The information below was extracted from a document provided
by the United States Environmental Protection Agency and the United States
Consumer Product Safety Commission Office of Radiation and Indoor Air
(6604J) EPA Document # 402-K-93-007, April 1995 URL: http://www.epa.gov/iaq/pubs/insidest.html#Look3
Biological contaminants include bacteria,
molds, mildew, viruses,
dander and cat saliva
and pollen. 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 biological's 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 trinities,
and some types of
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
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
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
- 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 these appliances according to the 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
- Keep your house clean. House dust
mites, pollens, animal dander, and other allergy-causing agents can be
reduced, although not eliminated, through regular
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.