severe mold contamination indoors (C) Daniel Friedman Guide to Biological Pollutants in Building Indoor Air
     

  • BIOLOGICAL POLLUTANTS - CONTENTS: Suggestions for Reducing Exposure to Biological Pollutants Indoors. Biological contaminants as indoor air quality hazards. Removing or keeping out indoor contaminants. Home ventilation strategies. Best methods for cleaning & filtering indoor air
  • POST a QUESTION or READ FAQs about identifying, testing, cleaning, or removing biological contaminants found in buildings
  • REFERENCES

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Here we provide a summary of common indoor biological contaminants such as mold, animal dander, pollen, viruses, and bacteria. We explain the requirements to remove these materials to improve indoor air quality and other health conditions in buildings.

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A Quick Guide to Indoor Biological Pollutants

Sewage backup (C) Daniel Friedman

Our page top photo shows an obviously moldy building that needs professional cleaning. But other mold and biological contaminants may be more difficult to spot..

Our photographs above show common sources of indoor biological pollutants including an un-discovered sewage backup in a crawl space (above left) and cockroach fragments and fecal dust (above right).

This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons.

For help looking for less obvious indoor mold contamination
see MOLD APPEARANCE - WHAT MOLD LOOKS LIKE.

Also
see ENVIRONMENTAL HAZARDS - INSPECT, TEST, REMEDY for our full list of environmental hazard identification and remedy related to buildings

Biological pollutants are or were living organisms. At least some of these are found in every home.

Common examples include molds, pollen, dust mites, animal dander, and cockroaches, as well as viruses and bacteria.

Our photo above shows gross evidence of a sewer backup in a crawl space that was ignored by the building owner, leaving a pathogenic hazards in the building (above left), and a cockroach fragment found in building dust (below left).

Cockroach carapace and hair parts (C) Daniel FriedmanWhether these biological hazards and particles are brought in to the building inadvertently by humans or pets or ride along on houseplants or their soil, living organisms tend to stay longer and breed more successfully in warm, damp conditions.

In fact, given temperatures of 50°F to 90°F and a material that stays wet for more than 48 hours, a colony of mold or other fungi will rapidly develop from their invisible spores, which are everywhere in our environment just waiting for the right conditions to spring to life.

Health Effects. Allergic reactions are among the most common health problems associated with indoor air quality.

They are often connected with molds, pollen, animal dander (mostly from cats and dogs), and dust mites, which are microscopic animals living in carpets, bedding, and furnishings. Allergic reactions can range from annoying to life-threatening, as in a severe asthma attack. Common symptoms include watery, itchy eyes, runny nose, sneezing, nasal congestion, coughing and breathing difficulties, headaches, and fatigue.

Dog allergens photo (C) Daniel Friedman

Asthma. Children and adults with asthma are particularly at risk. Asthmatics have very sensitive airways that react to irritants by narrowing, making breathing difficult.

Between 1980 and 1994, asthma rates in the United States rose by 75%, affecting over 20 million people today, including over 6 million children, according to the Centers for Disease Control and Prevention.

Our lab photo (left) shows skin cells and dog dander particles, dyed red with acid fuchsin for clarity.

Asthma “triggers” vary from person to person, but some of the most common indoor triggers are biological allergens, such as dust mites; molds; animal dander, urine, and saliva; and cockroach body parts, secretions, and droppings.

At ALLERGENS in buildings, RECOGNIZING we provide additional field and laboratory photographs of common indoor allergens.

Suggestions for Reducing Exposure to Biological Pollutants Indoors

Since most biological pollutants thrive in a moist environment, the key to reducing them is good moisture control. This starts with building houses correctly with good foundation drainage and waterproofing, proper flashings, continuous air and vapor barriers, and adequate ventilation. Household humidity levels should be maintained between 30% and 50%.

Basements should only be finished if they are dry year-round and detailed so finish materials and carpeting are not wetted by capillary action or condensation. If a building sustains water damage for any reason, it is essential that the wet materials be dried or removed within 24 to 48 hours or mold will grow. While wood, concrete, and other solid materials can be cleaned and disinfected, porous materials should be removed and replaced.

HVAC equipment and appliances that come in contact with water are other breeding grounds for biological contaminants. Have all such equipment serviced regularly and keep filters clean. Air conditioners can help filter out pollen, but dirty coils and drain pans can also become a source of biological pollutants. If using humidifiers, clean them according to manufacturers’ instructions and refill with fresh water daily.

Evaporation trays in air conditioners, dehumidifiers, and refrigerators should also be cleaned frequently. Duct cleaning may also be justified if an occupant is suffering from allergies and a visual inspection reveals that the air ducts are contaminated with large deposits of dust or mold. If so, choose a reputable company that follows the standards of the National Air Duct Cleaners Association (NADCA).

Good housekeeping is also an important part of the strategy for controlling household allergens. Bedding should be washed at 130°F. Using a HEPA vacuum or central vacuum with an exterior exhaust is recommended. Minimizing the use of carpeting, upholstered furniture, and dust-collecting shelving and furnishings can also help by eliminating hiding places for dust and contaminants (see CARPETING & INDOOR AIR QUALITY). In some case, portable or central air filtration may also play a role, but these are not a panacea for removing allergens (see Air Filtering Strategies).

-- Adapted with permission from Best Practices Guide to Residential Construction.

Common Sources of Biological Pollutants Indoors

According to the US EPA,

... indoor levels of pollutants may be 2-5 times, and occasionally more than 100 times higher than outdoor levels. These levels of indoor air pollutants may be of particular concern becaus3e it is estimated that most people [in the U.S.] spend about 90% of their time indoors. Comparative risk studies performed by EPA and its Science Aedvisory Board have consistently ranked indoor air pollution among the top five environmental health risks to the public. [5]

Basic checks for sources of biological contaminants in buildings: Here we provide biological contamination troubleshooting help for buildings by expanded annotated information from the US EPA [5] who provided suggestions for investigating for biological pollutant sources during an indoor air quality investigation.

 

Continue reading at BIOLOGICAL POLLUTANTS in the HOME - EPA or select a topic from the More Reading links shown below.

Or see CARPETING & INDOOR AIR QUALITY

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BIOLOGICAL POLLUTANTS at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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