Saturday, January 19, 2008

Nanotech Menace?

Ideas for nanotechnology began to come into wide circulation in the 1980s and 1990s, the focus at the time being on tiny nanomachines, the size of viruses, that could do everything from rewire brain to provide immortality to colonize space. The discussions about nanomachines also warned that they could destroy all life on Earth, disassembling it into a "gray goo" that covered the planet. Since nobody had the least practical idea of how to build any sort of nanomachines, it was all hand-waving and sci-fi speculation.

However, at the same time, materials and chemical researchers were learning to perform nanoscale fabrication, acquiring a new level of ability to manipulate matter. Nanomaterials are now being sold and promise to become a very big business. The fact that nanomaterials research doesn't have the least prospect of producing a gray-goo dissassembler doesn't mean that worries have forgotten. In October 2007, Dr. Andrew Maynard, a nanotech specialist at the Woodrow Wilson International Center for Scholars in Washington DC, stood up in front of a Congressional committee to hold up a packet of carbon nanotubes: Dr. Maynard pointed out that he had got the packet through the posts, and it was described as nothing more than graphite.

Superficially, that is true. Graphite is formed of planes of carbon atoms, with each plane made up of a mesh of hexagonal cells of atoms. Carbon nanotubes amount to the mesh rolled up into a tube, while similar carbon "buckyballs" are spheres formed out of that mesh. It is also true that such carbon nanostructures can be found in natural soot, but are they really as safe as graphite powder? Maybe they are, but given our state of knowledge about nanomaterials, we don't know enough to say one way or another. Another participant in the congressional hearing, Dr. Vicki Colvin -- a professor of chemistry at Rice University in Houston and a leader in nanotechnology risk research -- told the group: "If you fund five teams to understand nanotube toxicity, and they get five different answers, your research investment hurts you because it creates uncertainty. The bad news is that we have way over five different opinions about carbon-nanotube toxicity right now."

* Hundreds of products claiming to be nanomaterials-based are now on the market. In most cases, the only sense in which they are nanotech is that they use materials reduced to powders with particles a few nanometers -- billionths of a meter -- in diameter. In some cases, the particles are manipulated into structures such as rings, shells, beads, cages, and wires.

Some nanotech products are applied directly to the skin, for example cosmetics and sunscreens. Titanium dioxide has long been used as a sunscreen, being generally stereotyped as a white paste -- but the latest sunscreens use titanium dioxide nanoparticles, allowing them to block ultraviolet while passing visible light, making them more or less transparent. Silver nanoparticles are also popular since they can have antimicrobial properties, and they are used in products from bed linen to teddy bears to chopsticks to food preparation gear. The food industry is interested in using nanomaterial processing to include trace metals in foods and to make them less fattening.

Once people start talking about nanoparticles in food, nobody has to be a ranting luddite monkey-wrencher to stop and worry about matters for a moment. To be sure, we inhale and ingest nanoparticles from the environment all the time, but then again, we know that a portion of those nanoparticles, such as particulates from diesel engine exhaust, aren't good for us. Any chemist will freely admit that making supposedly harmless materials into nanoparticles may have unpredictable properties simply due to their small size. Bulk copper is soft, while copper nanoparticles are hard. Bulk gold is nonreactive, while gold nanoparticles react easily. Materials, such as carbon, that are safe enough in bulk form may become unsafe in nanoparticle form.

In fact, there's plenty of good reason to worry that may be the case. The reactivity of materials tends to increase with surface area, and given that volume deceases by the cube of the diameter while surface area decreases by the square, the ratio of surface area to volume gets much bigger at small sizes. Half the atoms of a five-nanometer particle are on its surface. Research suggests that nanoparticles could penetrate the body's defensive systems and accumulate in the brain, cells, blood, and nerves. There are suggestions that nanoparticles could cause pulmonary inflammation; move from the lungs to other organs; demonstrate surprising toxicity; be scavenged up by the lymphatic system; and possibly move across cell membranes. Worse, these phenomena tend to vary according to different nanoparticle configurations.

The applications of nanomaterials perceived as the most sensitive involve those that go in or on the body: food additives, cosmetics, drug delivery systems, new therapeutics, plus textile coatings and treatments. However, there are broader concerns: carbon nanotubes have been used for a number of years in plastics as a stiffener, and to make paints and the like conductive. What happens when products using such plastics and paints are dumped or broken up? Will the nanotubes enter the groundwater?

* In 2004, Britain's Royal Society recommended that nanomaterials be treated as entirely new substances as far as regulatory actions were concerned. Unfortunately, trying to assess the "environmental, health, & safety (EHS)" risks is troublesome.

Some governments don't see a particular issue over nanomaterials. Companies are responsible for the safety of their products to begin with, and so the specific nature of those products shouldn't make any difference -- if the products have been demonstrated to be safe, they will be certified as safe; if they haven't, they won't be allowed on the market. This is a reasonable point of view -- except for the fact that nanomaterials open up such a Pandora's box of ugly questions that it isn't reasonable to simply assume companies can do the job of assessing the EHS risks of nanomaterials themselves.

Many companies involved are not complacent about the issue, either, and are trying to come up with tests of their own so they can determine the nature and extent of problems. Big companies actually have the capability to perform very credible research on the subject, since they're familiar with the regulatory environment and have good research staffs. The same is not necessarily true of the smaller companies, and some of them have simply shrugged the matter off: "Titanium dioxide is a perfectly safe material, isn't it? Why should titanium dioxide nanopowders be any different?" Insurers are in a foggy state as well, and for the moment have simply shrugged and included nanomaterials as part of their general product liability coverage.

However, over the longer term, insurers have a strong vested interest in making sure that nanomaterials don't pose a significant EHS hazard. Governments also have a vested interest in making sure that nanomaterials are safe, since they will shoulder much of the blame if they aren't. The general belief is that government funding being pumped into nanotech development at this time should include money for EHS risk evaluation. The relevant businesses see that as all for the good, with the Nanotechnology Industries Association, a British trade group, calling for better coordination on risk evaluation research.

The Council for Science & Technology, an advisory group to the British government, has warned that research into the EHS risks of nanotech is going much too slowly, and in America some members of Congress have lit into the US government's National Nanotechnology Initiative for its lack of focus on safety issues. The US government currently spends the most money on nanotech research, estimated to be as much as $60 million USD a year. However, Dr. Maynard and his colleagues have suggested a program to perform EHS risk evaluation for nanotech that will need $100 million USD a year, at least until the level of risks are understood.

There is a lot of work to do. Regulation of any sort of materials use is based on measurement, monitoring, and risk estimation, and right now there's little ability to do any of that with regards to nanomaterials. We don't even have common terminology or tools to measure nanomaterials, characterise them, and assess their purity. Work towards that end is being coordinated by the International Standards Organization (ISO) in Geneva, Switzerland, and the general expectation is that it will happen.

Can it happen soon enough? Nobody is promoting a hysterical view of nanomaterials, claiming we're on the edge of a global disaster; the issue is that we simply don't have the knowledge to understand if they are really safe or not. That uncertainty casts a cloud over the nanomaterials industry, even as governments pump in money to ramp up work and produce significant new products -- new therapeutics, better batteries, cleaning up water, generating green energy. Getting rid of that cloud makes work on the EHS risks of nanotech very important; and on the positive side, once the risks are better understood, the money pumped into nanotech will go farther since it won't be sunk into dead-end research paths.

  • "A Little Risky Business", THE ECONOMIST, 24 November 2007, 81:84.

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