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Biological contaminants that contribute to indoor air pollution include bacteria, mold, mildew, dust mites, cockroaches and pollen. Biological contaminants can be traced to a variety of different sources. For example, pollen comes from plants, while bacteria can be carried by people, animals, and soil. Household pets contribute to the biological mix. Mold and mildew can grow in central air conditioning systems, which in turn distribute the contaminants throughout the building.

High humidity and wet surfaces provide an ideal breeding ground for biological contaminants. Damp, warm environments are also ideal for dust mites.

Biological contaminants can trigger allergic reactions. Infectious diseases can spread through air handling systems. Mold and mildew are responsible for disease-causing toxins. When indoor air pollution includes biological contaminants, health effects include sneezing, coughing, watery eyes, and more. Biological agents are particularly hard on children, the elderly, and persons with respiratory problems.

The first line of attack on biological contaminants is to reduce moisture. Exhaust fans that vent to the outdoors can significantly reduce moisture in areas like kitchens, bathrooms, and wherever your clothes dryer is located.

You should also take steps to prevent moisture buildup in attics and crawl spaces. Humidity levels below 50 percent are optimal. Appliances that are normally wet, especially humidifiers, should be cleaned daily. Also empty refrigerator evaporation trays on a regular basis.

Clean or replace any water-damaged carpets or building materials immediately. Mold and bacteria are especially fond of water-damaged materials.

Regular house cleaning can make a big impact on the level of biological agents in indoor air pollution. Allergic individuals should take extra precautions during activities that increase the level of airborne biological contaminants (like vacuuming).

Finally, if your home includes a basements, make sure you clean and disinfect regularly. Patch water leaks, increase outdoor ventilation, and operate a dehumidifier.