Nanoscale Silver: No Silver Lining?

Widespread use of nanoscale silver will challenge regulatory agencies to balance important potential benefits against the possibility of significant environmental risk, highlighting the need to identify research priorities concerning this emerging technology, according to a new report released today by the Project on Emerging Nanotechnologies (PEN).

But existing information about the impact of silver on the environment offers a starting point for some assessments of nanosilver, the report argues. You can see a copy of the report online.

Nanotechnology is the ability to measure, see, manipulate and manufacture things at the atomic scale. In 2007, the global market for nanotechnology-based products totaled $147 billion. Lux Research projects that figure will grow to $3.1 trillion by
2015.

The issue of assessing the risks posed by nanoscale silver was highlighted after the Environmental Protection Agency's (EPA) San Francisco office earlier this year imposed a landmark fine of more than $200,000 on a California company selling computer keyboards and mouses coated with nanosilver. EPA issued the fine on the grounds that the products should
have been registered under federal pesticide law because of the company's germ-killing claims, according to PEN.

Similar fines have not been imposed since, but the action is increasing attention on the potential risks posed by nanoscale silver and oversight of nanotechnology as a whole. There currently are more than 200 manufacturer-identified nanosilver products on the market and contained in
the online nanotechnology consumer products inventory maintained by PEN --everything from baby carriages and air filters to athletic socks and coin-operated washing machines.

Silver itself is classified as an environmental hazard by EPA because it is more toxic to aquatic plants and animals than any metal except mercury. Even if a nanoparticle itself is not especially toxic, silver nanoparticles increase the effectiveness of delivering toxic silver ions to locations where they can cause toxicity.

"We need not assume that because nano is new, we have no scientific basis for managing risks," says Samuel Luoma, the author of the PEN report Silver Nanotechnologies and The Environment: Old Problems or New Challenges?, which also offers a dozen lessons concerning silver in general that can be followed for managing the potential environmental risks posed
by nanosilver.

"Our existing knowledge of silver in the environment provides a starting point for some assessments, and points toward some of the new questions raised by the unique properties for nanoparticles that need to be addressed through new research."

The mass of silver dispersed to the environment from new products could be substantial if one product, or a combination of such products, becomes widespread, according to PEN.

"The silver that went into wastewaters when millions of people had their photographs developed taught us that small additions of silver to the environment make a big difference," says Luoma, a former senior researcher with the U.S. Geological Survey who now leads science policy coordination for the John Muir Institute of the Environment at the University of California, Davis. "Perhaps more significant, we have no means of detecting nanosilver in the environment once it is released, even if concentrations rise to levels that are toxic to aquatic ecosystems."

The U.S. federal government has invested only a small percentage of its overall nanotechnology research funding in understanding the risks posed by nanomaterials, according to an analysis conducted earlier this year by PEN, further highlighting the need for more research on the potential risks posed by nanomaterials. In addition, laws and institutions shaped in the mid-20th century are not likely to succeed in addressing 21st century problems.

"Silver is an old problem, and nanosilver is a new challenge. The scope of the new challenge is not yet clear because it is uncertain how much nanosilver is now used as an antimicrobial in commercial and consumer products, and because new uses are likely to be discovered in the future," says J. Clarence Davies, a PEN senior adviser and a former EPA policy official. "Regardless of the scope of the nanosilver problem, it underscores the need for more risk research and new approaches to oversight to deal with new technologies and problems of the new century."

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EPA Ignored Own Rules on Toxic Release, Watchdog Says

The U.S. Environmental Protection Agency (EPA) did not adhere to its own rulemaking guidelines in all respects when developing the proposal to change toxic chemical reporting requirements, a government watchdog finds.

U.S. industry uses billions of pounds of chemicals to produce the nation’s goods and services. Releases of these chemicals during use or disposal can harm human health and the environment.

The Emergency Planning and Community Right-to-Know Act of 1986 requires facilities that manufacture, process, or otherwise use more than specified amounts of nearly 650 toxic chemicals to report their releases to water, air, and land. The EPA makes this data available to the public in the Toxics Release Inventory (TRI).

EPA last month finalized a proposal to increase the TRI reporting threshold to 2,000 pounds, quadrupling what facilities can release before they must disclose their releases and other waste management practices.

But EPA did not adhere to its own rulemaking guidelines in all respects when developing the proposal to change TRI reporting requirements, according to the Government Accountability Office (GAO), the nonpartisan investigative arm of Congress.

"We have identified several significant differences between the guidelines and the process EPA followed," GAO says in a new report.

Such states as California, Massachusetts, and New Jersey would lose information about toxic chemical releases in those states, GAO says. Some states could lose all quantitative information about releases of some chemicals, ranging from South Dakota to Georgia, the agency adds.

"We believe that the TRI reporting changes will likely have a significant impact on information available to the public about dozens of toxic chemicals from thousands of facilities in states and communities across the country," GAO says.


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System Detects Hazardous, Toxic Material in Concealed Packaging

Researchers at Sandia National Laboratories are developing the next generation of screening devices that will identify hazardous and toxic materials even if concealed by clothing and packaging materials.

Working in the underutilized terahertz (THz) portion of the electromagnetic spectrum that lies between microwaves and infrared, a team of Labs scientists is harnessing Sandia’s strengths in a variety of technical areas with the goal of building a highly integrated miniaturized terahertz transmitter-receiver (transceiver) that could make a number of applications possible.

The project, the Terahertz Microelectronics Transceiver Grand Challenge, is in its second of three years of funding through Sandia's internal Laboratory Directed Research and Development program.

Sandia is a U.S. National Nuclear Security Administration (NNSA) laboratory.

“The technology being developed in the Grand Challenge can be used to scan for items such as concealed weapons or materials, explosives, and weapons of mass destruction,” says Mike Wanke, principal investigator. “In addition, we believe it will find applications in advanced communication systems and high-resolution radars. However, the infrastructure needed to move the terahertz technology from the laboratory to the field is unavailable right now. We want to develop that infrastructure and invent the necessary technologies.”

Wanke says over the past three years, “the terahertz situation has begun to change dramatically, primarily due to the revolutionary development of terahertz quantum cascade lasers.”

These tiny lasers are semiconductor sources of terahertz radiation capable of output powers in excess of 100 mW. Previously, such powers could only be obtained by molecular gas lasers occupying cubic meters and weighing more than 100 kg, or free electron lasers weighing tons and occupying entire buildings.

Quantum cascade laser-based systems can be less than the size of a baseball and powered from a nine-volt battery. Sandia has been a leader in developing this new technology and in collaboration with MIT is responsible for several world performance records for the lasers. Also, the Labs and its partners are the only US institutions that have demonstrated the ability to grow the unique semiconductor crystals such that they can be turned into operating terahertz quantum cascade lasers. The crystals are grown by Sandia research scientist John Reno, an expert in molecular beam epitaxy, a method of laying down layers of materials with atomic thicknesses onto substrates.

Sandia researchers spent the first year of the Grand Challenge using Sandia’s unique strengths in integrated microelectronics and device physics to develop components that are now being combined to create an integrated THz microelectronic transceiver, a core enabling element.

The team is currently developing the receiver, doing systems tests and exploring packaging requirements. At the end of three years, the researchers expect to have an actual working prototype capable of detecting the materials and chemicals by reading distinctive molecular spectral “signatures.”

“Most materials and chemicals have their own unique terahertz spectral signatures,” Wanke says. “A terahertz transceiver system would be able to measure, for example, the signature of a gas and determine what it is.”

“Atmospheric scientists and radio astronomers have spent years developing terahertz spectral signature databases to identify chemicals in nebula and planetary atmospheres,” says Greg Hebner, program manager. “Even though the current devices are washing machine-sized, they are located in a few observatories, and one is even flying on a satellite. To address specific national security problems, we are working on reducing the size, weight, and power requirement as well as expanding the existing spectral databases.”

In addition to monitoring for concealed hazardous materials, Mike believes a terahertz system can be used to monitor the air for toxic materials. Using air sampling technology developed at Sandia and other locations, hazardous vapors can be preconcentrated. Shining light from the quantum cascade laser through the concentrated sample provides a direct identification of the vapor. This technology can be used in conjunction with existing mass spectrometer-based systems to reduce false identifications.


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