environmental perspectives - exponent · nanomaterials in fertilizers. some of these studies...

C O N T E N T S

F e a t u r e A r t i c l e

T h e E c o l o g i c a l E f f e c t s o f N a n o m a t e r i a l s : A r e N e w S t r e s s o r s A s s o c i a t e d w i t h N e w T e c h n o l o g i e s ?

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R e c e n t /U p c o m i n g P u b l i c a t i o n s 4

R e c e n t /U p c o m i n g C o n f e r e n c e s & P r e s e n t a t i o n s 5

F o r m o r e i n f o r m a t i o n , c o n t a c t :

Paul D. Boehm, Ph.D.Principal Scientist and Group Vice President, Environmental Group

(978) 461-1220

[email protected]

www.exponent.com

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E N V I R O N M E N T A L A N D E C O S C I E N C E S N E W S

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A PUBLICATION OF EXPONENT’S ENVIRONMENTAL AND ECOSCIENCES PRACTICES

EnvironmentalPerspectives

The Ecological Effects of Nanomaterials: Are New Stressors Associated with New Technologies?

L. Ziccardi, M. McArdle, Y. Lowney, J. Tsuji

The U.S. Environmental Protection Agency (EPA) defines nanotechnology as “research and technology development at the atomic, molecular, or macromolecular levels using a length scale of approximately one to one hundred nanometers in any dimension.” Nanomaterials include naturally-occurring particles, those that are produced from combustion byproducts, and engineered or manufactured nanomaterials. Nanoparticles can be released to the environment from deliberate application (e.g., remedial applications), and from unintentional or incidental releases, where they could come into contact with fish, wildlife, and plants. These organisms, termed “ecological receptors,” can potentially be exposed to nanoparticles through inhalation, ingestion, movement across gills, passive transport, and cellular absorption.

The unique physicochemical properties of nanomaterials that make them beneficial in commercial applications might also result in unexpected biological interactions. For example, their large surface area relative to mass may translate to enhanced chemical binding capacity and reactivity. Another consideration in aquatic environments is that smaller particles will remain in suspension longer, which may affect their environmental transport, bioavailability, and toxicity. On the other hand, nanoparticles’ high surface area and associated intermolecular forces may increase agglomeration and adherence to suspended matter or sediments, potentially reducing bioaccessibility.

Because of the unique properties of nanomaterials, concerns have been expressed that their effects on aquatic and terrestrial organisms and ecosystems may be different from normal or fine-scale materials, although actual effects are likely complex and difficult to predict. Aquatic organisms and terrestrial plants have been the focus of concern for environmental effects.

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For regulation of products containing substances such as nanoscale metallic compounds, the central question for ecotoxicity is whether the substance is more toxic in nano-scale form than in the dissolved form used in standardized tests and for which toxicity-based limits are available. Studies for certain metal oxides, zinc oxide for example, have indicated that the nanoscale form is no more toxic to aquatic organisms or in vitro than the same concentration of soluble zinc, although one study suggested that nanoscale iron oxide particles were more toxic in vitro than soluble iron.

Emerging findings in aquatic toxicity studies using invertebrates, fish, and algae indicate greater toxicity associated with more reactive nanoscale substances such as engineered fullerenes, relative to more inert substances such as titanium dioxide particles. Greater reactivity in nanoscale

form has also been investigated for anti-bacterial applications of metal oxides such as silver, zinc oxide, and photo-catalytic forms of titanium dioxide. Such anti-bacterial effects, however, may have ecological implications. Therefore, the evaluation of regulatory limits for such materials will need to consider whether effects from exposure to the nanoscale forms are any greater than effects from these metals in ionic form or solution.

Nanoparticle ecotoxicity can vary with particle type, size, and attached functional groups. Nanoscale application appears to increase the efficacy of some chemical formulations, such as micronutrients or fertilizers, and may therefore increase potential reactivity and toxicity. The relationship between toxicity and particle size, however, is complicated. Greater reactivity may also be beneficial; this is the case for the effect of nanoscale titanium dioxide on spinach seed germination and growth by affecting enzymes involved in nitrogen metabolism. In another example, one study

Studies specific to the aquatic and terrestrial effects of nanomaterials in environmentally relevant species have been few in comparison to mammalian studies targeted primarily at understanding potential effects to humans. The ecotoxicological studies that are available focus on metal oxide particles, carbon nanotubes, and fullerenes, primarily in aquatic and plant toxicity tests. These initial studies have also generally used high concentrations to maximize exposure and ensure that effects are observed. Aquatic tests have examined the uptake of nanoparticles by fish, filter feeders (invertebrates), and algae, and have provided evidence of toxicity or behavioral changes associated with exposure. Studies on terrestrial species are limited to experiments with plants (e.g., root elongation, germination), primarily to investigate effects on crop species and the use of nanomaterials in fertilizers. Some of these studies conclude that nanoparticles can be taken up by or produce effects in biota, and that dose-response relationships and patterns of relative toxicity among types of particles are emerging.

Toxicity testing of nanomaterials is not yet standardized and certain challenges need to be addressed. For example, preparation methods of nanoparticle test suspensions may influence particle behavior in solution and toxicity, thereby confounding conclusions with regard to the toxicity of the nanoparticles themselves. Nearly all studies of nanoparticles attempt to counteract the natural tendency of the particles to stick to the sides of the test vessel or

agglomerate and form larger particles in solution by using techniques such as sonication, agitation, filtration, or addition of agents such as the solvent tetrahydrofuran (THF). For example, some research indicates that toxicity observed in aquatic exposure tests with C60 may in part be attributed to THF itself or its more toxic breakdown product (γ-butyrolactone) rather than purely to the effects of C60. Studies that removed much of the THF by extraction before exposures and have controls to check on the influence of adding THF would more accurately indicate the toxicity of the test particles.

Toxicity studies may not be representative of the real world. Studies that artificially produce nanoparticles in solution, or in vitro studies involving tissue cultures and isolated cells, must also be interpreted with caution. Such tests may indicate the potential of nanoparticles to cause toxicity, but in the actual environment or within organisms, agglomeration would occur, thereby potentially reducing their transport, migration, and toxicity. Studies indicate that higher concentrations of nanoparticles in solution are associated with greater agglomeration. Toxicity and mobility of nanoparticles in the environment may thus, in part, be self-limiting.

...the central question for ecotoxicity is whether the substance is more toxic in nano-scale form

than in the dissolved form used in standardized tests...

on daphnids, a freshwater filter feeder, reported a hormetic effect (i.e., beneficial effect at low exposures and an adverse effect at higher exposures) with exposure to single-walled carbon nanotubes; and similar patterns have been observed in plants. In addition, while several studies indicate that particle size can influence biological effects, others suggest that toxicity is more related to changes in nanoparticle surface characteristics, and that smaller size does not always result in

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emerging nanotechnologies and nanoformulations, so that research can target materials of industrial, and potential environmental, importance. Several sources of funding to expand these investigations are beginning to emerge. For example, EPA is funding current research under their grant program, Science to Achieve Results (STAR). STAR grants have been awarded to study the environmental and human health effects of engineered nanomaterials, and nanomaterials for use in environmental remediation. For more information on this program and this research please go to es.epa.gov/ncer/nano/research/ starawards.html.

greater toxicity. Size is likely only one of many characteristics that influences the environmental fate and toxicity of nanoparticles. In addition to surface characteristics, other factors include chemistry and crystal type, shape, and electromagnetic properties.

Some of the properties of nanomaterials that make them useful in biotechnology and remedial applications may also result in negative biological effects at high doses. For example, fullerenes bind to lipids, which makes them useful as drug carriers and for other therapeutic applications when functionalized; however, this same binding characteristic and reactivity may have been the cause of adverse effects such as the lipid peroxidation observed in the brains of fish exposed to high concentrations. Therefore, as the use of nanotechnology increases, it is important to improve our understanding of the potential effects of these materials on biota, as well as increase our knowledge to be able to better design future tests on these materials.

While more research is clearly needed to understand the potential for impacts on ecological receptors and systems, further guidance would be useful regarding appropriate study design to ensure that meaningful conclusions can be drawn from the investment in future research. Several important considerations have emerged in our review of the available literature on ecological effects. Each unique nanomaterial (e.g., fullerenes, metal oxides, etc.) and derivatives of these materials may cause unique effects

because of differences in particle size, shape, surface area, charge, solubility, and reactivity. Thus, the toxicity of each nanomaterial needs to be considered independently. Studies should also be designed to allow for an understanding of whether the nano-characteristics of the material are controlling toxicity, or whether toxicity is associated with the chemistry of the material being evaluated and is unrelated to particle size. Nanomaterials toxicity assessment should consider potential effects resulting from the test-material preparation method (e.g., solvent vehicles or sonication used to maintain aquatic dispersion), the presence of trace contaminants in commercial nano-products, and

Exponent scientists have presented the results of their review of the ecological effects of nanomaterials at the International Symposium on Nanotechnology in Environmental Protection and Pollution (ISNEPP 2007), and will also be presenting an update of their review at the NanoEco conference in Monte Verità, Switzerland, March 2–7, 2008. For more information on these conferences please visit www.isnepp.org/ and www.empa.ch/nanoECO/. For more information on the subject of nanomaterials, please contact Joyce Tsuji ([email protected]), or Linda Ziccardi ([email protected]).

Exponent toxicologists have teamed with our material scientists to evaluate the potential risks

of products containing nanomaterials.

the potential influence of nanoparticle agglomeration. The ability of nanoparticles to increase the transport of other chemicals via adsorption, and potential influence on environmental fate, absorption, bioaccumulation, and biological effects, should also be considered.

The existing body of research focuses on evaluation of relatively few types of nanoparticles, although the particles are generally those with the most current interest and application in consumer products (metals and carbonaceous materials; www.nanotechproject.org/inventories/ consumer/analysis/). Future research could benefit from early identification of

Given the lack of standard methodology for quantifying nanoparticle exposure and limitations in knowledge on toxicity, a key focus for manufacturers should be on engineering processes and consumer products that encapsulate or limit liberation of free nanomaterials. Such materials must also be durable and maintain their encapsulation even during wear or weathering of the product. Design of such products or evaluations of their wear behavior is within current knowledge through the well-established discipline of materials science. In this way, Exponent toxicologists have teamed with our material scientists to evaluate the potential risks of products containing nanomaterials.

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New Faces

Ken CerretoFreshwater Ecologist,EcoSciences, Maynard, MA

Mr. Cerreto specializes in ecological risk assessment and field sampling. He has a wealth of field sampling experience in aquatic and terrestrial systems, has managed field sampling programs, and is skilled at sampling both environmental media and biota. Prior to joining Exponent, Mr. Cerreto was an Aquatic Ecologist at ENSR, an Ecologist at AMEC Earth & Environmental, and a Research Assistant at the University of Wyoming, Laramie. He was also an Assistant Scientist at Menzie-Cura & Associates, Inc, where he worked with a number of his present colleagues at Exponent. He holds master’s degrees in Zoology and Physiology from the University of Wyoming and a bachelor’s degree in Biology and Pre-med from College of the Holy Cross.

Decision Support Tools for Environmental Remediation and Restoration

Making decisions involves making trade-offs. If a course of action is obvious, that doesn’t really require making a decision. Companies may face complex environmental decisions such as, “Should we remove all soils and sediments above 1 ppm and dig up forested wetland habitat areas in the process? What about restoration options? Should we spend $500,000 restoring non-contiguous areas of predominantly Phragmites, or is that money better spent enhancing existing contiguous habitat areas?”

Every decision has an overall objective. For example, a company may wish to maximize environmental benefits while minimizing cost, or more specifically, restore and augment a migratory flyway at lowest cost. Lowest cost does not mean choosing the least favorable option or shirking responsibility. It means allocating limited resources most efficiently. There is almost always uncertainty about the data (and/or models) that support a decision. “What

is the range of risks at our site? What are the consequences of making a wrong decision (e.g., reality is not at the expected value)?” If consequences are high, the importance of the decision is high, too.

There are tools and analytical methods that can help sort out such complexities. Net environmental benefits analysis, relative risk models, and a host of multi-criteria decision analysis tools are all available to help evaluate multiple alternatives against a consistent set of criteria. These tools are designed to integrate different kinds of information, analysis, and data that all contribute to the decision-making process, including, for example, stakeholder acceptance, cost, risk, and impacts on habitat. Such tools make the decision process more transparent, by providing an analytical framework for integrating disparate results. How do you directly compare human health and ecological risk, impact on habitat, and cost across competing alternatives when these all differ?

In the next newsletter, we will present some ideas, including case studies, on this topic.

Dr. Katherine (Johnson) Palmquist Senior Scientist,EcoSciences,Bellevue, WA

Dr. Palmquist has a strong interdisciplinary background in insect biology/physiology, toxicology, integrated pest management, and communications. She has developed and published methodology concerning the laboratory maintenance and rearing of several stream insect species. Additionally, she has experience in performing lotic and lentic benthic surveys, as well as terrestrial insect field sampling. She holds a Ph.D. in Toxicology from Oregon State University, and a B.S. in Entomology from Washington State University.

Brianne Duncan Scientist, Environmental Sciences,Bellevue, WA

Ms. Duncan's background is in biology and chemistry; she holds a B.S. in biology with a minor in chemistry from Seattle University.

Dr. Ann Michelle Morrison Aquatic Ecotoxicologist, Environmental Sciences, Maynard, MA

Dr. Morrison has a strong interest in data analysis, specifically in applying statistical methods from other fields (e.g., medical) to environmental data. Prior to joining Exponent, Dr. Morrison worked in the Benthic Ecology Research Program in Bermuda assisting in the assessment of Bermuda’s near shore environment by assessing the health of seagrass beds, coral reefs, and mangrove swamps. She holds an Sc.D. in Environmental Health from Harvard University, an M.S. in

Environmental Health from Harvard University, and a B.S. in Biology from Rhodes College.

Dr. Karen Murray Senior Scientist,Environmental Science,Maynard, MA

Dr. Murray studies the role of bacteria in the environmental transport and fate of metals. She has experience in field sampling in marine, freshwater, and soil systems. Her analytical expertise includes aerobic and anaerobic microbial culturing techniques, electrochemical and spectroscopic chemical analyses, and molecular biological methods. Dr. Murray holds a Ph.D. in Oceanography (Geochemistry) from the Scripps Institution of Oceanography, University of California, and a B.S. in Environmental Engineering Science from the Massachusetts Institute of Technology.

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Ramón PierceGIS Analyst, EcoSciences,Bellevue, WA

Mr. Pierce specializes in the functionality of the ESRI ArcGIS suite software and its extensions, including spatial analysis (e.g., short-path analysis, calculating the slope of an elevation, contour interpretation, reclassifying and creating cost data sets and weighting) and 3-D analysis (e.g., creating surface models, interpolating raster surfaces, and creating features from surfaces). Mr. Pierce’s previous experience is in traffic information. He holds a B.A. in Urban Studies from the University of Washington, and a Certificate in Geographic Information Systems and Spatial Modeling from the University of Washington.

Dr. David J. Rowan Senior Scientist EcoSciences,Boulder, CO

Dr. Rowan has more than 15 years of experience in environmental consulting and research. He has expertise in food web, bioenergetics, and transport and fate modeling of radionuclides, metals, and organics. Dr. Rowan has served on advisory boards for IAEA, NCRP, and EPRI and has managed many projects, both large and small, for government and industry. He holds a Ph.D. in Biology from McGill University, and an M.S. and B.S. in Geology, both from The Ohio State University.

Recent/Upcoming Publications

Bessinger, B.A., Redding, B., and Y.W. Lowney. 2007. Comments on “Release of Arsenic to the Environment from CCA-Treated Wood. 2. Leaching and Speciation during Disposal.” Environ. Sci. Technol. 41 (1):345–346.

Bigham, G., W. Chan, M. Dekermenjian, and A. Reza. Accepted. Indoor concentrations of mercury vapor following various spill scenarios. Environ. Foren.

Booth, P., N. Gard, S. Law, and R. Davis. 2007. Sustainability: Considerations for including eco-assets in a company’s bottom line. ABA Section of Environment, Energy, and Resources’ Climate Change, Sustainable Development, and Ecosystems Committee Newsletter 11(1):7–11.

Chan, W.R., W. Nazaroff, P. Price, and A. Gadgil. 2007. Effectiveness of urban shelter-in-place–II: Residential districts. Atmos. Environ. 41:7082–7095.

Goldstone, J.V., H.M.H. Goldstone, A.M. Morrison, A.M. Tarrant, S.E. Kern, B.R. Woodin, and J.J. Stegeman. In press. Cytochrome P450 1 genes in early deuterostomes (tunicates and sea urchins) and vertebrates (chicken and frog): Origin and diversification of the CYP1 gene family. Molec. Biol. Evol. MBE Advance Access published online October 4, 2007.

Johnson, M., M. Korcz, K. von Stackelberg, and B. Hope. In preparation. Spatial analytical techniques for risk based decision support systems. In: Decision Support Systems for Risk Based Management of Contaminated Sites. To be published by Springer Verlag.

Kay, D.P., J.L. Newsted, M.T. BenKinney, T.J. Iannuzzi, and J.P. Giesy. (In press). Passaic River sediment interstitial water Phase I toxicity identification evaluation. Chemosphere.

Menzie, C., P. Booth, S. Law, and K. von Stackelberg. In preparation. Defining the problem. In: DSSs for Inland and Coastal Waters Management section, Decision Support Systems for Risk Based Management of Contaminated Sites. To be published by Springer Verlag.

Murray, K.J., and B.M. Tebo. 2007. Cr(III) is indirectly oxidized by the Mn(II)-oxidizing bacterium Bacillus sp. strain SG-1. Environ. Sci. Technol. 41:528–533.

Murray, K.J., S.M. Webb, J.R. Bargar, and B.M. Tebo. 2007. Indirect oxidation of Co(II) in the presence of the marine Mn(II)-oxidizing bacterium Bacillus sp. strain SG-1. Appl. Environ. Microbiol. 73(21):6905–6909.

O’Reilly, K. 2007. Science, policy, and politics: The impact of the information quality act on risk-based regulatory activity at the EPA. Buffalo Environ. Law J. 14(2):249–288.

Shock, S.S., B.A. Bessinger, Y.W. Lowney, and J.L. Clark. 2007. Assessment of the solubility and bioaccessibility of barium and aluminum in soils affected by mine dust deposition. Environ. Sci. Technol. 41 (13):4813–4820.

von Stackelberg, K., M. Nelson, B. Southworth, J. Cura, and T. Bridges. In press. Evaluation of sources of uncertainty in a subset of risk assessments conducted for the U.S. Army. Integ. Assess. Environ. Manage.

Recent/Upcoming Conferences and Presentations

IEEE Symposium on Product Compliance Engineering Longmont, CO. October 22–23, 2007

The influence of regulatory changes on unique product designs.BenKinney, M., A. Arora, and J. Swart.

23rd Annual International Conference on Soils, Sediments, and Water University of Massachusetts at Amherst October 15–18, 2007

Identification of natural gas sources using geochemical forensic tools.Boehm, P., T. Saba, and L. Benton.

About Exponent

Exponent is a leading engineering and scientific consulting firm dedicated to providing solutions to complex problems.

Our environmental consulting services include:

•Ecological risk assessment•Environmental forensics •Environmental liability

management•Epidemiology•Human health risk

assessment/toxicology•Industrial hygiene/mold

investigations•Natural resource damage

assessment•Occupational medicine/

health•Product stewardship•Site investigation and

remediation.

Please visit our website, www.exponent.com, for information on all of our consulting services.

(888) [email protected] regional and 3 international offices

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North Atlantic Chapter of Society of Environmental Toxicology and Chemistry Bristol, RIJune 13–15, 2007

Experience in applying the weight-of-evidence approach to aquatic sites contaminated with heavy metals.McArdle, M.E., C.A. Menzie, and S. Kane-Driscoll.

Methyl Bromide Alternatives ConferenceSan Diego, CAOctober 29–November 1, 2007

Modeling and measurement of methyl bromide at food processing facilities.Winegar, E., R. Reiss, and W.R. Chan.

International Symposium on Nanotechnology in Environmental Protection and Pollution Fort Lauderdale, FLDecember 11–13 2007.

The ecological effects of nanomaterials: Are new stressors associated with new technologies?”Ziccardi, L., M. McArdle, and Y. Lowney.

environmental perspectives - exponent · nanomaterials in fertilizers. some of these studies...

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