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sexta-feira, 20 de abril de 2012

Are Nanomaterials Safe or Not?

Tim Studt, Editor-in-Chief
Tim StudtEditor in Chief

Man-made nanomaterials have been researched for the past thirty years and increasingly used in commercial manufactured products over the past decade.

The safety aspects or potential hazards of nanomaterials have also been researched for nearly as long with few experimental results indicating the exact nature of the potential hazards these materials might pose. Yet, their use continues to expand with $225 billion worth of products containing more than $1 billion of nanomaterials manufactured in 2009 and $3 trillion in nanomaterial-enabled products expected in 2015.

A recent report by the National Research Council (NRC), "A Research Strategy for Environmental, Health, and Safety Aspects of Engineered Nanomaterials (ENMs)," recommends a coordinated research method to guide plans to manage and avoid potential risks of ENMs. The report presents a strategic approach to accomplish this, but because the market is expected to explode, they recommend a narrow approach with just four research categories—1) identify the ENMs being released, 2) understand the processes that affect hazards, 3) examine ENM interactions in complex systems and 4) create an infrastructure to provide rapid feedback.

Over the past several years, some communities have passed local ordinances that require companies manufacturing ENM-enabled products to report risk-based guidelines for using ENMs just as they would for conventional hazardous materials. But without the characterization and identification of the specific hazards of ENMs, these ordinances/guidelines are mostly "toothless."

The diverse properties of ENMs and the lack of clinical trials make them challenging to understand from the perspective of risk. Also, depending on the environment where an ENM is present (surfaces, water, air), its surface properties may change and affect behavior and characterization—its like trying to identify a moving and, at the same time, morphing target. Additionally, little data is available on the quantity exposure of ENMs versus health risks.

The NRC's strategy is good and workable, especially from a cost standpoint, which is what it was planned to be. But as in a lot of science reports, I would not expect to see actual results from it more than what has occurred over the past five years with other ENM safety initiatives. 

The facts that ENMs have been used for roughly 10 years in manufactured products and no demonstratable significant hazards have been identified with their use should be recognized as indicators of the elusiveness of their identification as hazardous materials. The complexity of the challenges for users and manufacturers is so far from being characterized that even modeling scenarios are not practical in these studies.

Clearly, users of ENM-enabled materials (except in cosmetics and drugs) should not be targeted as investigative subjects for these studies. Alternatively, workers in facilities where these products are manufactured, who may be exposed to potentially large doses of ENMs on a daily basis, should be studied and their health characterized.

Little is known about the transport and distribution of ENMs in the human body and in the environment, according to the NRC report. The interactions of ENMs with biomolecules is similarly unknown as are their transformation into dissolved, aggregated, disaggregated or chemical entities in the environment. A few limited studies have shown that some nanoparticles can interact in cellular mechanisms, but even those studies are subject to practical considerations.

The tools for characterizing ENMs in the environment are adequate, but the diversity and complexity of the materials being manufactured and used is so large it is mostly unmanageable. Clinical trials are generally required for this type of potential human health challenge, yet there are no clear-cut aspects that would lend themselves to generic clinical trials.

This is not a simple problem like finding that CFC refrigerants chemically react with the earth's ozone layer or that strong chemical solvents are known carcinogens. These materials are more diverse and less chemically reactive. 

The only known characteristic that threatens society at this point is their nanoscale size. 

Even asbestos fibers had a size characteristic that was large enough to be categorized as to causing tears in lung emboli and creating human health problems. And asbestos has a clear aspect ratio that caused these problems, while the overall size of the fibers is roughly a thousand times larger than most ENMs. And still, we don’t even know if that makes any difference.

Fonte: Laboratory Equipmentd