 For exposure and risk assessments of airborne nanoparticles, it is important to know about the size distribution of aerosols.When inhaled by humans, particles with different diameters are deposited in varied locations of the central and periphery respiratory system.Particles in nanoscale have been shown to penetrate the air-blood barrier in lungs and be translocated into secondary organs in the human body, such as the brain, heart and liver.