The Environmental Impact of Engineered Nanomaterials - ACS

Chapter 4

The Environmental Impact of Engineered Nanomaterials

Downloaded by UNIV OF PITTSBURGH on February 9, 2015 | http://pubs.acs.org Publication Date: December 14, 2004 | doi: 10.1021/bk-2005-0890.ch004

KristenM.Kulinowski and VickiL.Colvin Department of Chemistry, Center for Biological and Environmental Nanotechnology (CBEN), Rice University, MS-60, 6100 Main Street, Houston, TX 77005

Nanoparticles are important in natural environments due to their size, tunable properties and accessible surfaces and our control over these properties can be exploited to create or add value to a variety of technologies. Many consumer products that incorporate nanoparticles, such as sunscreens and clothing, are already in the marketplace, and the industry is growing fast. This book highlights also the many valuable environmental technologies that can come from the applications of unique nanomaterial properties. As this nascent technology area matures, the debate about the whether the unknown risks of nanomaterial use balances its established benefits will only intensify. Traditionally, emerging technologies have faced risk assessments and the associated public acceptance issues long after products have been commercialized. In this new century, however, public debate about the relative merits of young technologies is starting much earlier in the development process with more substantial impact on the ultimate commercial enterprise. Genetically modified (GM) foods and the Human Genome Project present contrasting cases. G M enthusiasts ignored or dismissed concerns and soon faced a robust and organized activist campaign against G M products. While this has not had a major impact on sales of G M foods in the US, the European market for such products has essentially disappeared and a global debate has ensued over their use in the developing world. In contrast, the founders of the Human Genome Project acknowledged that the scientific discoveries spawned by their research would likely raise societal and ethical concerns and set aside a portion of their research dollars to address them. No significant backlash has developed against HGP. Some of the same critics of G M foods are now turning their attention to nanotechnology. This kind of negative attention at such an early stage in a new technology's development could profoundly impact its ability to gain a foothold in the marketplace. There is relatively little technical information and proactive public policy © 2005 American Chemical Society

In Nanotechnology and the Environment; Karn, B., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 2004.

21


22

concerning the implications of nanotechnology, and this only sustains the arguments of those organizations opposed to developing nanotechnology. While there are some nanotechnology critics that remain concerned about far-term applications such as nanorobots and human-machine hybrids, most focus on the near-term issues of nanoparticle exposure and toxicity. The actions these critics recommend range from calls for new laboratory protocols to protect workers from unknown risks, to a global moratorium on the manufacture and use of engineered nanoparticles until they can be certified as benign to both humans and the environment. [1, 2] Such concerns have received attention from both US and EU policymakers, and several governments are now contemplating an appropriate response. For example, in response to cautionary public statements made by the Prince of Wales, the UK Royal Society was commissioned to carry out an independent study to assess whether nanotechnology is likely to pose new risks not addressed by current regulations. [3, 4] The US House of Representatives passed a bill in 2003 that requires the integration of societal impact studies into nanotechnology research; similar language appears in the pending Senate version of the bill. [5, 6] While these policy deliberations are in an early, exploratory phase, the ultimate outcome may be a new regulatory stance towards nanotechnology aimed at minimizing exposure to the engineered nanoparticles of greatest concern.

Environmental Impact of Engineered Nanomaterials The question of the environmental impact of engineered nanomaterials is a technical one that scientists and engineers can address experimentally; however, until very recently the topic has received little attention. There are few directly relevant and peer-reviewed studies of engineered-nanoparticle toxicology or environmental impact in the open literature. By 'engineered nanoparticle' we mean nanoparticles with critical dimensions less than 50 nm engineered for a specific function. The modifier 'engineered' is an important one for this work, as it distinguishes nanoparticles created with high perfection and uniformity from the polydisperse, naturally occurring nanoparticles and ultra-fine particles produced in aerosols. The characterization of the environmental impacts of nanomaterials presents many challenges. Most daunting is the extraordinary breadth of nanoscale materials: not only are there many different types, but they can be of many sizes and possess different surface coatings. Moreover, there isn't one 'most important' class of materials on which to focus, nor is there likely to be in the near future. Like polymeric materials, nanomaterials are diverse and will be used in many forms and sizes. In this discussion we limit ourselves to an important class of nanomaterials, namely inorganic, engineered nanoparticles.



23 A key question to pose from the start is by what routes and in what concentrations will people and wildlife be exposed to engineered nanomaterials? A worker in a fullerene manufacturing plant has a different exposure profile than the bowler whose ball is coated with fullerenes. Clearly, it is essential to characterize the expected concentrations of engineered nanoparticles that may be present in the air, water and soil. A useful way to approach the problem is to consider several likely scenarios for how human populations, both in the present and near future, may be exposed to engineered nanoparticles. Each situation presents different issues for characterizing exposure, and their comparison highlights those scenarios most likely to be relevant for engineered nanomaterials. Occupational exposure to nanomaterials is growing as demand increases for nanoparticles that add value to consumer products. The number and diversity of companies building plants to manufacture nanoscale materials will only continue to increase as new applications are developed. Mitsubishi's Frontier Carbon Corporation has begun manufacturing multiton quantities of fullerenes and hopes to produce 300 metric tons annually within two years. [7, 8] Frontier envisions fullerenes being incorporated into thousands of applications, including pharmaceuticals, fuel cells, batteries and high-performance coatings. Mass production of a novel material raises different questions about exposure than does small-scale use in the research lab. However, in the US both groups can consult standardized material safety data sheets (MSDS) to assess the hazards of the compounds into which they may come in contact. The MSDS for most nanoparticles are identical to those of the bulk material of equivalent chemical composition. Thus, despite the extensive body of literature demonstrating the novel chemical and physical properties of most nanomaterial, no new formal requirements have been established for safe handling beyond those already in place for the bulk material. Consumer products containing engineered nanomaterials must also be considered as another potential route of human exposure. Nanoparticles have already been incorporated into personal care products such as sunscreens and cosmetics, where their small size confers benefits such as transparency and increased performance. [9-11] Detailed information on particle size and information is difficult to obtain since the product formulations are considered proprietary by most companies. In 1999, the US Food and Drug Administration considered two petitions regarding the regulation of nanoscopic or "micronized" titania in personal care products. One comment recommended that micronized titania be treated as a "new ingredient with several unresolved safety and efficacy issues." In its final rule, the FDA agreed with the second comment that micronized titania is "not a new material but is a selected distribution of existing material" and that it showed no deleterious effects in animal and human studies. [12] Exposure to micronized titania particles greater than 40 nm through skin



24 absorption has been ruled out in the literature.[13, 14] However, the photocatalytic activity of titania and zinc oxide particles may, through a free radical mechanism, degrade the stability of the organic components of sunscreens, thereby reducing their efficacy.[15-19] Free radical processes can also damage biological tissue, though the risk from sun exposure may be greater.[20, 21] Another question not explicitly addressed by the FDA rule is the relative importance of the physical size of a nanoparticle when considering its risk. The exposure to nanomaterials of factory workers and consumers of personal care products is a near-term issue worthy of more focused attention by the research community. Equally important is the scarcity of data in the literature regarding exposure mechanisms relevant over the long term, e.g., through the accumulation and transport of nanoparticles in the environment. As nanoparticle manufacture continues to increase, and as more products incorporating them are brought into the marketplace, their concentration in the air, water and soil is likely to rise. Therefore, it becomes important for both the technical and policy communities to understand and address the consequences of that possibility. The technical community can help by evaluating the fate and transport of model systems in these surroundings.

Recommendations In the absence of reliable scientific data, policymaking may become unduly politicized. Therefore, concrete actions must be taken to ensure that nanotechnology develops responsibly and with strong public support. The most essential component of a responsible policy is a scientific assessment of the impact of nanomaterials on human health and the environment. A body of solid, peer-reviewed data on potential toxicity, bioaccumulation, and fate of nanomaterials in the environment would identify the specific nanomaterials and applications of greatest potential risk so that the risk can be mitigated or avoided altogether. The technical community must also show itself to be responsive to public concerns by engaging in open dialogues with all stakeholders, including nanotechnology's critics, about the best way to ensure that nanotechnology does not have unintended consequences.

References 1. Arnall, A.H., Future technologies, today's choices: Nanotechnology, artificial intelligence and robotics; A technical, political and institutional map of emerging technologies. 2003, Greenpeace Environmental Trust: London, England.



25 2. ETC Group, No small matter II: The case for a global moratorium. April 2003. 3. Staff, Prince sparks row over nanotechnology, in The Guardian. April 28, 2003: London, England. 4. The Royal Society/Royal Academy of Engineering Study on Nanotechnology,http://www.nanotec.org.uk/index.htm.2003. 5. U.S. House. 108th Congress 1st Session., H.R. 766, Nanotechnology Research and Development Act of 2003. (H.R. 766). 6. U.S. Senate. 108th Congress 1st Session., S. 189, 21st Century Nanotechnology Research and Development Act. 7. Tremblay, J.-F., Mitsubishi chemical aims at breakthrough. Chemical & Engineering News, 2002. 80(49): p. 16-17. 8. Tremblay, J.-F., Fullerenes by the ton. Chemical and Engineering News, 2003. 81(32): p. 13-14. 9. Edwards, M.F. and T. Instone, Particulate products - their manufacture and use. Powder Technology, 2001. 119(1): p. 9-13. 10. Shefer, S. and A. Shefer, Controlled release-systems for skin care applications. Journal of Cosmetic Science, 2001. 52(5): p. 350-353. 11. Spiertz, C. and C. Korstanje, A method for assessing the tactile properties of dermatological cream bases. Journal of Dermatological Treatment, 1995. 6(3): p. 155-157. 12. Department of Health and Human Services, Sunscreen drug products for over-the-counter human use; Final monograph. Federal Register. Vol. 64. May 21, 1999: U. S. Government. 1-28 (see p. 6). 13. Lademann, J., et al., Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice. Skin Pharmacology and Applied Skin Physiology, 1999. 12(5): p. 247-256. 14. Schulz, J., et al., Distribution of sunscreens on skin. Advanced Drug Delivery Reviews, 2002. 54: p. S157-S163. 15. Bahnemann, D.W., et al., Photodestruction of dichloroacetic acid catalyzed by nano-sized TiO particles. Applied Catalysis B-Environmental, 2002. 36(2): p. 161-169. 16. Malato, S., et al., Photocatalysis with solar energy at a pilot-plant scale: an overview. Applied Catalysis B-Environmental, 2002. 37(1): p. 1-15. 17. Ricci, Α., et al., TiO -promoted mineralization of organic sunscreens in water suspension and sodium dodecyl sulfate micelles. Photochemical & Photobiological Sciences, 2003. 2(5): p. 487-492. 18. Picatonotto, T., et al., Photocatalytic activity of inorganic sunscreens. Journal of Dispersion Science and Technology, 2001. 22(4): p. 381-386. 19. Rossatto, V., et al., Behavior of some rheological modifiers used in cosmetics under photocatalytic conditions. Journal of Dispersion Science and Technology, 2003. 24(2): p. 259-271. 2

2


26


20. Hidaka, H., et al., In vitro photochemical damage to DNA, RNA and their bases by an inorganic sunscreen agent on exposure to U V A and UVB radiation. Journal of Photochemistry and Photobiology a-Chemistry, 1997. 111(1-3): p. 205-213. 21. Dunford, R., et al., Chemical oxidation and DNA damage catalysed by inorganic sunscreen ingredients. Febs Letters, 1997. 418(1-2): p. 87-90.


The Environmental Impact of Engineered Nanomaterials - ACS

Recommend Documents