July 2006 Symposium on Nanotechnology and the Environment: Overview of Nanotechnology and the Environment: Highlights, Question and Answer Session Session
July 12, 9:30-10:30 AM
Dr. Vicki Colvin, Professor of Chemistry and Professor of Chemical Engineering, Rice University
Highlights Nanoparticles are defined as being less than 100 nm in size. Such small particles have huge surface areas, which can lead to increased reactivity. A vast array of nanomaterials is possible, each with its own exposure scenarios and applications. Manufacturing processes can allow for very specific control over size and chemical composition. Some examples of nanomaterials in commerce include sunscreens formulated with nano-sized TiO2 and ZnO to be transparent, tennis balls lined with ceramic nanoparticles to enhance gas impermeability, and fabrics embedded with nanowhiskers to be stain/wrinkle resistant.
Balancing risks and benefits is key to the future of nanotechnology. We must be proactive in understanding risks, and ask difficult questions about risks/benefits for any new technology. We must be informed about implications as well as applications.
There are important applications for nanotechnology in drinking and waste water treatment – for example, magnetic filtration to treat arsenic in drinking water. The magnetic properties of iron oxide (magnetite) are such that arsenic strongly sorbs onto iron oxide. Smaller size improves magnetization because all dipoles point in the same direction. This can be applied to filtration by using magnets to control flow and distribution of the nano-sorbent. Advantages to magnetic filtration include the fact that there are no pressure gradients and no fouling of filters. Obstacles to the commercialization of this treatment system include the need for a testing site, a market, public confidence in the safety of the system, and funds for development.
Nanoparticles can interact with proteins, can be bioactive, and can be difficult to remove from environmental matrices or living organisms. There can be ecological, occupational, and residential risks for applications. Additionally, smaller materials are not necessarily more mobile; surface interactions can impact soil mobility. Strong interactions with clays, soils, etc. are possible. One example is C60 fullerenes. Fullerenes typically cluster in water, although the clustering is affected by water impurities (dirt, humic acid, etc.) and preparation conditions. Additionally, developmental toxicity investigations of C60 fullerenes in zebra fish indicate that oxidative stress can occur.
It is important to know the mechanisms by which nanomaterials behave in order to engineer safe nanoparticles. EPA has a crucial role to play in nanotechnology. Agency collaborations with researchers can help determine research directions and identify problems.
Question-and-Answer Session A questioner asked how one sorts out conflicting information on mechanisms of toxicity of nanomaterials (e.g., sometimes reactive oxygen species (ROS) are the issue; sometimes surface area is the issue). Dr. Colvin replied that we aren’t yet sure how to evaluate these things. Complete and careful characterization is essential; peer-reviewed journals should encourage publication of characterization papers. Researchers should participate in setting standards for characterization so that data from different studies can be compared. We can’t compare papers, because nanoparticles are made and characterized differently each time. Quality control is an issue of emergent technology. A questioner asked about developing a strategy for gleaning data from incomplete datasets. Dr. Colvin indicated that there is no way to conduct conventional risk assessments for nanomaterials and obtain full data sets. Testing of nanomaterials needs to be performed, especially by companies that already have products on the market. In order to know about the toxicity of nanoparticles as a regulator, you need structure/function relationships and predictive tools. A commenter suggested parallel research tracks: 1) generic research to determine mechanistic attributes; and 2) product development on a specific product, investigating toxicity endpoints as part of the development process.
A questioner asked, what past lessons can be used to inform the present situation? Dr. Colvin noted that risk communication is very important; we should always focus on giving the public the highest level of information possible as quickly as possible, and without spin. The key is to educate consumers on risks and benefits. Engaging the public early in the process is important to public acceptance.
A questioner asked what kind of testing has been done on materials that are in the marketplace now. Dr. Colvin indicated that it depends on whether the materials considered new. If they are not new, then no new testing is required. A questioner wondered about the difference between nanotechnology and colloid chemistry. Dr. Colvin indicated that the understanding of nanoparticles in liquids is based on colloid chemistry, but colloid chemistry does not explain structure/function of nanoparticles. Nanomaterials can be highly structured, often with additional optical and/or magnetic properties. One can’t rely on colloids to predict all nanoparticle behavior.
A questioner asked how we develop principles for being honest about what we know/don’t know about nanotechnology. Dr. Colvin responded that people want to hear either “these are the risks,” or “we don’t know what the risks are.” In development of other new technologies, investigators have engaged social scientists and ethicists early on (e.g., genome project). You can’t say “this is new and cool, so give me money to develop it” and at the same time say that it is no different from existing materials and does not need additional scrutiny. An industry representative commented that his industry is developing a product stewardship and framework for new products for health and environmental effects. A commenter also noted that the Federal government is doing work in this area (e.g., a report outlining needed information on environmental health and safety of nanoparticles, NSETC committee).