How Safe are Nanoparticles?

Iron oxide nanoparticles entangled with carbon nanotubes. (photo credit: Dr. Peng Wang)

Iron oxide nanoparticles entangled with carbon nanotubes. (photo credit: Dr. Peng Wang)

Think small. Really small. Thin as the wispiest wisp of hair. Now imagine something 100,000 times smaller than that wispy strand of hair. That’s nanoscale.

Manufacturers are developing new products – electronics, fabrics, medicine, foods – that incorporate materials made at that minuscule scale. Yet little is known about how some of these nanoscaled particles interact with and/or affect the environment. The UC Center for the Environmental Implications of Nanotechnology (UC CEIN) was established in 2009 to find out.

Funded with $24 million from the National Science Foundation, the interdisciplinary center is based at UCLA and led by researchers there and at UC Santa Barbara. UCSB’s Arturo Keller, professor of environmental science and management, is associate director of the new center.

“Nanoparticles can be seen only at the level of electron microscopy,” Keller explains. “The UC CEIN is concerned with how those tiny particles, particularly those that are manufactured, interact with the environment. We are not as concerned with natural nanoparticles like clays.”

Generally, there are more than 80,000 chemicals in use today, and there is good toxicity information on perhaps only 1,000 of those, Keller says. There is very little toxicological information about nanomaterials.

“Since we are at the beginning of using nanoparticles in industry, now is the time to test them, especially since many of these materials are planned for use in medicine or environmental applications. As a consumer it would be good to know if there are nanoparticles in the goods you purchase, and how they interact with other substances. Science always wants to be careful,” Keller explains.

Researchers already know that substances have different properties at the nanoscale versus larger particles. For example, gold nanoparticles interact with light differently depending on the size, shape and composition of the particle, Keller says. Although we typically think of gold as a bright yellow material, at the nanoscale it can exhibit a rainbow of colors, depending on the size of the particles. Thus, it is possible that the nanoparticles will have different toxicity based on these characteristics as well.

There are other properties that are likely to cause problems. For example, we know that most positively charged particles are toxic, because they interact with cell membranes, which are negatively charged. Thus, guidelines for designing nanomaterials that are less toxic will take this type of information into consideration.

UCSB scientists are studying five specific classes of nanomaterials already in use, including metals, metal oxides, semiconductors, carbon-based materials, silica-based materials, and combinations of them. These include gold, silver, carbon nanotubes, titanium dioxide, zinc oxide, cerium oxide, and cadmium selenide.

Nanotubes are novel cylindrical structures of extraordinary strength. Scientists are exploring numerous potential uses for them in nanotechnology, electronics, materials science and optics, among other areas. They could also be toxic under certain conditions.

The research is just beginning, but Keller says they have already seen some interesting results:

  • Titanium dioxide, a white pigment used widely in paint, makeup, sunscreens, and food colorings, is generally not very toxic and may even have some beneficial effects, for example algae benefit from it;
  • zinc oxide, also widely used in numerous materials and products including sunscreens, plastics, lubricants, adhesives and batteries, is quite toxic to algae and other aquatic organisms at certain concentrations, though not necessarily to humans;
  • cerium oxide, used as a fuel additive, especially in diesel to improve combustion, is generally not very toxic;
  • and cadmium selenide, found in quantum dots (a semiconductor used in light-emitting diodes, transistors, and solar cells), shows toxicity that moves up through the food chain. It is also being considered for pharmaceutical applications for medical imaging, where it would be ingested and excreted, and could get into water systems.

“We don’t see these substances in the environment much yet, but we also don’t have the equipment to measure them out there. The state of California is beginning to pay attention to nanomaterials, and has asked industry to self-report which nanoparticles they are using and how they are using them,” Keller says. “It’s a very ambitious project.”

Keller’s own research is focused on substances in water, and so his lab will be looking at these nanoparticles and their effects on marine and freshwater environments.

While UCSB scientists test the substances in different environmental media, UCLA researchers are developing rapid-testing protocols, models for how nanoparticles may affect humans and ecosystems, plus a framework for risk assessment.

“A measure of the success of the center will be whether we get people talking to each other who don’t normally interact, like biologists, environmental scientists, physicists, and material scientists ” Keller says. “By talking to each other, we can advance faster in the design of safer nanomaterials.”

Creating awareness is another goal. Recent surveys done by Barbara Herr Harthorn, director of the Center for Nanotechnology in Society at UCSB, indicate about 70 percent of the public has no opinion on nanoparticles.

“We have a chance to shape people’s understanding of this,” Keller says.

Researchers from UC Davis, UC Riverside, Columbia University, Germany’s University of Bremen, Nanyang Technological University in Singapore, and the University of British Columbia are also contributing to work done at the UC CEIN.