Aerosol

An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or artificial. Examples of natural aerosols are fog, forest exudates and geyser steam. Examples of artificial aerosols are haze, dust, particulate air pollutants and smoke. The liquid or solid particles have diameter mostly smaller than 1 μm or so; larger particles with a significant settling speed make the mixture a suspension, but the distinction is not clear-cut. In general conversation, aerosol usually refers to an aerosol spray that delivers a consumer product from a can or similar container. Other technological applications of aerosols include dispersal of pesticides, medical treatment of respiratory illnesses, and combustion technology.Diseases can also spread by means of small droplets in the breath, also called aerosols.

Aerosol science covers generation and removal of aerosols, technological application of aerosols, effects of aerosols on the environment and people, and a wide variety of other topics.

Bioaerosol

A bioaerosol (short for biological aerosol) is a suspension of airborne particles that contain living organisms or were released from living organisms. These particles are very small and range in size from less than one micrometer (0.00004") to one hundred micrometers (0.004"). Bioaerosols react to air currents and move quickly or slowly depending on the environment. Bioaerosols are impacted by gravity but due to their size air density and air currents play a large role in their movement. The intact cellular component has been given the name, primary biological aerosol (PBA), which consists of virus particles, bacteria, fungal spores and plant pollen. PBA can range in size from 10 nanometers (small virus particles) to 100 micrometers (pollen grains). The atmospheric lifetime of PBA particles can range from a near indefinite time frame for some of the smallest virus particles to a few hours for the larger pollen particles.

Background

Air often contains tiny organisms such as fungi, bacteria, mycotoxins, and viruses. It is currently thought that the majority of these airborne microorganisms are not in a viable state while in the atmosphere. However, current research has shown that certain groups of bacteria are capable of performing basic metabolic activity within cloud water. Groups of the small organisms clump up and enhance survival while airborne. Due to evaporation of water, bacterial cells usually die when they become airborne but under high humidity conditions bioaerosol levels are increased. Fungal cells such as spores, molds, and yeast can be active at low humidity levels and high or low temperatures.