G OV ERNM E NT & P O LICY
CRITICAL ANALYSIS
DAWN RAMSEY/NIOSH
Tests of singlewalled carbon nanotubes, shown here, indicate that many contain impurities that could affect toxicology studies.
NANOMATERIAL CHARACTERIZATION Grassroots effort AIMS TO IMPROVE QUALITY of nanotoxicology studies BRITT E. ERICKSON, C&EN WASHINGTON
THE NUMBER of peer-reviewed papers showing health or environmental effects of engineered nanoscale materials has grown exponentially during the past few years, but their quality in terms of the characterization of starting materials varies dramatically. The situation has left government agencies scrambling to determine which studies are relevant for regulatory purposes. When it comes to studying the environmental, health, and safety (EHS) aspects of nanomaterials, it is critical for researchers to know what material they are working with, experts say. Formal characterization standards are in the works, but such processes are slow and tend to be ignored by academic researchers. In the interim, a grassroots effort has emerged to fill the gap. “There is a great need for improved characterization of the nanomaterials used in toxicity studies. Everyone recognizes that the materials used in many of the earlier studies were not adequately characterized, and some of the conclusions should not have been drawn,” says E. Clayton Teague, director of the National Nanotechnology Coordination Office, which coordinates federal nanotechnology R&D activities. Studies with good characterization are
important because the stakes of nanotech EHS research are so high. “These are the early-stage research papers that help craft a consensus opinion about the field and ultimately inform policy,” says Vicki L. Colvin, a professor of chemistry and chemical engineering and director of the Center for Biological & Environmental Nanotechnology at Rice University. A paper that makes false conclusions because of poor characterization could damage the entire field, industry experts warn. “If a study were to come out today saying that a certain nanoparticle causes cancer, it would be picked up by the nongovernment organizations or the press,” says Shaun F. Clancy, director of product regulatory services at Evonik, a manufacturer of nanomaterials. If it is a bad paper, it would take a lot of time for somebody to refute it, he emphasizes. To address the lack of physicochemical characterization of nanomaterials used in toxicology studies, a group of more than 40 concerned stakeholders—representing government, industry, and academia— participated in a two-day workshop hosted by the nonprofit Project on Emerging Nanotechnologies (PEN) at the Woodrow WWW.CEN-ONLI NE.ORG
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Wilson International Center for Scholars, in Washington, D.C., in late October. The goal of the workshop was to develop a minimal list of recommended characterization parameters for nanotoxicology studies. Shortly after the workshop, the group, which calls itself the Minimum Information for Nanomaterial Characterization Initiative (MINChar Initiative), launched a community website— characterizationmatters.org—that it hopes will attract more supporters to the effort. The recommended parameters, listed on the group’s website, address three major questions: What does the material look like? What is it made of? What factors affect how it interacts with its surroundings? The parameters are intended to serve as guidance to the community and to encourage more robust physicochemical characterization of nanomaterials in toxicology studies. “This is a grassroots effort by practitioners in the field trying to do something to raise the bar of the science,” says Andrew D. Maynard, chief science adviser at PEN. “As the number of publications increases, there is much greater awareness that we need to make sure that the quality of these data are as good as possible.” Maynard is one of the lead organizers of the MINChar Initiative and a member of C&EN’s editorial advisory board. THE MINCHAR INITIATIVE comes just
months after a similar grassroots effort was launched to develop standard protocols for determining how nanomaterials interact with biological systems (C&EN, Sept. 15, page 5). That effort, called the International Alliance for NanoEHS Harmonization (IANH), focuses on biological characterization. It involves the use of round-robin studies, with scientists around the world performing the same experiments with the same materials to develop more reproducible methods. In contrast, the MINChar Initiative aims “to make sure that if somebody publishes peer-reviewed data, their physicochemical characterization data sets are as complete as they can be,” explains Colvin, who is involved in both the MINChar Initiative and IANH. Both efforts are international in scope and complement other standard-setting activities, such as those of the International Organization for Standardization (ISO), the Organization for Economic Cooperation & Development, and ASTM International. But formal standards can
It is critical for researchers to know what material they are working with. take years to develop, and the community is asking for something now. “ISO is slow. It would be nice if we could get something out faster,” Maynard says. Even when official standards do get finalized, “most academic and government research scientists are unaware of those activities. The standards really impact trade and industry folks,” says Angela R. Hight Walker, a physicist who works on nanotechnology at the National Institute of Standards & Technology (NIST). EFFORTS TO RAISE the quality of nano-
material characterization go back several years. In 2004, after a workshop at the University of Florida, researchers from the National Toxicology Program sent a letter to several editors of high-impact journals stressing the need for good characterization in nanotoxicology studies. Those letters, however, did little to change the situation. “Very clearly, the timing wasn’t right. There wasn’t that feeling of urgency within the publishing community at the time,” Maynard says. The issue bubbled up again at a nanotech meeting held at NIST in 2007. “There was a sense that it might be worth trying to tackle this issue again because it really hadn’t been resolved,” Maynard notes. After that NIST meeting, a small group of people brainstormed how they could engage influential nanotoxicology researchers to improve the quality of characterization. The result was the October workshop that led to the MINChar Initiative. At the October workshop it became clear that academic researchers do not want to be told how to conduct their experiments, Maynard notes. “If anything is going to happen, it’s really got to come from the academic community. You can’t take a top-down approach and tell academics what to do. They’ve got to realize that this is important and take action themselves,” he emphasizes. “I don’t think we know enough to know what to mandate of people. But in this guidance we are trying to help people understand what is important,” adds Clancy, who is also one of the lead organizers of the MINChar Initiative. The group intends to reach out to journal editors and funding agencies to change
partment of biological sciences at Clemson University and an editor of the journal Environmental Toxicology & Chemistry, also agrees that better characterization of nanomaterials in toxicology studies is needed. Klaine is the behavior of researchers so that they one of the organizers of the MINChar Iniwill be embarrassed to publish papers with tiative and has proposed to modify ET&C’s poor characterization. instructions to authors to include a clear Editors of high-impact journals say that statement of what should be considered in in general the characterization of nanomaterms of nanomaterial characterization. terials in toxicology studies is improving, Getting funding agencies to require good but it still varies considerably. “At a bare nanomaterial characterization is a bit more minimum, people typically characterize the complicated, but Klaine and others predict particle size or size distrithat eventually, requests bution,” says Pedro J. J. for proposals for nanoRESEARCH EXPLOSION Alvarez, an associate editoxicology research will Peer-reviewed papers in tor of the interdisciplininclude some mention of nanotoxicology are growing ary journal Environmental material characterization exponentially Science & Technology, pubbeyond particle size. lished by the American Efforts like the Number of papers Chemical Society, which MINChar Initiative 250 also publishes C&EN. could go a long way 200 “What we don’t see, and toward increasing the 150 need to see increasingly, quality of nanotoxicol100 is surface composition, ogy research. “The more 50 particularly the impurithere is efficient com0 ties,” he notes. munication among the 2003 04 05 06 07 Impurities are imresearchers, the more SOURCE: International Council on portant because “a lot of likely that better characNanotechnology NanoEHS Database times the main driver of terization will happen. I toxicity is not the nanothink it is going to come materials but impurities like transition from a lot of different directions. The more metals that accumulate at the surface,” directions it comes from, the more likely it Alvarez explains. “We need to raise awarewill be to happen,” Teague says. ness that nanomaterials are not like typical Kristen M. Kulinowski, director of the hazardous materials,” he emphasizes. The International Council on Nanotechnology properties of nanomaterials are system at Rice University, agrees. “All of these alspecific. They depend on everything from lied efforts, each doing something a little manufacturing history to storage condibit different, will someday advance the tions, he says. quality of nanotechnology-risk-relevant In some cases, however, the impurities research and help decision-making at the may decrease the toxicity of nanomaterials. policy level,” she says. “People often neglect the role of natural Many people hope that efforts like the organic matter or other coatings that nanoMINChar Initiative will speed up the promaterials may acquire in the environment cess. “We feel a sense of urgency that better or in the lab that significantly mitigate toxcharacterization has to be done because we icity,” Alvarez notes. His research group in think there are numerous benefits of nanothe department of civil and environmental technology,” says Mark D. Hoover, a senior engineering at Rice University has found scientist at the National Institute for Octhat low concentrations of natural organic cupational Safety & Health and one of the matter dissolved in water can completely organizers of the MINChar Initiative. “The eliminate the toxicity of C60 (Environ. Toxiasbestos and genetically modified food situations taught us a lot about what can col. Chem. 2008, 27, 1888). happen if the right things are not done in “The bottom line is that the characterizaa timely manner. If we can put the tools in tion of nanomaterials should be done pretty place to create a useful knowledge base for much at the time of exposure in the medium nanomaterials, we will able to develop and or in the organism or model cell component implement the hazard evaluations, expobeing exposed to the material. That is not sure assessments, and control measures often done,” Alvarez emphasizes. needed to support safe nanotechnology.” ■ Stephen J. Klaine, a professor in the de-
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