This document discusses the sources and forms of discharge of airborne microbes. It outlines that microbes can become airborne from soil, water, wind and tides, and human activities like coughing or sneezing. Microbes are expelled in three forms: droplets from sneezing or coughing that are large and fall quickly from the air; droplet nuclei that remain after droplets evaporate and are very small, remaining airborne for hours; and infectious dust particles that form when droplets dry on surfaces and become re-aerosolized. The size and moisture content of expelled particles determines how long microbes remain suspended in the air.

1. SOURCES OF
MICROBES
Kaviyalakshmi M
Assistant Professor

2. SOURCES OF AIR MICROBES
• Soil: Wind-agitated soil bacteria are released into the air and remain
suspended there for an extended amount of time. Human acts such as
digging or tilling the soil may also discharge germs from the soil into
the air.
• Water: Microorganisms that live in water release water droplets or
aerosols. The splashing of water caused by wind or tide can also
produce droplets or aerosols.
• Wind and tides: Air currents may transport germs from plant or
animal surfaces into the atmosphere. For instance, Puccinia graminis
spores
• Human beings: Human beings are the primary source of airborne
germs. Activities such as coughing, sneezing, speaking, and laughing
release pathogenic flora from the upper respiratory tract and mouth
into the air.

4. FORMS OF DISCHARGE OF AIR
MICROBES
Microorganisms are expelled in three distinct
forms, which are categorized according to their
relative size and moisture content.

5. 1 •Droplets
2 •Droplet nuclei
3 •Infectious dust

6. DROPLETS
• Typically, droplets are produced by sneezing, coughing, or speaking. Both are
composed of saliva and mucus.
• It has been estimated that a single sneeze may contain between 10,000 and
100,000 germs.
• The length of time droplets can remain suspended is determined by their size.
• In calm air, the majority of droplets are rather big and tend to settle swiftly.
• The pathogenic microorganism-containing droplets may be a source of
infectious illness.

7. DROPLETS

8. DROPLET NUCLEI
• In a warm, dry atmosphere, little droplets tend to evaporate quickly and
become droplet nuclei.
• The leftovers of solid material remaining after a droplet has dried out are
known as droplet nuclei.
• These are 1-4um in size and lightweight.
• Can remain airborne for hours or days and traverse great distances.
• If the germs remain viable when dried, it may serve as a continued source of
illness.
• Viability is governed by a number of complicated parameters, including
atmospheric conditions such as humidity, sunshine, and temperature, the
size of the particles carrying the organisms, and the sensitivity or
resistance of the specific microbial species to the new physical
environment.

9. DROPLET NUCLEI

10. INFECTIOUS DUST
• Large aerosol droplets quickly settle from the air onto various
surfaces and become dry.
• A patient’s nasal and throat discharges can potentially contaminate
surfaces and become dry.
• In the patient’s room, disturbing this dried material by changing the
bed, touching a handkerchief with dried secretions, or sweeping the
floors might generate dust particles that add bacteria to the circulating
air.
• Depending on their size, two types of droplets spread airborne
illnesses.
• Droplet infection proper applies to droplets with a diameter more than
100 um
• The other form is referred to as an airborne infection and pertains to
droplet remains that have dried.

13. THANK YOU
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