The Perils of Small Stuff: What We Know About Nanotech Safety Today
|Vincent Castranova studies the safety of nanotech and other small particles at the National Institute for Occupational Safety and Health in Morgantown, West Virginia.|
Though nanotechnology has only really taken off in the last 15 years or so, nano-size particles—materials that range roughly from 1/1,000 to 1/100,000 the diameter of a human hair— have been with us for much longer. Welding fumes, diesel fumes and fire smoke all have nanoparticles in them. Vincent Castranova has studied the health effects of all of these substances and more.
Castranova is chief of the Pathology and Physiology Research Branch at the National Institute for Occupational Safety and Health in Morgantown, W. Va. He joined the institute in 1977, soon after it opened. At the time, he studied black lung disease in West Virginian coal miners, providing scientific evidence that coal dust caused the disease. Now, he's leading an effort to study the safety of nanotechnology, analyzing how nanotech factories might affect workers and how cleaning sprays containing nano-silver particles affect people who use them at home.
Castranova's institute, which members call NIOSH (NYE-osh), does research and makes recommendations for rules to protect people from stress, injury and chemicals in their workplaces. It doesn't make laws itself, however; it's supposed to be an apolitical body that sticks to the science. Castronova told InnovationNewsDaily that it was the quality of the research at NIOSH that drew him to the institute after he received his doctoral degree.
InnovationNewsDaily spoke with Castranova over the phone about his nanotech research and his long career studying how very small things affect the lungs, blood vessels and heart. Here's an edited transcript of the conversation.
Why is NIOSH so interested in nanotechnology now?
In about 2004, it was forecast that the nanotechnology industry would grow substantially over the next decade or two, that there may be as many as a million people working in that industry worldwide, that the industry was going to produce materials where we knew very little about the health effects of exposure.
What’s interesting about that effort is this is probably the first time in occupational health where the science is trying to get information on health effects before there is known disease. With coal workers' pneumoconiosis, what we call black lung, there was known disease in coal workers. With asbestos, there was known disease in people who were working in the asbestos industry. So the science that proved causation came after there was actually human disease.
In this case, the industry is just in its infancy and there is no human disease as yet. So what we’re hoping is that we will be able to have recommended standards, have recommendations for controls and handling practices, to avoid disease altogether. So as a public health effort, this is sort of unique, in that it’s an opportunity to be preventative, rather than reactionary.
Tell us about the studies you've done on consumer products that have nano-size material in them.
We’ve been looking at titanium dioxide and silver nanoparticles used in antimicrobial sprays. People spray them on bathroom tile, to kill mold and mildew. They’re also used very often in hospitals. As you can imagine, when you’re spraying, the material becomes aerosolized and can be inhaled.
In our studies, we mimic what would be the consumer use of that material. We measure the airborne levels of the nanoparticles. And then we expose animals to those airborne levels of that nanoparticle and look at how the lungs, heart and blood vessels respond.
The titanium dioxide sprays study is completed and we have published a paper on it. We saw that there were minor lung effects and some significant cardiovascular effects: The small blood vessels couldn't dilate normally. Usually, when you exercise, you want your vessels to dilate. That will increase oxygen flow to the heart.
These effects are not likely to occur in consumers that are spraying two or three showers in their houses during the day. But if you were a janitor in a sports complex and spraying a number of showers, or if you were in a hospital, spraying every surface in every room in the hospital, you could reach the exposure levels that we saw were having effects in the animals.
So what do you think should appear on warning labels?
It’s possible that it may be as simple as, “Use this material in highly ventilated areas.” So that means when you’re spraying it on your bathroom tile, keep the window open, have a fan running. For janitors and people cleaning hospitals, perhaps we would recommend that they wear personal protective equipment, like a face mask.
Do nanoparticles pose a special threat that's different from coal dust or other small, but not nano-size, things?
If you make particles very, very small, they have unique physical and chemical characteristics and the question is, "Will you also have unique biological interaction?" And there's no reason to suspect you wouldn't.
The example I like to give is this famous glassware from the island of Burano in Venice, Italy. The famous color is red. That red color is from nano gold and you know gold is yellow, right? But if you make it small enough, it looks red. So that's the easiest way to see that if you make things very small, physical and chemical properties change.
In what industries are workers exposed to nanoparticles?
Well, nanoparticles are being developed for uses in almost all industries. For instance, they are being used in sunscreens because they absorb ultraviolet light. They’re used in cosmetics because the nanoparticles allow the cosmetics to be applied more smoothly and evenly.
They’re used in automotive industry because they can be used in composites for light weight and strength. They’re being used as an additive to diesel fuel because they decrease pollution in the exhaust.
They’re being used in athletic equipment such as tennis rackets, golf clubs. And lastly, they’re being explored for use in nanomedicine, in targeted drug delivery, medical imaging and dental implants.
What have you found in your worker safety studies?
With nanotitanium dioxide and carbon nanotubes, we do find there is the potential, after inhalation exposure, for adverse health effects in a worker.
We found that carbon nanotubes tend to cause chronic lung scarring, called interstitial fibrosis. The carbon nanotubes get into the tiny air sacs in the lungs and form a matrix upon which fibrous cells grow very rapidly.
Breathing in carbon nanotubes and titanium dioxide nanoparticles also seems to depress the ability of the small blood vessels in the circulatory system from dilating normally, as I mentioned before. So potentially, if we had a worker with who already had heart disease, it’s possible they would have a heart attack or stroke because of these exposures. So we’ve come up with a recommended exposure limit.
The good news is that the material is fairly easy to control, as far as airborne exposure. Increased ventilation has been shown to vastly decrease the airborne concentration of these nanoparticles. High-efficiency filters, or HEPA filters, capture the material very effectively, as do the filters used in facemask respirators. Our "current intelligence bulletins" on our website have sections that recommend exposure controls and how one could put those exposure controls in place.
How do you go from black lung to nanotech? Are these related at all?
In my career, at least, moving from coal dust to silica to these somewhat unusual exposures like artificial butter flavoring and now to nanoparticles—is sort of a natural progression. As one learns how the body responds to particulates, one gains the background that helps one move from one particle to another.
And so the types of particles in nanotechnology might be different in name or composition or shape, but the general problems might be somewhat similar. We didn’t have to reinvent the wheel. We knew how the material would be generated in the air, how we would measure that material in the air, and how we would go about testing the biological activity of those materials.