Transcript Bioaerosols (View Source PPT)

BIOAEROSOLS
Introduction
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Bioaerosols are integral part of our ecological system and play an important
role in its balance
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Viruses, bacteria, fungi etc. are collectively called airborne biological
contaminants or Bioaerosols
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Outdoor control of Bioaerosols is usually not possible but indoors, it is
achievable
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Most of the Bioaerosols host on humans and moist places, which provide
habitable conditions
General health Effects
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Bioaerosols induce into human body by inhalation or by deposition on wounds
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A possible reason of sick building syndrome (SBS) is the presence of
Bioaerosols in the building.
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Despite the defense mechanism of the body these Bioaerosols could cause
damage to the body
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The infections caused due to the Bioaerosols include:
 Legionnaire’s disease
 Humidifier fever
 Cold
 Influenza
Health Effects of Bioaerosols
 Viruses: Common cold, Influenza, Measles, Bronchitis
Rheumatic fever, Otitis media, Carditis, Diphtheria
Whooping cough, Tuberculosis, Meningitis and Q – fever
 Fungi: Histoplasmosis, Cocciodomycosis and Blastomycosis
 Antigens: Allergic diseases of hypersensitivity pneumonitis (HP)
Allergic asthma, Rhynitis and Pergillosis
FUNGI
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Fungi play a major role causing many ill-effects.
These are found in very ecological niche, and are necessary in the recycling of
organic building blocks that allow plant and animal lives to thrive.
Fungi need external organic food sources and water to survive.
Various groups of fungi are:
 Yeasts
 Molds
 Mildews
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Let us now know about molds, greatest problem creator for the researchers
now.
Molds
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Molds can grow on clothes, carpets, leather, wood, sheet rock, insulation and
on human foods wherever moist conditions exist.
As molds flourish in moist or wet indoor conditions, human exposure is
possible either by direct contact on surfaces or through the air if mold spores,
fragments, or mold products are airborne.
Mold reproduction is done by production of spores.
To support the mold growth proper conditions and food sources are provided
by wet indoor spaces with inorganic materials.
People are exposed to this mold spores or fragments through inhalation or by
contact through small breaks in skin.
Various effects of molds
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Effects of molds depend mainly on
 Species of mold
 Metabolic products being produced by molds
 Amount and duration of individual’s exposure to mold parts or products
 Specific susceptibility of those exposed.
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Various health effects:
 Allergy
 Infection
 Irritation (mucous membrane and sensory)
 Toxicity
Allergy
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This is the most common response from people to mold.
People who are genetically capable of producing an allergic reaction are
referred to as atrophic.
When an atrophic person’s respiratory system or skin is exposed to mold or
mold products that have become sensitized, symptoms will be developed.
Allergic reactions range from mild transitory responses, to severe chronic
illnesses.
In Americans one in every five suffer from allergic rhinitis, the single most
common disease that is experienced by humans.
Thousands of different molds contaminate indoor air, purified allergens have
been recovered from only a few.
So, atrophic individuals may be exposed to molds found indoors and develop
sensitization, yet not be identified as having mold allergy.
Infection
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Infection from molds that grow indoor is not common.
 A number of Aspergillus species that are found indoors are known to be
pathogenic.
 Most of the infections occur among immune-compromised patients, whoa re
suffering from various causes as well.
 Such infections mostly effect the skin, eyes and lungs and are also known to
effect other organs or systems.
Mucous Membrane and Trigeminal Nerve
Irritation
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This type of irritation is derived from VOC’s that are produced by fungal
metabolism.
Alcohol or aldehydes and acidic molecules may be produced by this fungi.
The nature of the food source from which the fungus grows may result in
pungent primary metabolic products, for instance, one fungus growing on wall
paper released the highly toxic gas arsenic from arsenic containing pigments.
Fungal volatile compounds may also impact the “common chemical sense”
associated with the trigeminal nerve, which is a mixed (motor and sensory)
nerve that responds to pungency, not odor, by initiating avoidance reactions
such as breath holding, paresthesias, itching, burning, skin crawling, dilation
of surface blood vessels, decreased attention, disorientation, diminished reflex
time, dizziness etc.
Toxicity
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Molds can also produce myotoxins, that are nearly cytotoxic and interfere with
vital cellular processes such as protein, RNA and DNA synthesis.
 Mold toxins increase the susceptibility of the exposed person to infectious
diseases, reduce the ability of their defense system to fight against other
contaminants and can also increase susceptibility to cancer.
Sources
Sources of Bioaerosols
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Major sources of bacteria and viruses are humans and pets - sneezing,
coughing, dander and saliva
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Fungi, many bacteria, protozoa, algae and green plants (pollen) are present
outdoors that are induced indoors by natural or mechanical ventilation
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Moist surfaces of leather, wood, carpets, soaps, cloth fabric, some pastes and
adhesives are examples of amplification sites
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Breeding sites for fungi and bacteria are humidifiers, air conditioning systems,
cooling towers, air distributing systems and areas of water damage
Types, Sizes, Pathogenic properties and
Common sources of selected Bacteria
Escherichia coli
1.1 – 1.5 x 2 – 6
(m)
Urinary tract
infections,
Diarrhea,
Dysentery
Human body
Staphylococcus
aeruginosa
0.5 – 1.0 (m)
(diameter)
Food poisoning,
Toxic shock,
Pneumonia,
Meningitis
Human body
Staphylococcus
epidermis
0.5 – 1.5 (m)
(diameter)
Cardiovascular
infections, Wound
infections, Ottis
media
Human body
Legionella
pneumonphilia
0.3 – 0.9 x 2 – 20
(m)
Legionnaire’s
disease, Pontiac
fever
Cooling towers,
Air conditioners
Types, Sizes, Pathogenic properties and
Common sources of selected Fungi
Thermoactinomyces
vulgaris, Acanthamoli
spp., Naegleria spp.
1 – 2 (m)
(diameter)
Humidifier fever,
Allergic reactions
Humidifiers
Pencillium
4 – 6 (m)
(diameter)
Irritation to
respiratory tract
Air, Soil
Aspergillosis fungus
4 – 6 (m)
(diameter)
Aspergillosis and
aspergilloma
Cooling towers,
Humidifiers
Coccidiodomycosis
immitis
60 – 200 (m)
(diameter)
Vegetative cell
Lung infections
Air, Soil
Types, Sizes, Pathogenic properties and
Common sources of selected Viruses
Rhinovirus
0.02 – 0.03 (m)
(diameter)
Common cold
Human body
Influenza virus
0.08 – 0.120 (m)
(diameter)
Influenza
Human body
Lymphocytic
choriomeningitis
Coxsackie virus
0.2 – 0.3 (m)
(diameter)
Congenital infections,
Neurological
infections
--
0.02 - 0.03 (m)
(diameter)
Gastrointestinal
infections, Upper
respiratory infections
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Introduction to sampling Techniques
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The sampling techniques are usually same as for other particles, but the
different types in Bioaerosols complicate the process
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Several factors are considered to get positive or conclusive reports:
 Not one sample is good for collecting all types of microorganisms
 No sampling device provides for 100% recovery of Bioaerosols
 The viability of Bioaerosol samples should be maintained in the sampler
for subsequent growth and identification
 Efficiency of the sampler depends on the size of the particular organism
Factors affecting choice of Sampling Techniques
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Growth and survival of the individual organism depends on the humidity,
temperature and pH of the culture medium
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Proper selection of sampling and identification media is necessary for accurate
sampling analysis
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Samplers must be calibrated and used according to the manufacturer’s flow
rate specifications
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Since no method is available for collection and identification or counting of all
Bioaerosols of interest, the selection of a method is guided by what is
suspected to be present
Samplers available
 Diffusive samplers
 Moulton air samplers
 Settling samplers
 Dip stickle samplers
 Filters
 All-glass Impingers (AGI)
 Impactors
Samplers preferred
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High volume filters
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High volume electrostatic precipitators
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AGI
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Impactors:
 Anderson impactors
 Silt impactors
Recommended samplers as per volume to be
handled
Sampler type
Principle
of
Operation
Sampling
rate
(l/min)
Recommended sampling type
Silt impactor
Impaction on
rotation or
stationary
plate
30 – 700,
Continuous
1- 60 min or 7 days
Cassette filter
Filtration
1–2
15 – 60 min or 8 hrs
High volume filtration
Filtration
140 - 1400
5 min to 24 hrs
High volume electrostatic filter
Electrostatic
collection
Up to 12000
Variable
All glass impinger
Impingement
into liquid
12.5
30 min
Sieve
Impactor
Single
stage
Impaction on
agar “rodac”
plate
90 or 185
0.5 or 0.3 min
Single
stage
Impaction on
agar 100 mm
plate
28
1 min
Two
stage
Impaction on
agar
28
1 – 5 min
Control Strategies
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Source Removal
 After identifying the airborne microorganisms the source can either be
eliminated or its strength can be reduced
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Regular Maintenance
 Preventive maintenance is one the most effective ways to control the
microorganisms indoors
 Maintenance of air handling systems and fan coil units, drain pans and
periodic replacement of the filters
 Humidifiers using the re-circulated water should not be used. Steam
should be used instead of cold water in humidifiers, heating and HVAC
systems
 Disinfectants and biocides should be used in the humidifier water
reservoirs, which kill the microorganisms
 Shock dosages have better results compared to the regular dosages
Biocides for controlling the most common
Legionella pneumophilia :
 Quaternary ammonia compounds
 1-bromo3-chloro-5
 5-dimethyl-hydantoin
 Bis(tri-n-butyltin)oxide
 n-alkyl-1
 Methylene-bis
 Dithiocarbamates
 Chlorine
Methods for controlling molds
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There is no practical way to eliminate mold and mold spores in the indoor
environment, the way to control indoor mold growth is to control moisture.
 If mold problem is their in your house or school, you must clean up the mold
and eliminate sources of moisture.
 Fix the source of water problem or leak to prevent mold growth.
 Reduce indoor humidity ( to 30%-60%) to decrease mold growth by:
- Venting bathrooms, dryers and other moisture-generating sources to the
outside
- using air conditioners and de-humidifiers
- Increasing ventilation
- Using exhaust fans whenever cooking, dishwashing and cleaning
Methods for controlling molds (contd…)
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Clean and dry any damp or wet building materials and furnishings within 2448 hours to prevent mold growth.
Clean mold off hard surfaces with water and detergent, and dry completely.
Absorbent materials such as ceiling tiles, that are moldy, may need to be
replaced.
Prevent condensation:Reduce the potential for condensation on cold surfaces
(i. e. ,windows, piping, exterior walls, roof, or floors) by adding insulation.
In areas where there is a perpetual moisture problem, do not install carpeting
(i. e. , by drinking fountains, by classroom sinks, or on concrete floors with
leaks or frequent condensation)
Molds can be found almost anywhere; they can grow on virtually any
substance, providing moisture is present. There are molds that can grow on
wood, paper, carpet and foods.
Other Strategies
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Humidity control
 Control of relative humidity significantly reduces the bacteria and viruses
 Maximum growth of viruses resulted at a relative humidity of 95% and
above
 Humidity range between 40% and 60% significantly reduces the risk to
human health
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Increased ventilation with filtration
 Proper intake of air indoor and using effective air filtration systems
significantly reduces the intake of Bioaerosols
 Mechanical filters have been successful in removing the fungi and other
microbial agents from the outdoor air
Other Strategies(contd.)
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Available air filters
 Coarse-fiber panel filters (efficiency – 10%)
 Electrostatic precipitators (efficiency – 60% to 90%)
 HEPA filters (efficiency – 90% to 100%)
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Air cleaning
 The air can be disinfected using various chemical compounds
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Sodium hypochlorite
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Hydroxy acids
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Glycols
Criteria for choosing Chemical disinfectants
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Lethal at low concentrations
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Non-toxic and non-irritant to humans
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Non-corrosive to metals and fabric
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Should easily vaporize
Other preferred options
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The most effective glycols are propylene and triethylene glycols
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Desiccant air conditioning systems perform well in control of the Bioaerosols
by:
 Capturing the organisms
 Killing them through severe desiccation