Nanotechnology is a branch of science that deals with particles 1-100 nanometers in size. Experts believe possible dangers of nanotechnology lie in how these tiny particles might interact with the environment, and more importantly, with the human body. Billions of dollars are being spent to incorporate nanoparticles into products that are already being marketed to the public; when this investment is compared to the the comparatively scant research into nanotech health issues, some scientists become concerned.

Experts say the issue is that elements encountered at the nanoscale behave differently than their larger counterparts. As an example, graphite's properties are well known and it holds specific position in toxicology guidelines. Nobel winning physicist Richard Smalley of Rice University discovered carbon nanotubes and fullerenes (buckyballs) — nanoparticles of carbon — which are legally categorized as graphite, yet they behave in ways unlike graphite making the classification a potentially dangerous one.

Case in point: in March 2004 tests conducted by environmental toxicologist Eva Oberdörster, Ph.D., with Southern Methodist University in Texas found extensive brain damage to fish exposed to fullerenes for a period of just 48 hours at a relatively moderate dose of 0.5 parts per million (commiserate with levels of other kinds of pollution found in bays). The fish also exhibited changed gene markers in their livers, indicating their entire physiology was affected. In a concurrent test, the fullerenes killed water fleas, an important link in the marine food chain.

Oberdörster could not say whether fullerenes would also cause brain damage in humans but cautioned that more studies are necessary and that the accumulation of fullerenes over time could be a concern, particularly if they were allowed to enter the food chain. Earlier studies in 2002 by CBEN (Center for Biological and Environmental Nanotechnology) indicated nanoparticles accumulated in the bodies of lab animals, and still other studies showed fullerenes travel freely through soil and could be absorbed by earthworms. This is a potential link up the food chain to humans and presents one of the possible dangers of nanotechnology.

Other nanoparticles have also been shown to have adverse effects. Research from University of California in San Diego in early 2002 revealed cadmium selenide nanoparticles, also called quantum dots, can cause cadmium poisoning in humans. In 2004 British scientist Vyvyan Howard published initial findings that indicated gold nanoparticles might move through a mother's placenta to the fetus; and as far back as 1997 scientists at Oxford discovered nanoparticles used in sunscreen created free radicals that damaged DNA.

Complicating the dangers of nanotechnology, size and shape of nanoparticles affect the level of toxicity, preempting the ease of uniform categories even when considering a single element. In general, experts report smaller particles are more bioactive and toxic. Their ability to interact with other living systems increases because they can easily cross the skin, lung, and in some cases the blood/brain barriers. Once inside the body, there may be further biochemical reactions like the creation of free radicals that damage cells.

While the body has built-in defenses for natural particles it encounters, the danger of nanotechnology is that it is introducing entirely new type of particles. Particles some experts say the body is likely to find toxic.

Highest at risk are workers employed by manufacturers producing products that contain nanoparticles. The National Institute for Occupational Safety and Health (NIOSH) reports over 2 million Americans are exposed to high levels of nanoparticles and they believe this figure will rise to 4 million in the near future. NIOSH publishes safety guidelines and other information for those employed in the nanoindustry.

There is no doubt that nanoparticles have interesting and useful properties. That said, many groups propose a moratorium on marketing and urge research to precede manufacturing rather than proceed it. Strong economic drives and competition in the marketplace may be taking precedence over methodical scientific prudence when it comes to public health and possible dangers of nanotechnology.

Some have compared the situation to that of asbestos dust -- another material that was assumed safe until it was learned that it can cause cancer from accumulation in the body. Today 3,000 deaths per year are still attributed to asbestos from decades-old use. Those concerned with possible dangers of nanotechnology wish to avoid a similar or even worse scenario down the road, especially considering the growing market for nanoparticles in such diverse products as car paint, tennis rackets, and make-up.

Nanotechnology should not be confused with molecular nanotechnology (MNT) a still theoretical science dedicated to manufacturing products from the atom up through use of nanoscale machines. 

Medical Robots (from: The Economist)