Guide to Biological Pollutants in Indoor Air InspectAPedia® -
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
Questions & answers about identifying, testing, cleaning, or removing biological contaminants found in buildings
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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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. 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
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). As reported in Best Practices Guide to Residential Construction:
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 photos above show 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 (above right).
Whether 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.
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.
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).
Steven Bliss served as editorial director and co-publisher of The Journal of Light Construction for 16 years and previously as building technology editor for Progressive Builder and Solar Age magazines. He worked in the building trades as a carpenter and design/build contractor for more than ten years and holds a masters degree from the Harvard Graduate School of Education.
Excerpts from his recent book, Best Practices Guide to Residential Construction, Wiley (November 18, 2005) ISBN-10: 0471648361, ISBN-13: 978-0471648369, appear throughout this website, with permission and courtesy of Wiley & Sons. Best Practices Guide is available from the publisher, J. Wiley & Sons, and also at Amazon.com.
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Additional technical contributors & reference sources for this article are listed below.
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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
Kansas State University, department of plant pathology, extension plant pathology web page on wheat rust fungus: see http://www.oznet.ksu.edu/path-ext/factSheets/Wheat/Wheat%20Leaf%20Rust.asp
"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
Allergen Tests in buildings advice about how to test, what to look for, in evaluating the level of dog, cat, or other animal allergens in a building
"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
Allergens: WebMD discusses allergy tests for humans at webmd.com/allergies/allergy-tests
Animal Allergens: Dog, Cat, and Other Animal Dander - Cleanup & Prevention Information for Asthmatics and regarding Indoor Air Quality.
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
Associations: Sick House, Sick Building, SBS - Air Quality, Government, Private Associations and Information Resources
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)
Atlas of Indoor Mold, Online Clinical Mold Atlas, Toxins, Pathogens, Allergens and Other Indoor Particles - Medical Health Effects of Mold (separate online document)
Black Mold that is Harmless Photos of recognizable, usually harmless black mold on wood, bluestain, ceratocystis, ophistoma
Building Floods: quick steps after a building flood or plumbing leak can prevent costly mold contamination
Classes of Mold: what types of cosmetic, allergenic, or toxic mold are a problem? Can mold be cleaned-up successfully?
"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
"Disease Prevention Program for Certain Vegetable Crops," David B. Langston, Jr., Extension Plant Pathologist - Vegetables, University of Georgia (PDF document) original source: www.reeis.usda.gov/web/crisprojectpages/209797.html
"Disease Prevention in Home Vegetable Gardens,"
Patricia Donald,
Department of Plant Microbiology and Pathology,
Lewis Jett
Department of Horticulture, University of Missouri Extension - extension.missouri.edu/publications/DisplayPub.aspx?P=G6202
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.
OTHER IAQ ISSUES: How To Find and Address Other Indoor Air or Indoor Environment Contaminants Besides Mold
Mold or allergens may not be the only or even the main indoor environmental contaminant. Don't let media attention to mold
cause so much enviro-scare fear that other, possibly more urgent hazards go un-addressed.
Ozone Warnings - Use of Ozone as a "mold"
remedy is ineffective and may be dangerous.
Pet control - if you can't say goodbye to your bird, cat, dog, guinea pig, hamster, tropical fish, then limit the
areas they occupy and limit the airflow from that area to sleeping or other areas of the building, use allergenic
bedding, eliminate wall-to-wall carpeting, improve housecleaning including use of a HEPA-rated vacuum cleaner. For more details
see our article Dog, Cat, and Other Animal Dander - Information for Asthmatics and Indoor Air Quality
Rodents, Mice, Squirrel Control - I find high levels of mouse and rodent dander, fecal dust, and urine-contaminated dust in some buildings,
and high levels of these materials in building insulation in those locations. If you have a mouse problem, particularly if mice and their waste (fecals or urine) are contaminating
the building HVAC or building insulation, may need both steps to clean up or remove infected materials and steps to stop an ongoing
rodent problem. If squirrels are a problem, the cleanup needs to include closing off entry openings into the building. Get some
help from a licensed pest control expert.
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