Lung carcinogenicity of inhaled multi-walled carbon nanotube in rats

Tatsuya Kasai,Yumi Umeda,Tetsuya Takeuchi,Hitomi Kondo,Michiharu Matsumoto,Shoji Fukushima,Takashi Mine,Makoto Ohnishi

doi:10.1186/s12989-016-0164-2

Tatsuya Kasai, Yumi Umeda + Show 6 more

Open Access

https://doi.org/10.1186/s12989-016-0164-2

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Abstract

BackgroundMulti-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.ResultsLung 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 duration-dependent manner.ConclusionThere is clear evidence that MWNT-7 is carcinogenic to the lungs of male and female F344 rats, however no plural mesothelioma was observed.Electronic supplementary materialThe online version of this article (doi:10.1186/s12989-016-0164-2) contains supplementary material, which is available to authorized users.

Highlights

Multi-walled carbon nanotubes (MWCNTs) constitute one of the most promising types of nanomaterials in industry today
Scanning electron microscope (SEM) of MWNT-7 collected on polycarbonate filters demonstrated that most MWNT-7 s were single straight fibers and were not aggregated, and no differences in MWNT-7 shape were found between the three target concentrations in any of the samples collected
Exposure to MWNT-7 aerosol for 104 weeks was found to cause statistically significant increases in the incidences of lung carcinomas and combined adenomas and carcinomas in males exposed to 0.2 and 2 mg/m3 MWNT-7 and in females exposed to 2 mg/m3 MWNT7

Summary

Introduction

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. 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]. Straight types of multi-walled carbon nanotube (MWCNT) fibers, like asbestos, have a high aspect ratio and are able to persist in biological tissues [2, 3]. Poland et al reported that intraperitoneal administration in rodents of long, straight types of asbestos or MWCNT fibers, but not nanoparticulate

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