Graphene is one popular nanomaterial. Made from single-atom-thick sheets of carbon, it is the strongest material ever tested and boasts superlative electronic properties, too. After a decade of research, it is on the verge of moving from the laboratory into commercial technologies, perhaps appearing soon as lightweight airplane parts or batteries with incredible capacities.

So now might be a good time to anticipate potential risks posed by graphene, before workers are exposed to it or it gets into the water supply, says Sharon Walker, an environmental engineer at the University of California, Riverside. In research described in May in Environmental Engineering Science, Walker's group observed how one form of the material, graphene oxide, behaves in water.

Walker found that in a solution mimicking groundwater, graphene oxide clumped and sank, suggesting it is not a risk. That was not the case in a solution mimicking surface water, which includes lakes and storage tanks for drinking water. Instead of falling to the bottom, it stuck to the organic matter produced by decomposing plants and animals and floated around. Such mobility might increase the chances that animals and people could ingest graphene oxide, which has shown toxicity in some early studies in mice and human lung cells.

“This is a good first glimpse of how graphene might behave in the water supply,” Walker says. If these materials do turn out to pose a risk to human health, their mobility in surface water could be a big problem. She hopes these studies are early enough in the conversation to inform how industry develops graphene and its derivatives and how agencies, such as the Environmental Protection Agency, regulate them.