The Big Three Nanoparticles, Part One: Hi-Ho Nanosilver

There are nanoparticles used in over 1,000 everyday products and counting, according to the Project on Emerging Nanotechnologies . Three particles in particular are currently raising the most concern with regards to public health: nanosilver, titanium dioxide, and carbon nanotubes. The primary issue, as with nanotechnology in general, is not that these particles are inherently “bad” or should be banned from use full-stop, but that it would have been better to know far more about them before they were released into the world. Nonetheless, we’ve pulled together the information that is known about these three, what sorts of products they’re in, and their respective risks and benefits, in an effort to arm consumers with at least some knowledge. One caveat: With no labeling in place for nanomaterials, it can be difficult to determine whether a particular product does or doesn’t contain a given nanoparticle.

Because they are just smaller versions of existing particles, nanoparticles are not regulated as separate entities. In fact, according to Michael Vassar, a scientist and former collaborator for the Center for Responsible Nanotechnology, the term “nanoparticle” is more of a marketing ploy than anything else, essentially cooked up by scientists looking for research funding. “It’s not a question of ‘are nanoparticles dangerous?’,” he says. “But more, what is the size at which this or that particular particle becomes a risk to human health. Asbestos is a good example of that–it’s dangerous because at small sizes it grows fibers that can infiltrate the lungs. But no one talks about nano-asbestos.”

The Project on Emerging Nanotechnology (PEN) has done a great job compiling a database of products with manufacturer-specified nanomaterials; you can find that database here, or download the PEN’s new “FindNano” app on your iPhone.

We start our series with nanosilver, not because it’s more or less worth studying than the others, but because it’s in such a wide range of products, and because the EPA seems to be the most comfortable with it being in consumer goods.

Nanosilver and Human Health

Nanosilver is added to products from pesticides to toothpaste to kitchen equipment because of its antibacterial properties. A key-word search for “nanosilver” in the PEN database delivers over 200 products, ranging from razors to food storage containers to slippers to soaps, shampoos and toothpastes.

As Vassar points out, people have been ingesting silver for its antibacterial properties since the Middle Ages. “Chances are, it’s not terrible for you,” he says. Vassar adds that because nano-sized silver particles are inert and don’t tend to form long fibers, they are likely less of a health risk than particles that do form fibers, like asbestos or carbon nanotubes. “Still, it would be great to see a reliable study done on it, and to see some sort of government oversight and labeling. Unfortunately, I just can’t see that happening in the United States.”

In fact, some nanosilver proponents go beyond saying “it’s not terrible for you,” and claim that nanosilver could be a cure for viruses ranging from MRSA (the so-called “superbug” Methicillin resistant staphylococcus aureus) to HIV to cancer. In a study published in the Journal of Nanotechnology, scientists from the University of Texas at Austin and Mexico University Nuevo Leon found that silver nanoparticles one to 10 nanometers in size, when attached to HIV-1, prevented the virus from bonding to host cells. A study of nanosilver published in 2007 in International Immunopharmacology found that nanosilver particles can alter the production of immune signaling compounds known as cytokines. The authors’ conclusion: “These experimental data suggest that nano-silver could be used to treat immunologic and inflammatory diseases.”

That’s great if their use is very well-controlled, but opponents of nanosilver fear the consequences of poorly controlled use of nanosilver in medical settings. A number of studies released over the past two years have revealed that if it runs loose in the body, nanosilver can interfere with healthy cells, adversely affecting human immune systems. Christopher Perkins, a scientist at the University of Connecticut, began researching nanosilver’s effect on human cells when he learned that the particles were already used in various types of tubing used in hospitals. He found that at the 10nanometer or smaller size, the particles did in fact attack “bad” cells, but that they also increased the production of free radicals, which is not good. “You’ve got all of these free radicals that have to go somewhere,” he told Science News. “And they’re pretty nonspecific in what they target. Which means they’ll kill healthy cells as well as bacteria or other pathogens.”

Nanosilver and the Environment

In 2009, scientists began voicing concern that the volume of nanosilver unleashed on the world in the last few years could lead to negative impacts on ecosystems, including everything from degrading wetlands to causing fish kills. A new study by Bernd Nowack, published this month in Science, however, evaluated wastewater treatment plants and found that the wastewater treatment process converts potentially dangerous nanosilver into benign nano silver sulfide particles. He adds that more study is needed to determine how these particles behave in the environment, but concludes that, from an environmental standpoint, the use of silver nanoparticles in consumer products is no different from the use of silver in other forms.

The problem, according to Jennifer Sass at the Natural Resources Defense Council (NRDC), is that nanosilver isn’t simply replacing silver in various manufacturing applications, it’s being used for entirely new things. The environmental impact of increased silver–nano or otherwise–in groundwater and soil are as yet unknown, and should be better understood before more uses for nanosilver are found. Unfortunately, the pace of innovation in terms of using nanoparticles to make products better or to streamline manufacturing in some way far outstrips the pace of research and regulation.

Companies are now beginning to tread lightly around nanotechnology for fear of consumer backlash. Some are even specifically calling out nanotechnology, or particular nanoparticles, in their sustainability reports. In the 2010 Sustainability Report from Colgate, for example, there is an entire section on nanotechnology, in which the company states, “At the present time, Colgate does not use any such ingredients or materials in its products anywhere in the world, although from time to time it has such ingredients or materials under study.”

Regulation of Nanosilver

Scientists and environmentalists have been calling for better regulation of nanoparticles for at least the past five years. In 2007, the NRDC’s Sass authored a report outlining a three-part framework for regulating nanomaterials. Countless other organizations have released similar reports, including the National Research Council, which concluded in its 2008 report that 18 government agencies, including the EPA and the FDA, had failed to prove that nanoparticles were not dangerous, and thus shirked their duties in regards to protecting the American people. Also in 2008, the International Center for Technology Assessment filed a legal petition with the EPA to halt the sale of consumer products containing nanosilver. At the time, Andrew Maynard, chief science adviser for the Project on Emerging Nanotechnologies, said: “Nanosilver and its use as a pesticide has got to be better regulated. It seems to be slipping under the radar.”

But in the United States at least, the cautions of the scientific community seem to have fallen on deaf ears. Or at least on broke and politically powerless ears. It’s not that as though the EPA is sitting around and doing nothing. In fact the agency is currently researching the big three nanoparticles, producing detailed case studies of each. The case study on nanosilver (as used in disinfectant sprays) was released August 18, 2010. The agency plans to host a public meeting to discuss its findings this month, and to refine its case study, releasing a final study in June.

The problem is that the agency is continuing to make regulatory decisions about nanosilver in the meantime, which seems like quite a dangerous example of putting the cart before the horse. Case in point: On August 12, 2010, six days before releasing its draft case study of nanosilver, the EPA announced its intention to conditionally register a pesticide product containing nanosilver. This would allow this product to be sold in the US for 4 years on the condition that the company provides data now lacking on toxicology, exposure, and environmental impacts.

According to Sass, in order to “conditionally register” a product, EPA must show three things:

The company has not had sufficient time to generate the data since EPA “first imposed” the data requirement
The use of the pesticide during this time will not cause any unreasonable adverse effect on the environment, and
The use of the pesticide is in the public interest.

In the case of nanosilver, she says, EPA has failed to meet these criteria, which is why the NRDC plans to sue the agency should it choose to proceed with the conditional registration.

In case the agency does move forward with its plan, and the lawsuit doesn’t go anywhere, scientists at Oregon State University and Ireland’s Centre for BioNano Interactions have published a list of recommendations for ensuring public safety if nanosilver-based pesticides are widely employed:

Manufacturers should disclose any nanoparticles—and their behavior—in a compound, so that regulators can assess the risks associated with them. This includes materials that might be used in processing or delivering the pesticide, not just the main ingredients.

Operate under what the authors call the “uncertainty factor” about nanoparticles, until more is known about what they do, both in the short and long term. That means manufacturers should be testing these ingredients and sharing that information, although this might make the registration process with the EPA longer.

Use a “route-specific” approach to determine health hazards. For example, inhaling nanoparticles might be more dangerous to people than absorbing them through the skin. It’s important for manufacturers and regulators to understand those differences and address them.

Regulators should require that pesticides containing nanomaterials be tested in their final form, not just as components. That way, they’ll have a better handle on what the entire product does, and how it interacts with people and the environment.

Manufacturers should be required to launch “health surveillance” program when they introduce new pesticides, so that they can track any health issues surrounding manufacture and application, as well as what happens to air, water and soil when it is deployed.

Since the possibility of a public outcry over nano-based pesticides is “high,” the authors recommend that regulators and manufacturers invest in education programs to inform the public about what’s in these compounds, and how to use them safely.

Although comprehensive and sensible, their recommendations are wildly optimistic in parts. It seems ludicrous to think that, while regulators have no problem opening the gates to nanoparticles, manufacturers will be extra careful as they include them in products, because we just don’t know what they do yet.