The Fate of Carbon-Based Nanomaterials in the Environment

Sean C. Smith; Debora F. Rodrigues

doi:10.4172/2155-6199.1000e129

ISSN: 2155-6199

Journal of Bioremediation & Biodegradation

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The Fate of Carbon-Based Nanomaterials in the Environment

Sean C. Smith and Debora F. Rodrigues^*
Department of Environmental Engineering, University of Houston, USA
Corresponding Author :	Debora F Rodrigues University of Houston 4800 Calhoun Road N136 Engineering Bldg. 1 Houston, TX 77204-4003, USA Tel: (713) 743-1495 Fax: (713) 743-4260 E-mail: dfrigirodrigues@uh.edu
Received: November 12, 2012; Accepted: November 15, 2012; Published: November 17, 2012
Citation: Smith SC, Rodrigues DF (2012) The Fate of Carbon-Based Nanomaterials in the Environment. J Bioremed Biodeg 4:e129. doi:10.4172/2155-6199.1000e129
Copyright: © 2012 Smith SC, et al. This is an open-a ccess article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
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Carbon-based nanomaterials such as carbon nanotubes, fullerenes, and graphene have undergone an explosion of interest in recent years. New, easy production methods and many new uses of these materials in vital industries, most notably possible roles as semiconductors, have initiated increased volumes of manufacture. Even higher levels are likely to eventuate as these new applications are brought to the market. As tons of materials are produced, however, their inevitable environmental release becomes cause for concern. The behavior of these synthetic substances in soil and water systems, as well as their effects on local microbial ecosystems, is largely unknown. Therefore, it is imperative that we understand how these nanomaterials affect the environment before they become widespread, so that they may be utilized, transported, and disposed off safely.

Studies with pure microbial cultures have shown that several carbonbased nanomaterials have significant antimicrobial activity, and a focus area of research is to harness this property for industrial applications [1-3]. Concentrations as low as 150 mg/L have demonstrated toxic effects on established microbial communities, although the effects are known to vary depending on the material and the class of organism [4]. Little is known, however, about whether these materials cause lasting damage to topsoil, aquifer or wastewater microbial ecosystems, which will almost certainly sustain localized contamination, at the least, in the near future. A recent study has suggested that multi-walled carbon nanotubes can adversely affect microorganisms responsible for conducting biological functions in waste water treatment [5]. This study, however, demonstrated that very high concentrations are necessary in order to affect the microbial community, which shows that the toxic effects observed in studies with pure cultures are not similar to the effects in the environment.

Knowledge of the long term fate and transport of carbon-based nanomaterials in the environment is also sparse. Some studies suggest some materials are transformed into less reactive forms, although it remains to be seen whether this can be replicated in situ [6,7]. Carbon nanomaterials are chemically similar to polyaromatic hydrocarbons which typically resist degradation, but can still be degraded by microorganisms. While the relatively large size of nanomaterials may imply physical degradation if biodegradation fails, it is likely that oligo-aromatics would be the final product. These oligo-aromatics can potentially be further biodegraded by microorganisms. However, it is also questionable whether carbon nanomaterials will even be physically available for biodegradation. Most are extremely hydrophobic, and thus likely to be sequestered in porous media. This in turn raises the possibility of bioaccumulation. Are carbon-based nanomaterials capable of causing a new silent spring?

Direct human toxicity is a primary concern as well. Some of these substances exhibit cytotoxic properties in human cells, which is cause for alarm if biomagnification of the active forms can be demonstrated [8]. Even ignoring this extreme possibility, however, there is plenty of opportunity for human exposure to these nanomaterials, if care is not taken to prevent their release. The effects this could have on human populations must be understood in order to properly assess risks of implementation.

Carbon nanomaterials show great promise for a number of revolutionary applications. Much remains still unknown about their effects in the environment, but preliminary results suggest that nothing should be left to chance. Widespread use and disposal of these materials must be carefully monitored until more is known about their interactions with life on the micro- and macro-scale, and their fate in complex environments.