Since the 1980s, the burgeoning nanomaterial field has led to a growing number of manufacturers worldwide making and using these materials in coatings, computers, clothing, cosmetics, sports equipment, and medical devices, among other items. As the word “nano” implies, these materials are extremely small, between approximately 1 and 100 nanometers in size by some definitions. Novel chemical and physical properties occur at this scale, making nanomaterials ideal for creating and manufacturing new or improved products. One of the most promising is the carbon nanotube, a nano-sized cylinder comprising either pure carbon or carbon with residual trace metal content. Available in one layer (single-walled) or many layers (multi-walled), carbon nanotubes’ unique chemical, electrical and mechanical strengthening properties make their use widespread in many materials in manufacturing, research, biomedicine, and other fields.
As with any new, rapidly expanding technology, questions about health and safety need to be resolved so that any unintended risks can be identified and addressed. The National Institute for Occupational Safety and Health (NIOSH) conducts robust research with diverse partners to better understand the occupational health and safety implications of nanoparticles and to recommend prudent strategies for controlling worker exposures as knowledge advances. The following two articles summarize two published papers by NIOSH investigators with partners at Kazan State Medical University, in Kazan, Russia, exploring whether workplace exposure to multi-walled carbon nanotubes could pose a risk for lung disease. For both studies, participants from the same facility in Kazan volunteered to participate. The findings from the studies by themselves do not answer the question of whether workplace exposure to multi-walled carbon nanotubes would result in occupational illness. However, they support the need for further research and underscore the importance of precautionary control measures.
Abnormalities in regulation of cell growth and cell death
Workers exposed to multi-walled carbon nanotubes were significantly more likely than were unexposed workers to have abnormal changes related to various cell functions including cell growth and cell death, according to a study by NIOSH and Kazan University investigators. This study, published in the peer-reviewed journalPLOS ONE, is the first to look at these cellular changes in blood samples from workers exposed to multi-walled carbon nanotubes.
Previous animal and cell culture studies indicated that exposure to multi-walled carbon nanotubes correlated with cellular changes that may lead to a greater potential risk for lung and heart disease, as well as cancer. Now, investigators want to know whether the effects they observed in laboratory studies also might be found in the cells of workers who may be exposed to multi-walled carbon nanotubes in the manufacture and industrial use of these materials. If so, these changes may offer promise as biomarkers to flag subtle effects that could point to risk for development of work-related diseases. To examine the effects, they looked at ribonucleic acid (RNA), molecules involved in many aspects of cellular function. Investigators compared the difference in RNA expression between exposed and unexposed workers at a multi-walled carbon nanotube manufacturing plant in Russia. First, they sampled workplace air during the production of the nanotubes to determine whether, and at what concentration, workers may have been exposed to airborne particles. Next, they examined blood samples from eight voluntary participants who had directly worked with the nanotubes for at least 6 months, and seven voluntary participants who had not worked with the nanotubes at all. The blood tests showed significant changes in those who had worked in nanotube production in the expression of RNAs that control the growth and death of cells. Furthermore, the changes were similar to those that laboratory studies had linked to increased risk for chronic diseases such as lung disease, heart disease, and cancer. Since this study only had a small number of participants, large-scale studies are needed to determine whether the observed RNA changes are useful markers of exposure in workers. Additional work also is needed to determine if the effects observed are specific to the multi-walled carbon nanotubes and if this information can assist in developing good risk management practices. These findings should be considered when comparing the results from similar studies in the United States, such as an ongoing study at NIOSH, the investigators recommended.
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