July 2006 Symposium on Nanotechnology and the Environment: Session 4: Fate and Transport of Nanomaterials
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July 12, 3:30-4:30 PM
Dr. Gregory V. Lowry, Carnegie Mellon University, Associate Professor, Civil and Environmental Engineering, Pittsburgh Pennsylvania
AbstractThe most evident near-term element of nanotechnology is the rapidly developing nanomaterials industry. Commercial applications of nanomaterials currently or will soon include nanoengineered titania particles for sunscreens and paints, carbon nanotube composites in tires, silica nanoparticles as solid lubricants, reagents for groundwater remediation, and protein-based nanomaterials in soaps, shampoos, and detergents. The production, use, and disposal of nanomaterials will inevitably lead to their appearance in air, water, soils, or organisms. The potential toxicity of engineered nanomaterials to indigenous microorganisms, to aquatic organisms, and to humans remains uncertain. Responsible uses of manufactured nanomaterials in commercial products and environmental applications, as well as prudent management of the associated risks, require a better understanding of their mobility, bioavailability, and impacts to a wide variety of organisms.
The matter of determining whether or not a substance is "dangerous" involves determining any toxicity presented by the material, but also the degree to which the material will come into contact with organisms. A higher mobility of nanomaterials in the environment implies a greater potential for exposure as nanomaterials are dispersed over greater distances and their effective persistence in the environment increases. There is an urgent need to evaluate the fate and transport of nanomaterials in the environment and to consider the possible impacts of nanomaterial fabrication and the manner in which conventional chemical feedstocks and wastes will be handled.
Several processes will control the fate and transport of nanomaterials in the environment including redox processes, aggregation, and deposition onto particles. Redox transformations may decrease or increase the toxicity of a nanoparticle. The propensity to attach to surfaces or to form aggregates will limit the mobility of nanomaterials in the environment. Natural and synthetic polymers or surfactants adsorbed onto nanoparticles, however, can dramatically increase their mobility. Environmental geochemical conditions, e.g. pH, ionic strength, and ionic composition can greatly affect the rate and extent of each of the processes controlling the fate and transport of engineered nanomaterials in the environment. The effect of each of these geochemical conditions on the fate and mobility of engineered nanomaterials in the environment is discussed. Implications of these findings on the environmental risks that engineered nanomaterials may pose and on the proper disposal and treatment of engineered nanomaterials.