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Environmental Factor, October 2012

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Challenges persist in the critical task of determining safety of nanomaterials

By Cindy Loose

Christopher Weis, Ph.D., Eric Saunders, and Mary Popovech

NIEHS representatives enjoy the fresh air during a workshop break. Shown, left to right, are Weis, Saunders, and Popovech. “[Nanotoxicology is] uncharted territory but, with preliminary data, we are definitely seeing changes in gene expression in key oxidative stress genes in both the lungs and livers of animals exposed to silver nano particles,” Popovech said. (Photo courtesy of Cindy Loose)

Experts from industry, academia, unions, and government explored questions about occupational safety of nanomaterials, at a two-day workshop Sept. 10-11 in Washington, D.C.

“The diversity and variety of engineered nanomaterials is tremendous, so the problem is particularly complex,” said NIEHS Senior Advisor Christopher Weis, Ph.D., during his presentation on concerns about how nanomaterials may affect living cells and organs.

Nanomaterials: promise and concerns

Already, thousands of products — clothing, food, sporting goods, and medicines, to name a few — are manufactured using engineered nanomaterials (ENMs). ENMs are extremely small, with at least one dimension no larger than approximately 1 to 100 nanometers. One nanometer is about 100,000 times smaller than the diameter of a human hair.

The promise of nanotechnology is great. Nanomaterials can, for example, make cement, cloth, and other materials stronger and more durable, yet lighter. Nanotechnology is also invaluable in electronics and drug delivery.

However, by definition, nano-sized particles have unique properties. Thus, even well-studied materials considered safe, such as silver, may pose a hazard when engineered to nano size. Nano-sized particles can enter the human body through ingestion, inhalation, and absorption through the skin, and certain nanoparticles have produced toxicologic reactions in the lungs of exposed experimental animals, according to published studies reviewed by the Occupational Safety and Health Administration.

In his workshop presentation, “Strategies for Setting Occupational Exposure Limits for Engineered Nano Materials,” Weis said, “Human exposure to ENMs is not theoretical — it is occurring everyday.” He noted that the respiratory system offers a large surface area for damage to occur. At the same time, he added, the bronchial alveolar area of the lung, which allows exchange of oxygen and carbon dioxide, is a delicate membrane only 0.2 microns thick. Damage to this membrane can cause an inflammatory response, as well as lung disease.

“Keeping particles out of this space is the goal,” he said. He added that nanoparticle behavior is dictated by their surface area and chemistry. When seeking safe levels of exposure to a particular nanoparticle, it is essential to consider particle shape, surface area, and physical chemistry of the corona of molecules on the particle’s outer layer. Weis noted that NIEHS is researching what populations may be more susceptible than most to potential nano hazards.

Additional perspectives

NIEHS grantee Günter Oberdorster, D.V.M., Ph.D., who presented on a panel with Weis, discussed the intricacies of hazard identification, exposure assessment, and risk management. As did many present, he lamented the lack of data currently available, but added, “Efforts at the workshop are very important, as we at least begin making decisions about how to establish occupational exposure levels.”

Two young Ph.D. candidates who are working on an NIEHS-sponsored project headed by Terry Gordon, Ph.D., at New York University (NYU), discussed their excitement and sense of purpose from working on nanotechnology from the perspective of environmental health.

“It is such a novel field,” said Mary Popovech. “The things we’re doing, no one has ever done before.” She is researching the effect on mice of inhaled exposures to silver nanoparticles, and the effect on their genes, which has implications for future generations.

Her NYU colleague, Eric Saunders, said his intention was to get a job after finishing his master’s degree, but his work on the NIEHS-funded project convinced him to stay for a Ph.D. and see the project through to the end. “The work,” he said, “is too important to abandon.”

The workshop, held at George Washington University, was sponsored by the American Chemical Council’s Nanotechnology Panel and the university. It drew more than 100 participants, most committed to being involved in continued efforts to develop a strategy to ensure workplace safety in this new and emerging technology.

(Cindy Loose is a contract writer with the NIEHS office in Bethesda, Md.)

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