Host: The Japanese Society of Toxicology
Name : The 49th Annual Meeting of the Japanese Society of Toxicology
Date : June 30, 2022 - July 02, 2022
Inhalation exposure to nanomaterials (NMs) is the most likely route to be unintentionally exposed in all life cycle of products from the manufacturing to being wasted, and greatest concern in harmfulness. With the progress of product development applying NMs, it is desired to develop an evaluation method that can rapidly and easily obtain fundamental and quantitative information necessary for preventing health damage. However, inhalation exposure study of particulate matter including NMs requires specialized equipment such as aerosol generators, particle concentration measuring equipment, and requires a great deal of time and cost. Furthermore, in the chronic inhalation exposure study of particulate matter, there has been controversy regarding, as it is called, overload; the accumulation of particles in the lungs throughout the exposure period. We have been developing an intermittent exposure method as an alternative to a chronic inhalation exposure study that is more efficient than the usual two-year continuous inhalation exposure study. We first initiated a 4-week intermittent exposure inhalation study, mimicking the lung burden of the rat study reported by Kasai et al., 2016. Male C57BL/6 mice were exposed to 53 μm mesh-filtered Mitsui MWNT-7 aerosol by Taquann system (J. Toxicol. Sci. 2013) at the mass concentrations of ca. 2.6 and 5.0 mg/m3, for 6 hours per day every 4 weeks. MMAD was ca. 500 nm. Lung burden at 6 months were ca. 6.4 and 15.2μg per animal, and at 12 months 22.3 and 45.8μg per animal, respectively. Histologically, MWNT-7-laden macrophages were found at the terminal bronchioles to alveolar region. Microgranulomas were often observed. MWNT-7 were also found in pleural cavity, local lymphnodes and, distally, in renal glomeruli. Further details will be presented. (Health and Labour Sciences Research Grant, Japan)
