SCIENCE & TECHNOLOGY FROM
PACIFICHEM
CRYSTAL BALL ON THE ENVIRONMENT Detective work and expertise are used to evaluate environmental contaminants of emerging concern
One reason for that shortcoming is simply that the Environmental Protection Agency doesn't have the time or the resources to collect or measure all of the chemical property and toxicity data, commented Eric J. Weber, acting director of EPA's Ecosystems Research Division of the National Exposure Research Laboratory in Athens, Ga. Some 60,000 chemicals need to be assessed, and that list is growing, Weber noted. "EPA is losing the battle," he said. "We are getting further and further behind."
STEPHEN K. RITTER, C&EN WASHINGTON COMPUTATIONAL CHEMISTRY is one way
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F CHEMISTS COULD EASILY PREDICT
Roberts went on to describe her group's research on monitoring the degradation products of chloroacetamide herbicides. Acetochlor, metolachlor, and other compounds in this class are some of the most widely used agricultural chemicals. In sampling part of the Chesapeake Bay, graduate student Michelle L. Hladik in Roberts' group found that the total concentration of 19 chloroacetamide degradation products, each detected in the parts-per-trillion range, was 20 to 30 times greater than that of the parent compounds {Environ. Sci. Techno/. 2005,39,6561). Many of these degradates satisfy the
which new chemicals would lead to environmental health and safety problems, they could forestall a lot of problems. Chemicals sometimes end up being used for years before they are found to be contributing to an environmental problem; polychlorinated biphenyls (PCBs) and chlorofluorocarbons are just a couple of examples. Today, armed with hindsight, ever-better analytical techniques, and the tenets of green chemistry, chemists are starting to ferret out troublemaking chemicals early on, before problems get out of hand. And once manufacturers or regulatory agencies get an inkling that a class of compounds potentially could become an environmental concern, they can work together to solve the problem. Perchlorate, polybrominated flame retardants, and long-chain perfluoroalkyl compounds are a few current examples. Discussions involving these concepts and descriptions of environmental studies in progress were the highlights of a symposium on environmental pollutants of emerging concern held last month at the 5th International WATERWORKS UC Berkeley's Fono Chemical Congress of Pacific samples water in a wetland Basin Societies (Pacifichem) in on the Santa Ana River in Hawaii. California to measure the ratio of propranolol enantiomers, To qualify as a contaminant of which will reveal if the river is emerging concern, a compound being affected by raw sewage. must meet three criteria, according to environmental chemist A. Lynn Roberts ofjohns Hopkins University. emerging contaminants criteria, Roberts Appreciable amounts of the compound must said, and they need to be studied further be entering or be generated in the environto fully assess the potential impact of chloment, the compound must have "a modicum roacetamides on the environment. But the of persistence," and it must exhibit deletedegradates haven't yet received much attenrious effects on organisms, Roberts said. tion in the U.S. because regulating degraCompounds that satisfy these criteria, if dates is a relatively new practice and there not already regulated or considered priority is a lack of commercially available reference pollutants, should be candidates for environstandards and validated test methods for mental monitoring, she noted. their analysis, she pointed out. WWW.CEN-0NLINE.ORG
to fight back and narrow the list down to a manageable level, Weber said. He discussed a "major new EPA program" to develop computational toxicology software that can use measured and computed data to drive environmental fate and toxicity pathway simulations based on functional group reactivity and overall chemical structure. The software should help EPA over the next decade "to prioritize and test chemicals that really need testing and identify chemicals of emerging concern," he said. Civil and environmental engineering professor David L. Sedlak of the University of California, Berkeley, echoed the views of Roberts and Weber. "It's relatively easy for researchers to ask questions about new contaminants, but it's difficult to assess the overall significance of the problems," Sedlak commented. Municipal wastewater is probably the biggest concern. Even after being treated, the water still contains very low concentrations of dozens of contaminants of concern, principally human drug metabolites and animal steroid hormones and antibiotics, Sedlak said. Complicating matters is that chlorine or chloramines used for wastewater treatment can actually convert contaminants into more problematic compounds. Gaining a better understanding of the nature of these contaminants is becoming critical, he noted, because wastewater effluent flowing into rivers is starting to become an important source of potable water in arid regions. To address this need, Sedlak's group is developing a suite of in situ chemical indicators—contaminants that are already in the water—that can be used to analyze water-supply systems and aquatic ecosystems. Application of these analytical tools could provide a better understanding of how wastewater-derived contaminants are elimiC & E N / J A N U A R Y 3 0 . 2006
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SCIENCE & TECHNOLOGY radation, accumulate in the environment, nated in treatment systems, in the environmostly C 8 and C 9 compounds—are used in and are potentially toxic. ment, and in engineered wetlands designed small amounts as surfactants to aid industo remove contaminants, Sedlak said. In one talk, chemistry professor Scott trial production of polytetrafluoroethylene A. Mabury of the University of Toronto (DuPont's Teflon) and other fluoropolyFor example, untreated sewage often gets explained how and why perfluorinated carmers, Mabury added. Significant amounts into waterways from leaking sewer lines or boxylic acids have been detected in people of PFOA and other perfluorocarboxylates from overflows of "combined" sewer systems and wildlife around the globe, even in the have been released during their producthat also handle rainwater, he pointed out. remote Arctic region. tion and during subsequent manufacturing Wastewater-treatment plants also have "bad processes that use them, but days" when they aren't workthese emissions can't fully acing efficiently, he added. count for the spread of PFOA Sedlak and graduate stuin the global environment, dent Lorien J. Fono figured he said. out that monitoring the highvolume beta-blocker drug PFOA and most long-chain propranolol, which is used perfluoroalkyl compounds to treat high blood pressure, have low volatility, and their could provide evidence that main route of transport is in raw sewage had entered a wawater, he noted. That means terway {Environ. Sci. Techno/. that most PFOA emissions 2005,39, 9244). Propranolol will end up in the oceans, is a 50:50 mixture of R and where PFOA is detected. S enantiomers, but in wasteSome of the compounds are water-treatment plants mislowly transported around crobes preferentially degrade the world by ocean currents CHAIN OF EVENTS Long-chain the R enantiomer, Sedlak or perhaps more quickly by fluorotelomer alcohol building noted. In field tests, the remigrating fish and birds, as blocks used to make stain-, oil-, searchers have shown that shown in studies of PCBs and water-resistant polymers and surfactants for myriad water containing untreated and mercury. Mabury began consumer products appear to degrade to environmentally sewage has an even proporto suspect several years ago persistent carboxylic acids that are potentially toxic. tion of the enantiomers, but that the uniform distribuwater that was treated has less of the R tion of perfluorocarboxylic acids observed "This is a great story because we have enantiomer. across the remote Arctic region meant that an opportunity to potentially head off an there also must be an atmospheric piece to environmental problem before most peothe puzzle. ple even appreciate we have one," Mabury THE TECHNIQUE could be particularly toldC&EN. useful for discovering leaking sewer lines He believes the real culprits are fluoor tracking untreated water, and it could rotelomer alcohols (FTOHs), such as Perfluorooctane sulfonate (PFOS) was CF3(CF2)7CH2CH2OH. FTOHs are known double as a warning for potentially harmful one of the key perfluorinated compounds from lab studies to degrade to the carboxylic originally observed in the environment in waterborne pathogens, Sedlak said. With acids. The alcohols are produced in much the late 1990s, Mabury explained. This further work, monitoring propranolol or a larger amounts than the perfluorocarboxylcompound was identified as a breakdown combination of contaminants could provide ates and are used as building blocks to make product of perfluorooctanesulfonamide, the a quantitative measure of how much raw perfluorocarbon surface-treated products. key ingredient in 3M's Scotchgard brand of sewage entered a waterway. The alcohols are added to the backbone of stain-protection products. 3M took a proSeveral presentations at Pacifichem various polymers and surfactants, which in active step and voluntarily phased out the addressed long-chain perfluoroalkyl comturn are used to produce carpeting, clothsulfonamide when faced with evidence that pounds and their degradation products, ing, food packaging, and paints and floor PFOS was accumulating in the environment which currently are at the head of the list coatings. and was potentially toxic to humans. EPA of compounds of emerging concern. These also issued regulations to limit U.S. manuSome FTOHs escape during manufacturchemicals are used in a wide array of confacturing and imports of the sulfonamide. ing processes, Mabury said. "A fundamental sumer products ranging from pizza-delivery question is whether F T O H emissions also Attention has now turned to perfluoroboxes and nonstick cookware to car parts arise indirectly from outgassing of residual carboxylates, primarily perfluorooctanoic and stain-resistant carpet. The inertness of material in products or from degradation of acid (PFOA), which also have been detected the C-F bond helps provide the stain-, oil-, the perfluorinated products," he added. in people and animals around the world. and water-resistance that makes these perEPA is evaluating whether PFOA should be In smog-chamber studies carried out fluoroalkyl compounds useful. But when classified as a likely human carcinogen. with atmospheric chemist Timothy J. the perfluorocarbon chain is seven carbon Wallington of Ford Motor Co., Mabury Ammonium perfluorocarboxylates— atoms or longer, the compounds resist deg-
"It's relatively easy for researchers to ask questions about new contaminants, but it's difficult to assess the overall significance of the problems/' 38
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and his colleagues determined the atmospheric lifetimes of FTOHs and that they are oxidized to aldehyde intermediates by chlorine and hydroxyl radicals under UV light. T h e intermediate aldehydes undergo additional radical reactions to form peroxyl radicals, eventually leading to perfluorocarboxylic acids and other compounds. Lifetimes of FTOHs and the aldehyde intermediates are as long as three weeks, which is long enough for them to be transported in the atmosphere to the Arctic, Mabury said. METABOLISM STUDIES in microbes and in rats, carried out by Mabury, graduate student Joyce A. Dinglasan, and postdocJonathan W. Martin, show that small amounts of FTOHs are transformed into PFOA and other perfluorinated carboxylic acids in living systems. These findings are important when potential human exposures are being considered. "Some of the intermediates may be more important toxicologically than the perfluorocarboxylic acids," Mabury noted. Mabury, Derek C. G. Muir of Environment Canada, and their coworkers also have carried out a number of environmental-monitoring studies. These show that PFOA and other perfluorocarboxylic acids (chains up to C15) are in samples from the Great Lakes and in remote Arctic regions, including in polar bears, which are at the top of the food chain. One of the group's latest projects is a modeling study led by Wallington that shows the smog-chamber results correlate to real atmospheric processes {Environ. Sci. Technoi 2006,40, 924). The modeling also provides a quantitative estimate of how much FTOH-derived PFOA might be expected to be found in the environment. On the basis of known production and emission rates of perfluoroalkyl compounds, Mabury said that about half a ton of perfluorocarboxylic acids per year might be deposited across the Arctic. That's a relatively small amount, but because PFOA can persist for years in the environment, the compound is expected to build up over time. Preliminary measurements by Mabury's group at locations in Canada place PFOA concentrations at about 1 ng/L (1 ppt), "which comes out pretty close to the model predictions," Mabury commented. Mabury's group is also just finishing up work that shows unbound C 6 to Q 4 FTOHs are present in up to about 4% by mass in some off-the-shelf carpet- and fabric-protection products, windshield-washing fluid, and other products. It appears the FTOHs are residual unreacted reagents, rather than compounds formed by cleaving off branches
from the polymer or surfactant backbone, he said. A recent review of the scientific evidence on perfluorocarboxylates in the environment corroborates many of the observations made by Mabury and his coworkers but draws a different set of conclusions. The study, carried out by Ian T Cousins of Stockholm University, Robert C. Buck of DuPont, and their colleagues as part of a European Union program, is the first detailed accounting of the production history,
direct and indirect emissions, and fate of PFOA and its homologs {Environ. Sci. Technol. 2 0 0 6 , 4 0 , 32). Most of the PFOA in the environment, including in the Arctic, likely is the result of PFOA releases dating as far back as the late 1940s, Cousins told C&EN. His conclusion, based on the study, is that eliminating F T O H s likely would have little future impact on PFOA and other acids in the Arctic. Cousins and his coauthors recommended "aggressive action" to
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SCIENCE & TECHNOLOGY AT THE CORE Toronto graduate student Craig Butt (right) works with graduate student Bronwyn Keatley and technical director John R. Glew of Queen's University to section a sediment core from remote Char Lake in Nunavit, Canada, looking for signs of perfluorinated compounds.
eliminate direct sources of PFOA, such as plant emissions. For DuPont's part, the company already has been working to cut PFOA emissions in fluoropolymer production in the U.S., with
plans to reach a 98% reduction by next year. DuPont also recently reached a settlement with EPA over allegations that the company withheld health and safety information related to PFOA (C&EN, Dec. 19,2005, page 10). As part of the settlement, the company will spend $5 million over three years for contract labs to evaluate the potential for nine unnamed DuPont products to break down into PFOA. DuPont also has announced that it will remove more than 90% of FTOH residuals from its products by the end of 2007 "If our overall theory on indirect sources is correct, with the elimination of residuals we should see a very rapid response in air concentrations and in the generation of perfluorocarboxylic acids in remote environments," Mabury said in an interview with
C&EN. He allows that if the problem is the result of degradation of the polymers and surfactants rather than residual FTOHs, that makes for "a more intractable problem" that will need more work to resolve. Either way, chemists are already at work finding environmentally friendlier next-generation replacements. 3M unveiled a new version of Scotchgard in 2003 that uses the short-chain compound perfluorobutane sulfonate, which doesn't accumulate in the environment and has been evaluated by EPA and is considered safe. Other companies and academic researchers also are coming out with replacement products that have been patented and are starting to enter the marketplace. Mabury isn't opposed to the continued use of the perfluoroalkyl chemicals because of their high utility. In fact, he views his detective work as being complementary to the work by DuPont, EPA, and other scientists. "We would like to eventually give regulators and industry all the information they need to allow the chemistry to be optimized so that these fascinating and highly important chemicals can continue to be used," he told C&EN.B
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