Guide to Biological Pollutants in Indoor Air

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
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.

A Quick Guide to Indoor Biological Pollutants

Cockroach carapace and hair parts (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 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.

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.

Are animals or fungi (mold) present in the building? See ANIMAL ENTRY POINTS in buildings and also MOLD APPEARANCE - WHAT MOLD LOOKS LIKE
Is there a mold or "mildew" odor in or near the complaint area? See MVOCs & MOLDY MUSTY ODORS as well as our complete odor troubleshooting guide beginning at ODORS GASES SMELLS, DIAGNOSIS & CURE and see
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 and WATER ENTRY in buildings
Has there ever been a sewage backup or have there been toilet overflows in the building? See SEWAGE CONTAMINATION in buildings
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
Is the indoor relative humidity level often above 60%? See HUMIDITY CONTROL & TARGETS INDOORS.
Are there contagious occupants nearby in the building? Consult with appropriate physicians and health experts.
Is the building served by a private well? See Well Pollution

Frequently Asked Questions (FAQs)

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
"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
Atlas of Mold Related Illness Symptoms & Complaints - long list of both documented, studied mold related illness, and complaints ascribed to mold contamination or allergens in buildings
[5] 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

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.

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.

Building inspection education & report writing systems from Carson, Dunlop & Associates Ltd

Environmental Health & Investigation Bibliography - our technical library on indoor air quality inspection, testing, laboratory procedures, forensic microscopy, etc.
Adkins and Adkins Dictionary of Roman Religion discusses Robigus, the Roman god of crop protection and the legendary progenitor of wheat rust fungus.
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

Allergies, Allergens, Allergy Testing in buildings - References & Products

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
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.
Atlas of Mold Related Illness Symptoms & Complaints - long list of both documented, studied mold related illness, and complaints ascribed to mold contamination or allergens in buildings
Cat Dander: how to inspect and test a building for past or current presence of cats, cat hair, cat dander, and cat allergens
Clinical Atlas of Mold Toxicity - An Online Description of Toxic, Pathogenic, Allergenic Fungi, Fungal Diseases
Fiberglass Insulation Contains Mold© 2005 comments about a field study in process, & more about health hazards from fiberglass insulation
Humidity: What indoor humidity should we maintain in order to avoid a mold problem?
Mold Action Guide detailed guide on finding, removing, and preventing indoor mold contamination
Odors, Odor Detection, Smells, & Gases how to find and identify sources of noxious or toxic odors and gases
Other environmental risks, Our much longer list: Asbestos, carbon monoxide, electromagnetic fields, etc.
Ozone: The Use of Ozone Indoors for Control of Odors and Mold Removal in buildings: A Summary of Hazards and False Claims.
Pollen Allergens: identification, plant pollen and indoor air quality
Products to Reduce Mold & Allergy Problems to reduce indoor mold or allergen levels: air cleaners, air purifiers, dust mite covers, vacuum cleaners, crawl space vents
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
Sewage and Septic backup contamination in buildings: inspection, testing, remediation, & references to expert sources
Action Guide: What to do about mold, mildew, and other indoor allergens
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Mold Contamination Testing, Cleanup, Prevention: references & products

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
Atlas of Mold Related Illness: Index of Symptoms and health, physical, neurological, psychological, and other complaint which people suspect may be mold or building-related.
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?
Clinical Mold References - Detailed bibliography of mold reference texts
"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.
Fungi, Identifying Filamentous, A Clinical Laboratory Handbook, Guy St-Germain, Richard Summerbell, Star Publishing, 1996, ISBN 0-89863-177-7 (English) (buy at Amazon)
Mycology, Fundamentals of Diagnostic, Fran Fisher, Norma B. Cook, W.B. Saunders Co. 1998, ISBN 0-7216-5006-6 (buy this book at Amazon)
US EPA: Una Breva Guia a Moho - Hongo [Copy on file as /sickhouse/EPA_Moho_Guia_sp.pdf - en Espanol


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