quote:When it comes to assessing the occupational health hazards of exposure to nanoparticles, what can we learn from other small particles and fibers such as asbestos?
That question was the subject of an Oct. 5 presentation made by Fionna Mowat, Ph.D., managing scientist for the Health Sciences Practice of Menlo Park, Calif.-based Exponent, at the Second International Symposium on Nanotechnology and Occupational Health in Minneapolis.
While Mowat's presentation, like many others at the symposium, raised more questions than answers, she concluded that current knowledge of materials such as asbestos, welding fumes and ultrafine particulate matter may be useful in the assessment of the toxicity of nanomaterials.
Drawing a possible parallel to asbestos, Mowat noted that asbestos once was considered a "miracle mineral" before it was discovered to be a human health risk at certain doses.
"Materials like asbestos show us we really need to use caution when developing novel materials and [we need to] use the information we have to develop a health risk assessment paradigm," Mowat said. She noted that information on materials such as asbestos could help to shape future toxicity testing and health assessment of nanomaterials – particularly nanotubes, as asbestos and nanotubes share a common geometry (both are long, thin fibers).
Nanotechnology – which is the manipulation of matter at the molecular level for the purpose of creating extremely small-scale (less than 100 nanometers) materials with unique properties – may be a relatively recent concept, but Mowat noted that human exposure to nanomaterials is not. Forest fires, cooking, vehicle exhaust emissions and the ash from volcanic eruptions are examples of sources of nanoscale particles, she explained.
However, the wide range of applications in which nanomaterials are being used or considered for – from cancer treatment to cell phone batteries – "confers wide opportunity for exposure to humans."
"As for now, workers are experiencing the highest exposures while using the raw materials and synthesizing them [for product applications]," Mowat said. "But we also must think about the end-users and the environment, which is the ultimate sink for these materials."
This all makes sense to me - the concept is pretty basic.
My question is, having this supposition based on similarities to other materials, how do we proceed? If we want to avoid another asbestos situation, what tests could be run to determine if nanotubes and other nanomaterials are safe?
With asbestos, the link was confirmed by epidemilogical studies, although there were also lab studies. But epidemilogical studies would be too late to save some of the victims, and lab studies can't always be generalized.
So, scientific jatraqueros, what testing process would you recommend we implement now, before nanotubes go in to wider spread use than asbestos was.
Posts: 26071 | Registered: Oct 2003
| IP: Logged |
posted
One thing that isn't stated (in your quote at least) is that nanotubes are already being used commerically. Some plastic parts of GM cars already have nanotubes in them. (Better material properties, without the added weight) Is this use a problem? Probably not. Likewise I suspect that there are numerous uses where exposure isn't the same issure that asbestos was.
Edit: source for the GM statement: Mamalis, A.G.V., L.O.G.; Markopoulos, A., Nanotechnology and nanostructured materials: Trends in carbon nanotubes. Precision Engineering, 2004. 28 16-30
Posts: 1621 | Registered: Oct 2001
| IP: Logged |
posted
I think this may be an "artificial sweetener" problem.
This is what I mean by that: we don't know how widespread these materials will become, so it is hard to say what a "normal exposure" to them will be. The same thing happened to a lot of artificial sweeteners..they were intended to be used sparingly, but the US consumers loved them so much they were soon found in all sorts of products they were never intended for use in...and as a result the overall exposure to them was much higher than expected or tested, at least at first.
We have no idea what large amounts of these materials we will be exposed to in the future, and estimating a "normal exposure level" is almost impossible because of the very versatility of these things. They could becomce so widespread that they could pose unforseen risks to large segmants of teh population, or they could be rendered safe by some very simnple percausions...we just don't know yet.
posted
It might sound cruel, but the only way to test such a material for safety is expose an animal model to extreme amounts and use that response to infer a similar response in humans. If done properly the experiment could be done on a relatively small scale, less than a hundred animals. The most likely animal model would be a small mammal like a rat or mouse, as they are relatively easy to obtain and keep in a laboratory setting, and they have organ functions similar to humans. If I were designing the study, I might use a powdered version of the product in question as a bedding for the animals, or have the test group subjected to a ventilation system with a quantified concentrations of the product for a specific period of time. Since we are searching for long term effects, I would probably continue the exposure for a specific period of time, maybe six months, maybe a year or two if I could get funding, then autopsy all animals involved in the study including the control groups. In addition to keeping track of the animal's overall health, the autopsy will let me see if any lesions, tumors, plaques etc. built up as a result of the treatment, but were asymptomatic. I would autopsy the control group to be sure that the entire study hadn't been contaminated by outside factors.
Alternative study options would be to compare these particles to known dangerous substances like asbestos on a chemical level. A chemist or chemical engineer, perhaps working with a physiologist, would try to determine if there was anything inherent in the known substances that could have caused the known problems and compare that with the new substance to decide what features they share, and which of those features are likely to cause similar effects.
I think that the quantified exposure to the substance would provide the most reliable results, not least because it would allow for the set-up of a threshold levels that were unsafe. Drawbacks include the use of animals, the amount of time, a rather labor intensive set-up, and potential exposure of scientist to the questioned substance.
Posts: 349 | Registered: May 2003
| IP: Logged |
posted
We could just allow Monsanto to "oops" let them loose in cornfields and then, "oops" harvest that crop and send it to market and see what happens.
I always prefer the corporate sponsorship of research with huge randomized samples.
Posts: 22497 | Registered: Sep 2000
| IP: Logged |
Printer-friendly view of this topic
![[Razz]](tongue.gif)
![[Big Grin]](biggrin.gif)
