Future Worker Safety Concerns Prompt Study

Dr. Nancy Monteiro-Riviere’s research is much more than skin deep. That’s the very reason her research needs to be done, she says. The College of Veterinary Medicine professor studies the effects of compounds—from drugs to chemicals to cosmetics—that come in contact with the skin. Her latest concern: nanoparticles.

“We can’t generalize and say that all nanomaterials are good or bad. ...If they are made properly, hazard may not be an issue.”

These nanoscale structures are being added to products like sunscreen, paint, and car wax for improved properties like UV protection and mildew resistance. But Monteiro-Riviere says more studies assessing whether nanoparticles are a health hazard are needed to protect workers and consumers who come into contact with them. “People remember asbestos and PCBs, and they want to know about potential problems before health issues occur,” she says. “We need to ensure they are made properly so they don’t negatively affect consumers.”

With funding from the National Academies’ KECK Futures Initiative and the U.S. Environmental Protection Agency, Monteiro-Riviere looked at multi-walled carbon nanotubes to determine their impact on skin cells. Within 24 hours of exposure, almost 60 percent of the skin cells in the culture were found to have taken up the nanotubes. The affected cells showed more irritation and died more quickly than other cells, she says. Protein expression revealed that 36 proteins were affected by the nanotubes, including those controlling metabolism and cell growth.

For tests on carbon nanoparticles known as buckyballs, former graduate student Jillian Rouse created a motorized, hinged device to mimic the flexing of skin at a joint. She and Monteiro-Riviere attached pig skin–anatomically and physiologically similar to human skin–to the device to assess the penetration of derivatized buckyballs (see figure below). The flexing action was shown to increase the rate of skin penetration which, she says, points to a potential exposure problem at the wrists or other joints of workers using nanoparticles in manufacturing.

When Monteiro-Riviere examined quantum nanoparticles themselves, she found size isn’t always a factor in determining the rate of penetration through the skin and into cells. Instead, a positive or negative charge on the particle’s surface or an exterior coating plays the key role in how the particles work their way through the layers of skin or into skin cells. “We can’t generalize and say that all nanomaterials are good or bad,” she says. “It depends on their physicochemical properties. If they are made properly, hazard may not be an issue.”



Dr. Nancy Monteiro-Riviere and graduate student Leshuai Zhang run tests on skin cell cultures to measure the penetration of nanoparticles.

Confocal scanning microscopy images of three skin samples showing derivatized buckyballs penetrating skin layers after various time intervals. For each sample, row (a) is normal skin; (b) shows fluorescence penetration; (c) shows fluorescence intensity.