Abstract


Benefits of nanoscience and nanotechnology have been carefully implemented in many areas of engineering to enhance the performance and quality of living conditions. Even though the novel technology offers enormous benefits, the serious concerns in that need to be addressed before commercializing the technology. Proper implementation of the technology needs careful assessment of the impact on environment, health hazards that may arise to the workers, users of the products and also to the environment. An attempt has been made to highlight the potential hazards of nanotechnology in some of the areas and the possible remedial measures, though the availability of the data to substantiate the claims are very much limited.


Introduction


Nanotechnology employs "bottom up" as well as "top down" approaches to produce nanomaterials in all the three dimensions. Nanoparticles, nanotubes and carbon nanocrystals called Bucky Balls are now being manufactured in large quantities [1, 2, 3]. Quantum effects begin to dominate the behaviour of matters at the nanoscale and affect the optical, electrical and magnetic behaviours. Applications of nanotechnology in terms of nanofibres, nanoparticles, nanocomposites and nanotubes have been reviewed recently by many researchers [4, 5, 6, 7, 8]. Nanofibres, nanotubes and nano-particles for imparting functional finishes find increased applications in various forms of textile materials [5, 6, 7]. Though the advantages of the nanomaterials are unending, the potential risks or hazards to ecosystem or to the humans have drawn very little attention. Potential hazards exist in production of man made fibres where nanosized dope additives are mixed and, in the post manufacturing operations, where the continuous filaments are cut into staple fibres. The post spinning processes are capable of producing respirable fibre flocks, tiny fibres that can result in diseases related to lungs [4, 9].


Even though the nanomaterials appear to be a single class of material they differ in terms of size, shape, surface area, chemical compositions, biopersistance [10]; the possible environmental and health impact need to be assessed for each type of nanomaterial separately. Two factors that are responsible for occupational risk of nano-particles include size and massive surface area, which can absorb toxins and similar substances that can be transported into the body [11].


2.0 Potential Hazards


Proper implementation of nanotechnology increases the exposure to nanoparticles through various routes like inhalation, ingestion, dermal and injection [11, 12, 13]. Factors that can alter the risk levels in nanoparticles include:


  • The quantum of material (mass / number of particles)
  • Condition of materials (solution / powder)
  • Degree of exposure
  • Dosage levels


The particles of similar dimensions and elemental compositions can have different properties if the chemical architecture of such particles are modified e.g. diamond crystal and bucky balls. Nanoparticles in the aggregates are likely exhibit the biological effects that could be different from the bigger particles obtained from the same substrate.


Nanomaterials, like single walled carbon nanotubes, vary in terms of the physical forms and physical properties, which make difficult to apply generic rules about the potential health effects. A list of potential hazards due to nanomaterials has been published regardless of their quantitative effects [14]. In many cases, analogies have been drawn with results from very small particles present in large numbers in the urban air, and in some workplaces.


Also, there is no established literature available regarding removal of nanomaterials from human body, water or soil. Inhalation of the nano spheres and nanotubes could cause serious troubles, especially for workers, who are involved in manufacturing and handling.


 

2.1 Environmental Impact


Nanoparticles are not used as such in textile applications and are generally applied on to the substrates in the form of speciality coatings. Without sufficient data on the effects of the nanomaterial in their individual form and aggregates, the impact on environment remains highly hypothetical [10, 14, 15, 16]. Nanoparticles in the environment represent a new class of pollutants for which not much expertise is available.


Air borne nanoparticles have the tendency to float for very long periods and do not settle onto the surfaces easily. Unfortunately, larger surface also means that the nanoparticles can collect and transport pollutants in a larger way compared to any nanoparticles. Also, as the particle size decreases, the reactivity increases, harmful effects are intensified and harmless substances can assume hazardous characteristics. Combustible nanoparticles might cause an increased risk of explosion because of their increased surface area and potential for enhanced reaction.


Nanomaterials suffer from poor water solubility, favour the persistence of chemical in the environment and biological systems, where it can remain for long periods of time.


Even in soil, the nanoparticles may move in the unexpected ways, perhaps, penetrate the roots of the plants and enter into the food chain of humans and animals. Aggregates of nanomaterials are taken up by the living cells, which facilitate the access into the food chain. Nanomaterials are easily absorbed by the earthworms also.

2.2 Health Risks


Nanomaterials, in the human body and other living creatures, are likely to cause multiple problems to various physiological functions [10, 14, 17, 18, 19, 20, 21, 22]. One of the new properties of nanosized particles is their extreme mobility and unrestricted access inside the human body. Nanoparticles can have access through various routes into the body and across membranes such as the blood-brain barrier. During pregnancy, nanoparticles could cross placenta and enter fetus.

Nanoparticles


Nanoparticles harm living tissues, such as lungs through chemical reactivity or by damaging phagocytes, the scavenger cells that remove the foreign substances. Phagocytes become "over loaded" by nanoparticles and result in reduced functioning levels. Successive additions of particles are able to cause reactive damage, and antibodies such as bacteria can penetrate without hinderance. Nanoparticles can carry metals, carcinogenic hydrocarbons deep into the lung to cause asthma serious breathing problems and formation of free radicals. The surface reactivity of nanoparticles gives rise to "free radicals", which in turn can cause inflammation, tissue damages and initiate serious harms such as growth of tumors.


The adverse interactions between negatively charged nanoparticles with positively charged blood cells can result in blood clotting or clumping. The nanoparticles can enter the brain via olfactory nerves. Bucky Balls are found to cause brain damage in juvenile fish along with changes in gene function, which necessitates the assessment of the risks and benefits of this new technology. Juvenile largemouth (Micropterus Salmoides) bass exposed to 0.5 ppm aqueous uncoated fullerenes (C60) for 48 hours has showed a significant increase in lipids peroxidation in the brain, glutathione depletion in the gills [16]. In the case of nanofullerenes (C60), upto 500 nm, a very small concentration (20 ppb) is capable of killing half of the human liver and skin cells. Nano-fullerenes damage brain cells in fish and also halts the growth of bacteria [22].


Ingested nanoparticles can be, potentially, absorbed through 'Peyer's Plaques', the immune system lining the intestines, from where, the nanoparticles can gain entrance into the blood stream, transported through bone marrow, ovaries, muscles, brain, liver, spleen and lymph nodes.


Nanoparticle-protein complex affects the protein metabolism and cause protein degradation at the large surface area of these particles, which may lead to changes in the proteins and their functions. TiO2 / ZnO nanoparticles present in the sunscreens are found to cause free radicals in skin cells and damaging DNA.


 

Carbon Nanotubes


The effects of carbon nanotubes (CNTs) have been studied in the past and the studies reveal that the CNTs can affect mitochondrial DNA in the heart and its aortic artery and result in onset the atherosclerosis. The immune cells called macrophages trap the nanotubes and die subsequently.


Intratracheal installation of single walled carbon nanotubes in the experimental animals has showed pulmonary inflammation and granulomas. Both, the duration of exposure and material characteristics can affect the respiratory process and induce pathological reaction in lung tissues [21]. Mices exposed to nanotubes have showed substantial DNA damage that persisted for at least 6 months. Also, oxidative damages, leading to atherosclerosis risk have been found in animals' heart, aortas, and lungs. The cytotoxicity apparently follows a sequence order on a mass basis [23]


SWNT>MWNT>C60


Phagocytosis of alveolar macrophage can be impaired at the concentration level of about 0.38 g/cm2 in the case of SWNT while injury is induced at 3.08g/cm2 in the case of MWNT and fullerene. At these levels, macrophages show necrosis and degeneration. A 3 hour exposure to nanospheres at a concentration of 70gm/m3 results clotting in less than half an hour. While in the blood stream, nanoparticles have been observed entering the blood cells themselves.


Under different situations, suggestions have been given regarding the communication of the risks associated, precautions to be adopted during development of nanomaterials, measurements and safety measures [1, 13, 24, 25, 26, 27, 28]. Collection of the details related to the types of nanomaterials manufactured and methods of manufacturing nanomaterials from various manufacturers seems to be a logical beginning to address the problems related to nanomaterials. Three areas that need favourable attention [29] are toxicological hazard assessment, measurement and detection, and worker protection and industrial hygiene. Nanotoxicology is slated to be helpful by providing data about safety details of engineered nanostructures, devices and the undesirable properties of nanomaterials.


3.0 Conclusions


The health and safety issues related to nanomaterials are in an early phase of analysis and as a consequence it appears to be impossible to draw far-ranging conclusions about the potential hazards and risks related to exposure to these materials with certainty. Very less reports are available about the effects of nanoparticles on species other than humans or about their behaviour in the air, water or soil and accumulation in the food chains. However, the general framework of assessment methodology could be useful, even at this early stage.


References:


  1. Anon, Nanoscience and Nanotechnologies: Opportunities and Uncertainities- The Royal Society & The Royal Academy of Engineering, Nanoscience and Nanotechnologies, 2004 (7) 2 - 11
  2. Park R.L., Tiny Terrors, New Scientist , 5 July 2003 179 (2402) 22
  3. Haavind R., Let's Not Get Nano-crazy, Solid State Technology, 48 (2005), 12 & 43
  4. Warheit D.B., Hart G.A., Hesterberg T.W., Collins J.J., Dyer W.M., Swaen G.M.H., Castranova V., Soiefer A.I., Kennedy G.L., Potential Pulmonary Effects of Man-Made Organic Fiber (MMOF) Dusts, Current Reviews in Toxicology, 31 (2001) 697 - 736
  5. Thiry M.C., Nanosearch, AATCC Review, 2003 (9) 33 - 36
  6. Qian L., Hinestroza J.P., Application of Nanotechnology for High Performance Textiles, Journal of Textile and Apparel, Technology and Management, Vol. 4 (1), 2004,, Summer
  7. Thiry M.C., Think Small, AATCC Review, 2004 (5) 9 - 13
  8. Qian L., Nanotechnology in Textiles: Recent Developments and Future Prospects, AATCC Review, 2004 (5) 14 16
  9. Stryker L., Titanium Dioxide-Toxic or Safe? Through http://www.usedarticles.com/view /health/733.html accessed March 2006
  10. Hoet P.H.M., Nemmar A., Nemery B., Health Impact of Nanomaterials, Nature Biotechnology, 22 (2004 ) 19
  11. http://www.hazards.org/nanotech/safety.htm, accessed November, 2005
  12. http://www.hse.gov.uk/pubns/hsin1.pdf, accessed November, 2005
  13. Vinardell M.P., In vitro Cytotoxicity of Nanoparticles in Mammalian Germ-line Stem Cell, Toxicological Sciences, 88 (2005) 285 286
  1. Parikh N.N., Thorat B.N., Kanetkar V.R., Safety in Nanotechnology?, Asian Dyer, 2004 (11-12) 63-64
  2. Montague P., Nanotechnology and the Precautionary Principles, The Multinational, 9 (2004) 16-19
  3. Oberdorster E., Manufactured Nanomaterials (Fullerenes) Induce Oxidative Stress in the Brain of Juvenile Largemouths Bass, Environ Health Prospect, 112 (2004) 1058-1062
  4. Raloff J., Nano Hazards, Science News, 19 March 2005 167 (12) 179
  5. Donaldson K., Stone V., Tran C.L., Kreyling W., Borm P.J.A., Nanotoxicology, through www.occenvmed.com accessed Jan 2006
  6. Lee B.I., Nanoparticles for Materials Design: Present and Future, J. of Ceramic Processing Research, 6 (2005) 31 - 40
  7. Hoet P.M., Hohlfeld I.B., Salata O.V., Nanoparticles Known and Unknown Health Risks, J. of Nanotechnology, 2 (2004) 1 12
  8. Huczko A., Lange H., Bystrzejewski M., Baranowski P., Haworska H.G., Nejman P., Przybylowski T., Czuminska K., Glapinski J., Walton D.R.M., Kroto H.W., Pulmonary Toxicity of 1D Nanocarbon materials, Fullerenes, Nanotubes and Carbon Nanostructures 13 (2005) 141 145
  9. Mraz S.J., Nanowaste The Next Big Threat?, Machine Design, 77 (22) 2005 46 53
  10. Jia G., Wang H., Yan L., Wang X., Pei R., Yan T., Zhao Y., Guo X., Cytotoxicity of Carbon Nanomaterials SWMT, MWNT and Fullerene, Environ. Sci. Technology, 39 (2005) 1378 1383
  11. Schuler E., A Prospective Look at Risk Communication in the Nanotechnology Field, Health Review, 2004 (9) 28 32
  12. Dreher K.L., Health and Environmental Impact of Nanotechnology Toxicological Assessment of Manufactured Nanoparticles, Toxicological Sciences, 77 (2004), 3- 5
  13. Albert M., JIMTOF puts Nanotechnology under Magnification, Modern Machine Shop, 77 (8) 2005 98 101
  14. Colvin V.L., The Potential Environmental Impact of Engineered Nanomaterials, Nature Biotechnology, 21 (2003) 1166 1170
  15. Service R.F., EPA Ponders Voluntary Nanotechnology Regulations, Science, 1 July 2005 Vol. 309 p 36
  16. Chow J.C., Watson J.G., Savaga N., Solomon C.J., Cheng Y.S., McCurny P.H., Corey L.M., Bruce G.M., Pleus R.C., Pleus R.C., Biswas P., Wu C.Y., Nanoparticles and the Environment, J. of the Air and Waste Management Association, 55 (2005) 1411 1417



About the Authors:


The authors are associated with the Department of Textile Technology, Bannari Amman Institute of Technology, Erode.