This
document contains a definition of terms and answers the following questions:
-
What
are bioaerosols?
-
Can
bioaerosols cause health problems?
-
What
are the sources of bioaerosols in the home?
-
What
measures can be taken to control bioaerosols in the home?
-
How
can I control the causes of bioaerosols?
-
Summary
-
Mold, dust
mites, fungi, spores, and pollen:
Bioaerosols in the human environment
What are bioaerosols?
A healthy indoor environment is important
to you and your family. This includes keeping the air free of biological
contaminants, which can cause health problems. Scientists call these airborne
contaminants bioaerosols.
Bioaerosols are extremely small living
organisms or fragments of living things suspended in the air. Dust mites, molds,
fungi, spores, pollen, bacteria, viruses, amoebas, fragments of plant materials,
and human and pet dander (skin which has been shed) are some examples. They
cannot be seen without a magnifying glass or microscope.
Can bioaerosols cause health problems?
They can cause severe health problems.
Some, like viruses and bacteria, cause infections (like a cold or pneumonia).
Others cause allergies. Both allergic responses and infections may be serious or
even fatal.
An allergic reaction occurs when a
substance provokes formation of antibodies in a susceptible person. We call
substances which will cause an allergic reaction in some people antigens
or allergens. Bioaerosols may cause allergic reactions on the skin or in
the respiratory tract. Rashes, hay fever, asthma (tightness in the chest,
difficulty in breathing), and runny noses are common allergic reactions.
A few people develop a severe allergic
reaction in the lung, which can destroy lung tissue. This is called
hypersensitivity pneumonitis. It is not an infection, but repeated episodes
can lead to infections of the lung, such as bacterial pneumonia.
Hypersensitivity pneumonitis can be
triggered by exposure to very small amounts of the allergen, once a person is
sensitive to it. Symptoms can range from tightness in the chest, cough, and
difficulty in breathing, to low-grade fever, muscle aches, and headaches.
What are sources of bioaerosols in the
home?
Molds, mildews, bacteria, and dust mites
like the same conditions that we do--warmth and moderate to high humidity. They
need little more than a constant moisture supply for survival. You may find
bacteria, molds, and mildews in air conditioning equipment, humidifier
reservoirs, dehumidifier drip pans, shower heads, toilets, and ice machines.
Water damaged carpets, ceiling panels, walls, and paneling are prime sites for
new growth if they are allowed to stay damp. When molds, mildew, dust mites, and
bacteria are disrupted or release their spores into the air, this results in
bioaerosol formation.
Molds and mildews develop from spores,
which are in the air all around you. As soon as spores settle in an area with
the right conditions for growth, they establish colonies, which are often
visible to the naked eye. These colonies are a source of more spores, can cause
unsightly stains, and may release low levels of toxic chemicals called
mycotoxins into the air.
Humidifiers are such a common source of
bioaeorsols that cause health problems that doctors now use the term
humidifier fever. Protozoa, amoebas, and strains of bacteria have been found
in humidifiers, and these are readily released into the air with the moisture
produced by humidifiers. These have ben linked to allergic responses in
sensitive people.
Mold and mildew may be found in the
ductwork of your heating or cooling systems. If there are leaks in the ductwork,
or places where moisture and outside air get into the system, mold and mildew
can grow. Sometimes they are found in the coils of an air conditioner or in the
connection between the unit and the ductwork. Moisture problems are worse where
ductwork insulation is on the inside as opposed to the outside of the duct. The
insulation's porous surface collects dust and moisture. Mold and mildew may also
grow on dirty furnace and air conditioning filters. Plumbing leaks and dampness
in attics, basements, and crawl spaces can increase humidity inside your home
and promote the growth of agents that will be released as bioaerosols. Bathrooms
without outside-vented exhaust fans, combustion appliances like kerosene space
heaters, drying laundry indoors, and venting clothes dryers to attics or crawl
spaces can also increase the humidity levels in your home.
Dust mites and their waste products are
the most common allergens in indoor air. Dust mites eat human and pet skin
(dander) as it is shed. It has been estimated that we shed about seven million
cells per minute! Dust mites live in rugs and carpets, sheets, mattresses and
pillows, and upholstered furniture. Ten to 15 percent of people are allergic to
dust mites. Of the people who have other allergies, 40 percent are also allergic
to dust mites.
Back to Top
What measures can be taken to control bioaerosols in the home?
First, lower the relative humidity in your
home, basement or crawl space, and attic. Relative humidity is the amount of
moisture in the air at a given temperature. You may want to see
Identifying and Correcting Moisture
Problems in Homes. The humidity fluctuates in your home, depending on:
-
How warm or cool the air is
indoors.
-
How many moisture-producing
activities (drying clothes indoors, showers) are taking place.
-
Whether there is a constant
source of moisture (leaks, damp foundations and attics).
-
How much moisture is being
vented to the outside.
If you can keep relative humidity below 50
percent, you can reduce problems with dust mites, mold, and mildew. A hygrometer
can be used to measure indoor humidity levels. You can buy a hygrometer from
some nursery or garden stores, and from hardware stores.
There is little medical research
supporting the use of a humidifier, so try to avoid using one. If your home is
extremely dry and you must use a humidifier, a steam vaporizer or warm mist
humidifier causes fewer problems. Do not humidify indoor air to a relative
humidity level higher than 50 percent.
Ultrasonic and cool mist (impeller-type)
humidifiers can send microorganisms from their water tanks into the air.
Ultrasonic humidifiers use sound vibrations to create a cool mist. Impeller
humidifiers create a cool mist by means of a high-speed rotating disk. If you do
use a humidifier:
-
Empty the tank, wipe all
surfaces dry, and refill the water in portable humidifiers each day.
-
Clean portable humidifiers every
third day. Unplug the humidifier before cleaning and follow the
manufacturer's recommendations on the use of cleaning agents or
disinfectants.
If you have no specific instructions on
cleaning your humidifier, use a 3 percent solution of hydrogen peroxide. Never
use the humidifier with any of the cleaning agent or disinfectant in the tank.
Rinse the tank thoroughly several times with tap water to keep cleaning or
disinfecting chemicals out of the air.
Back to Top
How can I control the causes of bioaerosols?
Molds, mildew, and dust mites are the most
common causes of problems in the home. These bioaerosols can be controlled
relatively easily.
Molds and Mildews
-
Reduce relative humidity.
-
If you find mold or mildew in
your home, try to find and eliminate sources of moisture, such as plumbing
leaks.
-
Dry the air. Use a chemical or
mechanical dehumidifier. Empty collecting (drip) pan daily.
-
Open closet doors to allow air
to circulate. Use a 40-watt light bulb to dry and heat air in closets.
-
Vent bathrooms and clothes
dryers to the outside.
-
Do not use humidifiers.
-
Trim back trees and shrubs
around the house to reduce shade.
-
Remove debris from your yard,
roof, and gutters.
-
Clean mold and mildew growth
from walls with water mixed with chlorine bleach, diluted three parts water
to one part bleach. Commercial products can also remove mildew and mold.
Follow product instructions carefully. Very moldy items should be replaced.
-
Change heating and cooling
system filters monthly.
-
Vacuum air return covers or
screens regularly.
-
Check air conditioners for mold
before each cooling season and have coils cleaned as needed.
-
Have heating/cooling system
ductwork checked for loose insulation, leaks, or signs of condensation where
the system enters the house. Insulate ducts on the outside of the ductwork.
-
Air cleaners and filters are
other options. Electronic and hePA (high efficiency particulate absolute)
cleaners and filters are best at taking mold, mildew, and dust out of the
air.
-
Make sure that crawl space vents work
and are not blocked. If your cooling ductwork runs through the crawl space,
consider closing crawl space vents during summer cooling months.
-
Using vent fans in crawl spaces
during the summer when humidity is high may increase the relative humidity
in the crawl space and inside the home. Use fans only when outside humidity
is well below 50 percent.
-
Mechanical dehumidifiers reduce
humidity in basements, but they should not be used in crawl spaces when
vents are open.
-
Heating/cooling contractors or
duct cleaning firms can clean the ductwork in your home to reduce mold and
mildew growth.
Duct cleaning may involve compressed
air-washing, vacuuming and/or scrubbing of duct surfaces. Some firms advertise
disinfectants and sealants to prevent further fungal growth. It is uncertain
whether these processes are appropriate for most homes. Have microbial
contamination verified by an industrial hygienist or other environmental testing
agency before sanitizing products are used in your ductwork. Commercial fogging
or misting agents should not be used because of possible health problems from
breathing these chemicals. Use of a sealant in the ductwork is generally not
appropriate unless the mold, mildew, or dust source has been removed.
Back to Top
Dust Mites
It is not known how well any single
measure controls dust mite populations. However, it is known that effective mite
control requires that relative humidity be maintained below 50 percent. In
addition, since you spend about a third of each day in your bedroom, concentrate
your efforts there.
-
Wash sheets, pillowcases, and
mattress covers frequently in hot soapy water. If someone in your family is
allergic to dust mites, buy special vinyl covers for the pillow and
mattress.
-
Ordinary vacuuming does not
remove or reduce mite populations. Mites are so tiny that they pass through
the vacuum cleaner bag. High-efficiency filters for vacuum cleaners may be
used in place of conventional filters.
-
Remove stuffed animals and
objects that collect dust. If carpeting is used, short-pile is best.
-
Some new products may help
reduce dust mite populations. Ask your doctor about control solutions for
upholstered furniture and bedding.
SUMMARY
Bioaerosols, such as mold, mildew, and
dust mites, are commonly found in indoor air. Control measures include reducing
sources of moisture, reducing the relative humidity, and removing materials
which contribute to the growth of these agents. Make your house a healthier
house. Check periodically for moisture problems and maintain the air handling
systems and filters.
For more information,
contact us on:
Identifying and Correcting Moisture Problems in Homes.
Definition of Terms
Allergens --
medical term for foreign proteins that cause allergic reactions in susceptible
individuals
Biocides -- chemicals or processes that kill living cells
Dander -- skin and hair fragments shed by humans and other animals
Disinfection -- process of killing disease-causing organisms
Dust Mites -- microscopic organisms that feed on human and animal dander
Hygrometer -- instrument used to measure relative humidity
Mycotoxins -- toxic substances produced by fungi
Sanitizing -- process to reduce the number of disease-causing organisms
Back to Top
|
Mold, dust
mites, fungi, spores, and pollen:
Bioaerosols in the human environment
What are bioaerosols?
A healthy indoor environment is important
to you and your family. This includes keeping the air free of biological
contaminants, which can cause health problems. Scientists call these airborne
contaminants bioaerosols.
Bioaerosols are extremely small living
organisms or fragments of living things suspended in the air. Dust mites, molds,
fungi, spores, pollen, bacteria, viruses, amoebas, fragments of plant materials,
and human and pet dander (skin which has been shed) are some examples. They
cannot be seen without a magnifying glass or microscope.
Can bioaerosols cause health problems?
They can cause severe health problems.
Some, like viruses and bacteria, cause infections (like a cold or pneumonia).
Others cause allergies. Both allergic responses and infections may be serious or
even fatal.
An allergic reaction occurs when a
substance provokes formation of antibodies in a susceptible person. We call
substances which will cause an allergic reaction in some people antigens
or allergens. Bioaerosols may cause allergic reactions on the skin or in
the respiratory tract. Rashes, hay fever, asthma (tightness in the chest,
difficulty in breathing), and runny noses are common allergic reactions.
A few people develop a severe allergic
reaction in the lung, which can destroy lung tissue. This is called
hypersensitivity pneumonitis. It is not an infection, but repeated episodes
can lead to infections of the lung, such as bacterial pneumonia.
Hypersensitivity pneumonitis can be
triggered by exposure to very small amounts of the allergen, once a person is
sensitive to it. Symptoms can range from tightness in the chest, cough, and
difficulty in breathing, to low-grade fever, muscle aches, and headaches.
What are sources of bioaerosols in the
home?
Molds, mildews, bacteria, and dust mites
like the same conditions that we do--warmth and moderate to high humidity. They
need little more than a constant moisture supply for survival. You may find
bacteria, molds, and mildews in air conditioning equipment, humidifier
reservoirs, dehumidifier drip pans, shower heads, toilets, and ice machines.
Water damaged carpets, ceiling panels, walls, and paneling are prime sites for
new growth if they are allowed to stay damp. When molds, mildew, dust mites, and
bacteria are disrupted or release their spores into the air, this results in
bioaerosol formation.
Molds and mildews develop from spores,
which are in the air all around you. As soon as spores settle in an area with
the right conditions for growth, they establish colonies, which are often
visible to the naked eye. These colonies are a source of more spores, can cause
unsightly stains, and may release low levels of toxic chemicals called
mycotoxins into the air.
Humidifiers are such a common source of
bioaeorsols that cause health problems that doctors now use the term
humidifier fever. Protozoa, amoebas, and strains of bacteria have been found
in humidifiers, and these are readily released into the air with the moisture
produced by humidifiers. These have ben linked to allergic responses in
sensitive people.
Mold and mildew may be found in the
ductwork of your heating or cooling systems. If there are leaks in the ductwork,
or places where moisture and outside air get into the system, mold and mildew
can grow. Sometimes they are found in the coils of an air conditioner or in the
connection between the unit and the ductwork. Moisture problems are worse where
ductwork insulation is on the inside as opposed to the outside of the duct. The
insulation's porous surface collects dust and moisture. Mold and mildew may also
grow on dirty furnace and air conditioning filters. Plumbing leaks and dampness
in attics, basements, and crawl spaces can increase humidity inside your home
and promote the growth of agents that will be released as bioaerosols. Bathrooms
without outside-vented exhaust fans, combustion appliances like kerosene space
heaters, drying laundry indoors, and venting clothes dryers to attics or crawl
spaces can also increase the humidity levels in your home.
Dust mites and their waste products are
the most common allergens in indoor air. Dust mites eat human and pet skin
(dander) as it is shed. It has been estimated that we shed about seven million
cells per minute! Dust mites live in rugs and carpets, sheets, mattresses and
pillows, and upholstered furniture. Ten to 15 percent of people are allergic to
dust mites. Of the people who have other allergies, 40 percent are also allergic
to dust mites.
Back to Top
What measures can be taken to control bioaerosols in the home?
First, lower the relative humidity in your
home, basement or crawl space, and attic. Relative humidity is the amount of
moisture in the air at a given temperature. You may want to see
Identifying and Correcting Moisture
Problems in Homes. The humidity fluctuates in your home, depending on:
-
How warm or cool the air is
indoors.
-
How many moisture-producing
activities (drying clothes indoors, showers) are taking place.
-
Whether there is a constant
source of moisture (leaks, damp foundations and attics).
-
How much moisture is being
vented to the outside.
If you can keep relative humidity below 50
percent, you can reduce problems with dust mites, mold, and mildew. A hygrometer
can be used to measure indoor humidity levels. You can buy a hygrometer from
some nursery or garden stores, and from hardware stores.
There is little medical research
supporting the use of a humidifier, so try to avoid using one. If your home is
extremely dry and you must use a humidifier, a steam vaporizer or warm mist
humidifier causes fewer problems. Do not humidify indoor air to a relative
humidity level higher than 50 percent.
Ultrasonic and cool mist (impeller-type)
humidifiers can send microorganisms from their water tanks into the air.
Ultrasonic humidifiers use sound vibrations to create a cool mist. Impeller
humidifiers create a cool mist by means of a high-speed rotating disk. If you do
use a humidifier:
-
Empty the tank, wipe all
surfaces dry, and refill the water in portable humidifiers each day.
-
Clean portable humidifiers every
third day. Unplug the humidifier before cleaning and follow the
manufacturer's recommendations on the use of cleaning agents or
disinfectants.
If you have no specific instructions on
cleaning your humidifier, use a 3 percent solution of hydrogen peroxide. Never
use the humidifier with any of the cleaning agent or disinfectant in the tank.
Rinse the tank thoroughly several times with tap water to keep cleaning or
disinfecting chemicals out of the air.
Back to Top
How can I control the causes of bioaerosols?
Molds, mildew, and dust mites are the most
common causes of problems in the home. These bioaerosols can be controlled
relatively easily.
Molds and Mildews
-
Reduce relative humidity.
-
If you find mold or mildew in
your home, try to find and eliminate sources of moisture, such as plumbing
leaks.
-
Dry the air. Use a chemical or
mechanical dehumidifier. Empty collecting (drip) pan daily.
-
Open closet doors to allow air
to circulate. Use a 40-watt light bulb to dry and heat air in closets.
-
Vent bathrooms and clothes
dryers to the outside.
-
Do not use humidifiers.
-
Trim back trees and shrubs
around the house to reduce shade.
-
Remove debris from your yard,
roof, and gutters.
-
Clean mold and mildew growth
from walls with water mixed with chlorine bleach, diluted three parts water
to one part bleach. Commercial products can also remove mildew and mold.
Follow product instructions carefully. Very moldy items should be replaced.
-
Change heating and cooling
system filters monthly.
-
Vacuum air return covers or
screens regularly.
-
Check air conditioners for mold
before each cooling season and have coils cleaned as needed.
-
Have heating/cooling system
ductwork checked for loose insulation, leaks, or signs of condensation where
the system enters the house. Insulate ducts on the outside of the ductwork.
-
Air cleaners and filters are
other options. Electronic and hePA (high efficiency particulate absolute)
cleaners and filters are best at taking mold, mildew, and dust out of the
air.
-
Make sure that crawl space vents work
and are not blocked. If your cooling ductwork runs through the crawl space,
consider closing crawl space vents during summer cooling months.
-
Using vent fans in crawl spaces
during the summer when humidity is high may increase the relative humidity
in the crawl space and inside the home. Use fans only when outside humidity
is well below 50 percent.
-
Mechanical dehumidifiers reduce
humidity in basements, but they should not be used in crawl spaces when
vents are open.
-
Heating/cooling contractors or
duct cleaning firms can clean the ductwork in your home to reduce mold and
mildew growth.
Duct cleaning may involve compressed
air-washing, vacuuming and/or scrubbing of duct surfaces. Some firms advertise
disinfectants and sealants to prevent further fungal growth. It is uncertain
whether these processes are appropriate for most homes. Have microbial
contamination verified by an industrial hygienist or other environmental testing
agency before sanitizing products are used in your ductwork. Commercial fogging
or misting agents should not be used because of possible health problems from
breathing these chemicals. Use of a sealant in the ductwork is generally not
appropriate unless the mold, mildew, or dust source has been removed.
Back to Top
Dust Mites
It is not known how well any single
measure controls dust mite populations. However, it is known that effective mite
control requires that relative humidity be maintained below 50 percent. In
addition, since you spend about a third of each day in your bedroom, concentrate
your efforts there.
-
Wash sheets, pillowcases, and
mattress covers frequently in hot soapy water. If someone in your family is
allergic to dust mites, buy special vinyl covers for the pillow and
mattress.
-
Ordinary vacuuming does not
remove or reduce mite populations. Mites are so tiny that they pass through
the vacuum cleaner bag. High-efficiency filters for vacuum cleaners may be
used in place of conventional filters.
-
Remove stuffed animals and
objects that collect dust. If carpeting is used, short-pile is best.
-
Some new products may help
reduce dust mite populations. Ask your doctor about control solutions for
upholstered furniture and bedding.
SUMMARY
Bioaerosols, such as mold, mildew, and
dust mites, are commonly found in indoor air. Control measures include reducing
sources of moisture, reducing the relative humidity, and removing materials
which contribute to the growth of these agents. Make your house a healthier
house. Check periodically for moisture problems and maintain the air handling
systems and filters.
For more information,
contact us on:
Identifying and Correcting Moisture Problems in Homes.
Definition of Terms
Allergens --
medical term for foreign proteins that cause allergic reactions in susceptible
individuals
Biocides -- chemicals or processes that kill living cells
Dander -- skin and hair fragments shed by humans and other animals
Disinfection -- process of killing disease-causing organisms
Dust Mites -- microscopic organisms that feed on human and animal dander
Hygrometer -- instrument used to measure relative humidity
Mycotoxins -- toxic substances produced by fungi
Sanitizing -- process to reduce the number of disease-causing organisms
Back to Top
|
