Nanotechnology poses a question for occupational health and safety professionals. Does this technology, and the tiny nanoparticles that are its tools, pose an unintended risk of illness or injury for workers employed in the industry?
National Institute for Occupational Safety and Health in an effort to understand the health and safety consequences of nanomaterials forefront of work. A growing number of scientific publications of large research institutions, including just this week, the address of one type of nano-materials, especially Single-walled Carbon Nanotubes issued a new study, and seek to determine whether they have biological behave like asbestos. That is, if inhaled, is likely to cause irreparable nanotubes and deadly effects, such as those associated with asbestos exposure? Effects of asbestos, including severe lung fibrosis, or scarring, lung cancer, including lung or pleura called mesothelioma, a cancer of the lining.
The question of a comparison between carbon nanotubes and asbestos arises for several reasons. Some varieties of carbon nanotubes are similar in shape to asbestos fibers, and like asbestos, some varieties of carbon nanotubes have been shown in laboratory studies to persist in the lungs of laboratory animals. Some animal studies have even shown effects similar to those of asbestos.
Carbon nanotubes are tiny, cylindrical, manufactured forms of carbon. There is no single type of carbon nanotube. One type can differ from another in terms of shape (single-walled or multi-walled) or in chemical composition (pure carbon or containing metals or other materials). Carbon nanotube exposures can potentially occur not only in the process of manufacturing them, but also at the point of incorporating these materials into polymer composites, medical nanoapplications, and electronics.
The question of whether carbon nanotubes pose a toxicological hazard has been investigated since at least 2003. A challenge has been in determining if carbon nanotube materials used in the workplace have the same characteristics as those associated with biological responses in laboratory studies. Earlier studies used materials with high levels of other forms of carbon such as carbon black and high levels of metal catalyst.
Carbon nanotubes can vary widely in diameter, length, number of layers, and structures. They can also vary widely in surface composition, since certain carbon nanotubes may be “coated” with specific metals or other materials in order to perform specific functions. Also, they can clump together or agglomerate, which can affect their potential for settling in the lungs if inhaled, their ability to penetrate the body’s membranes and consequently move from the lungs to other organs, and their interaction with cells and tissue. Such variations bring an additional degree of complexity to risk assessment analysis for carbon nanotubes.
Asbestos-like responses to carbon nanotubes may not be entirely surprising to scientists, given previous toxicological and epidemiological studies of other biopersistent fibers since such studies show that once fibers are deposited in the lung, they stay there.6 However, questions have been raised about using these research findings for risk assessment analysis in the light of study limitations such as use of model animals, artificial administration methods, and sometimes extremely high doses, which are not representative of those exposures usually present in the workplace environment. Such limitations are not unusual for pioneering scientific studies. They simply mean that at this stage of the research, gaps remain that need to be closed by further study before quantitative risk assessment can be conducted.
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