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As super-small carbon cylinders slip their way into products like computer chips and smartphones, the potential risk to workers, consumers and the post-landfill environment is coming under scrutiny. New research from a group of University of Florida scientists may have identified a way to minimize some of those hazards.
Jean-Claude Bonzongo, one of the authors of a new paper outlining some of the findings, said this work focuses on some of the chemicals used to keep the ultra-tiny carbon nanotubes from sticking together. That type of agglomeration is a problem, he said, because it affects some of the very properties that make these tubes so useful.
But these chemicals, called surfactants, can be toxic on their own, he said. A commonly used surfactant, sodium dodecyl sulfate, “is so toxic even by itself,” said Bonzongo, an associate professor of environmental engineering at Florida. “It kills everything.”
Adding carbon nanotubes made things worse.
“We found out that most of the suspensions produced with surfactants were highly toxic,” Bonzongo said, to both marine organisms and human cells.
What to do? Bonzongo and his co-authors are working with a number of alternatives. Their new paper, recently published in the journal Nanotoxicology, focuses on gum arabic. They found that the substance is not only non-toxic on its own, but actually mitigates the toxicity of the nanotubes until a high concentration is reached.
While there is some loss of efficacy of the nanotubes, Bonzongo said, it’s relatively minor.
This research — which is ongoing — could offer manufacturers and researchers a better way to build safer workplaces and products.
Nanotechnology leverages the often-unique properties of super-small particles (a nanometer is a billionth of a meter) to create products with amazing qualities. These materials can make better batteries or lighter and stronger bike frames, as well as new medical instruments and medicines that can save lives. They’re increasingly common in consumer products, from “mineral-based” sunscreens to stain-repellent pants to boat paints that resist algae growth.
Nanomaterials are believed to hold great promise for a wide variety of applications. Their ultra-tiny size also gives them different properties; scientists are struggling to figure out whether that can make them dangerous in the process, and how and why it happens.
Carbon nanotubes have raised alarm because they’re small enough to be inhaled, and potentially become lodged in the lungs. Studies on rats show they can cause inflammation, which could lead to cancer. While the National Institute for Occupational Safety and Health has issued draft guidelines for protecting workers, there is no formal regulation by the U.S. government.
The U.S. Environmental Protection Agency, at least so far, regulates carbon nanotube manufacturers on what’s essentially a case-by-case basis.
“In the U.S., we don’t really have regulations in place on how to deal with nanomaterials and how to deal with waste nanomaterials,” Bonzongo said. “Most labs when people do research on nanomaterials, the waste is kind of discarded without worrying about these things.”
Consumers don’t seem to be at much risk, he said. Your iPad might contain carbon nanotubes, but you won’t come into contact with them touching the screen. It’s a different story for workers who make these materials, and the environment around us after they’re tossed away.
“Everything we’re doing right now is just going through the sink and not being discharged in a careful manner,” Bonzongo said.
Surfactants are used for dispersal — they’re common in laundry detergents, where they draw the dirt out and make sure it washes down the drain. Using them to keep carbon nanotubes separated is a different thing, Bonzongo said.
“It’s just borrowing an existing technology — except in past technology, you would not carry around that surfactant,” he said. “You move on and take care of the surfactant as a waste. In this case here, you’re moving along with both carbon nanotubes and the surfactant toward the application.”
He said he and his colleagues hope to start talking to manufacturers about adopting the less-toxic surfactants to minimize potential damage. They’re part of a larger effort to look at the full life cycle of a nano-enabled product—from manufacturing to disposal — to assess the risks at each stage.
The other co-authors of the paper are Sejin Youn, Randy Wange, Jie Gao, Anna Hovesyan, Kirk Ziegler and Gabriel Bitton.
For example, Bonzongo said, laboratory results seem to indicate that carbon nanotubes show a “significant decrease in toxicity” in simulated environmental releases, suggesting that they might not be hazardous in a landfill. But those are not real life, a fact nano safety researchers know all too well.
“What we can’t really predict is a nanotube in the environment for, say, five years, what it will be like,” Bonzongo said.
