Where There’s Smoke, There’s ... Nano?

A fire engulfs your home, torching a mattress and sofa as it tears through the rooms. Your life is spared, thanks to flame-retardant chemicals in the couch foam.

But did the smoke you inhaled contain super-small particles that might hurt you later?

That kind of scenario is what keeps scientists who study the safety of ultra-tiny “nanoparticles” toiling in their labs. As more and more consumer products contain shrunken versions of substances from carbon to silver, these researchers are digging into their impact on people, animals and the environment.

In the case of fire, the question is whether some of the materials that could be used to make furniture less flammable, including carbon nanotubes, can wind up in the smoke when it does burn. For other applications, including building materials, what matters is how a plastic that incorporates nanoparticles holds up under conditions such as sunlight, rain or other weathering.

So these scientists are trying to duplicate real-world conditions in the lab: lighting foam on fire, sanding concrete and baking plastics under UV lights. What they’re finding is that nano-infused products are resilient, but not perfect.

NIST PhotoGetting answers about the full lifespan of a product is important, because of both the short-term implications and the long-term possibilities, said Tinh Nguyen (pictured), a physical scientist in the Building and Fire Research Laboratory at the National Institute of Standards and Technology. Nguyen has recently studied plastics strengthened with nanomaterials.

“Maybe in my lifetime, we don’t see them in the water, but maybe in 50 years, our children and grandchildren will have to deal with that,” Nguyen said of the array of nano-sized substances now being used in products ranging from sweat socks to sunscreens.

It’s an increasingly important issue in the burgeoning field of nanotechnology, which leverages the often-unique properties of the super-small particles to create products with amazing properties. These materials can make better batteries or lighter and stronger bike frames, as well as new medical instruments and medicines that can save lives.

These nanomaterials are believed to hold great promise for a wide variety of applications. But shrinking these substances can change their properties, and scientists are struggling to figure out whether, how and why that shift can make them dangerous in the process.

Getting a sense of what happens to a product over the course of its lifetime—from the factory to the landfill—helps shape the picture of its safety at each point.

Nguyen and his co-authors have found, for example, that nano-sized silicon dioxide can be released from its plastic encapsulation when exposed to UV radiation to simulate sunlight, which erodes the surface. In similar studies, carbon nanotubes seem to come together in a layer on the new surface, but it’s difficult to tell whether they escape from the polymer, Nguyen said.

Nguyen and other researchers presented their work during sessions on safety and consumer products at the recent TechConnect World conference in Boston.

One of Nguyen’s NIST colleagues, Nasir Uddin, discussed a study that found nanoparticles in the char left behind from a fire, raising questions about whether the cleanup from a conflagration might be dangerous. A researcher with a French safety agency, Dominique Fleury, talked about how his team’s experiment found “isolated” carbon nanotubes in the smoke when a polymer embedded with multi-walled carbon nanotubes was baked in an oven at more than 1,000 degrees.

Fleury called the team’s results evidence of a “new safety issue” in thinking about where and how to use carbon nanotubes.

The idea that nano-products release some of their star ingredients isn’t new. Researchers studying nanosilver, prized for its antibacterial properties, have found it leaching into the wash water and turning up in end-stage sewage sludge, as well as escaping into the air from aerosol spray applications. Others are busy looking at what happens to nano-sized titanium dioxide and zinc oxide, which are increasingly used in sunscreens and other cosmetics.

Fire, weathering and other exposures are slightly different, however, since they’re not something that happens immediately. Fire testing is especially important for discerning the best way to dispose of nano-enabled products, since common trash is often burned. Weathering is critical to understand for building products, since carbon nanotubes and other substances are becoming more prevalent in reinforced concerete, steel and other materials.

With that in mind, a team at the chemical company BASF, led by Wenden Wohlleben, ran several composite materials through their paces.

Researchers are focusing “a lot on the question of what is released,” he said. “What is it that comes free?”

The answer, in Wohlleben’s study: not much. For example, when his team used sandpaper to scrape at nano-reinforced concrete, then tested the dust, they found that “the sample stayed intact, but the sandpaper degraded.”

Gwyneth K. Shaw PhotoAnother scientist, Andrew Whelton, an assistant professor of civil engineering at the University of South Alabama, is focused on nano-plastics and our food and water supply. In concert with researchers from the U.S. Food and Drug Administration, Whelton (pictured) has looked into what’s in our food packaging, and what might come out.

“The first question that consumers ask is: Will these leach out into my food?” he said.

Whelton’s research usually focuses on potable water infrastructure, also known as the vast network of pipes that deliver our drinking water. While he said he doesn’t know of any plastic pipes that currently use nanoparticles, he anticipates that pipe manufacturers will be interested in what the technology can do for them.

If manufacturers could make a thinner, lighter pipe, that would save money, Whelton said. With the nation’s water infrastructure in need of major renovations—he put the price tag in the neighborhood of $200 billion—those changes, if they come, could have huge implications, he said.

Pipe companies rely on a single not-for-profit company to test pipes and other components for safety, Whelton said.

“But the testing doesn’t include nanoparticles, because there are no limits for nanoparticles in drinking water,” he said. “We’re trying to advance the science, so that people can make decisions about what’s out there.”





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