Nanotoxicity: A New Discipline

Dr. Mae-Wan Ho

Nanoparticles – billionths of metre in dimensions - produced by nanotechnology have unusual properties not found in the bulk material, which can be exploited in numerous applications such as biosensing, electronics, photovoltaics, diagnostics and drug delivery. However, research within the past few years has turned up a range of potential health hazards, which has given birth to the new discipline of nanotoxicity.

• Researchers in the University of Texas in the United States found that carbon nanotubes squirted into the trachea of mice caused serious inflammation of the lungs and granulomas (tumour-like nodules of bloated white blood cells in the lining of the lungs), and five of the nine mice treated with the higher dose died (“Nanotubes highly toxic”, SiS 21) [1, 2].
• In a similar experiment carried out at the National Institute of Occupational Safety and Health in Morgantown, West Virginia, in the Unites States, researchers not only found granulomas in the lungs, but also damage to mitochondrial DNA in the heart and the aortic artery, and substantial oxidative damage, both foreshadowing atherosclerosis (hardening of the arteries) [3].
• In yet another similar experiment in Tottori University, Japan, researchers showed that within a minute of contacting the mice’s tiniest airways, carbon nanotubes began to burrow through gaps between the surface lining cells and into the blood capillaries, where the negatively charged nanoparticles latched onto the normally positively charged red blood cells surface, thereby potentially causing the red blood cells to clump and the blood to clot [3].
• Researchers from the University of Rochester, New York, reported an increased susceptibility to clotting in rabbits that had inhaled carbon nanospheres (buckyballs, an isotope of carbon shaped like a tiny football) [3].
• Buckballs present in water at 0.5 parts per million were taken up by largemouth bass, which suffered severe brain damage 48 hours later, the extent of damage being 17 times greater than that seen in controls [4].
• Nanoparticles in the lungs are translocated to the circulatory system and from there throughout the body, accumulating in the liver, spleen, and bone marrow [5].
• Nanoparticles inhaled through the nose and air passages are translocated to the brain through the olfactory nerves, and accumulate in the brain [5].
• Nanoparticles can enter the body through the skin; and quantum dots injected into the skin accumulate in lymph nodes with potential effects on the immune system [5].
• Quantum dots consisting of a core of fluorescent cadmium selenide, touted as a non-invasive way to image internal body tissues, break down in the body, releasing cadmium, a toxic heavy metal [6].

In August 2005, the International Council on Nanotechnology (ICON) and Rice University’s Center for Biological and environmental Nanotechnology (CBEN) launched an online database of scientific findings related to the risks as well as benefits of nanotechnology [7] (http://icon.rice.edu/research.cfm). Searches using common key words such as “quantum dots” and “nanospheres” gave zero returns in September 2005, which shows it is far from adequate and hence could well be misleading.

Article first published 10/10/05

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References

1. Lam CW, James JLt, McCluskey R and Hunter RL. ToxSci Advance Access published 26, 2003. Pulmonary toxicity of single-wall carbon nanotubes in mice 7 and 90 days after intratracheal instillation. Chemical and Engineering News, December 16, 2002, vol. 80 (50), 46-47.
2. Ho MW. Nanotubes highly toxic. Science in Society 2004, 21, 36-37.
3. “Nano hazards: exposure to minute particles harms lungs, circulatory system”, Janet Raloff, ScienceNews Online, 19 March 2005, http://www.sciencenews.org/articles/20050319/fob1.asp
4. “What’s the damage? Buckyballs and fish brains.” Dennis Loney,  Chemistry.org. The website of the Amercian Chemical Society, http://www.chemistry.org/portal/a/c/s/1/feature_ent.html?DOC=enthusiasts%5Cent_fishbrains.html
5. Oberdorster G, Oberdorster E and Oberdorster J. Nanotoxicology: an emerging discipline evolving from studies of ultrafine particles. Environmental Health Perspectives 2005, 113, 823-39.
6. “Safety concerns over injectable quantum dots. Justin Mullins. New Scientist 2004, 28 Feb., 10.
7. “Nano coalition unveils environment, health and safety database” 19 August 2005, Physorg.com, http://www.physorg.com/news5921.html