Nanotechnology Slowly Gives Up Its Secrets
The confusing puzzle that is nanotechnology has led to many questions and concerns--first and foremost about our safety.
- By Marc Barrera
- May 01, 2006
PICTURE the manufacturing industry as the process of constructing walls. Early manufacturing began by piling one large, irregular-shaped stone atop another, resulting in a wall that was sturdy because of its weight and size but demanding maximum space and materials and reaching only a fraction of its strength potential. As the industry progressed, these stones were shaped into blocks that fit one along another, increasing stability while reducing space and materials.
With further progress, the massive, pyramid-sized stones shrank to brick-size, the same as those used in modern-day homes. With the emergence of nanotechnology, these blocks have become even smaller--down to the molecular level. Their shape has changed, as well, from blocks into interlocking shapes like puzzle pieces. This increases their efficiency by adding strength and flexibility to walls while again minimizing the materials needed. Yet this development has sent up many red flags within the safety community.
Rather than cutting off large sections of material to shape our blocks, microscopic pieces would be removed. Workers in a mine may wear a helmet, gloves, safety glasses, and respirator to protect themselves from harmful debris, but how does someone protect himself from debris that is invisible to the human eye? Can modern-day filters stop particles of this size? Can particles this small be absorbed through our clothes and skin? Does their small size make them harmless or more dangerous?
The National Institute for Occupational Safety and Health describes it this way: "Nanotechnology is somewhat loosely defined, although in general terms it covers engineered structures, devices, and systems that have a length scale of 1-100 nanometers (a nanometer is a billionth of a meter). At these length scales, materials begin to exhibit unique properties that affect physical, chemical, and biological behavior. Researching, developing, and utilizing these properties is at the heart of the new technology." This broad definition illustrates the wide range of possibilities encompassing this science. Nanotechnology already is present in or holds promise in many markets: toothpaste, sunscreen, solar panels, pharmaceuticals, membrane technology, computer chips, medical instruments, stain-resistant clothing, food, and cosmetics, to name just a few.
One industry poised for significant gains is pharmaceuticals. Researchers are discovering ways of administering medication by way of nanostructures released into the body. These structures would eventually be able to seek out and treat disease. Researchers at The University of Texas M.D. Anderson Cancer Center have worked to fabricate nanoplatforms or scaffolds, referred to as "nanoshuttles," that are a combination of gold particles and viruses that infect only bacteria. The virus would act as a guide that would steer the nanoshuttle to specific targets through a process called Vascular Targeting, which uses peptides that are displayed by these viruses that match certain protein receptors on certain tissues or cell types, thus seeking them out. This presents the possibility of delivering targeted treatment of medicines. For example, nanoshuttles could deliver stem cells to treat damaged arteries or could be used with a laser to heat up these gold particles to destroy tumor tissue.
Nanoelectronics is another promising area. Researcher are developing single-molecule diodes, a thousand times smaller than diodes currently in use, to increase the computing power and speed of microchips. At the University at Buffalo (Buffalo, N.Y.), engineers are tackling the problem of electromigration and thermomigration, two of the technology's biggest roadblocks because as the electrical currents necessary to power new devices increase while circuit size decreases, atoms tend to behave erratically and become more susceptible to circuitry breakdown. These engineers intend to build semiconductor devices that are made from materials with precisely placed atoms in order to control their properties and eliminate this destructive behavior.
Applications in industrial hygiene exist, as well. Portland, Ore.,-based AcryMed Inc. received FDA clearance last year for the use of SilvaGard™, catheters treated with an ionic-silver nanoparticle antibacterial coating that protects against the formation of infection-causing biofilm. Currently, the company is pursuing clearance for other uses of this coating in hopes that their product will render other medical devices impervious to bacteria growth, decreasing nosocomial infections.
Dealing With the Unknowns
The main concerns at the forefront of the development of nanotechnology are the possible effects of exposure. The most widely acknowledged exposure scenarios are inhalation and absorption. The natural tendency is to first look to protective equipment, such as respirators and clean suits to protect against exposure, but many experts contend that the first course of action should be to understand the properties of nanomaterials.
So many new materials are created that researchers are busy trying to identify any toxic or harmful properties. Mark R. Wiesner, Ph.D., of the Department of Chemical and Biomolecular Engineering at Rice University in Houston, feels more research is needed before jumping to conclusions. "Many of the nanomaterials, we don't even know if they're hazardous; we don't know if they have a toxic affect," said Wiesner, who is a member of the Santa Barbara, Calif.-based Nanoethics Group's advisory board, a group concerned with nanotechnology's impact on ethics and society. "Yes, they might penetrate the skin; yes, they might deposit in the lungs. But in some cases we don't know if they ever will get to the lungs, and in some cases we don't know that if they do get to the lungs, if they'll have some sort of a toxic effect."
Owen Moss, Ph.D., of the CIIT Centers for Health Research in Research Triangle Park, N.C., said he is concerned that when people learn about the latest toxicology finding of a nanoparticle, they do not take into consideration that such findings deal with test exposures to cells involving huge numbers of nanoparticles, enough to cover the exposed cell many times over. Simply because this proved toxic does not mean the particle itself is always harmful. Moss refers to this as the "avalanche effect."
"When we do research of nanoparticles, at least as we are now recording them, we run the risk of drawing conclusions which are equivalent to [saying] that snowflakes are toxic because avalanches are lethal," Moss said. "We currently are just developing the experimental approaches to determine whether or not individual nanoparticles are toxic or beneficial."
One approach in development by researchers at the U.S. Department of Energy's Pacific Northwest National Laboratory (PNNL) in Richland, Wash., is to test and observe living cells through a process called Fourier transform infrared spectroscopy (FTIR). Theoretically, the FTIR method would allow scientists to observe the effects of exposure to certain nanoparticles in real time, testing nanoparticles down to their chemical bond and monitoring any biological effects that may not fall under the category of "toxic" in traditional testing standards.
"If all nanomaterials were simply inflammatory, we could test for that now very well," said Thomas J. Weber, Ph.D., senior research scientist at PNNL. "Say you've screened a hundred nanomaterials, and acutely half of them were toxic and you could detect that very readily, so you know how to deal with those, you know how to prioritize that now. The other half show absolutely no toxicity in an acute screening assay. So here, by the FTIR method, we can screen those that were not toxic or didn't show any acute toxicity and determine which of those have biological activity. And then we try and work backward from there and understand what the molecular basis is for that biological activity that we're detecting."
At UCLA, researchers are drawing from the strong foundation of air pollution testing to approach the problem. Researchers have developed a module that incorporates toxicity testing for occupational and air pollution particles (which happens to include nanoparticles) that is used by the federal government's National Toxicology Program to evaluate chemical agents. The module uses a series of tests to assess toxicity in non-biological environments, tissue cultures, and animal models. It is hoped this predictive strategy of simple, high-quality toxicity tests will speed up the process of classifying materials.
Keeping It All In Order
As test data continue to accumulate, more must be done to take this information and make it readily available in a useable catalog or framework listing the different classes of nanomaterials and their established effects. Currently, if a safety manager wants to know more about the current state of nanotechnology research, a search will pull him in many different directions and force him to pick up the pieces along the way. Those working in this area agree a central hub or database for all known information must be created and accepted by experts in the field.
To tackle this problem, several experts have formed organizations and advisory groups across the world with the focus of creating a nanotechnology dialogue and formulating standards and best practices. NIOSH has recently made available a searchable online database prototype called the Nanoparticle Information Library (NIL, www2a.cdc.gov/niosh-nil/index.asp). NIL is described as part of a cooperative effort by national and international partners "to help occupational health professionals, industrial users, worker groups, and researchers organize and share information on nanomaterials, including their health and safety-associated properties." NIL's information includes nanomaterial composition; method of production; particle size, surface area, and morphology (including scanning, transmission, or other electron micrographic images); demonstrated or intended applications of the nanomaterials; associated or relevant publications; points of contact for additional details or partnering; and more. The creation of an authoritative, universally accepted database, whether it be NIL or another, would accelerate understanding and development of these materials and lead to the creation of standards to regulate their use and exposure. This would allow already established agencies, such as OSHA and EPA, to work toward guarding against harmful exposures.
Protection in the Present
While harmful particles are identified and communicated, the issue of protecting from exposure remains. Can current filtration and clothing protect against inhalation or skin absorption of these particles? Moss points out that government agencies have protected workers from exposure using current technology, such as High Efficiency Particulate Air (HEPA) filters.
"The nuclear industry has been filtering out nanometer-sized particles for decades; the industry and the Department of Energy use HEPA filters," Moss said. "The efficiency of these filters is certified at 99.97 to 99.999 percent where the collection efficiency reported is for particles having diameters of 300 nanometers."
Although nanoparticles can get as small as 0.2 nanometers, based on the diffusion properties of nano-sized particles, in which these small particles are more susceptible to sticking to surfaces and/or other particles, both Wiesner and Moss believe present filtration systems protect workers from exposure as particles get smaller. Diffusion increases the likelihood that particles will either aggregate into larger particles that are easier to filter or stick to the filter membrane itself, increasing the efficiency of a HEPA filter certified at 99.97 to 99.999 percent for 300 nanometer-sized particles.
Wiesner added that proper protection requires that proper research is done to determine the appropriate filter for a particular nanomaterial's diffusion properties. "If you think about it, there are filters for removing just gases from the air. A gas molecule is typically smaller than a nanoparticle, so if you can remove that, being able to remove a nanoparticle should be possible, as well," Wiesner said. "Many of the nanomaterials that we worry about don't actually exist down at the size of the individual nanoparticles because they spontaneously form aggregates that are much larger. And so, depending on the aggregation of these materials, you'd pick the certain filter that you might use."
Calming Public Fears
A growing, non-health-related problem--but one no less detrimental to nanotechnology's development--is public fear caused by a lack of communication. When left with little or no information, imaginations fill in the gaps. This can lead to doomsday scenarios, irrational fears, and even fictional stories about deadly nano-robots bent on world domination.
Public education is needed. Specifically, children should be introduced to this emerging science at an early age. Imagine a similar situation in decades past when very few people knew anything about computers. Many students in this era got their first glimpse of a computer in high school or college, while many adults irrationally feared this device and refused to go near it. Yet more and more people began to embrace computers, and students embraced them at earlier ages, from middle school to elementary. Children today grow up with a better understanding of computers than most present-day adults could ever hope to achieve.
Although nanotechnology is still in its infancy, efforts have begun to better inform the public at an earlier age. Cornell University's Nanobiotechnology Center has a 3,000-square-foot science exhibition titled "It's a Nano World" that has toured cities across the country. The interactive exhibit was created with the purpose of providing a hands-on approach through use of walk-through props to give 5- to 8-year-olds and their families a better grasp of the conceptual scale involved in this invisible world. A second, 5,000-square-foot traveling exhibit is in development that will be directed to middle school children and will focus on explaining how nanotechnologies create and use devices on a molecular scale.
Eventually, the day may come when nanotechnology becomes the norm for all technology and present-day health and safety concerns will be adequately addressed and forgotten. But early efforts to make this transition a safe one will always have a defining role in its future. The key to reaching that future safely is keeping an open dialogue.
This article appears in the May 2006 issue of Occupational Health & Safety.
This article originally appeared in the May 2006 issue of Occupational Health & Safety.