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The nanotechnology effort is such an enabling science, that there are broad applications across both environmental and commercial, medical, and the information technology fields. It’s almost touted as being to the next revolution, analogous to being the next industrial revolution.

There’s a lot of government and federal support in this area because of the potential benefits, and we are now entering the area where we’re seeing these to fruition, and now we want to make sure that we look at the implications associated with nanotechnology.

Some of the implications deal with exposure at the occupational level, where we want to make sure, along with other federal agencies, that the appropriate safety measures are taken, from limiting or eliminating exposure to these particles or materials. We want to know what the impact is of these particles that are being developed for specific applications, what impact they have as a result of the application. For example, if you develop a material that can decrease pollution, what’s the impact potential on other pollutants? So, we’re looking at a bigger picture from that standpoint so that we know what the full extant of the implications from a public health and environmental perspective.

Well, there have been a number of very good reports that put the risk assessment of nanotechnology in perspective. These are specifically, there’s an NNI, the National Nanotech Initiative, they put out, in conjunction with the National Science Foundation, and other federal agencies such as the EPA, and they put out reports that they term “Grand Challenges.” And they’ve put a document out since 2003 looking at the implications of nanotechnology from an environmental and global climate perspective. There is one put out by the United Kingdom Royal Society, as well as a European Nanosafe report, and finally there is another report that’s come out of the United Kingdom from there Health and Safety Executive Council, they are the occupational counterpart to the U.S. NIOSH. And they all indicate that there are some risks associated with nanotechnology, ranging from exposure, toxicological assessment, fate transport, and deposition of nanomaterial, both in the environment, and in biological systems, as well as the ability to identify potentially unique groups that may be particularly susceptible to these types of particles, or their by–products, worker protection, what type of waste streams will be generated, are they similar to what we have currently, or will they be unique waste streams, and how do we handle those. So those are some broad areas where the knowledge gaps have been identified.

As you said, I’m a pulmonary toxicologist. I study particle toxicity on the lung and cardio–vascular system for over ten years, mainly particles derived from combustion emissions. But the same issues that we face on that area, we face with nanomaterials. And some of the challenge is just the broad array of the types of nanoparticles that we may encounter, and how to assess their toxicity in a timely fashion. So, some of my research is directed towards developing validated invitro methods to assess and screen nanomaterials for toxicity. Another area is also looking at what are the acute and chronic toxicities with nanoparticles, and can we conduct comparative toxicological studies to maybe determine how good we can extrapolate from our existing databases on particle toxicity to new nanomaterial – and let me explain that a little further. For example, there are carbon nanotubes that are being made – that’s one of the major, one of the higher products that are entering more into the commercial sector. And these materials are made from carbon. They are made with unique shape and morphology. They’re in the nano range, which is defined as anything below 100 nanometers. But they are made out of carbon, and there is a large database of carbon black toxicities in the literature. So the example would be, can we extrapolate what we know about carbon black nanomaterial to carbon nanotubes. Now, there has been a study by Dr. Lamb and Dr. Warheit in Toxicological Sciences, in 2004, where they in essence addressed that question. And they found something interesting. They found that no, we really can’t. The nanomaterial, these carbon nanotubes, seem to have a unique type of toxicity associated with them that we wouldn’t expect by looking at the literature on small, or nano carbon black particles. So that’s one example of some of the unique challenges that we face in the area of assessing the toxicity of material that’s made smaller, but they’re made of the same composition of other particles that have been looked at in the toxicity area. [

Let me just clarify – I don’t think that all nanomaterial is toxic. Particle toxicity is multi–factorial. And size is just one factor that may relate to toxicological responses. But by no means is size the only factor. One has to essentially do risk–benefit assessment, in terms of a person’s medical condition. But EPA is interested in the environmental and public health impact of nanomaterial and its applications. Speaking in the medical area, that’s more of an FDA issue. But, FDA does have a program that they’ve implemented in looking at the toxicity of these materials, just as they do in other drug applications and assays. So there is in place, with the US FDA, a program to assess the toxicities of nanomaterials that may be used in therapy, diagnostics, imaging. These are all areas where nanotechnology will have an impact. But they all will go through US FDA’s risk evaluation scheme. So people should feel comfortable that they will be looked at before they will be used in those applications.

Yes there have been a number of toxicities that have been evaluated in a number of animal studies as well as tissue culture, where we use specific cells and look at the responses to the various particles from the standpoint of cell survival and change certain biological endpoints. The carbon based nanomaterials, the fullerenes, the buckyballs, and carbon nanotubes – those are all being looked at. And there are a number of papers in the literature, showing at high doses some effects on cell survival – that is they do kill certain cells. But again, I must stress that these are at high exposure doses. Now, the key thing with these toxicological studies is that we need to correlate, or give this information to people that do the exposure assessment of these particles in whatever environment that they’re going to be used in, in terms of their application. That I mean, for example, a company manufactures carbon nanotubes. So, from an occupational setting, we need to know what, if any, exposure they have, and from that, one can estimate a dose, and put the toxicological findings in perspective. One may be exposed to very low levels, and if inhaled, these levels may not trigger responses that we see at the high doses in the cell culture studies. So we need to put into perspective the actual exposure assessment with a toxicological assessment. Now, you mention the carbon–based nanomaterials, the other major areas are the metal nanomaterials. And these are functioned as nanocatalysts. So I would also suggest that that class of nanomaterials is also a very significant component right now, and one application is being used in diesel fuel additives to cut down emissions and increase mileage. So that has been being used in Europe right now, and the impact of that technology is being currently investigated.

The issue of exposure, certainly the documents I mentioned to you earlier in our conversation, indicates the occupational exposure will be the first, most probably area of potential risk for exposure. From the standpoint of environmental exposures to these materials, all of that is linked to their application. I mentioned the impact of nanomaterial on fuel technology. That certainly is a higher risk of exposure by inhalation to the general public. Now, those studies are ongoing, so I can’t tell you where they stand right now, but I can tell you that they are being looked at from a monitoring perspective. So we’re basically at the initial phases of looking at the implication of the applications of nanotechnology. That’s what I’m trying to get at. And there is a very high priority in the federal agencies that have a nanotechnology component, both from environmental and public health.

Well, as you know, most areas of technology generally move faster than people can keep up with, but in terms of the areas of the implications of the applications of nanotechnology, this is a very wide government effort. And it involves the FDA, the EPA, Department of Energy, NIH; all of them have unique missions where nanotechnology will impact them. Each one of these government agencies and institutions has a nanotechnology implications component to their program. For instance, the FDA is looking at the effect of nano titanium dioxide particles as it relates in the use of cosmetics. The National Toxicology Program is evaluating carbon nanotubes and fullerenes. EPA s developing their program to look at the nanomaterial that will most directly impact its mission, both from the standpoint of pollution detection, prevention, and emissions. So, these questions are quite broad, but there is a structure in place now for quite some time throughout the government to look at how technology impacts these various agencies’ missions, because nanotech has such a broad applications in this science.

To answer your question, I think that we are pretty close to being in step with the major types of nanomaterials that are going to be used, either in commercial area, the cosmetic area, the medical area, and the environmental area. Each one of those applications has a corresponding government agency program to assess the risk associated with those materials.

I have not heard of anyone whose health has been adversely impacted, specifically from an manufactured, engineered nanoparticle. A lot of this research and development work has been conducted in academic labs. There has been an exposure assessment study done by Dr. Maynard out of the National Institute of Occupational Safety and Health, that has been published I believe this year or last year, where he went into these academic labs and tried to assess the degree to which these particles will be suspended in the air, what is the risk of exposure, and he was able to monitor the level of these in the air in a controlled study where he tried to do an extreme scenario where these materials will be aerosolized. And he reported those results in the literature in addition, they also assess thermal exposures. So, from the standpoint of carbon nanotubes, there has been a study that has been done from an exposure assessment to these particles. As far as I know, I’m not aware of anyone coming down with diseases that can be attributed to working with these types of particles.

Well, let me just clarify – EPA, in our intramural program, we are not looking directly, we are not conducting active experiments at this time. Essentially, we’re looking at what are the future implications of this technology within EPA’s mission. EPA’s extramural program, in the National Center of Environmental Research, which you’ve talked to Barbara Karn about, they’ve invested funds in the area of developing application of nanotechnology from controlling or detecting pollution. They’ve also invested in detecting health effects of nanomaterials under controlled toxicological studies; again, to get an impact on how different is this material and particle size from what we’ve seen in other types of particle type studies. So, we are just at the initiation studies, or the beginning stages of doing these toxicological assessments.

Well, when we do a toxicological assessment of particles, you can be exposed to particles from a number of routes – inhalation, dermal, or ingestion. So each one of those routes has its own unique toxicological endpoints that we look at. Some of the endpoints that we look at are how any abnormal pathology of the tissues where these materials are deposited in. We look for alterations in physiology associated with these organs. So those are some of the broad types of endpoints that we look at in animal studies. We also look at direct interaction with specific cell types associated with exposure. For example, if inhalation is a route of exposure for the particles, we look at the impact of particles on airway lining cells that regulate mucous secretion, that regulate inflammation, that would be analogous to bronchitis in the lung. So we look at the impact of those particles on the ability of those cells to stay alive. So, those are all of the endpoints that we look at in a general sense, to evaluate the toxicological risk that these particles have. And certainly the dose is also an issue – so we look at dose response relationships for each one of those types of endpoints.

Well, I’m going to speak from the EPA perspective, since I’m not that familiar with the other government agencies, although I’m sure that there are similar types of regulations in place that these materials fall under. But with respect to EPA there’s the Office of Pollution Prevention and Toxic Substances, OPPTS, within EPA, that regulates new chemicals. And, this is probably the Toxic Substances Act where these materials will fall under in terms of regulations. So that if these materials are made, and they’re going to be marketed for open use, for example, an application that impacts the environment and health, these chemicals will fall under the TOSCA regulation. So there are acts in place that will deal with regulating these nanomaterials.

We realize that nanotechnology is a very enabling science, and there are efforts underway and ongoing to make sure that we get the benefits of the science with the full understanding of its implications.

Again, this is a new area that we’re entering into… One thing that you should know is that we’re exposed to small particles throughout our daily lives. You walk outside, and you’re exposed to automobile exhaust, combustion exhaust. There are very small particles in the air in the nanometer range, so it’s not like we have not been exposed to the size ranges of particles in our development. We are exposed to these articles indoors. So we have been exposed to nano–sized particles for as long as we’ve had combustion.

Well, I mean there has been exposure to ultra fine in occupation – welders, smelting areas, so like I’m saying, there is a database relating toxicological responses to small particles. So this is not a new area. The new area is that these particles now are engineered or manufactured with unique characteristics, which may impart to them a unique toxicity or unique exposure routes that we have not encountered before.

Thanks to:

Kevin Dreher, Ph.D.
Pulmonary Toxicology Branch
Experimental Toxicology Division
National Health and Environmental Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, NC