Nanosilver in consumer products: a topic for integration of ethical & social implications with biology.
Lessons incorporating specific nanoparticles and applications can be built upon the students' general conceptual grasp of nanotechnology. Titanium dioxide nanoparticles or carbon nanotubes are excellent candidates for this purpose, but in this brief article I have chosen to elaborate on nanosilver. Interest in silver nanoparticles stems from the element's historically established, broad use as an antimicrobial agent-in ancient drinking vessels, the eyes of newborn infants, battlefield wounds, and more-prior to the advent of antibiotics. Even minute quantities of nanosilver particles shed vast numbers of silver ions, because reactive surface area per mass is increased by several orders of magnitude compared to bulk material. Wound dressings made with nanocrystalline silver have shortened healing times due to unexpected immunomodulatory properties. Their use has decreased the frequency of painful dressing changes for burn and chronic wound patients. Nanosilver has also been incorporated into numerous consumer products, including textiles, food storage materials, dietary supplements, coatings, and cleaning products. The Project on Emerging Nanotechnologies offers a consumer product inventory file specific to nanosilver (http://www.nanotechproject.org/inventories/silver/) as well as a searchable inventory for consumer products containing nanomaterials (http://www.nanotechproject.org/inventories/consumer/search/).
Why is the incorporation of nanosilver into consumer products the subject of controversy? One reason is that the scale of production, use, and disposal is unknown; mechanisms for acquiring these data are lacking nationally and internationally Although silver has been used for centuries without evidence of life-threatening toxicity and infrequent emergence of resistance, some toxicological studies of nanosilver in rodents have indicated cause for concern: distribution to multiple target organs, liver damage, inflammation, and production of reactive oxygen species (reviewed in Wijnhoven et al., 2009). Environmental concerns include toxicity for aquatic organisms and nitrogen-fixing bacteria (Kumar et al., 2011; Musee et al., 2011). In the face of this uncertainty, concerned stakeholder responses have included calls for a moratorium, additional data, and/or increased regulation. Others have advocated for decreased barriers to commercialization of nanotechnology-enabled products in the interest of boosting the struggling economy.
The controversy surrounding the use of nanosilver in commercial products can draw students into debate with clusters of related questions and many possible topics. In the limited scope of this article, I will suggest three short sets of questions.
Asking students whether killing bacteria is always a good idea or to describe appropriate contexts for germ-killing products may serve to facilitate discussion of microbial diversity, beneficial bacteria, the Human Microbiome project, the immune system, nitrogen fixation, and/or antibiotic resistance.
Students may be invited to consider cultural norms about hygiene, and how they vary by place and through historical time. If evidence for the "hygiene hypothesis" (that attributes increased rates of asthma and allergies to overuse of antimicrobials) continues to mount, how would students weigh risks and benefits of antimicrobial consumer products?
Exploring human factors in the development of novel technologies, one may ask students to identify stakeholders, their interests, and the benefits and risks they face. This line of questioning may also lead in many different ways: How can we determine whether a new product, or any product, is safe and effective? What does "safe" mean? Who is responsible for safeguarding public health? How can human concerns be weighed against the well-being of other creatures, or of the earth itself? Do future generations of humanity merit as much consideration as present ones?
** Rationale & Objectives
Students will learn what nanotechnology is and gain understanding of biology at the nano scale, even as many American adults remain unfamiliar with the term "nanotechnology" (Satterfield et al., 2009). This classroom experience should increase student comfort with science-based questions where the answers are not definitive. In debate about issues with broad societal implications, students should learn to recognize multiple stakeholders and the validity of diverse viewpoints. Discussions should increase student appreciation of the is-ought distinction and demonstrate the value in exploring both "Can ... " and "Should ... " questions about an emerging technology. Consideration of nanosilver encourages increased knowledge about microorganisms and infectious disease. Selection of nanotechnology rather than, or in addition to, established bioethics controversies will encourage students to spontaneously recognize and explore inherent ethical and social issues related to biological science beyond familiar or apparent ones. This lesson may also prime students' critical attention to advertising and media portrayals of emerging technologies and novel products. Together, these objectives aim to foster maturation of students as thinkers, consumers, and citizens in the biological science classroom.
Kumar, N., Shah, V. & Walker, V.K. (2011). Perturbation of an arctic soil microbial community by metal nanoparticles. Journal of Hazardous Materials, 190, 816-822.
Musee, N., Thwala, M. & Nota, N. (2011). The antibacterial effects of engineered nanomaterials: implications for wastewater treatment plants. Journal of Environmental Monitoring, 13, 1164-1183.
Satterfield, T., Kandlikar, M., Beaudrie, C.E.H., Conti, J. & Harthorn, B.H. (2009). Anticipating the perceived risk of nanotechnologies. Nature Nanotechnology, 4, 752-758.
Wijnhoven, S.W.P., Peijnenburg, W.J.G.M., Herberts, C.A., Hagens, W.I., Oomen, A.G., Heugens, E.H.W. & others. (2009). Nano-silver - a review of available data and knowledge gaps in human and environmental risk assessment. Nanotoxicology, 3, 109-138.
KATHLEEN EGGLESON is a Research Scientist in the Center for Nano Science and Technology at the University of Notre Dame, 275 Fitzpatrick Hall, Notre Dame, IN 46556. E-mail: firstname.lastname@example.org.
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|Title Annotation:||Quick Fix|
|Publication:||The American Biology Teacher|
|Date:||Jan 1, 2013|
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