— by Lauren Rugani
Asbestos was once heralded as a miracle material, only to cause hundreds of thousands of deaths. Genetically modified foods were supposed to cure world hunger, but ended up creating the first artificial cancer. Now, as nanotechnology promises improved consumer products, potential cancer therapies and a cleaner global environment, should we take a hint from the past and abandon all efforts, or should we give this emerging technology the benefit of the doubt as it grows into a trillion dollar industry?
Nanotechnology has grown steadily over the past few decades, but has also faced questions about its unforeseen and unintended health and environmental consequences. Because nanoparticles are so small – on the scale of one billionth of a meter – most of the atoms sit at the surface and are able to interact with other materials better than their bulk counterparts. However, the unique physical and chemical properties that make them so useful are also cause for concern, since relatively little is known about their long-term effects.
“Everything that is positive can be negative if we use it in the wrong way,” says Ron Turco, the project coordinator for the Assessment of Nanomaterials in the Environment at Purdue University. For example, the anti-microbial properties of silver nanoparticles come in handy for healing wounds, but could pose a threat to soil microbes, the feeding grounds for many ecosystems. “But there are all kinds of things on the positive side, and I’d hate to see that stifled,” he says. Carbon nanotubes – long, straw-like structures with a molecular arrangement similar to diamonds – are one example of a nanotechnology that has been developed for a wide variety of applications. They are stronger yet lighter than steel, more flexible than plastic and can be either conductors or insulators, depending on how they are “grown.”
Countless possibilities exist for nanomaterials, but because they behave so differently, both researchers and activists think more risk assessment is necessary before they can reach their true potential. Several activist groups are calling for a “complete moratorium” on laboratory use and commercial development of nanotechnology until scientists know more about its long-term effects. “It’s like walking blind on a tightrope without a net,” says George Kimbrell, a staff attorney for the International Center for Technology Assessment (CTA).
Over 500 consumer products contain nanomaterials, from sunscreen and stain-resistant pants to stronger, lighter bicycle frames and golf clubs. But the CTA and other advocacy groups demand a total recall of all consumer nanotech products. They are most concerned about products like sunscreens and cosmetics that are applied directly to the skin, and worry that nanoparticles could slip into the blood stream or harmfully interact with cells. “I’m not sure we know enough about that to paint a clear picture yet,” says Dr. Sheree Cross, a pharmacology researcher at the University of Queensland in Australia. But whether nanoparticles will ever come into contact with living cells is still up for debate. Cross studied the affects of zinc-oxide nanoparticles (a common ingredient in sunscreens) on human skin membranes, and found “negligible penetration” by the nanoparticles.
Concerned activist groups also argue that the nanomaterials only make a product more marketable and don’t really improve them. They frequently use zinc oxide in sunscreen as an example, because these nanoparticles turn a sloppy white mess into a clear mist. However, recent studies have found that nanoparticles like zinc oxide reflect damaging ultraviolet light better than conventional sunscreen ingredients due to their size.
There have been no reported cases of injury or illness from using products made with nanomaterials, but Kimbrell warns consumers that this lack of data cannot be substituted for evidence of a product’s safety. “The jury is still out,” he says, when it comes to the level of toxicity that might result from the unique properties of nanoparticles.
Scientists agree that more work is needed to understand the specific toxic effects of nanomaterials. Most toxicology studies to date have focused on naturally occurring nanoparticles, like volcanic ash, or on incidental nanoparticles that result from manufacturing processes like combustion and mining. But relatively little safety research has been done for the newest type of nanoparticles: engineered nanoparticles. The toxicity of these new nanomaterials and delivery methods are tested in the laboratory “under somewhat unrealistic conditions,” says Pedro Alvarez, a professor of engineering at Rice University. What happens to cell cultures in the laboratory might not be representative of what happens in a live human body or an ecosystem.
Despite this relative uncertainty, scientists are moving toward the development of nanotechnology to benefit personal health and the environment. One of the most rapidly growing areas of nanotechnology research is for the detection and treatment of cancer. Several developing nanotechnologies could help improve imaging resolution and detection accuracy, and could deliver drugs more efficiently. There is even hope of multifunctional nanoparticles that can do all three at once.
Quantum dots have emerged as a leading player for imaging at the cellular and molecular level, and could help catch signs of cancer at the earliest stages. Quantum dots are tiny metal shells that glow under a simple light source – a single ultraviolet lamp, for example – allowing researchers to track them as they travel through a network of blood vessels or tissue. If a quantum dot wanders into a neighborhood of tumor cells, researchers will know the exact location of the growth and can take measures to treat it.
Nanoparticles could also deliver drugs to malignant cells while sparing the healthy, normal cells that they encounter. Most tumor cells have weak membranes, and some research has suggested that nanoparticles can squeeze through the blood vessels into the surrounding tissue. Drugs attached to the surface of the nanoparticle can be designed to activate when they are in a cancerous environment so normal cells are not killed in the process. Such accurate targeting would require a much smaller dose than in conventional treatments that require drugs to travel through the whole body.
“I’m not that optimistic,” says Hua Zhang, a post-doctoral associate at the University of Minnesota Cancer Center. “Quantum dots are a great method to use in vitro, but it would be a long way to go for humans.” Most quantum dots are made from heavy metals, which are known to be toxic inside the body. She also says that because of their size, nanoparticles might accumulate in the liver, spleen or bone marrow, and few groups have studied these long-term effects.
Although some researchers express concern, the public is actually more likely to accept nanotechnology when it comes to treating disease. According to several researchers, this has a lot to do with how the public perceives the benefits in relation to the risks. Kimbrell concedes that some risk is acceptable when it comes to treating cancer, because doing nothing or even using current treatments might not be successful. “Would I take the same risks for manufacturing lightweight tennis rackets? Probably not,” he says.
It also concerns scientists that most nanoparticles will likely end up somewhere in the environment. But no one is certain about what role they will play in an ecosystem over the long term. “This is a whole new class of environmental pollutants,” says Alvarez. Mark Wiesner, a civil and environmental engineering professor at Duke University, says that in order for a nanomaterial to be a risk, it must be exposed to the environment, have the ability to move through the environment, and present a potential hazard, such as toxicity, once it gets there. Alvarez says his group is taking a “proactive approach to risk management,” when it comes to manufacturing and disposing nanomaterials.
Risks aside, nanotechnology also has the potential to resolve environmental problems, promising cost-effective pollutant detection and removal, soil and water treatment, waste reduction in manufacturing, and especially more efficient energy sources to reduce consumption and emissions. “It would be irresponsible to turn our backs on what nanotechnology can do for the planet, but we need to proceed carefully,” says Wiesner.
The benefits and risks of nanotechnology must be balanced from a public perspective, and “it’s a difficult balance to strike,” says Andrew Maynard, the chief science advisor for the Project on Emerging Nanotechnologies at the Woodrow Wilson International Center for Scholars. But new products and long-term safety studies “can be developed concurrently,” says Alvarez. “We have to be careful, not afraid.”
There is some debate over the exact role government should play in regulating nanotechnology. Groups like the CTA that call for overarching regulation, want a government agency to define nanotechnology, require manufacturers to label products containing nanomaterials, and address health and environmental impacts. ” I’d rather have my safety and my family’s safety rest on government determination,” says Kimbrell. Others, like Turco, “don’t think regulatory agencies can do anything.”
“First of all, nanotechnology is poorly defined,” says Wiesner. While nanotechnology technically refers to any material less than 100 nanometers, Wiesner questions whether there really is a difference between something that is 99 nanometers long and something that is 101 nanometers long. “Even if you could define a nanomaterial, how would you measure it?” he continues. There is no tool, for example, for measuring the concentration of nanoparticles in drinking water.
Both researchers and activists do agree, however, that testing methods should be more specific. Not only do nanomaterials act much differently than bulk materials, scientists say there are many parameters, including size, shape, composition, mobility, and surface chemistry that could play a part in determining the toxicity of a nanomaterial. “In order to revise or create new regulation, we must first understand the science,” says Maynard. They also agree that more funding is needed for safety and risk studies to recognize problems before they get out of hand. “As Americans, we tend to have a reactive rather than a proactive attitude, and that is reflected in the funding,” says Alvarez.
Nanotechnology is one of the first emerging technologies to have so much dialogue so early in the game, and this could help to avoid the mistakes of previous technologies that were surrounded by hype. “It is frightening, theoretically, what we might be able to do with it,” says Kimbrell. Others, like Alvarez, are more optimistic: “I think it will cure cancer. That is the holy grail.”