Carbon fibers are high aspect ratio structures with diameters on the submicron scale. Vapor grown carbon fibers are contained within multi-walled carbon tubes, with VGCF™-H commonly applied as a conductive additive in lithium-ion batteries. However, several multi-walled carbon fibers, including MWNT-7, have been reported to induce lung carcinogenicity in rats. This study investigated the carcinogenic potential of VGCF™-H fibers in F344 rats of both sexes with the vapor grown carbon fibers VGCF™-H and MWNT-7 over 2 years. The carbon fibers were administered to rats by intratracheal instillation at doses of 0, 0.016, 0.08, and 0.4 mg/kg (total doses of 0, 0.128, 0.64, and 3.2 mg/kg) once per week for eight weeks and the rats were observed for up to 2 years after the first instillation. Histopathological examination showed the induction of malignant mesothelioma on the pleural cavity with dose-dependent increases observed at 0, 0.128, 0.64, and 3.2 mg/kg in rats of both sexes that were exposed to MWNT-7. On the other hand, only two cases of pleural malignant mesothelioma were observed in the VGCF™-H groups; both rats that received 3.2 mg/kg in male. The animals in the MWNT-7 groups either died or became moribund earlier than those in the VGCF™-H groups, which is thought related to the development of malignant mesothelioma. The survival rates were higher in the VGCF™-H group, and more carbon fibers were observed in the pleural lavage fluid (PLF) of the MWNT-7 groups. These results suggest that malignant mesothelioma is related to the transfer of carbon fibers into the pleural cavity. The intratracheal instillation of MWNT-7 clearly led to carcinogenicity in both male and female rats at all doses. The equivocal evidence for carcinogenic potential that was observed in male rats exposed to VGCF™-H was not seen in the females. The differences in the carcinogenicities of the two types of carbon fibers are thought due to differences in the number of carbon fibers reaching the pleural cavity. The results indicate that the carcinogenic activity of VGCF™-H is lower than that of MWNT-7.

中文翻译：

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两种不同理化特性的气相生长碳纤维对大鼠气管滴注致癌性的差异

碳纤维是直径为亚微米级的高纵横比结构。气相生长碳纤维包含在多壁碳管内，VGCF™-H 通常用作锂离子电池中的导电添加剂。然而，据报道，包括 MWNT-7 在内的几种多壁碳纤维会诱发大鼠肺癌。本研究使用气相生长碳纤维 VGCF™-H 和 MWNT-7，研究了 VGCF™-H 纤维在 2 年多的时间里对两性 F344 大鼠的致癌潜力。通过气管内滴注的方式对大鼠施用碳纤维，剂量为0、0.016、0.08和0.4 mg/kg（总剂量为0、0.128、0.64和3.2 mg/kg），每周一次，持续八周，并首次滴注后观察长达 2 年。组织病理学检查显示，在暴露于 MWNT-7 的雌雄大鼠中，在 0、0.128、0.64 和 3.2 mg/kg 浓度下，可诱导胸膜腔恶性间皮瘤，且呈剂量依赖性增加。另一方面，VGCF™-H组中仅观察到两例胸膜恶性间皮瘤；两只雄性大鼠均接受 3.2 mg/kg 剂量。MWNT-7组中的动物比VGCF™-H组中的动物更早死亡或濒临死亡，这被认为与恶性间皮瘤的发展有关。VGCF™-H 组的存活率较高，并且 MWNT-7 组的胸腔灌洗液 (PLF) 中观察到更多的碳纤维。这些结果表明恶性间皮瘤与碳纤维转移到胸膜腔有关。气管内滴注 MWNT-7 在所有剂量下均明显导致雄性和雌性大鼠致癌。在暴露于 VGCF™-H 的雄性大鼠中观察到的致癌潜力的可疑证据在雌性大鼠中没有观察到。两种碳纤维的致癌性差异被认为是由于到达胸膜腔的碳纤维数量不同所致。结果表明，VGCF™-H的致癌活性低于MWNT-7。