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
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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.
Biological pollutants are or were living organisms. At least
some of these are found in every home.
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).
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
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.
Asthma. Children and adults with asthma are particularly
at risk. Asthmatics have very sensitive airways
that react to irritants by narrowing, making breathing
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.
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%.
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).
... 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.
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  who provided suggestions for investigating for biological pollutant sources during an indoor air quality investigation.
Is there standing water (or are there wet areas) near the complaint area, such as a wet crawl space or basement, or an air conditioner condensate drain system that is not working?
See CONDENSATE HANDLING, A/C
Is there condensation often present or seasonally present on windows or on other cold surfaces such as water piping and water tanks in or near the complaint area?
See CONDENSATION on WINDOWS & SKYLIGHTS
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Questions & answers or comments about identifying, testing, cleaning, or removing biological contaminants found in buildings
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"IgG Food Allergy Testing by ELISA/EIA, What do they really tell us?" Sheryl B. Miller, MT (ASCP), PhD, Clinical Laboratory Director, Bastyr University Natural Health Clinic - ELISA testing accuracy: Here is an example of Miller's critique of ELISA
http://www.betterhealthusa.com/public/282.cfm - Townsend Letter for Doctors and Patients
The critique included in that article raises compelling questions about IgG testing assays, which prompts our interest in actually screening for the presence of high levels of particles that could carry allergens - dog dander or cat dander in the case at hand.
http://www.tldp.com/issue/174/IgG%20Food%20Allergy.html contains similar criticism in another venue but interestingly by the same author, Sheryl Miller. Sheryl Miller, MT (ASCP), PhD, is an Immunologist and Associate Professor of Basic and Medical Sciences at Bastyr University in Bothell, Washington. She is also the Laboratory Director of the Bastyr Natural Health Clinic Laboratory.
Allergens: Testing for the level of exposure to animal allergens is discussed at http://www.animalhealthchannel.com/animalallergy/diagnosis.shtml (lab animal exposure study is interesting because it involves a higher exposure level in some cases
 US EPA - Mold Remediation in Schools and Commercial Building [ copy on file as /sickhouse/EPA_Mold_Remediation_in_Schools.pdf ] - US EPA
"A Brief Guide to Mold, Moisture, and Your Home",
U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
US EPA - Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol
Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
Recognizing Allergens: What various indoor allergens look like - identification photos to help identify pollen, dust mites, animal dander, toxic or allergenic mold - Common Mold and other Allergens, Irritants, Remedies & Advice
Rodent control issues, including dander, fecal, and urine contamination of buildings and Building insulation are discussed at our
Atlas of Clinical Fungi, 2nd Ed., GS deHoog, J Guarro, J Gene, & MJ Figueras, Centraalbureau voor Schimmelcultures, Universitat Rovira I Virgili, 2000, ISBN 90-70351-43-9 (you can buy this book at Amazon) - The Atlas of Clinical Fungi is also available on CD ROM
"A Brief Guide to Mold, Moisture, and Your Home", U.S. Environmental Protection Agency US EPA - includes basic advice for building owners, occupants, and mold cleanup operations. See http://www.epa.gov/mold/moldguide.htm
Fifth Kingdom, Bryce Kendrick, ISBN13: 9781585100224, is available from the InspectAPedia online bookstore - we recommend the CD-ROM version of this book. This 3rd/edition is a compact but comprehensive encyclopedia of all things mycological. Every aspect of the fungi, from aflatoxin to zppspores, with an accessible blend of verve and wit. The 24 chapters are filled with up-to-date information of classification, yeast, lichens, spore dispersal, allergies, ecology, genetics, plant pathology, predatory fungi, biological control, mutualistic symbioses with animals and plants, fungi as food, food spoilage and mycotoxins.