The Science of Small

Targeted delivery of drugs. Innovative ways to filter water. Stain-free slacks... The benefits of nanotechnology—the engineering of materials on a molecular scale—seem limited only by human imagination. Nanoparticles like titanium dioxide are already used in sunscreen lotions to filter out harmful ultraviolet light. Other nanoparticles are currently helping clinicians diagnose and treat disease by attaching themselves to cancer cells or other targets. In addition to such clinical goals, the emerging discipline of nanobiotechnology, a marriage of nanotechnology with biotechnology, seeks to limit the health risks of nano-based products. No one knows, for example, what will happen when nanomaterials used in tennis rackets and car bumpers—not to mention cosmetic products—inevitably find their way into the environment and our bodies. Jonathan Links, a co-founder of the Johns Hopkins Institute for NanoBioTechnology, met recently with Johns Hopkins Public Health editor Brian W. Simpson to discuss the public health aspects of this new technology. Links, PhD '83, is a professor of Environmental Health Sciences at the Bloomberg School.

The benefits of nanotechnology—new drugs, new diagnostic tools and new ways to keep your clothes from getting stained—sound terrific. Why is this a public health issue?

If you look at the history of technological development, the potential benefits are what folks almost exclusively focus on at the beginning. But we've seen in virtually every case, after the fact, that there is a recognition of at least some potential threats to human health and to the environment.

Give us a few examples.

Propellants in aerosol cans. Asbestos. Genetically modified organisms. The list goes on and on. Now here is the important point. Absolutely, positively, every one of these technological advances is truly an advance; it truly does bring benefits. But the delayed recognition of the potential risks is harmful because the beneficial technologies are not rolled out in an optimal way to mitigate and reduce risks. With nanotechnology, there's been more of an early recognition of the need to look at risks hand in hand with looking at benefits and technological development.

Have there already been any reported health consequences of nanobiotechnology?

Over the past several years, there's been a modest emergence of original research papers focused on what's now a new field, called nanotoxicology. However, most of what we know about the potential risks of nanotechnology is really based on extrapolation from other environmental agents.

Tell us about some of the specific public health issues involved with nanotechnology.

In the Institute, we've conceptualized things into four sets of questions. The first set has to do with the environment: How does a nanomaterial get introduced into the environment? And once there, where does it go? Air, water, soil, food? The second set of questions is under the heading of exposure assessment: What are the routes of human exposure—inhalation, ingestion or skin absorption? The third category is what we would call basic toxicologic assessment: What does the body do to the materials, and what do the materials do to the body? In the fourth group, epidemiologic investigations, we're interested in identifying the most relevant and significant patterns and pathways of human exposure to engineered nanomaterials, and the most relevant adverse human health outcomes. And we want to identify cohorts within populations who are most susceptible.

Is there any real oversight in terms of industry developing these materials and then just rolling them out?

It depends on the type of product. For drugs, absolutely. Drugs are regulated from the get-go. You have to provide upfront any information about toxicity or the lack thereof. For consumer products like sunscreens, human hazard evaluations aren't required. But we really need to broaden our thinking about exposure. The vast majority of environmental exposures are unintentional and unwanted. Consider asbestos. Fifty years ago you would have said, "Why the heck would we need to evaluate its effects on human health? It's an insulation and a flame retardant. We're not giving it to people."

So today, if you're using nanomaterials to make clothing resistant to stains, would anybody notice?

If it's a consumer product, it may or may not get noticed. What's interesting is that the Feds have identified inhalation and skin absorption as the two primary routes of exposure of interest. If a textile is rubbing against your skin, is there transfer? No one knows the answer. It's likely if you're slathering on sunscreen, there's some transfer.

Should we be using this stuff or not?

It's a philosophical decision as much as anything. There's a concept in environmental health called "prudent avoidance." It says that in the face of uncertainty it's prudent to avoid exposure—but then you're also avoiding the potential benefits. So when anyone asks me about exposure to a toxin in the context of a beneficial activity, I always say it's the balance between the risk and the benefit. I think it's no different than when I get called by somebody who wants to buy a house and the radon test came back at some level above the EPA action level. Should they buy the house? I always ask them: How much do you like the house?

There seems to be an unavoidable tension between creating and selling new products and ensuring they are safe.

Historically there has been a tension, but there's no need for it. The consumer applications ultimately depend on minimizing risk. Your best shot at minimizing risk is to simultaneously think about benefits and risks as you develop the technologies.

This is one goal of the Institute?

Yes. And the cool thing is that this notion of studying benefits and risks together is epitomized by what we're doing in the Institute. The same exact products that you're developing for their beneficial uses can be used to study their own risks. For example, the guy on the next lab bench in the Institute may be developing a diagnostic nanomaterial (meaning a material that's introduced into the body and then externally detected), and I'm saying, can I have a little bit so that I can study the risks? I can use the same technologies to learn how much of the nanomaterial gets into the body, where it goes and if it presents a risk.

In 10 years, will the proper regulatory mechanisms be in place to evaluate nanoproducts before they hit the marketplace?

I think it will look remarkably advanced compared to where we are now, but I hesitate to ever say that for any type of testing of any materials, not just nanomaterials, we will have hit the nail square on the head and done everything that needs to be done. In Environmental Health Sciences, we're constantly finding out bad things about stuff that has been in use for years and years.