Engineered versus incidental nanoparticles in the atmosphere

"Take a deep breath. You just inhaled about 1 million particles. Figure 1 shows various types of airborne particles, also known as aerosols, under a microscope..."

Resource:

http://blogs.lt.vt.edu/sustainablenano/2015/02/16/engineered-versus-incidental-nanoparticles-in-the-atmosphere/