Biological Pollutants

Alex Manning, Clean Air Advice
June 2006

Biological contributors to poor indoor air quality include toxic mold, bacteria, mildew, viruses, animal dander, dust mites, and pollen. These agents have the ability to travel through the air and are often so small that they cannot be seen. Exposure to them usually occurs through inhalation, either attached to particles of dust or as stand-alone particles.

The majority of these biological pollutants are found indoors, however some originate outside of the home. Regardless of origin, at least some of these contaminants can be found in every home.

All biological growth requires two conditions to survive: Nutrients and Moisture. Improperly maintained air ducts, air conditioners, dehumidifiers, air-cleaning filters and improperly ventilated rooms are common places that bacteria, fungi and mold find ample nourishment. Any place where water is likely to collect such as bathrooms, kitchens and basements are also likely targets for these contaminants to thrive in.

Viruses can be carried indoors and spread from person to person, while plants, pets and insects are potential sources of allergens such as pollen and dander. Dust mites and other insects can live in carpet, bedding material, draperies, sofas and stuffed chairs. Any areas in which dust collects may potentially collect biological contaminants as well.

Health Effects are a serious concern when dealing with poor indoor air quality. As far as biological pollutants are concerned, the effects on health are dependent on the type and amount of biological contaminants a person is exposed to, as well as the sensitivity of that person. For some people, exposure to certain biological contaminants may cause no health effects at all. While for others, exposure to the same contaminants may cause allergic, infectious or even toxic reactions.

Allergic reactions are one of, if not the most, common health problem related to poor indoor air quality. Most allergic reactions are associated with animal dander, dust mites and pollen. They occur after repeated exposure to a specific biological allergen. These reactions can range from a mere annoyance to a life-threatening asthma attack. Common symptoms include watery eyes, runny nose and sneezing, nasal congestion, itching, coughing, wheezing and difficulty breathing, headaches and fatigue.

Infections diseases such as influenza, measles, chicken pox and tuberculosis are examples of diseases caused by bacteria and viruses that can be spread indoors. Most of these diseases pass by direct contact. However, poor indoor air circulation can promote their spread. Some bacteria and viruses can thrive in the ventilation systems, constantly being circulated through buildings with the indoor air supply. These types of biological pollutants are potentially very harmful to children, the elderly and those with breathing problems, allergies and lung disease.

Toxic reactions are the least understood health problem related to indoor biological pollutants. Certain fungi and toxic mold are known culprits for producing toxic by-products as part of their metabolism. Short-term symptoms of exposure to toxic mold may include dermatitis, respiratory irritation, headaches and fatigue. More serious long-term effects may include cancer, central nervous system damage, chronic sinusitis and immune system suppression. Stachybotrys atra, a slimy black mold, is the toxic mold that has received much attention in recent years. It has been associated with pulmonary hemorrhages in infants, as well as several deaths. Other types of toxic mold include Aspergillus, Fusarium and Trichoderma, all of which are commonly found in the presence of a standing water problem. If you suspect you have a toxic mold problem, mold testing may be necessary.

There is no easy fix for determining levels of biological pollutants indoors. It is not really known what pollutants cause illnesses. The quantity of pollutants necessary to cause illness also greatly varies from person to person. While there will always be some level of biological pollutants found indoors, steps can be made to control the problem and improve your indoor air quality.

Moisture levels must be controlled indoors. Pay close attention to rooms that have a musty odor, moisture on hard surfaces, water stains and open leaks. Common ways to combat problematic areas are to repair all leaks, clean appliance drip pans, thoroughly clean water damaged materials, and improve ventilation. The best method for controlling the growth and spread of biological pollutants is to use common sense. Keeping areas of common growth clean and dry will greatly improve indoor air quality. While you will never be able to completely rid your home of these pollutants, with some care and attention you can greatly inhibit their growth.

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