Fate and Transport of Micro-organisms in Air
The atmosphere is inhospitable place for microbes because of stress due to environmental factors like desiccation, temperature, relative humidity, radiation and oxygen. The majority of airborne micro-organisms are immediately inactivated as the result of this.
Those hardy microbes that can survive these factors are able to cause the diseases.
Oxygen stress relates to the reactive oxygen species. Another term, Open Air Factor (OAF) in this connection describes the environmental effect that cannot be replicated in the laboratory settings.
When ozone and hydrocarbons (usually ethylene) alone with the oxygen act together the inactivation rates of microbes is greatly affected. Micro-organisms like fungi cannot survive and complete their life cycles by staying afloat in air for an indefinite period of time. Bioaerosols in the air harbor the microbes.
Read Also: Air Microbiology and Causes of Air-Borne Diseases
They vary in size. Large droplets in the air are of 100 μ and like dust, settles rapidly in quiet air. Small droplets on the other hand in warm, dry atmosphere dry quickly to form droplet nuclei. These are of 2-5 μm size, light and may float about for many minutes or even hours.
The micro-organisms in them are protected by dried mucus which coats them. Being small, these escape the mechanical traps of the upper respiratory tract and enter the lungs. They may settle on the alveolar tissue. Transmission of airborne pathogens usually occurs via droplet nuclei.
The aeromicrobiological pathway (AMB) describes the launching of the aerosols in the air, the subsequent transport via diffusion and dispersion, and finally their deposition e.g. droplet nuclei having influenza virus which is launched via coughing, sneezing or taking in the air.
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