Final answer:
Aerosol contaminants are typically microscopic in size, including particulate matter that can cause respiratory diseases and ultramicroscopic viruses.
Step-by-step explanation:
Aerosol contaminants, which include a variety of particles such as dust, dirt, viral particles, and bacteria, are typically microscopic in size. These particles are so small that they require a microscope or similar tools to be seen clearly. For instance, particulate matter like PM2.5s are less than 2.5 micrometers in diameter and are small enough to penetrate deeply into the lungs, potentially causing respiratory diseases. Viruses, another form of aerosol contaminants, range from 20 nanometers to 900 nanometers in length and are considered ultramicroscopic.