to harbor bacteria that reductively demethylate mercury; oxidative demethylation appeared to prevail in the Everglades. This finding changes a prevailing assumption about mercury fluxes in freshwater ecosystems, says USGS scientist David Krabbenhoft. When mercury scientists try to understand the causes of methylmercury levels in fish at a particular site, “We tend to assume that demethylation rates are constant across systems,” he says. “We expect that it’s changes in methylation rates that account for the variability.” The findings have no significance for bioremediation, cautions Barkay. You can’t dump mercury into a system and expect the amount of methylmercury to go down, she says, pointing out that the bacteria in contaminated systems only reduce the fraction of mercury that remains methylated. The contaminated lakes still have higher levels of methylmercury, she says. —REBECCA RENNER
Genomics data are no panacea Genomics, proteomics, and other systems biology data offer a promising solution to the U.S. EPA’s enormous task of evaluating an ever-increasing number of chemicals in the environment. But the agency must overcome significant challenges before it can fully apply such an approach to risk assessment, according to a draft EPA white paper released this spring. The paper outlines the “overarching challenges” in the areas of research, technical development, and staffing that EPA needs to address as these data become increasingly common. The white paper is the latest step in EPA’s effort to develop a genomics policy. It builds on EPA’s 2002 Interim Policy on Genomics that states that the agency can use genomic data in the decision-making process,
but that the data alone are insufficient as a basis for decisions. EPA scientists wrote the white paper at the request of the agency’s Science Policy Council (SPC), which asked them to examine the broader implications that genomics could have for EPA. The paper takes a careful position, say observers, and recommends practical steps that EPA could take to strengthen its capability to use genomics information. It raises technical issues such as how to standardize and specify quality controls for genomic tests when the field is changing so quickly and how to statistically evaluate systems biology data. The paper also recommends that EPA hire staff with expertise in systems biology and train existing staff.
News Briefs Kids in Europe One in three child deaths across Europe can be attributed to environmental problems, according to a report published by the World Health Organization in June. The report examined the effects of indoor and outdoor pollution, water sanitation, injury, and lead exposure on children and adolescents up to 19 years old. Of note, outdoor air pollution kills 13,000 children under age 4 annually, with an additional 10,000 deaths from pollution created while heating homes with solid fuel. Poor water sanitation kills 13,000 kids under 14. Much of the problem resides in the former Soviet bloc countries. The authors conclude that intervention measures to reduce environmental factors will result in substantial gains in human health. (Lancet 2004, 363 [9426], 2032–2039).
Water research agenda The science necessary to practically resolve the growing number of serious water resource issues in the United States is not available, according to a report by the U.S. National Research Council (NRC) released in June. Over the past 30 years, federal investment in water science, much of which has been deferred to states, has remained stagnant, the NRC panel finds. As a result, most studies have focused on short-term problems, “with a limited outlook for cross-cutting issues, longer-term problems, and more basic research that often portends future solutions.” Because of the growing competition and emerging challenges, the NRC panel recommends that an additional $70 million in federal funding go annually to water research. For more information on Confronting the Nation’s Water Problems: The Role of Research, go to www.nap.edu.
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tions varied only from 0.03 to 1.6 ng/L for lakes in both regions, with only slightly lower concentrations in Pine Barrens waters. Fish from these waters had similar levels of methylmercury. The Rutgers scientists found a higher proportion of mercury-resistant bacteria from the Meadowlands site, which expressed mer genes and, in lab tests, reductively demethylated methylmercury. The Pine Barrens bacteria demethylated mercury much slowly, producing carbon dioxide and some methane, which suggests that these bacteria are engaged in oxidative demethylation. The observation that lakes have different bacterial communities that demethylate mercury is consistent with an earlier study by MarinDiPasquale and co-workers that compared some of the most contaminated sites in the world with the relatively pristine Florida everglades (Environ. Sci. Technol. 2000, 34, 4906–4908). The sediments at their most contaminated sites appeared
Environmental▼News But beneath the paper’s State 1 calm prose, the research debate inside and outside the agency is turbulent. EPA managers are striving Extract Proteolytic to tap the enormous poproteins digestion tential of genomics-related technologies to speed up State 2 toxicity testing, provide Peptide mixture sensitive biomarkers of exposure, and unravel genetic Protein mixture susceptibilities to contaminants. But such data must be linked to adverse outcomes before they can be employed in a regulatory Mass spectrometer Protein A setting. Researchers can now Protein B use an astounding variety Liquid chromatograph/ Protein C of technologies and bioinautosampler formatics tools to study • the expression of genes, • the function of proteins, Protein N metabolism, and genetic differences within popuOne approach to proteomics: The proteins isolated from two different cell types (states 1 and 2) lations and between indiare extracted and digested. The resulting proteins contained in each cell type are identified, and viduals. These technolotheir relative abundances compared. gies are developing at an unprecedented rate. The white paper notes that in 1994, a of the traditional uncertainties of the need to link systems changes gene chip maker could fit 16,000 risk assessment but will bring their to adverse outcomes is one of the DNA probes on a gene chip, and by own vexing uncertainties. “We may greatest research challenges de2002, the same manufacturer was find out that a particular genetic scribed in the paper. packing in more than 500,000. variant increases susceptibility,” he Many EPA scientists see promise The white paper takes a “reasonsays. “But we’ll have to estimate in an approach that creates systems able and proactive approach,” says how many people have the variant, biology fingerprints that identify Arizona State law professor and geand that estimate is likely to be distinctive changes across genes, neticist Gary Marchant. “The agency highly uncertain.” proteins, and metabolites. Such daneeds to be prepared for what’s The white paper notes that EPA tabases are already being developed coming,” he says, adding that he alhas already received genomic data for drugs by the pharmaceutical inready gets calls from trial lawyers along with conventional toxicologidustry. EPA would like to test this eager to use genomics in litigation. cal data from an unspecified pestiapproach with environmental con“This document has the right mix of cide registrant. Several state agencies taminants by first conducting blind caution and action.” and public utilities are poised to use studies that compare chemically Many scientists agree that EPA genetic data to “fingerprint” sources similar environmental contamishould go slow with genomics. of fecal contamination at swimming nants that are known to have differ“There’s a big push to take advantage beaches and other bodies of water. ent toxicities, says Robert Kavlock, of genomics’ benefits,” says UniverEPA could use genomics to prioriwho heads EPA’s computational toxsity of Washington toxicologist David tize and screen chemicals. For examicology program, an initiative that is Eaton, who also chairs a National ple, genomics data could be applied one of the Office of Research and Research Council committee on to the voluntary high-productionDevelopment’s highest priorities. Emerging Issues and Data on Envivolume chemicals screening process The advantage of this approach ronmental Contaminants. “But it all and may play a role in prioritizing would be that once a library of addepends on the validity and veracity waterborne disease pathogens by verse responses was set up, toxicolof the association between patterns identifying which pathogens contain ogy testing would take much less of change with adverse outcomes.” virulent genes of concern, according time than it does now, he says. But For instance, genomics will deto the paper’s authors. he adds, “It will take a while to get liver new data on human genetic For risk assessment, systems bithere. This approach has a lot of susceptibility to contaminants, says ology data promise very sensitive promise, but a fair bit of hype too.” Eaton. These data may reduce some indicators of exposure. However, —REBECCA RENNER 304A ■ ENVIRONMENTAL SCIENCE & TECHNOLOGY / AUGUST 15, 2004
