Jun Kanno, M.D., Ph.D., Director, Japan Bioassay Research Center (JBRC), Japan Organization of Occupational Health and Safety and Visiting Researcher, National Institute of Health Sciences (NIHS)
His research includes molecular toxicology focused on “signal toxicity” mainly of endocrine and central nervous system, carcinogenesis, toxicogenomics, nanomatrial toxicity, and other newly emerged issues. He participated in “Endocrine Disrupting Chemicals Screening and Testing Scheme of Ministry of Health, Labour and Welfare,” OECD Uterotrophic Assay (TG440), rat Toxicogenomics (TGP, 2002-), murine Percellome Toxicogenomics Projects (2003-) followed by Sick-Building-Syndrome Inhalation, Developmental, Neurobehavioral and other Toxicogenomics projects, and Nanomaterials toxicology (2004-).
He is a council member of the Japanese Society of Toxicology (JSOT) since 2002, its Board of Directors (2004-2009), and the President of JSOT (2012-2013). He joined IUTOX Executive Committee as Vice President (2009-2013), President-Elect (2013-2015) and President (2016-2019)
Keynote – Carbon Nanotube Toxicity
One of the reasons that the chronic toxicity study on nanomaterials (NMs) has not been well developed, compared to general chemicals or “soluble” compounds, is because they are one of the particulate matter (PM), and PM toxicology is a very difficult subfield of Toxicology to engage. Perhaps the most important route of exposure of PMs is inhalation. This inhalation is another big hurdle for toxicologists; inhalation facilities are usually expensive to build and run, and requires skillful operators. Methods to generate well-dispersed aerosol and quantitatively measure the aerosol density often need case-by-case innovation for each NM specimen.
And yet, fortunately, we find a few hints from the PM-related human diseases that are reported in the past. One example is asbestos. Studies ranges from foreign body inflammation, granulomatous responses, responses towards fibrosis, to the most important “frustrated phagocytosis” for a specific size and shape of a fiber related to the oxidative stress mechanisms to initiate and promote mesotheliomagenesis and lung adenocarcinomagenesis.
Here, biological responses against multi-wall carbon nanotubes (MWCNT) monitored in intraperitoneal studies and whole body inhalation studies are presented. Histologically, non-granulomatous persistent chronic inflammatory micro lesions with single fibers were considered to be important for the development of mesothelioma, whereas granulomas formed against aggregates/agglomerates were not directly involved in the process.
The most challenging part of the inhalation study is to generate well-dispersed aerosol. We would like to report some data on the “Taquann” dispersion method and direct injection system using a MWCNT (Mitsui MWNT-7) at NIHS. In addition, the summary of the result of two-year rat whole body inhalation carcinogenesis study of MWNT-7 performed at JBRC will be presented.
In vitro and in vivo acute toxicity data are accumulating fast. The extrapolation of such data to in vivo chronic toxicity awaits further accumulation of bridging data. For the sound growth of nanomaterial industry and protection of workers and users, usage of both acute and chronic toxicity data in a reasonable balance is practical and essential.