Researchers at the University of California at Riverside (UCR) have published the results of what they claim is the first study featuring the environmental impact from graphene use. From the April 29, 2014 news item on ScienceDaily,
In a first-of-its-kind study of how a material some think could transform the electronics industry moves in water, researchers at the University of California, Riverside Bourns College of Engineering found graphene oxide nanoparticles are very mobile in lakes or streams and therefore may well cause negative environmental impacts if released.
Graphene oxide nanoparticles are an oxidized form of graphene, a single layer of carbon atoms prized for its strength, conductivity and flexibility. Applications for graphene include everything from cell phones and tablet computers to biomedical devices and solar panels.
The use of graphene and other carbon-based nanomaterials, such as carbon nanotubes, are growing rapidly. At the same time, recent studies have suggested graphene oxide may be toxic to humans. [emphasis mine]
As production of these nanomaterials increase, it is important for regulators, such as the Environmental Protection Agency, to understand their potential environmental impacts, said Jacob D. Lanphere, a UC Riverside graduate student who co-authored a just-published paper about graphene oxide nanoparticles transport in ground and surface water environments.
I wish they had cited the studies suggesting graphene oxide (GO) may be toxic. After a quick search I found: Internalization and cytotoxicity of graphene oxide and carboxyl graphene nanoplatelets in the human hepatocellular carcinoma cell line Hep G2 by Tobias Lammel, Paul Boisseaux, Maria-Luisa Fernández-Cruz, and José M Navas (free access paper in Particle and Fibre Toxicology 2013, 10:27 http://www.particleandfibretoxicology.com/content/10/1/27). From what I can tell, this was a highly specialized investigation conducted in a laboratory. While the results seem concerning it’s difficult to draw conclusions from this study or others that may have been conducted.
Dexter Johnson in a May 1, 2014 post on his Nanoclast blog (on the IEEE [Institute of Electrical and Electronics Engineers] website) provides more relevant citations and some answers (Note: Links have been removed),
While the UC Riverside did not look at the toxicity of GO in their study, researchers at the Hersam group from Northwestern University did report in a paper published in the journal Nano Letters (“Minimizing Oxidation and Stable Nanoscale Dispersion Improves the Biocompatibility of Graphene in the Lung”) that GO was the most toxic form of graphene-based materials that were tested in mice lungs. In other research published in the Journal of Hazardous Materials (“Investigation of acute effects of graphene oxide on wastewater microbial community: A case study”), investigators determined that the toxicity of GO was dose dependent and was toxic in the range of 50 to 300 mg/L. So, below 50 mg/L there appear to be no toxic effects to GO. To give you some context, arsenic is considered toxic at 0.01 mg/L.
Dexter also contrasts graphene oxide with graphene (from his May 1, 2014 post; Note: A link has been removed),
While GO is quite different from graphene in terms of its properties (GO is an insulator while graphene is a conductor), there are many applications that are similar for both GO and graphene. This is the result of GO’s functional groups allowing for different derivatives to be made on the surface of GO, which in turn allows for additional chemical modification. Some have suggested that GO would make a great material to be deposited on additional substrates for thin conductive films where the surface could be tuned for use in optical data storage, sensors, or even biomedical applications.
Walker’s [Sharon L. Walker, an associate professor and the John Babbage Chair in Environmental Engineering at UC Riverside] lab is one of only a few in the country studying the environmental impact of graphene oxide. The research that led to the Environmental Engineering Science paper focused on understanding graphene oxide nanoparticles’ stability, or how well they hold together, and movement in groundwater versus surface water.
The researchers found significant differences.
In groundwater, which typically has a higher degree of hardness and a lower concentration of natural organic matter, the graphene oxide nanoparticles tended to become less stable and eventually settle out or be removed in subsurface environments.
In surface waters, where there is more organic material and less hardness, the nanoparticles remained stable and moved farther, especially in the subsurface layers of the water bodies.
The researchers also found that graphene oxide nanoparticles, despite being nearly flat, as opposed to spherical, like many other engineered nanoparticles, follow the same theories of stability and transport.
I don’t know what conclusions to draw from the information that the graphene nanoparticles remain stable and moved further in the water. Is a potential buildup of graphene nanoparticles considered a problem because it could end up in our water supply and we would be poisoned by these particles? Dexter provides an answer (from his May 1, 2014 post),
Ultimately, the question of danger of any material or chemical comes down to the simple equation: Hazard x Exposure=Risk. To determine what the real risk is of GO reaching concentrations equal to those that have been found to be toxic (50-300 mg/L) is the key question.
The results of this latest study don’t really answer that question, but only offer a tool by which to measure the level of exposure to groundwater if there was a sudden spill of GO at a manufacturing facility.
While I was focused on ingestion by humans, it seems this research was more focused on the natural environment and possible future poisoning by graphene oxide.
Here’s a link to and a citation for the paper,
Stability and Transport of Graphene Oxide Nanoparticles in Groundwater and Surface Water by Jacob D. Lanphere, Brandon Rogers, Corey Luth, Carl H. Bolster, and Sharon L. Walker. Environmental Engineering Science. -Not available-, ahead of print. doi:10.1089/ees.2013.0392.
Online Ahead of Print: March 17, 2014
If available online, this is behind a paywall.