There is a lot of excitement about nanotechnology. “Nano” has become a familiar term in the world today but there is often little understanding of what it is. For example, a poll of 1,001 adults in 2009 found 90 percent of Americans think that the public should be better informed about the development of cutting-edge technologies like nanotechnology (Project on Emerging Nanotechnologies). We will provide some basics that can help you understand more about nanotechnology and especially about how the safety of products made with nanotechnology is established.
What is nanotechnology?
Nanotechnology is the phenomenon and manipulation of materials at atomic, molecular and macromolecular scales. Within this definition are the particles and other forms of materials that are created or manipulated at the nanoscale. Most attempts to describe and categorize nanomaterials have used size to define nanomaterials. The most commonly used size range is 1-100 nanometers (nm) although some definitions include sizes up to 1,000 nm. For perspective, a nanometer is one billionth of a meter. A single grain of salt is about 300,000 nm in diameter. A human hair is about 100,000 nm in diameter. For a fascinating perspective of this scale, click here.
The picture above accompanying this topic shows stylized images of nanoscale forms of carbon called fullerenes. The fullerene forms of carbon can take on various shapes including spheres (buckministerfullerenes), tubes (carbon nanotubes) and sheets (fullerene). At the nanoscale, materials begin to display properties not observed at the larger scale. They reflect light differently. In addition, some other fundamental properties like melting point, electrical conductivity, magnetic properties, fluorescence, and chemical reactivity can change as a function of the size of the material.
Gold is a good example of a material which displays different properties at the nanoscale. We are all familiar with gold as a precious metal. Its yellow color and resistance to tarnishing makes it an attractive choice for jewelry or as a corrosion-resistant material for high-end electrical connectors. However, take some gold particles and pound them down to a thin film of just a few nanometers in thickness as goldsmiths in the middle ages did and the color shifts from yellow to red and purple. In addition, at this scale, rather than being an inert metal, gold becomes capable of catalyzing chemical reactions. This makes nanoscale gold a very different material from its larger form. Click here to learn more about how, even further back in history, the ancients took advantage of the properties of nanotechnology. One example is the Lycurgus cup pictured here.
What else makes nanoscale materials useful?
In nature, nanoscale properties are responsible for the self-cleaning properties of the lotus leaf (https://www.youtube.com/watch?v=VHcd_4ftsNY) or the intense and iridescent colors of the monarch butterfly or the shimmering opalescence of pearls. By studying these types of effects in nature, man has been able to reapply some of these properties to bring new functions and capabilities that can be useful for a wide variety of applications from environmental clean-up, energy production, electronics, medicine, cleaning products, cosmetics, and food production.
Some specific examples of how nanotechnology has been applied include:
• Ground water clean-up – Nanoscale materials such as iron have been used to successfully clean up groundwater contaminated with chlorinated solvents such as trichloroethylene. Nanotechnology has also been applied to groundwater remediation of many other types of contaminants as well. Click here for a link to a review of the use of nanotechnology in the remediation of several examples of contaminants.
• Flat panel displays – Modern flat panel displays, such as on your TV or computer display, are brighter and can produce more realistic colors thanks to the tunable light-emitting properties of the materials used to generate the images.
• Sunscreen – Many sunscreens contain nanoparticles of zinc oxide or titanium oxide. Sunscreen formulas using nanoscale forms of these materials are almost invisible on the skin compared to the older formulations using the larger size particles. The small size also improves the uniformity of coverage on the skin and improves the overall effectiveness the sunscreen at protecting from UV radiation.
• Self-cleaning glass – Some materials such as silicon dioxide (ordinary sand) can have photocatalytic effects at the nanoscale. When UV radiation from light hits the glass, the nanoparticles become energized and begin to break down and loosen organic molecules (“dirt”) on the glass.
• Clothing – Nanotechnology is being used to enhance your clothing. By coating fabrics with a thin layer of zinc oxide nanoparticles, manufacturers can create clothes that give better protection from UV radiation. Some clothes have nanoparticles in the form of little hairs or whiskers that help repel water and other materials, making the clothing stain-resistant.
• Scratch-resistant coatings – Engineers discovered that adding aluminum silicate nanoparticles to scratch-resistant polymer coatings made the coatings more effective, increasing resistance to chipping and scratching. Scratch-resistant coatings are common on everything from cars to eyeglass lenses.
• Nano-enabled packaging – Common packaging films such as polyethylene are being improved by including nanoscale materials such as clays in the film to further reduce permeability to gases and moisture. The result is a packaging film that is more effective at protecting freshness.
There are many other examples how nanotechnology is being used. Since 2007 the Woodrow Wilson Center project on Emerging Nanotechnologies has been compiling a list of consumer projects on the market that utilize, or claim to use, some aspect of nanotechnology to improve performance over conventional products. Click here to see this list, which, while not necessarily comprehensive, illustrates how broadly nanotechnology can be applied.
How do we know if products made with nanotechnology are safe?
Now that we know what it is and how it can be used, we come to the next question of how the safety of nanotechnology is determined. As with any material, the risks associated with using nanoscale materials depends on understanding both hazards and exposure. Recall that hazard is the inherent ability of something to cause harm while exposure is the level that is predicted to cause the harm. Together these two elements form the basis for assessing the risk posed by a chemical. See our post on Hazard vs Risk for a more complete description.
The primary uncertainty in understanding for potential hazards associated with nanotechnology whether there are unique biological effects caused by novel surface chemistry found only at the nanoscale. This has been an area of intense study and a pattern is emerging that suggests these effects may be predicted with tools provided by quantum theory. In the meantime, the biological effects caused by surface chemistry are currently evaluated by toxicologists on a case-by-case basis for each nanomaterial through by testing each of the variants of a nanoscale material.
There are also other questions related to exposure. Because of their small size, do nanoparticles reach parts of the body that larger size particles cannot? It appears that nanoparticles applied to the skin tend to stay on the surface of the skin and are not likely to reach other parts of the body. However, we also know that some inhaled nanomaterials can move to parts of the body that their larger scale cousins cannot reach. Do they cause harm in this case?
Fortunately it appears that most methods available for answering these questions for traditional materials can be used to answer questions about nanomaterials. In a massive multi-national effort sponsored by the Organization for Economic Cooperation and Development (OECD) that spanned more than seven years, the methods used to evaluate the toxicity of more traditional chemicals were found to be appropriate for the evaluation of nanomaterials (http://www.oecd.org/chemicalsafety/nanosafety/testing-programme-manufactured-nanomaterials.htm).
In 2007 a framework for evaluating nanomaterial was developed in a joint effort between DuPont and Environmental Defense that has served to guide the development and sustainable application of nanotechnology across numerous industries. Government agencies around the world have also been developing regulatory strategies to ensure that nanomaterials in commerce and products using nanotechnology are safe. For instance, in the United States, both the Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) have issued guidelines for the responsible development of nanomaterials and expectations for assessing safety.
Work continues to improve techniques and approaches for evaluating nanoscale materials but the fundamental tools are in place to evaluate potential health or environmental effects from nanoscale materials.
Nanotechnology holds great promise for improving lives and protecting the environment. However, there is a continuous need to evaluate whether there are risks associated with specific nanomaterials and determine whether a particular application is safe. Fortunately this is well recognized across the scientific and regulatory community and efforts are ongoing to ensure that the best tools are developed and applied appropriately to evaluate these materials.
Resources for further information:
FDA on nanotechnology— http://www.fda.gov/scienceresearch/specialtopics/nanotechnology/default.htm
National Institutes of Health/National Institute of Environmental Health Science on nanomaterials – http://www.niehs.nih.gov/health/topics/agents/sya-nano/
National Nanotechnology Initiative (NNI)—http://www.nano.gov/about-nni
Risk Bytes (University of Michigan Center for Risk Analysis)
Nanoparticles and Sun Screens: https://www.youtube.com/watch?v=VV0cCg4clMw
What you should know about silver nanoparticles: https://www.youtube.com/watch?v=Yz6LuH-11II
Society of Toxicology on nanotechnology–https://www.toxicology.org/script/admin/toxtopics/114719_AM_TT4_NanotechnologySOT.pdf
Woodrow Wilson Center – Project on Emerging Nanotechnologies—http://www.nanotechproject.org/
Source of image showing nanoscale forms of carbon: Wikimedia Commons
Related topic: Hazard vs risk