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Sources of Indoor Air Pollution - Biological Pollutants
Biological contaminants include bacteria,
molds,
mildew, viruses, animal dander and cat
saliva, house dust, mites, cockroaches, and pollen (see more about Asthma
triggers at www.epa.gov/asthma). There are many
sources of these pollutants. 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.
By controlling the relative humidity level in a home, the growth of some sources
of biologicals can be minimized. A relative humidity of 30-50 percent is
generally recommended for homes. Standing water, water-damaged materials, or wet
surfaces also serve as a breeding ground for molds, mildews, bacteria, and
insects. House dust mites, the source of one of the most powerful biological
allergens, grow in damp, warm environments.
Health Effects From Biological Contaminants
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.
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.
Reducing Exposure to Biological Contaminants
- Install and use exhaust fans that are
vented to the outdoors in kitchens and bathrooms and vent clothes dryers
outdoors.
These actions can eliminate much of the
moisture that builds up from everyday activities. There are exhaust fans on
the market that produce little noise, an important consideration for some
people. Another benefit to using kitchen and bathroom exhaust fans is that
they can reduce levels of organic pollutants that vaporize from hot water
used in showers and dishwashers.
- Ventilate the attic and crawl spaces to
prevent moisture build-up.
Keeping humidity levels in these areas below
50 percent can prevent water condensation on building materials.
- If using cool mist or ultrasonic
humidifiers, clean appliances according to manufacturer's instructions and
refill with fresh water daily.
Because these humidifiers can become breeding
grounds for biological contaminants, they have the potential for causing
diseases such as hypersensitivity pneumonitis and humidifier fever.
Evaporation trays in air conditioners, dehumidifiers, and refrigerators
should also be cleaned frequently.
- Thoroughly clean and dry water-damaged
carpets and building materials (within 24 hours if possible) or consider
removal and replacement.
Water-damaged carpets and building materials
can harbor mold and bacteria. It is very difficult to completely rid such
materials of biological contaminants.
- Keep the house clean. House dust mites,
pollens, animal dander, and other allergy-causing agents can be reduced,
although not eliminated, through regular cleaning.
People who are allergic to these pollutants
should use allergen-proof mattress encasements, wash bedding in hot (130°
F) water, and avoid room furnishings that accumulate dust, especially if
they cannot be washed in hot water. Allergic individuals should also leave
the house while it is being vacuumed because vacuuming can actually increase
airborne levels of mite allergens and other biological contaminants. Using
central vacuum systems that are vented to the outdoors or vacuums with high
efficiency filters may also be of help.
- Take steps to minimize biological
pollutants in basements.
Clean and disinfect the basement floor drain
regularly. Do not finish a basement below ground level unless all water
leaks are patched and outdoor ventilation and adequate heat to prevent
condensation are provided. Operate a dehumidifier in the basement if needed
to keep relative humidity levels between 30 - 50 percent.
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Biological Contaminants - From the IAQ Tools for Schools Kit - IAQ Coordinator's Guide -
www.epa.gov/iaq/schools/tfs/guidee.html
Description |
Sources |
Standards
or Guidelines |
Common biological contaminants include
mold, dust mites, pet dander (skin flakes),
droppings and body parts from cockroaches, rodents
and other pests or insects, viruses, and bacteria.
Many of these biological contaminants are small enough to be inhaled. |
Biological contaminants are, or are produced
by, living things. Biological contaminants are
often found in areas that provide food and moisture
or water. For example, damp or wet areas such
as cooling coils, humidifiers, condensate pans,
or unvented bathrooms can be moldy. Draperies, bedding,
carpet, and other areas where dust collects may accumulate
biological contaminants. |
There are currently no federal
government standards for biologicals in school indoor
air environments (as of 1999). |
Health
Effects |
Control
Measures |
Mold, dust mites, pet dander, and pest
droppings or body parts can trigger asthma.
Biological contaminants, including molds and pollens
can cause allergic reactions for a significant
portion of the population. Tuberculosis, measles, staphylococcus infections,
Legionella and influenza are known to be transmitted by air. |
General good housekeeping, and maintenance
of heating and air conditioning equipment, are
very important. Adequate ventilation and good air distribution also help. The key to
mold control is moisture control. If mold is a problem, clean
up the mold and get rid of excess water or moisture.
Maintaining the relative humidity between 30% - 60% will help control
mold, dust mites, and cockroaches. Employ integrated pest
management to control insect and animal allergens.
Cooling tower treatment procedures exist to reduce levels of
Legionella and other organisms. |
Additional Resources
EPA's Asthma Web Site -
www.epa.gov/asthma
EPA's Mold Web Site -
www.epa.gov/mold
Publications/Fact Sheets
Biological
Pollutants in Your Home, January 1990 (402-F-90-102)
Explains indoor biological pollution, health
effects of biological pollutants, and how to control their growth and buildup.
One third of all structures have damp conditions that may encourage
development of pollutants such as mold and bacteria, which can cause allergic
reactions - including asthma - and spread
infectious diseases. Describes corrective measures for achieving moisture
control and cleanliness. This brochure was prepared by the American Lung
Association and the U.S. Consumer Product Safety Commission.
Indoor Allergens: Assessing and Controlling
Adverse Health Effects, Andrew M. Pope, Roy Patterson, and Harriet
Burge, editors; Committee on the Health Effects of Indoor Allergens, Division of
Health Promotion and Disease Prevention, Institute of Medicine. National Academy
Press, 1993. 308 pages. ISBN 0-309-04831-1.
This project was supported by funds from the Environmental Protection Agency,
National Institute of Environmental Health Sciences, National Institute of
Allergy and Infectious Diseases, National Heart, Lung, and Blood Institute,
and Agency for Toxic Substances and Disease Registry. Copies of this book are
available from the National Academy Press, 2101 Constitution Ave., N.W., Box
285, Washington, DC 20055. Call 1-800-624-6242 or 202-334-3313 (in the
Washington DC metro area).
Indoor Air Fact Sheet No. 8 - Use
and Care of Home Humidifiers, February 1991 (402-F-91-101)
Explains that some types of home humidifiers
can disperse microorganisms from their water tanks into the indoor air.
Describes the different types of humidifiers and provides recommendations for
their use and maintenance.
Fact Sheet - Flood
Cleanup: Avoiding Indoor Air Quality Problems, August 1993
(402-F-93-005)
Discusses steps to take when cleaning and
repairing a home after flooding. Excess moisture in the home is cause for
concern about indoor air quality primarily because it provides breeding
conditions for microorganisms. This fact sheet provides tips to avoid creating
indoor air quality problems during cleanup.
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