Lung carcinogenicity of inhaled multi-walled carbon nanotube in rats
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RESEARCH
Open Access
Lung carcinogenicity of inhaled multiwalled carbon nanotube in rats Tatsuya Kasai*, Yumi Umeda, Makoto Ohnishi, Takashi Mine, Hitomi Kondo, Tetsuya Takeuchi, Michiharu Matsumoto and Shoji Fukushima
Abstract Background: Multi-walled carbon nanotubes (MWCNTs) constitute one of the most promising types of nanomaterials in industry today. With their increasing use, the potential toxicity and carcinogenicity of MWCNT needs to be evaluated in bioassay studies using rodents. Since humans are mainly exposed to MWCNT by inhalation, we performed a 104-week carcinogenicity study using whole-body inhalation exposure chambers with a fibrous straight type of MWCNT at concentrations of 0, 0.02, 0.2, and 2 mg/m3 using male and female F344 rats. Results: Lung carcinomas, mainly bronchiolo-alveolar carcinoma, and combined carcinomas and adenomas were significantly increased in males exposed to 0.2 and 2 mg/m3 MWNT-7 and in females exposed to 2 mg/m3 MWNT-7 compared to the clean air control group. However, no development of pleural mesothelioma was observed. Concentration-dependent toxic effects in the lung such as epithelial hyperplasia, granulomatous change, localized fibrosis, and alteration in BALF parameters were found in MWNT-7 treatment groups of both sexes. There were no MWNT-7-specific macroscopic findings in the other organs, including the pleura and peritoneum. Absolute and relative lung weights were significantly elevated in male rats exposed to 0.2 and 2 mg/m3 MWNT-7 and in all exposed female groups. The lung burdens of MWNT-7 were clearly increased in a concentration-dependent as well as a durationdependent manner. Conclusion: There is clear evidence that MWNT-7 is carcinogenic to the lungs of male and female F344 rats, however no plural mesothelioma was observed. Keywords: Lung carcinoma, Lung carcinogenicity, Multi-walled carbon nanotube, MWCNT, MWNT-7, Inhalation carcinogenicity, Whole body inhalation, Rat
Background One of the most important developments in industrial technology is nanotechnology. Various nanomaterials, especially carbon nanotubes (CNTs), have exceptional electrical, mechanical, and thermal properties, enabling the commercialization of various types of CNTs for use with numerous applications in industry, and in recent years the production of CNTs has significantly increased [1]. On the other hand, with the rapid growth of CNT use, serious concerns have been expressed about their adverse effects on the health of workers during CNT manufacturing and handling processes and on the health of consumers exposed to commercial end products * Correspondence: [email protected] Japan Bioassay Research Center, Japan Organization of Occupational Health and Safety, 2445 Hirasawa, Hadano, Kanagawa 257-0015, Japan
containing CNTs. At present, however, neither epidemiological nor medical case studies have been reported on health consequences in CNT-exposed workers or consumers. Long, straight types of multi-walled carbon nanotube (MWCNT) fibers, like asbestos, have a high aspect
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