title: Risk Assessment of the Carbon Nanotube Group.
abstract: This study assessed the health risks via inhalation and derived the occupational exposure limit (OEL) for the carbon nanotube (CNT) group rather than individual CNT material. We devised two methods: the integration of the intratracheal instillation (IT) data with the inhalation (IH) data, and the "biaxial approach." A four-week IH test and IT test were performed in rats exposed to representative materials to obtain the no observed adverse effect level, based on which the OEL was derived. We used the biaxial approach to conduct a relative toxicity assessment of six types of CNTs. An OEL of 0.03 mg/m(3) was selected as the criterion for the CNT group. We proposed that the OEL be limited to 15 years. We adopted adaptive management, in which the values are reviewed whenever new data are obtained. The toxicity level was found to be correlated with the Brunauer-Emmett-Teller (BET)-specific surface area (BET-SSA) of CNT, suggesting the BET-SSA to have potential for use in toxicity estimation. We used the published exposure data and measurement results of dustiness tests to compute the risk in relation to particle size at the workplace and showed that controlling micron-sized respirable particles was of utmost importance. Our genotoxicity studies indicated that CNT did not directly interact with genetic materials. They supported the concept that, even if CNT is genotoxic, it is secondary genotoxicity mediated via a pathway of genotoxic damage resulting from oxidative DNA attack by free radicals generated during CNT-elicited inflammation. Secondary genotoxicity appears to involve a threshold.
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Junko
authors.initials: J
authors.lastname: Nakanishi
authors.affiliation: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan (UOEH), Kitakyushu, Japan.
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Morimoto
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Isamu
authors.initials: I
authors.lastname: Ogura
authors.affiliation: Division of Environmental Chemistry, National Institute of Health Sciences, Tokyo, Japan.
authors.forename: Norihiro
authors.initials: N
authors.lastname: Kobayashi
authors.affiliation: Public Interest Incorporated Foundation BioSafety Research Center (BSRC), Iwata, Japan.
authors.forename: Masato
authors.initials: M
authors.lastname: Naya
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ema
authors.affiliation: Research Institute for Environmental Management Technology, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan.
authors.forename: Shigehisa
authors.initials: S
authors.lastname: Endoh
authors.affiliation: Department of Chemical Engineering, Faculty of Engineering, Hiroshima University, Higashihiroshima, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Shimada
authors.affiliation: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan (UOEH), Kitakyushu, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Ogami
authors.affiliation: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan (UOEH), Kitakyushu, Japan.
authors.forename: Toshihiko
authors.initials: T
authors.lastname: Myojyo
authors.affiliation: Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan (UOEH), Kitakyushu, Japan.
authors.forename: Takako
authors.initials: T
authors.lastname: Oyabu
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Gamo
authors.affiliation: Policy Alternatives Research Institute, Graduate School of Public Policy, the Tokyo University, Tokyo, Japan.
authors.forename: Atsuo
authors.initials: A
authors.lastname: Kishimoto
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Igarashi
authors.affiliation: Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Japan.
authors.forename: Sosuke
authors.initials: S
authors.lastname: Hanai
mesh_terms: D000818:Animals; D006801:Humans; D019570:Inhalation Exposure; D037742:Nanotubes, Carbon / Q000009:adverse effects*; D019055:No-Observed-Adverse-Effect Level; D016273:Occupational Exposure; D051381:Rats; D017208:Rats, Wistar; D018570:Risk Assessment
chemical_list: D037742:Nanotubes, Carbon
keywords: CNT; CNT toxicity; OEL; risk assessment