Mold (filamentous fungi)
|Mold spore with single hypha
extending from main body
Mold is a fuzzy growth on moist organic matter by several types of fungi. Mildew is mold growing on fabric.
The quantity of mold fragments and spores needed to cause health problems varies from person to person. Besides inhalation, people can become exposed to mold through skin contact and eating moldy food.
Toxic molds can produce several toxic chemicals called mycotoxins that can damage your health. These chemicals are present on the spores and small mold fragments that are released into the air.
In high concentrations, mold fragments, spores, and mycotoxins can trigger symptoms even in individuals who have no allergies.
- Recent studies have linked mold to the rapid rise of the asthma rate over the past 20 years.
- A 1999 Mayo Clinic study implicates fungus as the cause of almost all of the chronic sinusitus afflicting 37 million Americans.
- Toxic molds can increase your susceptibility to a wide variety of diseases by weakening your immune system.
Molds reproduce by spreading microscopic spores. Mold spores waft through the indoor and outdoor air continually. When mold spores land on damp organic material, such as wood, paper, feathers, hair, cellulose, petroleum products, rubber, carpet, etc., they may begin growing and digesting the material.
Some molds live in temperatures below freezing, and some like it as warm as 122° F. Molds primarily thrive and become a problem when the relative humidity level is above 60%, with temperatures between 50 and 90 degrees F. (10 to 32 degrees C.) and a pH from 3 to 8. Molds also tend to be more robust in poorly ventilated areas with little air movement to disrupt their growth.
There is no practical way to eliminate all mold and mold spores in the indoor environment; the way to control indoor mold growth is to limit moisture. During humid weather, avoid excessive ventilation and use an air conditioners and/or dehumidifier to keep relative humidity below 60%. Sealing air leaks in the building’s exterior and using a mechanical ventilation system to provide fresh filtered air can help to reduce entry of mold spores and make it easier to keep indoor relative humidity below 60%.
Indoor mold growth usually can be seen or smelled. In most cases, if visible mold growth is present, sampling is not needed. There are no health or exposure-based standards that individuals can use to evaluate a mold sample. The amount of mold it takes to cause illness varies from person to person.
Health Effects and Symptoms Associated with Mold Exposure
There are four kinds of health problems that come from exposure to mold:
Mold can trigger an allergic reaction and asthma in sensitized individuals (repeated exposure to mold or mold spores sometimes causes previously non-sensitive individuals to become sensitized). About 15 million Americans are allergic to mold. The most common reactions are flu-like symptoms and asthma. Those with chronic lung or immune problems, are at risk for more serious reactions like fever, lung infections and a pneumonia-like illness.
When mold grows indoors in moist organic materials, building occupants may begin to notice odors and suffer a variety of health problems associated with mold exposure.
Inhaling or touching mold or mold spores can cause allergic reactions in sensitive individuals. Allergic reactions to mold are common — these reactions can be immediate or delayed up to six hours. Allergic reactions include:
- Respiratory problems, such as cough, sneezing, wheezing, infection, and/or difficulty in breathing
- Hay fever-type symptoms
- Nose and throat irritation
- Nasal or sinus congestion
- Watery, reddened, or burning eyes
- Sensitivity to light
- Red eyes
- Runny nose
- Dermatitis ( skin rash or irritation)
Molds can trigger asthma attacks in persons who are allergic (sensitized) to molds.
Even in non-allergic (non-sensitized) people, mold exposure can cause irritation of the eyes, skin, nose, throat, and lungs of both mold-allergic and nonallergic people.
People with weak immune systems (i.e., immune-compromised or immune-suppressed individuals) are more vulnerable to infections by molds (as well as more vulnerable than healthy persons to mold toxins). Aspergillus fumigatus, for example, has been known to cause aspergillosis in the lungs of immune-compromised individuals. These individuals inhale the mold spores which then start growing in their lungs. Trichoderma has also been known to infect immune-compromised children.
Healthy individuals are usually not vulnerable to opportunistic infections from airborne mold exposure. However, molds can cause common skin diseases, such as athlete’s foot, as well as other infections such as yeast infections.
Hypersensitivity pneumonitis may develop following either short-term (acute) or long-term (chronic) exposure to molds. The disease resembles bacterial pneumonia and is uncommon.
Mold spores are hardened containers, which possess all the DNA instructions needed to create new mold creatures, aerial eggs as it were. If they bump into dry walls they just rebound and go back to floating, but when they bump into wet walls they stick. Out of the broken open shell a single creature’s body appears, then a groping arm grows from that body, a leathery hypha, albino and clear, and then from that hypha grows another, and another, and then many, many others more. These hyphae are used by molds to obtain nourishment. For some species it is the sulfur grains in concrete that are sought, in others it’s the metals in paint, or the glue in wallpaper, or even, for one especially abundant species, found at some time in almost every house in northern temperate climates, it will be the actual antibiotic poisons that the wood they land on produces which they slurp up and use as food. The hyphae excrete enzymes that break down complex organic materials. All over your house these freshly appearing mold creatures will plug into the walls via their hyphae.
Nutrition and Metabolism
Molds require one or more organic nutrients. Because molds must absorb or transport their nutrients through the cell surface, they compete with bacteria for organic nutrients. Many molds have an advantage over the bacteria in this competition, because they can secrete digestive extra cellular enzymes such as cellulases. Thus they can degrade an otherwise insoluble organic substrate into its smaller soluble subunits, which they then absorb and use as sources of carbon and energy. This enables the molds to use carbon sources — including cellulose, lignin, and keratin (a common component of hair, nails, and feathers — that are unavailable to most other microorganisms.
|Click on a picture to enlarge it.|
|Stachybotrys (pronounced stack-ee-BOT-ris) is a toxic mold that grows especially well on moist sheet rock.|
Physiologically the molds are very “hardy” and versatile organisms. They tolerate and often thrive at environmental extremes, such as the high sugar concentrations of jams and jellies, the acid pH occurring in acid-curdled milk and in fruit juices used to make wine, and the near-freezing temperatures in a refrigerator (hence the common appearance of mold in refrigerated foods).
Testing for Mold
The U.S. Government’s Centers for Disease Control (CDC) does not recommend routine sampling for molds. Since the susceptibility of individuals can vary greatly either because of the amount or type of mold, sampling and culturing are not reliable in determining your health risk. Furthermore, reliable sampling for mold can be expensive, and government standards for judging what is and what is not an acceptable or tolerable quantity of mold have not been established. See the CDC’s Basic Facts about Mold.
Current evidence indicates that the most common symptoms caused by molds are allergies. If you are susceptible to mold and mold is seen or smelled, there is a potential health risk; therefore, no matter what type of mold is present, you should arrange for its removal.
Mold in Your Home?
- If you have symptoms that may be due to mold, ask your doctor to consider antifungal treatment.
- Have someone use a HEPA vacuum to thoroughly clean your floors and furniture while anyone who is sensitive to mold is out of the house.
- To minimize further exposure to mold, seal air leaks in the envelope of the home. Bring fresh air in through a pleated air filter to remove mold spores and other particles. Consistent ventilation will dilute and flush-out volatile organic compounds that molds emit.
- If you have a forced-air furnace, install a 6-inch thick pleated air filter.
- Make certain that all of the interior mold has been removed.
- Consider wearing an N-95 rated mask until the symptoms disappear. Choose the kind with an exhaust valve and two elastic straps.
Insurance Coverage for Mold Damage
An insurance company is more likely to cover mold contamination if it results from a covered accident, such as a water line break. If you feel that your insurance company is unfairly denying your claim, you can contact a law firm that has been successful in helping other policy holders that have mold damage to their health or property. For further details, see:
Additional Sources of Information
The following sources seem to offer honest and useful information:
Mold in Houses and Apartments:
- Household Mold Making People Sick — MSN Health
- The Mold Survival Guide: For Your Home and for Your Health — Jeffrey and Connie May
- Indoor Air – Mold — Environmental Protection Agency
- Mold in My Home: What Do I Do? — California Department of Health Services
- A Brief Guide to Mold, Moisture, and Your Home — Environmental Protection Agency
- Mold Control in the House — Johns Hopkins
- Identifying and Eliminating Household Mold (PDF) — American Lung Association’s Health House Project
- Breaking the Mold — EnviroMysteries
- Mold, Mildew, and Musty Odors
- Mold: A Health Alert — USA Today
- Mold in Homes — Minnesota Department of Health
- The Impact of Environmental Molds in the Home
- My House is Killing Me! : The Home Guide for Families with Allergies and Asthma — Book by Jeffrey C. May of May Indoor Air Investigations LLC
- Practical Information for Meeting Your Ventilation Requirements: Read This Before You Ventilate
- Mold: The Fungus Among Us
- Healthy Homes Issues: Mold — U.S. Department of Housing and Urban Development
- Mold Remediation in Occupied Homes — Building Science Corporation (pdf format)
- Mold’s Harm Lurks — The Olympian
- Haunted by Mold — The New York Times
- Managing Mold during Humid Seasons — A Consumer Guide
- Mold in Your Home — Douglas Pencille
- Mold’s Untold Damage — USA Today
- Mold in Houses
- Why Houses Work – Or Don’t — Home Energy Magazine
- Toxic Mold Seen as Growing Household Hazard
- May Indoor Air Investigations LLC — Jeffrey C. May
- What to do if toxic mold invades your apartment
- Rental Home Mold, Rental House Mold, and Rental Apartment Mold Q and A
- Mold in Nebraska Rental Property
- Toxic Mold Found in San Diego
- The Secret House: 24 Hours in the Strange and Unexpected World in Which We Spend Our Nights and Days
Mold in Schools:
- Mold Remediation in Schools and Commercial Buildings — U.S. Environmental Protection Agency
- Mold in Schools — National Clearing House for Educational Facilities
- Sick Schools Can Mean Sick Kids
- Health Effects of Mold Exposure in Public Schools
- Indoor Air Quality (IAQ) Tools for Schools — U.S. Environmental Protection Agency
- School Districts Scramble to Rid Buildings of Mold
- School Mold Frequently Asked Questions — Ball State University
- Managing Asthma in the School Environment — U.S. Environmental Protection Agency
- Health Risk Shuts Grade School — U.S. Environmental Protection Agency
- Mold is a School Health Risk — The Honolulu Advertiser
- Mold in Schools: A Health Alert — USA Today
- Mystery of Mold: Is it a Hidden Hazard?
- Mold in Schools: A Health Alert — USA Weekend
- ‘Black Mold’ Closes Bristol Elementary School
- Mold Infestations Shut Brownsville, Texas, Schools
Mold in Any Building:
- Basic Facts about Mold — Centers for Disease Control
- Mold Issues — Building Science Corporation
- Asthma Triggers: Mold — U.S. Environmental Protection Agency
- Allergic Conditions: Mold — American Academy of Allergy, Asthma and Immunology
- Health Effects of Airborne Mycotoxin Exposure in Fungi-Contaminated Indoor Environments
- Mold Resources — U.S. Environmental Protection Agency
- Mold — Centers for Disease Control
- Indoor Air – Mold — U.S. Environmental Protection Agency
- Mold … What is it all about?
- A Brief Guide to Mold in the Workplace
- Mold Problem Spreading — The Wall Street Journal
- Indoor Mold: Health Hazard Identification and Control — Minnesota Department of Health
- Indoor Toxic Molds and Their Symptoms — Nachman Brautbar, M.D.
- Mold in Buildings
- Mold — Stanford University
- Dealing with mold problems after a flood
- Mold Allergy — Asthma and Allergy Foundation of America
- Mold/Moisture/Mildew — U.S. Environmental Protection Agency
- Facts About Mold — New York City Department of Health
- The Facts About Mold — New York Committee for Occupational Safety and Health
- When Mold Takes Hold — USA Weekend Special Reports
- The Facts About Mold: What Everyone Needs to Know
- Indoor Mold — University of Minnesota
- Mold: Causes, Health Effects and Clean-Up — Building Science Corporation (pdf format)
- What You Need to Know About Mold — Building Science Corporation (pdf format)
- Mold Related Web Sites — California Indoor Air Quality Program
- Mold/Moisture Resources on the Internet — Minnesota Department of Health
- Compendium of Toxigenic Mold and Indoor Air Quality Internet Links
- Fungal Abatement: Safe Operating Procedures — University of Minnesota
- Guidelines for Assessment and Remediation of Fungi (Mold) in Indoor Environments
- Fungi and Bacteria in Ventilation Systems
- Fungi and Indoor Air Quality
- Pathogenic Fungi
- Assessment for Environmental Molds
- Doctor Fungus
- Indoor Fungi Resources
- Health and Safety Risks of Entering Flooded Buildings
- Better Health Through Indoor Air Quality Awareness — Aerias
- Mold Control in Museums — Stanford University
- Mold in Libraries: Its Causes and How to Reduce the Threat — Stanford University
- Causes, Detection, And Prevention Of Mold And Mildew On Textiles — National Park Service
- What Consumers Should Know About Mold
- Toxic Mold
- Mold Problems
- Adverse Human Health Effects Associated with Molds in the Indoor Environment — American College of Occupational and Environmental Medicine
- Indoor Dampness and Molds and Development of Adult-Onset Asthma
- Information about ASHRAE’s work on mold and moisture
- Mold Becomes Growing Problem
- Mold spores and allergenic enzymes in dust mite fecal pellets
- Index of Common Fungal Genera
- May Indoor Air Investigations LLC, Cambridge, Massachusetts
- Health and Energy Company, Omaha, Nebraska
- Closer Look Inspections, Cleveland, Ohio
Mold Prevention and Mitigation
- Preventing Moisture Problems in Walls — Building Science Corporation
- Keeping mold and moisture at bay — Oregon Department of Energy
- How to Prevent and Remove Mildew
- Mold and Indoor Air Pressure
- Controlling Mold Growth in Exterior Walls by Controlling Indoor Air Pressure
- Mold Remediation
- Moisture Control in Buildings: Putting Building Science in Green Building
- Out with the MOLD, in with the NEW! — American Academy of Allergy, Asthma and Immunology
- Hiring a Mold Consultant or Contractor
- Sample Limited Microbial Investigation Report
The following organizations are listed to help you compare products and services. No endorsement is expressed or implied.
- Achoo! Allergy and Air Products, Inc.
- Air Quality Sciences, Inc.
- Bennett Laboratories, Inc.
- Bio-Science Environmental Services and Laboratory, Inc.
- DSP Inspections — Rochester, Minnesota
- Envirotech Clean Air, Inc.
- Marine and Environmental Testing, Inc.
- MCS Environmental — Mold Inspection for Homeowners, Businesses, Realtors and Insurance Companies
- Mold Free Company — Toxic Mold Inspection and Remediation
- Mold Inspector
- Pro-Lab — Home safety test kits.
- Pure Air Control Services Inc.
- Recommendations for prevention of mold: ASHRAE