Biological Contaminants
What Are Biological Contaminants?
Biological contaminants are or were living organisms. They can cause poor indoor
air quality and some can damage surfaces inside and outside the home. These contaminants
can travel through the air and are often invisible. Common indoor 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:
- Bacteria are carried by people, animals, and soil and plant debris.
- Viruses are transmitted by people and animals.
- Pollens originate from plants.
- The protein in urine from rats and mice is a potent allergen. When it dries, it
can become airborne.
The two conditions that are necessary to support biological growth are nutrients
and moisture. These conditions can be found in many locations, such as bathrooms,
damp or flooded basements, wet appliances (humidifiers and air conditioners), and
some carpets and furniture. Mold, mildew and other biological contaminants can grow
in contaminated central air handling systems. These systems can distribute the contaminants
through the home.
What Are the Health Effects?
Many health effects are associated with biological contaminants:
- Some may trigger allergic reactions, including hypersensitivity pneumonitis, allergic
rhinitis, and some types of asthma. Allergic reactions occur only after repeated
exposure to a specific biological allergen. However, that reaction may occur immediately
upon reexposure or after multiple exposures over time. As a result, people who have
noticed only mild allergic reactions, or none at all, may suddenly find themselves
very sensitive to particular allergens.
- Infectious diseases, such as influenza, measles, tuberculosis, and chicken pox,
are transmitted through the air.
- Some molds and mildews can release disease-causing toxins. These
toxins can damage a variety of organs and tissues in the body, including the liver,
central nervous system, digestive tract, and immune system. Some diseases, like
humidifier fever, can be traced to microorganisms that grow in home heating and
cooling systems, although it is not certain whether the disease is an allergic reaction
or a toxic response.
- Symptoms of exposure to biological contaminants include sneezing, watery eyes, coughing,
shortness of breath, dizziness, lethargy, fever, and digestive problems. Children,
elderly people, and people with breathing problems, allergies, and lung diseases
are particularly susceptible to disease-causing biological agents in the indoor
air.
How Can I Reduce Exposure?
You can reduce your exposure to biological contaminants in several ways:
- Install and use exhaust fans that are vented to the outdoors in kitchens and bathrooms.
Vent clothes dryer air to the outdoors.
- Keep the relative humidity level of the house between 30 to 50 percent. Dry off
wet surfaces and correct water problems.
- Thoroughly clean and dry water-damaged carpets and building materials (within 24
hours if possible) or consider removal and replacement.
- Dust mites, pollens, animal dander, and other allergy-causing agents can be r educed,
although not eliminated, through regular cleaning.
- Ventilate the attic and crawl spaces to prevent moisture buildup.
- Take steps to minimize biological pollutants in basements. Regularly clean and disinfect
any basement floor drain. If needed, use a dehumidifier to keep relative humidity
levels between 30 to 50 percent.
- Maintain and clean all appliances that come in contact with water. Have a professional
inspect and clean appliances, such as furnaces, heat pumps, central and wall air-conditioning
units, and furnace-attached humidifiers. Change the filters on heating and cooling
systems frequently according to the manufacturer's directions.
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