States and industry groups are likely to sue EPA over the designation listings, those involved with the rules say. The decision can be found at http://pacer.cadc. uscourts.gov/common/opinions/ 200203/97-1440c.txt.
DU weapon contamination
ENVIRON. SCI. TECHNOL. 2002, 36, 2322–2329
Müller evaluated pathways of removal of triclosan from surface waters and found that it is degraded primarily by direct photolysis. Although inputs of methyl triclosan into two major Swiss lakes, Greifensee and Zürichsee, from wastewater treatment plants are estimated to be relatively low, Poiger and colleagues found concentrations of methyl triclosan comparable to those of some persistent chlorinated organic pollutants (up to 33 ng/g lipid), using semipermeable membrane devices (SPMDs). Surprisingly, no parent triclosan was found using the sampling devices, which were placed in Swiss lakes at depths of 1–2 m and exposed for 21–48 days. SPMDs collect lipophilic compounds that tend to accumulate in sediments and biota. Triclosan is likely being methylated in wastewater treatment plants, where there is a high density of microorganisms, rather than in the lakes, although some data do not support that assumption, says Poiger. Once methylated, the lipophilicity of triclosan increases, meaning that it will be more likely to bioaccumulate in fatty tissue and isn’t likely to photodegrade. In photolysis experiments, the researchers showed that methyl triclosan is stable in the presence of natural sunlight.
The United Nations Environment Programme (UNEP) has recommended that authorities in Serbia and Montenegro monitor groundwater and air annually for contamination of depleted uranium (DU), left from weapons used during the 1999 Kosovo conflict. DU, a waste product from the production of enriched uranium (238U), is radioactive and has a half-life of 4.5 billion years. It is used to attack tanks and raises a fine dust on impact. The recommendation comes after international experts conducted field studies in the two countries of sites that had been struck with DU ordnance in 1999. The findings are consistent with those of UNEP’s 2001 DU study in Kosovo. Together, the studies Continued on Page 231A
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EnvironmentalM News From triclosan to dioxin Triclosan dissolved in water can photochemically break down to create a member of the dioxin family, according to laboratory research presented by University of Minnesota scientists at the American Chemical Society meeting in Orlando, Fla., in April. The authors say that this is the first time such a reaction has been observed in water, and it raises the possibility that triclosan could break down to form dioxin in the environment. Other researchers previously observed triclosan photolysis to dioxin in the solid phase and in solvents. Photolysis of triclosan created 2,8-dichlorodibenzodioxin, with a nearly 4% conversion rate in the Minnesota laboratory experiments, which used Pyrex-filtered mercury vapor lamps
in the methyl triclosan but also in the triclosan itself, he emphasizes. Even when conditions are suitable for triclosan to photodegrade, it is unclear whether it degrades into less toxic compounds. “We could not identify the main meta-
as a light source. Dioxins have been previously reported as contaminants in triclosan, but using liquid chromatographic analysis, the researchers only found dioxin after running the experiments, ruling out contamination as the source, says chemist Kristopher McNeill. The dioxin formed during photolysis of triclosan is not a very potent one, says environmental engineer William Arnold, who notes that further chlorination, during water treatment might result in more potent, higher chlorinated derivatives. “The question is whether the levels of chlorine used during water treatment are high enough and the contact times long enough to allow this to happen,” he says. The Minnesota researchers will be investigating this in the future. —REBECCA RENNER
bolite product [of triclosan] because it quickly degraded,” says Singer. Poiger’s group could not identify a product either. There have been some reports of the transformation of triclosan into chlorodioxins upon incineration
and in the presence of sunlight (see sidebar above). The concentrations of dioxins, however, resulting from the photodegradation of triclosan in the environment are likely to be very low, says Singer. —BRITT E. ERICKSON
proach in many ways under its current director John Graham, founder of the Harvard Center for Risk The Bush administration is taking a OIRA staff review drafts of major Analysis. Examples include steps new, proactive approach toward rules—those expected to have an to make deliberations more open rules developed by federal agencies, economic effect of $100 million or and transparent, letters to agencies according to the White House Office more—and if a problem is found, suggesting new policy actions and of Information and Regulatory Affairs it’s returned to the agency for addiactual reviews of federal rules after (OIRA). In a report to Congress, OIRA tional analysis and/or revision. Unthey have been issued to see if they officials explain new procedures der previous administrations, OIRA are cost-effective, clear, and supthey’ll use when asking an agency focused on costs and benefits. But ported by law. to revise a rule or policy and to enOIRA is taking a more proactive apOIRA’s report to Congress courage agencies to take acindicates that staff will imtion. The report also seeks prove “transparency” by upTA B L E 1 comment on any rules the dating its Web page much public believes are unduly burmore frequently with notes densome, costly, or confusing. on meetings held by staff Total annual monetized costs and OIRA operates within the with agencies and the public, benefits of environmental, health, and White House Office of Mannotes on letters sent to OIRA, safety regulations agement and Budget (OMB) and copies of letters returnas the gatekeeper of major ing a rule to an agency. A The benefits from these so-called social regulations federal rules by reviewing their new prompt letter will be range from one-half to more than 3 times their costs and benefits, as well as sent to alert agencies to iscost. Amounts are given in billions of third-quarter making sure the policy decisues that OMB considers 2001 dollars. sions reflect the views of the worthy of “priority status”, Costs ($) Benefits ($) current administration. the report adds. Although Environmental 120 to 203 120 to 1,783 Created by Congress in 1980, agencies are not forced to act Transportation 17 to 22 95 to 126 it operates under principles on the letters, they might Labor 20 to 22 32 to 34 spelled out in presidential exfind it beneficial to do so, obOther 24 to 30 61 to 66 ecutive orders. OIRA also anservers note. Total 181 to 277 308 to 2,009 nually calculates the costs and OIRA has already issued benefits of major regulations five prompt letters, including Source: OIRA. (see table). two to EPA. One urges the
Putting regulations under a microscope
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CHERYL HOGUE, C&EN
agency and Congress “to take acbe expected to credibly replace the tion” to reduce public exposure to substantive work of the army of scifine particles in the air and to deentists at the various federal agenvelop a multiyear research program cies,” the Natural Resources Defense to discover which sources of air Council (NRDC) writes in a report particles are most responsible for released on Earth Day. “adverse health impacts”. Another The groups also charge OIRA prompt letter suggested ways EPA staff of listening exclusively to incould improve dissemination of dustry groups when it developed its Toxics Release Inventory data. list of rules it may revise. “The 13 OIRA also is aggresrules that OMB has sively seeking rules that placed on its hit list inneed revision because clude some of the they’re outdated, conmost significant regufusing, or unduly burlations currently being densome. OIRA debated nationally for officials consider 13 their potential to immajor environmental prove environmental rules a high priority for quality,” NRDC writes revision, including in Rewriting the Rules: eight issued by EPA. OIRA’s newest director John The Bush These include EPA’s Administration’s Graham is seeking to rerule on the New Source move the mystery from the Assault on the office’s work. Review program reEnvironment. quiring older power However, Robert plants to install emissions control Hahn, who has analyzed OMB retechnology, and the Total Daily ports to Congress over several Maximum Load program requiring years, says OIRA’s proactive efforts states to develop cleanup plans for are well within its authority. OIRA’s water bodies. approach “is new and it’s different,” Environmental groups say the says Hahn, director of the AEIadministration has, in an unpreceBrookings Joint Center for Regulatory dented step, centralized environAffairs, a think tank. The report mental policy decision making shows that OIRA is going beyond its within OMB. Noting that one of the traditional role of simply analyzing first acts of President Bush was to the costs and benefits of each rule freeze new regulations signed by and is now suggesting agency acthe Clinton administration, they say tions that might extend human life, this White House is ignoring the exHahn says. pertise on issues built up within The Draft Report to Congress on agency staff. OIRA staff has directed the Costs and Benefits of Federal agencies to submit their proposals Regulations was published in the to a new outside review panel, March 28 Federal Register and can adding to rule delays, the groups be found at www.whitehouse. say, and the office is hiring more gov/omb/inforeg/cbreport.pdf. scientific staff. “The OMB can never —CATHERINE M. COONEY
Ice cores open new window on historical mercury deposition For the first time, scientists can resolve historical mercury emission events, such as major volcanic eruptions, the California Gold Rush, and the manufacturing push associated with World War II. The improvement in resolution comes from the first comprehensive analy-
sis of mercury deposition in midlatitude ice cores. The ice core analysis, which is published in this issue (Environ. Sci. Technol. 2002, 36, 2303–2310), involved hundreds of meters of continuous ice cores collected in 1991 and 1998 from the Upper
Governm cover the entire geographical area affected by DU munitions during the Kosovo conflict. Overall, the team confirmed widespread DU contamination at five out of the six sites it examined. However, the levels of DU did not present immediate radioactive or toxic risks. They recommend monitoring “as a matter of precaution”, because one of the main findings showed that the speed of corrosion of DU ammunition in the soil is very rapid, according to Pekka Haavisto, chair of the UNEP Depleted Uranium Assessment Team. “Something like 700 kg of DU is geographically located in a very limited area,” Haavisto says. In addition, the UNEP team discovered that some DU ammunition tips had lost 10–15% of their mass through corrosion while lying on the battlefield. At two sites DU particles still lingered in the air two years after the conflict’s end. “Based on these findings, the authorities should carefully plan how DU-targeted sites are used in the future,” Haavisto says. “Any soil disturbance at these sites could risk releasing DU particles into the air.” The report is available at http://postconflict.unep.ch.
GE cleanup of Hudson River in the offing On April 8, General Electric Corporation (GE) submitted to the U.S. EPA its good faith offer on cleaning up the Hudson River, agreeing “to perform all aspects of the remedial design consistent with the [Record of Decision] ROD.” The letter includes an agreement to pay for costs associated with predesign characterization activities, sediment inventory sampling, habitat delineation and assessment, and baseline monitoring activities, while it excludes costs for siting the treatment/transfer facilities, establishing the performance standards, and public outreach efforts. Continued on Page 233A
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EnvironmentalM News 270 years of mercury deposition The profile of historic mercury concentrations in ice cores from the Upper Fremont glacier in Wyoming shows for the first time the mercury signature of volcanic eruptions of Tambora, Krakatoa, and Mt. St. Helen’s, as well as the California Gold Rush.
2000 4000 6000
Global Hg production (t/yr)
2000
A Industrialization ca. 1880–present
Mount St. Helens (1980)
C 1950
Background
1950
1990
World War II manufacturing (ca. 1940–45)
1910
Krakatoa (1883)
1900
1884 Sawyer decision
1890
One Flask = 76 lbs
Year
Gold Rush
1870
Ca. 1850–84
1850
B
1850 0
Unknown
20 60 40 Hg production (1000 flasks/yr)
80
Tambora (1815)
Preindustrial
1800
1750
1998 core 1991 core 1700 0
5
10
15
20
25
30
35
40
Total mercury (ng/L) Source: Paul F. Schuster, U. S. Geological Survey.
Fremont Glacier in Wyoming’s Wind River Range, which is part of the Rocky Mountains. For several years, Paul Schuster and his USGS colleagues studied other aspects of these cores, establishing a detailed chronology based on isotopic dating, volcanic events, and other data. For the mercury analyses, the scientists focused on ice core sections from times of particular interest, 232 A
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says coauthor David Krabbenhoft. The scientists measured mercury in a total of 97 ice-core samples using great care to avoid contamination. They used dual-amalgamation cold vapor atomic fluorescence spectrometry with a method detection limit of 0.04 ng/L to analyze for total mercury. The time resolution of this core is unprecedented, says Krabbenhoft. Each 7-cm ice-core sample
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that the scientists analyzed represents less than a year. In comparison, a 1-cm sediment core sample could represent 10–15 years, he says. Other ice core records of atmospheric mercury deposition cover much greater spans of time with fewer samples. “We knew what events we were searching for, so we sampled heavily at those parts of the core” he says. The 270-year-old ice core preserves mercury released by the California gold rush, which, according to the ice core record, elevated mercury emissions for some 40 years and contributed 13% of the total mercury in the 270-year record. Demand for mercury soared after the gold rush began in 1848 because miners used the metal to amalgamate their gold. Because the mercury mines were also in California and prevailing winds blow from California to Wyoming, the glacier was ideally positioned to record the Gold Rush. The ice core also reveals for the first time, the mercury signature of historical super-volcanoes Krakatoa and Tambora in the Pacific Ocean and the Mt. St. Helens volcanic eruption in Washington State. The two largest volcanic eruptions in recorded history contributed higher, sharper mercury spikes to the ice core record. Compared to the evidence from sediment cores, the new ice core record indicates that relative to preindustrial times, anthropogenic mercury emissions may have been much higher than previously estimated. The new record indicates a 20–fold increase from preindustrial times to peak emissions in the mid1980s. Sediment cores suggest a two- to sevenfold increase. A comparison between recorded accumulation in recent years and actual deposition over the same time frame indicates that the ice core record is a good reflection of deposition, the authors write. However, the significant and inherent differences between what controls accumulation of mercury in ice versus sediments, however, makes it difficult to compare these results, Krabbenhoft says. —REBECCA RENNER
Governm
measurements, we can see how the compounds are partitioned between the vapor and particulate phases within the air, and then look at how much is transferred to the plant matter,” says Gareth Thomas, lead author of the study. Dioxins, like other semivolatile organic compounds, cover a wide range of octanol–air partition coefficients, the chemical–physical property used to determine how much of a compound is in the vapor phase and how much is attached to particulate matter in air. “At the lower values, most of the compounds will be in the vapor phase. At the higher end of the range, almost all of the compounds will be stuck to particulates in the atmosphere,” Thomas explains. The more chlorinated the dioxins, the larger the percentage attached to particulate matter in air. Plants do not uptake dioxins in the vapor and particulate phases in the same way, Thomas says. As a result, the researchers saw more variable concentrations of the higher chlorinated dioxins. Concentrations of the less chlorinated dioxins (up to and including the pentachlorinated forms) remained constant in GARETH THOMAS, LANCASTER UNIVERSITY
On a windy hillside, about 3 km from the sea in the northwest of England, a team of researchers from Lancaster University set up field experiments to investigate the uptake of atmospheric dioxins by pasture grasses. After only two weeks of exposure, the levels of the less chlorinated dioxins reached steady state in the grasses, suggesting that the transfer of atmospheric organic pollutants into the food chain can occur during one growing season. The uptake of dioxins by pasture grasses has previously been shown to be much slower. Uptake by vegetation is the main route by which atmospheric organic pollutants get into the food chain. Pastureland used by grazing farm animals is of particular concern from a human health perspective because the bulk of human exposure to dioxins comes from consumption of meat and dairy products. The new kinetics study, which is published in this issue of ES&T (2002, 36, 2372–2378), examines the levels of dioxins in pasture grasses, air, and soil, from June 1998 to January 1999. “Because we did air measurements as well as vegetation
Researchers at Lancaster University's experimental field station in northwest England have found that dioxins in the atmosphere are rapidly transferred to plant matter.
EPA Administrator Christie Whitman ushered in the long-disputed cleanup of the Hudson River with her signature of the ROD on February 1. Under the ROD, 2.65 million cubic yards of sediment contaminated with polychlorinated biphenyls (PCBs), will be dredged from a 40-mile stretch of the Hudson River. The good faith offer may mark the first time in more than two decades that GE has assumed any responsibility for the cleanup, according to environmentalists. For this reason, the President of Scenic Rivers, Ned Sullivan, says the offer is a positive step forward. “EPA [officials] were very clear in the threshold of what would meet the definition of a good faith offer,” Sullivan says. “They were looking for an unambiguous statement of GE’s intention to perform or pay for both the remedial design and the cleanup itself. GE has failed to meet that threshold.” EPA’s Special Notice letter had also requested that GE reimburse the United States $37 million in past response costs, which the company has failed to address. A coalition of 11 national and local environmental organizations called Friends of a Clean Hudson, of which Scenic Hudson is a member, criticized GE’s offer in an April 12 letter, urging EPA to reject it and negotiate a more comprehensive commitment. Sediment will be removed along three sections of the upper Hudson River with a goal of reaching a residual value of ~1 mg/kg Tri+ (3–10 chlorine atoms per molecule) of PCBs in the sediments and a level of 0.05 mg/kg in fish. Actual dredging is scheduled to begin in 2005 and is expected to last for five years. The Record of Decision, as well as a summary of the 70,000 public
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Uptake of dioxins by pastures more rapid than previously thought
Continued on Page 235A
JUNE 1, 2002 / ENVIRONMENTAL SCIENCE & TECHNOLOGY
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EnvironmentalM News Levels of polychlorinated dibenzo-p-dioxins and furans in air and pastures at a U.K. experimental field station in June 1998
Cl8DD
Cl7DD
Cl6DD
Cl5DD
Cl4DD
Cl3DD
0 Cl2DD
0 Cl8DF
200
Cl7DF
2
Cl6DF
400
Cl5DF
4
Cl4DF
600
Cl3DF
6
fg/m3 air
800
Pasture Air
Cl2DF*
pg/g/DM pasture
8
*Dichlorinated furans in pasture = 620 pg/g; in air = 62,000 fg/m3.
pasture grasses harvested after 2, 6, and 12 weeks, suggesting that steady state had been reached within 2 weeks. “We do think the kinetics are faster at the lighter [less chlorinated] end,” Thomas adds. The researchers speculate that the transfer of the heavier compounds from particulate matter in air to plants is affected more by rainfall and wind speed than transfer from the vapor phase. They believe this is why they saw more variable concentrations of the more chlorinated dioxins and steady levels of the less chlorinated dioxins. In a previous report, steady-state concentrations of dioxins were not reached in pasture grasses after several weeks (Environ. Sci. Technol. 1995, 29, 1998–2004). That field study was conducted in central Germany, where it is a lot less windy than the Lancaster University field station, Thomas says. Although they do not have data on wind speeds to confirm their assumption, the U.K. researchers believe that higher wind speeds allow for more rapid uptake of dioxins. Most of the uptake of dioxins by grasses is via atmospheric deposition, but Thomas and colleagues estimated that during summer, as much as 15% of the higher chlorinated dioxins were supplied by soil particles, and less than 4% of the di- to tetra-chlorodioxins were supplied by soil. Even lesser amounts were supplied by soil during winter. 234 A
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The remainder was supplied by atmospheric deposition. The researchers observed a seasonal trend in dioxin concentrations, with higher concentrations in the winter due to local burning sources, including wood and coalburning for home heating. “You see an increase in dioxins in the grasses because of the higher atmospheric concentrations,” Thomas says. In addition, the lower temperatures in winter cause more partitioning from the air to the solid phase, which is the grass, he says. Over a typical growing season in the United Kingdom (June–October), Thomas and colleagues estimate that between 0.04 and 0.66 kg of each dioxin homologue group (2–8 chlorinated dibenzo-p-dioxins and dibenzofurans, excluding the dichlorinated dibenzofurans) are transferred to pasture grasses. The next step, say the researchers, is to
compare those numbers with estimates of annual dioxin emissions and transfers to the human diet. The results could then be used by regulatory agencies to control sources of dioxins and help remove it from the food supply. In terms of the toxicity of dioxins in the environment, about 80% is dominated by five congeners— 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD); 2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD); 1,2,3,6,7,8hexachlorodibenzo-p-dioxin; 2,3,4, 7,8-pentachlorodibenzofuran; and polychlorinated biphenyl 126. This does not mean that these are the five most toxic congeners because their contribution to the total toxicity in the environment is a combination of their potency and their prevalence. Although 2,3,7,8-TCDD and -PCDD are the most potent of the compounds, the prevalence of the others in the environment makes them players as well, says Dwain Winters, director of the Dioxin Policy Project in the U.S. EPA’s Office of Pollution Prevention and Toxics. At the request of the U.S. Department of Agriculture and the Food and Drug Administration, the National Academies has formed a committee to investigate the implications of dioxins in the food supply (Environ. Sci. Technol. 2002, 36, 93A–94A). According to Kevin Jones, coauthor of the ES&T paper, the committee has already expressed interest in this work on the kinetics of dioxin uptake by pastures by asking for a formal presentation. A final report from the committee is expected in spring 2003. —BRITT E. ERICKSON
New ES&T editor appointed
ENVIRONMENTAL SCIENCE & TECHNOLOGY / JUNE 1, 2002
Jerald Schnoor will be Environmental Science & Technology’s new editor beginning January 1, 2003, the American
Chemical Society announced in April. Schnoor holds the Allen S. Henry Chair of Engineering at the University of Iowa’s department of civil and environmental engineering. He also serves as codirector of the school’s Center for Global and Regional Environmental Research and is a professor of occupational and environmental health in the
College of Public Health. A reader and subscriber to ES&T since 1972, Schnoor’s affiliation with ES&T’s Editorial Advisory Board dates back to 1987. He was an associate editor from 1991 to 2000. “My overall goal is for Environmental Science & Technology to be the best journal in its field—peerless,” Schnoor says. “It is already the top journal, but I would like to see us expand relevancy in the post-genomic era. ... Environmental chemistry will always be a predominant strength of the journal, but biology and chemistry are becoming increasingly linked and indistinguishable.” He credits ES&T’s current editor, Bill Glaze, and associate editors Joe Suflita, Gary Sayler, and Alexander Zehnder for drawing microbiology and ecotoxicology research into the journal and says he wants to continue their efforts to broaden the publication’s focus. Glaze applauds Schnoor’s appointment. “I am extremely pleased to know that Jerry Schnoor will become the editor in chief of ES&T when I retire from the position,” he says. “I was always impressed by his good judgment and quiet, efficient way. A fine scholar, teacher, and public servant, Jerry has all of the credentials, talents, and personal integrity to lead ES&T to even higher levels of excellence. I couldn’t be more confident about its future.” Schnoor will be the second engineer to direct ES&T, and he considers his background similar to that of the publication’s first editor, James Morgan, who was also trained as an engineer. Schnoor earned his Ph.D. in civil engineering at the University of Texas at Austin in 1975, where he also earned an M.S. in environmental health engineering; he studied chemical engineering as an undergraduate at Iowa State University. “I became more interested in the environmental sciences after I became a professor and got involved in acid deposition problems, which took me into lake and forest ecology issues,” he explains, stressing that he has cared deeply about the environment since growing up along
the Mississippi River in Iowa. In the early 1980s, Schnoor was the first to recognize that the acid rain issues plaguing the eastern United States also affected Switzerland because of the similarities in their geology. This insight led to his longtime collaboration with Werner Stumm, who was then the director of the influential Swiss Federal Institute for Environmental Science and Technology (EAWAG). In addition to aquatic chemistry, Schnoor’s diverse research interests include the mathematical modeling of surface water and groundwater quality, the biogeochemistry of climate change, and hazardous waste remediation; and he helped pioneer the use of plants to clean up contaminated sites. Schnoor had a hand in shaping the National Acid Precipitation Assessment Program and the Clean Air Act amendments of 1990. He also solicited the first scientific research about the environmental effects of the Exxon Valdez oil spill on Alaska’s Prince William Sound, the results of which were published in ES&T—and chronicled in the A-pages in 1991. Schnoor has the ability to perceive the issues that can drive environmental science forward, says Zehnder, who is now EAWAG’s director. “One of Jerry’s great strengths is his breadth of vision,” agrees Morgan. Zehnder says that Schnoor’s interest in sustainability is probably his most important qualification as ES&T’s editor. “I think that ecological health must be a big focus of our profession in the future,” Schnoor says. Schnoor is the editor of four books and the author of Environmental Modeling, which is promoted as the only textbook to combine engineering transport fundamentals and equilibrium aquatic chemistry. He is on the U.S. EPA’s Science Advisory Board and the chair of the agency’s Office of Research and Development’s Board of Scientific Counselors. He is also a member of the National Academy of Engineering and on the National Research Council’s Water Science and Technology Board. —KELLYN S. BETTS
comments submitted, can be found at www.epa.gov/hudson; a description and video of environmental dredging are provided at www. epa.gov/hudson/dredge_truth.htm.
Canada curbs dioxin Emissions of dioxins and furans from electric arc furnaces and iron sintering plants in Canada should be cut by 73% under new national standards. The federal government developed the levels through cooperative agreements with the provinces— making them goals—which are not enforceable in and of themselves, says Paul Muldoon, executive director of the Canadian Environmental Law Association, a legal aid clinic. The iron sintering standards, which will become effective May 23, call for existing facilities to cut stack emissions to less than 1350 pg/m3 toxic equivalency quotient (TEQ) by 2002 and to less than 200 pg/m3 TEQ by 2010. The standards will slash yearly dioxin and furan releases from iron sintering plants by 90%, from 6 to 0.6 g TEQ in 2010, according to Environment Canada, the country’s environmental agency. The standards for electric arc furnaces will not go into effect until the federal and provincial ministers of the environment sign a Canada-wide O Cl Environmental Standards AgreeCl ment sometime O this fall. These standards will reduce the furnaces’ yearly dioxin and furan releases 60% from 11 to 4 g TEQ by 2010. The standards will nudge Canada closer toward meeting its goal of virtual elimination of releases of dioxins and furans into the environment. However, because the provinces can implement the standards any way they want, through voluntary or regulatory measures, it is unclear whether the standards will be met, Muldoon says.
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News M Briefs
Vast sections of the world’s oldgrowth and primary forests are rapidly being degraded because of unsustainable logging and mining practices, concludes a series of reports by the World Resources Institute’s Global Forest Watch. The reports, which evaluate nearly half of the world’s forests, provide detailed maps of forests in Chile, Venezuela, Indonesia, Russia, Central Africa, and North America, based on information from both ground-based measurements and satellite images. Better forest management practices and enforcement of legislation to protect forests are needed to slow down the current rate of destruction, say the reports, which are available at www.globalforestwatch.org. The U.S. Army Corp of Engineers is responsible for the degradation of four of the most endangered rivers in the United States, according to a new report by American Rivers, a nonprofit group. Many of the Corps’ 1004 projects are “boondoggles,” and its more than $50 billion project backlog wastes taxpayers’ money, charges the report. It faults the agency’s dredging practices, outdated dams, and irrigation of surplus crops for contributing to the high rate of extinctions of freshwater fish and wildlife species, which are oc236 A
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curring five times faster than landbased species. America’s Most Endangered Rivers of 2002 can be found at www.AmericanRivers.org.
Smoky National Park. For more information, go to www.npca.org. Traditional cathode ray tube (CRT) computer monitors use 7 times more energy than their newer counterparts, liquid-crystal display (LCD) flat screens, over the course of their respective lifetimes, according to researchers at the Center for Clean Products and Clean Technologies at the University of Tennessee. Their detailed “cradle-to-grave” analysis shows that more mercury is emitted into the environment to produce the power needed to run a CRT than is used in an LCD’s fluorescent backlight. Overall, the life cycle assessment report shows that CRTs, which also contain more lead than LCDs, have a greater environmental impact. For more information, go to www.epa.gov/oppt/dfe/pubs/ comp-dic/lca.
The number of bald eagle nests along the United States’ largest estuary, the Chesapeake Bay, shot up 16% in 2001, with 618 active nests producing 900 eaglets, according to bald eagle counts released by the Chesapeake Bay Program (CBP). The birds, which have been reclassified from endangered to threatened by the U.S. Fish & Wildlife Service, are flourishing in the bay because of improvements in water quality and bald eagle habitat, CBP officials say. CBP is a partnership of state agencies and organizations dedicated to restoring the ecosystem of the bay, which includes parts of six eastern states. For more information, go to www. chesapeakebay.net. PHOTODISC
Industrial agriculture consumes fossil fuel, water, and topsoil at unsustainable rates, according to researchers at Johns Hopkins’ Bloomberg School of Public Health. They site the U.S. system as one of the worst-case examples because of its emphasis on meat production. In beef production, seven pounds of grain are required to produce one pound of beef, and 35 kilocalories (kcal) of fossil energy are required for every 1 kcal of food energy, compared to other U.S. food crops, which average 3 kcal of fossil energy to produce 1 kcal of food energy. Sustainable agriculture systems could help to stem the environmental degradation caused by conventional farming practices, they conclude (Environ. Health Perspec. 2002, 110, 445–456).
Emissions from aging power plants, snowmobile traffic, and inappropriate development threaten the wildlife and natural resources of U.S. national parks, according to the National Parks Conservation Association (NPCA). In releasing the fourth annual list of “America’s Ten Most Endangered National Parks,” NPCA highlighted the Bush administration’s failure to phase out snowmobile traffic in Yellowstone and Grand Teton National Parks and its proposed weakening of the Clean Air Act’s regulations for aging power plants as a threat to the Great
ENVIRONMENTAL SCIENCE & TECHNOLOGY / JUNE 1, 2002
To aid the development and testing of environmental transport models, the U.S. Centers for Disease Control and Prevention (CDC) and SENES Oak Ridge, Inc., a risk analysis company based in Oak Ridge, Tenn., are making a rare collection of validated data sets available for free. Most of the data are from radiation measurements made after the 1986 Chernobyl accident. All of the data sets currently available were used in international model-testing studies such as the Biosphere Modelling and Assessment Methods (BIOMASS) assessment that ended in 2000, but CDC promises that several additional data sets from the former Soviet Union that have not been previously used in test exercises will be made available at a later date. Each set includes a summary of the model-testing situation, complete input information, and tables of endpoint data to which model predictions may be compared. An overview of the collection and five data sets are presently available in PDF format from the CDC Radiation Studies branch’s Web site (www.cdc.gov/ nceh/radiation/brochure/profile_ intl_projects.htm; see the “international data sets” entry).
