Air Purifier Advice
Test Your Air
Are Biological Pollutants Making Your Home A BioHazard?
What Are Biological Pollutants?
Biological pollutants are or were living
organisms. They promote poor indoor air quality and may be a major cause of
days lost from work or school, and of doctor and hospital visits. Some can
even damage surfaces inside and outside your house. Biological pollutants can
travel through the air and are often invisible. Biological contaminants include bacteria, molds, mildew, viruses, animal dander and cat saliva, house dust mites, cockroaches, and pollen. There are many sources of these pollutants. Our extensive chart of Biological Pollutants and BioAerosols lists many sources of biological pollutants, diseases these bioparticles cause, method of transmission, and particle size.
Other biological pollutants such as pollens originate from plants; viruses are transmitted by people and animals; bacteria are carried by people, animals, and soil and plant debris; and household pets are sources of saliva and animal dander. The protein in urine from rats and mice is a potent allergen. When it dries, it can become airborne. Contaminated central air handling systems can become breeding grounds for mold, mildew, and other sources of biological contaminants and can then distribute these contaminants through the home.
Other common indoor biological pollutants
- Animal Dander (minute scales from
hair, feathers, or skin)
- Dust Mite and Cockroach parts
- Fungi (Molds)
- Infectious agents (bacteria or
Some of these substances are in every
home. It is impossible to get rid of them all. Even a spotless home may permit
the growth of biological pollutants. Two conditions are essential to support
biological growth: nutrients and moisture. These conditions can be found in
many locations, such as bathrooms, damp or flooded basements, wet appliances
(such as humidifiers or air conditioners), and even some carpets and
Modern materials and construction
techniques may reduce the amount of outside air brought into buildings which
may result in high moisture levels inside. Using humidifiers, unvented
heaters, and air conditioners in our homes has increased the chances of
moisture forming on interior surfaces. This encourages the growth of certain
The Scope Of The Problem
Most information about sources and
health effects of biological pollutants is based on studies of large office
buildings and two surveys of homes in northern U.S. and Canada. These surveys
show that 30% to 50% of all structures have damp conditions which may
encourage the growth and buildup of biological pollutants. This percentage is
likely to be higher in warm, moist climates.
Some diseases or illnesses have been
linked with biological pollutants in the indoor environment. However, many of
them also have causes unrelated to the indoor environment. Therefore, we do
not know how many health problems relate only to poor indoor air.
Health Effects Of Biological Pollutants
All of us are exposed to biological
pollutants. However, the effects on our health depend upon the type and amount
of biological pollution and the individual person. Some people do not
experience health reactions from certain biological pollutants, while others
may experience one or more of the following reactions:
Except for the spread of infections
indoors, ALLERGIC REACTIONS may be the most common health problem with
indoor air quality in homes. They are often connected with animal dander
(mostly from cats and dogs), with house dust mites (microscopic animals living
in household dust), and with pollen. Some biological contaminants trigger allergic reactions, including hypersensitivity pneumonitis, allergic rhinitis, and some types of asthma. Infectious illnesses, such as influenza, measles, and chicken pox are transmitted through the air. Molds and mildews release disease-causing toxins. Symptoms of health problems caused by biological pollutants include sneezing, watery eyes, coughing, shortness of breath, dizziness, lethargy, fever, and digestive problems.
Allergic reactions occur only after repeated exposure to a specific biological allergen. However, that reaction may occur immediately upon re-exposure or after multiple exposures over time. As a result, people who have noticed only mild allergic reactions, or no reactions at all, may suddenly find themselves very sensitive to particular allergens.
Allergic reactions can range from mildly
uncomfortable to life-threatening, as in a severe asthma attack. Some common
signs and symptoms are:
- Watery eyes
- Runny nose and sneezing
- Nasal congestion
- Wheezing and difficulty breathing
Health experts are especially concerned
about people with asthma. These people have very sensitive airways that can
react to various irritants, making breathing difficult. The number of people
who have asthma has greatly increased in recent years. The number of people
with asthma has gone up by 59 percent since 1970, to a total of 9.6 million
people. Asthma in children under 15 years of age has increased 41 percent in
the same period, to a total of 2.6 million children. The number of deaths from
asthma is up by 68 percent since 1979, to a total of almost 4,400 deaths per
INFECTIOUS DISEASES caused by
bacteria and viruses, such as flu, measles, chicken pox, and tuberculosis, may
be spread indoors. Most infectious diseases pass from person to person through
physical contact. Crowded conditions with poor air circulation can promote
this spread. Some bacteria and viruses thrive in buildings and circulate
through indoor ventilation systems. For example, the bacterium causing
Legionnaire's disease, a serious and sometimes lethal infection, and Pontiac
Fever, a flu-like illness, have circulated in some large buildings. Some diseases, like humidifier fever, are associated with exposure to toxins from microorganisms that can grow in large building ventilation systems. However, these diseases can also be traced to microorganisms that grow in home heating and cooling systems and humidifiers. Children, elderly people, and people with breathing problems, allergies, and lung diseases are particularly susceptible to disease-causing biological agents in the indoor air.
Talking To Your Doctor
Are you concerned about the effects on
your health that may be related to biological pollutants in your home? Before
you discuss your concerns with your doctor, you should know the answers to the
following questions. This information can help the doctor determine whether
your health problems may be related to biological pollution.
- Does anyone in the family have
frequent headaches, fevers, itchy watery eyes, a stuffy nose, dry throat,
or a cough? Does anyone complain of feeling tired or dizzy all the time?
Is anyone wheezing or having difficulties breathing on a regular basis?
- Did these symptoms appear after you
moved to a new or different home?
- Do the symptoms disappear when you go
to school or the office or go away on a trip, and return when you come
- Have you recently remodeled your home
or done any energy conservation work, such as installing insulation, storm
windows, or weather stripping? Did your symptoms occur during or after
- Does your home feel humid? Can you
see moisture on the windows or on other surfaces, such as walls and
- What is the usual temperature in your
home? Is it very hot or cold?
- Have you recently had water damage?
- Is your basement wet or damp?
- Is there any obvious mold or mildew?
- Does any part of your home have a
musty or moldy odor?
- Is the air stale?
- Do you have pets?
- Do your house plants show signs of
- Do you have air conditioners or
humidifiers that have not been properly cleaned?
- Does your home have cockroaches or
TOXIC REACTIONS are the least
studied and understood health problem caused by some biological air pollutants
in the home. Toxins can damage a variety of organs and tissues in the body,
including the liver, the central nervous system, the digestive tract, and the
Coping With the Problem
Checking Your Home
There is no simple and cheap way to
sample the air in your home to determine the level of all biological
pollutants. Experts suggest that sampling for biological pollutants is not a
useful problem-solving tool. Even if you had your home tested, it is almost
impossible to know which biological pollutant(s) cause various symptoms or
health problems. The amount of most biological substances required to cause
disease is unknown and varies from one person to the next.
Does this make the problem sound
hopeless? On the contrary, you can take several simple, practical actions to
help remove sources of biological pollutants, to help get rid of pollutants,
and to prevent their return.
Self-Inspection: A Walk Through
Begin by touring your household. Follow
your nose, and use your eyes. Two major factors help create conditions for
biological pollutants to grow: nutrients and constant moisture with poor air
- Dust and construction materials, such
as wood, wallboard, and insulation, contain nutrients that allow
biological pollutants to grow. Firewood also is a source of moisture,
fungi, and bugs.
- Appliances such as humidifiers,
kerosene and gas heaters, and gas stoves add moisture to the air.
- A musty odor, moisture on hard
surfaces, or even water stains, may be caused by:
- Air-conditioning units
- Basements, attics, and crawlspaces
- Heating and air-conditioning ducts
- Humidifiers and dehumidifiers
- Refrigerator drip pans
What You Can Do About Biological
Before you give away the family pet or
move, there are less drastic steps that can be taken to reduce potential
problems. Properly cleaning and maintaining your home can help reduce the
problem and may avoid interrupting your normal routine. People who have health
problems such as asthma, or are allergic, may need to do this and more.
Discuss this with your doctor.
Water in your home can come from many
sources. Water can enter your home by leaking or by seeping through basement
floors. Showers or even cooking can add moisture to the air in your home. The
amount of moisture that the air in your home can hold depends on the
temperature of the air. As the temperature goes down, the air is able to hold
less moisture. This is why, in cold weather, moisture condenses on cold
surfaces (for example, drops of water form on the inside of a window). This
moisture can encourage biological pollutants to grow.
There are many ways to control moisture
in your home:
- Fix leaks and seepage. If water is
entering the house from the outside, your options range from simple
landscaping to extensive excavation and waterproofing. (The ground should
slope away from the house.) Water in the basement can result from the lack
of gutters or a water flow toward the house. Water leaks in pipes or
around tubs and sinks can provide a place for biological pollutants to
- Put a plastic cover over dirt in
crawlspaces to prevent moisture from coming in from the ground. Be sure
crawlspaces are well-ventilated.
- Use exhaust fans in bathrooms and
kitchens to remove moisture to the outside (not into the attic). Vent your
clothes dryer to the outside.
- Turn off certain appliances (such as
humidifiers or kerosene heaters) if you notice moisture on windows and
- Use dehumidifiers and air
conditioners, especially in hot, humid climates, to reduce moisture in the
air, but be sure that the appliances themselves don't become sources of
- Raise the temperature of cold
surfaces where moisture condenses. Use insulation or storm windows. (A
storm window installed on the inside works better than one installed on
the outside.) Open doors between rooms (especially doors to closets which
may be colder than the rooms) to increase circulation. Circulation carries
heat to the cold surfaces. Increase air circulation by using fans and by
moving furniture from wall corners to promote air and heat circulation. Be
sure that your house has a source of fresh air and can expel excessive
moisture from the home.
- Pay special attention to carpet on
concrete floors. Carpet can absorb moisture and serve as a place for
biological pollutants to grow. Use area rugs which can be taken up and
washed often. In certain climates, if carpet is to be installed over a
concrete floor, it may be necessary to use a vapor barrier (plastic
sheeting) over the concrete and cover that with sub-flooring (insulation
covered with plywood) to prevent a moisture problem.
- Moisture problems and their solutions
differ from one climate to another. The Northeast is cold and wet; the
Southwest is hot and dry; the South is hot and wet; and the Western
Mountain states are cold and dry. All of these regions can have moisture
problems. For example, evaporative coolers used in the Southwest can
encourage the growth of biological pollutants. In other hot regions, the
use of air conditioners which cool the air too quickly may prevent the air
conditioners from running long enough to remove excess moisture from the
air. The types of construction and weatherization for the different
climates can lead to different problems and solutions.
Maintain And Clean All Appliances That
Come In Contact With Water
- Have major appliances, such as
furnaces, heat pumps and central air conditioners, inspected and cleaned
regularly by a professional, especially before seasonal use. Change
filters on heating and cooling systems according to manufacturer's
directions. (In general, change filters monthly during use.) When first
turning on the heating or air conditioning at the start of the season,
consider leaving your home until it airs out.
- Have window or wall air-conditioning
units cleaned and serviced regularly by a professional, especially before
the cooling season. Air conditioners can help reduce the entry of
allergy-causing pollen. But they may also become a source of biological
pollutants if not properly maintained. Clean the coils and incline the
drain pans according to manufacturer's instructions, so water cannot
collect in pools.
- Have furnace-attached humidifiers
cleaned and serviced regularly by a professional, especially before the
- Follow manufacturer's instructions
when using any type of humidifier. Experts differ on the benefits of using
humidifiers. If you do use a portable humidifier (approximately 1 to 2
gallon tanks), be sure to empty its tank every day and refill with
distilled or demineralized water, or even fresh tap water if the other
types of water are unavailable. For larger portable humidifiers, change
the water as recommended by the manufacturer. Unplug the appliance before
cleaning. Every third day, clean all surfaces coming in contact with water
with a 3% solution of hydrogen peroxide, using a brush to loosen deposits.
Some manufacturers recommend using diluted household bleach for cleaning
and maintenance, generally in a solution of one-half cup bleach to one
gallon water. When using any household chemical, rinse well to remove all
traces of chemical before refilling humidifier.
- Empty dehumidifiers daily and clean
often. If possible, have the appliance drip directly into a drain. Follow
manufacturer's instructions for cleaning and maintenance. Always
disconnect the appliance before cleaning.
- Clean refrigerator drip pans
regularly according to manufacturer's instructions. If refrigerator and
freezer doors don't seal properly, moisture may build up and mold can
grow. Remove any mold on door gaskets and replace faulty gaskets.
- Clean mold surfaces, such as showers
and kitchen counters.
- Remove meld from walls, ceilings,
floors, and panelling. Do not simply cover mold with paint, stain,
varnish, or a moisture-proof sealer, as it may resurface.
- Replace moldy shower curtains, or
remove them and scrub well with a household cleaner and rinse before
Controlling dust is very important for
people who are allergic to animal dander and mites. You cannot see mites, but
you can either remove their favorite breeding grounds or keep these areas dry
and clean. Dust mites can thrive in sofas, stuffed chairs, carpets, and
bedding. Open shelves, fabric wallpaper, knickknacks, and venetian blinds are
also sources of dust mites. Dust mites live deep in the carpet and are not
removed by vacuuming. Many doctors suggest that their mite-allergic patients
use washable area rugs rather than wall-to-wall carpet.
- Always wash bedding in hot water (at
F) to kill dust mites. Cold water won't do the job. Launder bedding at
least every 7 to 10 days.
- Use synthetic or foam rubber mattress
pads and pillows, and plastic mattress covers if you are allergic. Do not
use fuzzy wool blankets, feather or wool-stuffed comforters, and feather
- Clean rooms and closets well; dust
and vacuum often to remove surface dust. Vacuuming and other cleaning may
not remove all animal dander, dust mite material, and other biological
pollutants. Some particles are so small they can pass through vacuum bags
and remain in the air. If you are allergic to dust, wear a mask when
vacuuming or dusting. People who are highly allergy-prone should not
perform these tasks. They may even need to leave the house when someone
else is cleaning.
Before You Move
Protect yourself by inspecting your
potential new home. If you identify problems, have the landlord or seller
correct them before you move in, or even consider moving elsewhere.
- Have professionals check the heating
and cooling system, including humidifiers and vents. Have duct lining and
insulation checked for growth.
- Check for exhaust fans in bathrooms
and kitchens. If there are no vents, do the kitchen and bathrooms have at
least one window apiece? Does the cooktop have a hood vented outside? Does
the clothes dryer vent outside? Are all vents to the outside of the
building, not into attics or crawlspaces?
- Look for obvious mold growth
throughout the house, including attics, basements, and crawlspaces, and
around the foundation. See if there are many plants close to the house,
particularly if they are damp and rotting. They are a potential source of
biological pollutants. Downspouts from roof gutters should route water
away from the building.
- Look for stains on the walls, floor
or carpet (including any carpet over concrete floors) as evidence of
previous flooding or moisture problems. Is there moisture on windows and
surfaces? Are there signs of leaks or seepage in the basement?
- Look for rotted building materials
which may suggest moisture or water damage.
- If you or anyone else in the family
has a pet allergy, ask if any pets have lived in the home.
- Examine the design of the building.
Remember that in cold climates, overhanging areas, rooms over unheated
garages, and closets on outside walls may be prone to problems with
- Look for signs of cockroaches.
Where Biological Pollutants May
Be Found In The Home
- Dirty air conditioners
- Dirty humidifiers and/or
- Bathroom without vents or windows
- Kitchen without vents or windows
- Dirty refrigerator drip pans
- Laundry room with unvented dryer
- Unventilated attic
- Carpet on damp basement floor
- Closet on outside wall
- Dirty heating/air conditioning system
- dogs or cats
- Water damage (around windows, the
roof, or the basement)
read instructions for use and any cautionary labeling on cleaning products
before beginning cleaning procedures.
- Do not mix any chemical products.
Especially, never mix cleaners containing bleach with any product (such as
ammonia) which does not have instructions for such mixing. When chemicals
are combined, a dangerous gas can sometimes be formed.
- Household chemicals may cause burning
or irritation to skin and eyes.
- Household chemicals may be harmful if
swallowed, or inhaled.
- Avoid contact with skin, eyes, mucous
membranes and clothing.
- Avoid breathing vapor. Open all
windows and doors and use an exhaust fan that sends the air outside.
- Keep household chemicals out of reach
- Rinse treated surface areas well to
remove all traces of chemicals.
Correcting Water Damage
What if damage is already done? Follow
these guidelines for correcting water damage:
- Throw out mattresses, wicker
furniture, straw baskets and the like that have been water damaged or
contain mold. These cannot be recovered.
- Discard any water-damaged furnishings
such as carpets, drapes, stuffed toys, upholstered furniture and ceiling
tiles, unless they can be recovered by steam cleaning or hot water washing
and thorough drying.
- Remove and replace wet insulation to
prevent conditions where biological pollutants can grow.
Extensive Chart of Biological Pollutants, Toxins, and Allergenic BioAerosols
Know thy Biological enemy! This chart is an extensive list of information regarding the below listed biological contaminants, aerosols, toxins, and allergens. Many of these biological pollutants are commonly found in indoor air. The chart shows the type, resulting disease, contractability or contagiousness, source, and diameter of particles in microns.
AirBorne Pathogens covered:
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Arenavirus - Junin
Arenavirus - Lassa
Arenavirus - Machupo
Filovirus - Marburg
Orthomyxovirus - Influenza
Poxvirus - Vaccinia
Poxvirus - Variola
Respiratory Syncytial Virus
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