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No other metal has this property of behaving one way in freshwater and another way in salt water. This presents a regulatory problem that's unique to silver, especially at the nano scale. According to Luoma, most toxicity testing is done in freshwater. "But a silver nanoparticle could look innocuous in freshwater and be extremely toxic in sea water," he says. How significant is this? Nobody really knows -- but Luoma is concerned. It's reasonable, he says, to expect that nanosilver will shed from treated fabrics and from the linings of washing machines and food containers and make its way into rivers and streams, eventually ending up in the ocean.
There is also some evidence that excessive use of silver as an antimicrobial can lead to silver resistance in bacteria, in much the same way that excessive use of antibiotics can lead to the development of antibiotic-resistant organisms. If E. coli could do it, could other, potentially more dangerous microbes do the same thing? And if it happened with normal-scale silver, would it be more or less likely to happen with nanosilver? At the very least, nanosilver complicates the picture, since it allows silver to be used in so many more products. "If we use it too widely," Maynard says, "we may be giving away our best weapon."
Are we foolish to forge ahead in developing nanosilver products without full toxicology information? Perhaps. Luoma, who lives in Silicon Valley, says that the frenzy surrounding nanotechnology, the rush to be first at any cost, reminds him of the heedless gold-rush mentality of the dot-com era. A lot of nano-promises might fail to materialize, as happened with so many brilliant Internet startup ideas. The crucial difference is that the dot-com boom did no harm to the environment or to human health while the Darwinian struggle for survival played itself out. Nanotechnology might.
Here's how one product made from nanosilver, a set of kitchen utensils available in the United States, is being promoted by its manufacturer, Nano Care Technology of Hong Kong: "People always use traditional ways such as sterilizer to kill bacteria and germs but the result is not satisfied [sic], because many bacteria and viruses survive or relive [sic] very quickly." But the company's nanosilver kitchen utensils may do the job permanently, its Web site continues, and "can prevent people from the following diseases: duodenitis caused by spirillums, virosis hepatitis, dysentery caused by salmonella and food poisoning caused by golden staphylococcus."
The Korean appliance manufacturer Daewoo makes similar claims for its products treated with nanosilver (currently distributed only in Europe), which include a washing machine, refrigerator, and vacuum cleaner. It's clear from the Daewoo Web site that the company is using nanosilver for its antimicrobial properties: "After splitting the particles of silver known to have superior deodorant and antibiotic power by 1/1,000,000 mm, we have applied it to major parts of [the] refrigerator in order to restrain the growth and increase of a wide variety of bacteria and eliminate odor particles." Not only is nanosilver a disinfectant and deodorant, the company writes, in an English-language translation so elliptical as to make the true meaning unclear. It also "maintains balance of hormone [sic] within our body and intercepts electromagnetic waves significantly."
At the moment, claims like Nano Care's and Daewoo's exist in a regulatory limbo. No single agency has jurisdiction over nanomaterials (the same applies to many materials of conventional size); it depends largely on how a product is used or where it is in its life cycle. During its manufacture, a nanoparticle might fall under the jurisdiction of the Occupational Safety and Health Administration, which deals with workplace exposure. After that, if it is to be ingested or used in a drug or a medical device, it might be regulated by the Food and Drug Administration. Once it's discarded, it might fall under the purview of the Environmental Protection Agency (EPA), charged with minimizing air- and water-borne toxins.
Federal agencies have been turning their backs on regulating nanotechnology, according to a report issued in May by the Wilson Center, largely because they are not convinced it warrants anything beyond the regulations already in place for standard-scale chemicals. But this might be a dangerous assumption, writes J. Clarence Davies, a senior fellow at Resources for the Future, a nonpartisan research center, in "EPA and Nanotechnology: Oversight for the 21st Century." According to Davies, "The relationship between science and regulation is complex" and filled with uncertainties. The best course is therefore "striking a balance between the harm that could be done by proceeding with an innovation and the harm that could be done by not proceeding."
Nanosilver is something of a jurisdictional oddity. Initially the EPA decided that a nanosilver-releasing Samsung washing machine was a device, like a flyswatter, and not a pesticide. But after public pressure from several interest groups, including NRDC, the agency reversed itself. It placed nanosilver -- an antimicrobial agent -- under the authority of the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) rather than the Toxic Substance Control Act (TSCA), under which most other chemicals are regulated. FIFRA requires manufacturers to submit toxicity data before a product can be approved for sale and gives EPA broad authority to prohibit or limit the sale of pesticides.
"There is something surreal about asking whether washing machines or food-storage containers are pesticides," notes Davies in his report, "and it is a type of problem not envisioned by the drafters of the FIFRA statute." His reading of the act is that what matters in classifying an ingredient as a pesticide is not so much what the manufacturer says it does as what the ingredient has been put there to do. "It's less a matter of claim than intent," he says. "And in my opinion, it's pretty easy to show that the silver isn't doing anything in the products we're talking about other than acting as a pesticide."
After EPA's initial FIFRA decision, however, the agency decided to regulate only specific nanosilver products -- those that make explicit claims of antibacterial action. The result has been that several manufacturers have changed their claims from "kills germs" to less obvious formulations, such as "specially patented" or "stays fresh longer."
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