It was previously thought that the particles inhaled by humans and having adverse effects were micron-sized
particles with a particularly high content of crystalline silica were thought to have harmful effects. In recent years, manufactured materials have been further refined to nano-level particles, and it has been reported that these ultrafine particles have different adverse effects, making it necessary to perform occupational health management for chemicals that differ from micron-sized particles. Here we report the adverse effects of carbon nanotubes, welding fumes, and organic substances as examples of nanoparticles.