ENSPEC - Mold and Indoor Air Quality Frequently Asked Questions

What Is Mold?

Molds are forms of fungi that are found everywhere -- both indoors and outdoors all year round. Outdoors, molds live in the soil, on plants and on dead or decaying matter. Another common term for mold is mildew. Mold growth is encouraged by warm and humid conditions, although it can grow during cold weather also. There are many thousands of species of mold and they can be in any color, including white, orange, green, brown, or black. Many times, mold can be detected by a musty odor. Most fungi, including molds, produce microscopic cells called "spores" that spread easily through the air. Live spores act like seeds, forming new mold growths (colonies) when they find the right conditions. All of us are exposed to fungal spores daily in the air we breathe, both outside and inside.

How Does Mold Get Into A House Or Building?

Most if not all of the mold found indoors comes from outdoor sources. It seems likely to grow and become a problem only where there is water damage, high humidity, or dampness. All molds need moisture to grow. Common sources of indoor moisture that can cause mold problems include flooding, roof and plumbing leaks, damp basement or crawl spaces, or anywhere moist air condenses on cold surfaces. Bathroom showers and steam from cooking may also create problems if not well ventilated.

How Can I Prevent Mold Growth?

Controlling excess moisture is the key to preventing and stopping indoor mold growth. Keeping susceptible areas in the home clean and dry is very important. Ventilate or use exhaust fans (to the outdoors) to remove moisture where it accumulates: bathrooms; kitchens; and laundry areas. Be sure the clothes dryer vents to outside the house. Repair water leaks promptly, and either dry out and clean or replace any water-damaged materials. Materials that stay wet for longer than 48 hours are likely to produce mold growth. Lowering the humidity in the home also helps prevent condensation problems. To lower humidity during humid weather, air conditioners and dehumidifiers may be used. Proper exterior wall insulation helps prevent condensation inside the home during cold weather that could cause mold growth.

Can Mold Be Toxic?

Some molds can produce toxic substances called mycotoxins. Airborne mycotoxins have not been shown to cause health problems to occupants in residential or commercial buildings. The health effects of breathing mycotoxins are not well understood and are currently under study.

High or chronic airborne exposures, typically associated with certain occupations like agricultural work, have been associated with illnesses, although these are rare. More is known about eating mycotoxins (from humans and animals consuming moldy foods or feed) and the resulting health effects than is known about breathing mycotoxins.

What Is "Black Mold"?

The news media often refer to "black mold" or "toxic black mold." It has usually been associated with the mold Stachybotrys chartarum, a type of greenish-black mold commonly associated with heavy water damage. Known health effects are similar to other common molds. It has been inconclusively associated with more severe health effects in some people. While there are only a few molds that are truly black, many can appear black. Not all mold that appears to be black is Stachybotrys.

Why Are We Concerned About Mold?

Small amounts of mold growth in workplaces or homes (such as mildew on a shower curtain) or workplaces are not a major concern, but no mold should be permitted to grow and multiply indoors. When molds are present in large quantities, they may cause nuisance odors and health problems for some people. Mold can damage building materials, finishes and home furnishings. Some molds can cause structural damage to wood.

How Do Molds Affect People?

Most people will have no reaction at all when exposed to molds. Allergic reactions, similar to common pollen or animal allergies, are the most common health effects for individuals sensitive to molds. Flu-like symptoms and skin rash may occur. Molds may also aggravate asthma. Fungal infections from building-associated molds may occur in people with serious immune disease but this is very rare. Most symptoms are temporary and eliminated by correcting the mold problem in the home.

Who Is Affected By Exposure To Mold?

For those who are affected by mold exposure, there can be a wide variation in how they react. People who may be affected more severely and quickly than others include:

infants and children
elderly people
pregnant women
individuals with respiratory conditions or allergies and asthma
persons with weakened immune systems (for example, people with HIV infection, chemotherapy patients, or organ or bone marrow transplant recipients, autoimmune diseases.)

Those with special health concerns should consult their doctor if they are concerned about mold exposure. The symptoms that may seem to occur from mold exposure can also be due to other causes such as bacterial or viral infections, or other allergies.

If You Are A Homeowner

What Should I Do If I See Or Smell Mold In My Home?

The most important step in solving a mold problem is to identify and fix the moisture sources that caused the mold growth. For small mold problems, use detergent and water to wash mold off hard surfaces and dry completely. Porous or absorbent materials (such as ceiling tiles, wallboard and carpeting) that become moldy should be replaced. If you do not see mold growth, but notice a musty odor, mold may be growing behind water-damaged materials, such as walls, carpeting or wallpaper. Persons cleaning mold should wear gloves, eye protection and a dust mask or respirator to protect against breathing airborne spores (an N95 dust mask or respirator may be purchased in hardware stores). If you have health concerns, you should consult your doctor before doing any mold cleanup.

Should I Test My Home For Mold?

Probably not. It should not be your first step. Your first step should be to inspect your home for any evidence of water damage and any visible mold growth. Testing for mold is expensive, and you should have a clear reason for doing so. In most cases, it is not economically practical or useful to test for mold growth on surfaces or for airborne spores in the home. Testing also tells you little about where mold is located and how to clean it up. In addition, there are no standards for "acceptable" levels of mold in buildings, so when testing is done, it is usually to compare the levels and types of mold spores found inside the home with those found outside the home. If you know you have a mold problem, it is more important to spend time and resources to get rid of the mold and solve the moisture problem causing the moldy conditions rather than to test for the mold problem.

What Can A Homeowner Do About A Mold Problem?

One third to one half of all buildings have damp conditions that may encourage the growth of bacteria and fungi. Bacteria and fungi can cause allergic reactions (asthma) and spread infectious diseases.

Mold spores are everywhere in the environment. Mold can begin to grow and digest whatever they are growing on to survive. Molds grow on wood, paper, carpets, wallboard and food. When excessive moisture or water accumulates indoors, mold growth can occur - particularly if the problem remains undiscovered or un-addressed. There is no practical way to eliminate all microbes from the indoor environment. The way to control indoor mold growth is to control moisture and humidity.

The key to mold control is moisture control. Excess moisture caused by leaky roofs, malfunctioning plumbing, and poor air circulation, particularly in the bathroom and kitchen should be immediately addressed. Extensive remediation procedures will do absolutely no good if the source of the problem is not corrected. Repair roof leaks and check plumbing where telltale stains on the walls or ceiling appear. Determine what building materials were damaged and need to be replaced. Be sure that the HVAC system is adequate for the square footage and that the system is functioning to keep the air properly filtered.

Water in your home can come from a variety of sources. Water can enter your home by leaking through windows, roofs, basement walls and floors. Even laundry, showers or cooking can add humidity to the air in your home. The amount of moisture in the air in your home depends on the temperature of the air. As the temperature gets colder, the air is able to hold less moisture. This is why moisture condenses on cold surfaces (e.g., windows) in colder weather. This moisture can encourage the growth of bacteria and fungi.

There are many ways to control moisture in your home:

Fix leaks and seepage. When water enters the house from the outside, the options range from landscaping to extensive excavation and waterproofing. (The ground should slope away from the home). Water in the basement can be from a lack of gutters or a water flow towards the house. Water leaks in the roof, around showers, tubs, pipes and windows can provide a place for growth of microbes.
Cover dirt in crawlspaces to prevent moisture from coming in from the ground. Be sure crawlspaces are well-ventilated. Make sure that your bathroom is not vented into the attic and the clothes dryer is vented to the outside of the building.
Use dehumidifiers and air conditioners to reduce moisture inside the home.
Raise the temperature of cold surfaces where moisture condenses. Use insulation or storm windows. Open doors between rooms to increase circulation and warm those colder rooms. Increase air circulation by using fans and by removing furniture from corners to promote air and heat circulation. Be sure your home has a fresh source of air and can expel extra moisture.
Wall-to-wall carpet on concrete floors can absorb moisture and serve as a reservoir for microbial growth. Use area rugs instead. If you must carpet, use a vapor barrier (plastic sheeting) over concrete and cover that with sub-flooring to prevent a moisture problem.

If You Are A Commercial Building Owner/Manager

Who Do I Call To Deal With Extensive Mold Growth In A Building?

A professional experienced in mold cleanup may need to be hired to address extensive mold growth in a building. It is important to correct large mold problems as soon as possible by first fixing the source of the moisture problem, then cleaning the surfaces, and finally by drying the area completely. If you use outside contractors or professionals, make sure they have experience cleaning up mold, and always check their references.

How Should A Building Be Evaluated For Mold Growth?

Check building materials and spaces for visible mold and signs of moisture damage indicating a history of water leaks, high humidity levels, and/or condensation. Any occupant complaints or reported health problems should be noted as well as any musty or moldy odors.

Components of the building's ventilation system should also be inspected. A moisture meter is often very helpful in identifying wet or damp building materials. If mold growth or moisture problems are found, the air pressure differentials between the area of growth and surrounding areas should be determined and potential air pathways from the source should be characterized to determine its impact on the building and its occupants.

When Is Sampling Necessary In A Building Evaluation?

Sampling may not be necessary. If visible mold is present, then it should be remediated, regardless of what species are present and whether samples are taken. In specific instances, such as cases where health concerns are an issue, litigation is involved, or where the source(s) of contamination is unclear, sampling may be considered as part of a building evaluation. In situations where visible mold is present, and there is a need to have the mold identified, sampling is needed. Any sampling must be conducted by professionals experienced with mold issues, and familiar with current guidelines.

If mold is suspected, but not visibly detectable after an inspection, then sampling may reveal evidence of mold amplification or reservoirs indoors. If mold is being removed and there is a question about how far the colonization extends, then surface or bulk sampling in combination with moisture readings may be useful. Sampling for airborne mold spores can indicate whether the mix of indoor molds is "typical" of the outdoor mix or conversely, "atypical" or unusual, at least at that time. If samples are taken, regardless of the purpose, there should be a clear question that the sample results should help answer. Sampling without a specific purpose greatly increases the chances of generating useless data. Note that laboratories vary in experience and proficiency; using an AIHA EMLAC accredited lab is recommended.

Why Is There Controversy About The Health Effects Of Exposure To Mold Growth?

Not all health effects of molds are controversial. Fungal infections are well known. Fungal allergies are also well known and accepted among medical experts, although the allergens themselves are poorly characterized. Infections and allergies have objective and well-established clinical effects. These effects can be measured and reproducibly demonstrated, and the mechanisms are fully understood. The resulting health effects caused by eating mycotoxins (from humans and animals consuming moldy foods or feed) are also well known.

Other health effects have been proposed for mold metabolites that are irritants or mycotoxins, and plausible mechanisms exist for health effects due to these mold metabolites. However, the clinical relevance of these mycotoxins and irritants under realistic airborne exposure levels is not fully established. Further, some or much of the supporting evidence for these other health effects is based on: case studies rather than controlled studies; studies that have not yet been reproduced; or involves symptoms that are subjective.

While case studies certainly indicate the possibility or even the plausibility of an effect, such studies by their nature cannot address whether an effect is common or widespread among building occupants. Results from studies that have not been reproduced may be spurious or have yet to be confirmed by well-designed follow up studies. In large epidemiologic studies, general symptoms have been associated with moisture damaged and presumably moldy buildings. Many of the reported symptoms are subjective and difficult to quantify. Results are confounded by the fact that the association is general, and mold is not the only possible cause of the symptoms. Neither condition proves that mold is NOT a cause.

Since much remains unproven, controversy has developed about the presumed health effects. This controversy is intensified since the health effects attributed to mycotoxins are often serious and sometimes are claimed to be permanent. Dampness in buildings is associated with respiratory effects, but the extent to which mold contributes to these effects is not known. Some health effects of exposure to mold growth remain controversial because the potential consequences may be significant; yet crucial and legitimate scientific questions remain unanswered. Our incomplete knowledge of non-infectious health effects related to mold exposure is due as much to limited research support as it is to limited actual effects. In summary, mold growth in the built environment should be considered unacceptable from the perspectives of potential adverse health effects and building performance.

Why Are There No Standards For Mold Exposure?

Health hazards of exposure to environmental molds relate to four broad categories of chemical/ biological attributes of molds and their metabolites. These materials may be: 1) irritants, 2) allergens, 3) toxins, and rarely 4) pathogens. Different mold species may be more or less hazardous with respect to any or all of these categories. However, the risks from exposure to a particular mold species may vary depending on a number of factors. This uncertainty is complicated further by the almost complete lack of information on specific human responses to well-defined exposures to mold contaminants. In combination, these knowledge gaps have made it impossible to set simple exposure standards to molds and mold-related contaminants.

With No Standards, How Do I Interpret Sampling Results?

A useful method for interpreting microbiological results is to compare the kinds and levels of organisms detected in different environments. Usual comparisons are indoors to outdoors or complaint areas to non-complaint areas. Specifically, in buildings without mold problems, the qualitative diversity of airborne fungi indoors and outdoors should be similar. Conversely, the dominating presence of one or two kinds of fungi indoors and the absence of the same kind outdoors may indicate a moisture problem and degraded air quality. Also, the consistent presence of fungi such as Stachybotrys chartarum, Aspergillus versicolor, or various Penicillium species over and beyond background concentrations may indicate the occurrence of a moisture problem that should be addressed and a potential atypical exposure. Generally indoor mold types should be similar and levels should be no greater than outdoor and non-complaint areas. Analytical results from bulk material or dust samples may also be compared to results of similar samples collected from reasonable comparison areas.

Comparisons of total bacterial levels indoors versus outdoors may not be as useful as with fungi, since natural reservoirs exist in both places. Comparisons of specific taxa of bacteria present, excluding those of known human origin, can help determine building-related sources.

Does Mold Remediation Always Require Isolation / Containment?

Mold remediation should always require some level of isolation of materials or containment. The lower level of containment or isolation would involve sealing removed moldy materials in a plastic bag for disposal. Local area or full area containment decisions should be made based upon the size of the area of growth and the potential for occupant exposure or building contamination without containment. These decisions should be based on an understanding of the full scope of mold contamination, including visible and hidden mold sources.

Are Biocides Required Or Useful In Remediation Projects?

Biocides are disinfectant chemicals used to kill germs in order to prevent infections resulting from contact with these materials. In most mold remediations, biocides are not a substitute for thorough cleaning. Biocides are of limited use in remediation of indoor mold contamination for two main reasons:

The adverse effects caused by mold (other than infection) are due to metabolites present in their spores and secreted into the materials upon which molds have grown. The application of biocides may kill mold spores but it does not necessarily eliminate these metabolites. The only sure way to do this requires the physical elimination of mold and moldy materials by thorough cleaning or removal of the affected materials.
Most commonly used biocides do not kill molds effectively. Active fungal growth on a surface may produce a spore density of one million spores per square inch. Treating an active mold growth site with a spore density of one million spores per square inch with a biocide with an effectiveness of 99.999% would then leave an estimated 10 viable spores per square inch. As such, if the underlying moisture problem is not resolved, mold growth may re-occur.

The only situation where biocidal treatments are indicated is where the contaminant is one of the few fungi that are known to cause human infection. This is particularly important in health care facilities or other places with occupants who have impaired immune systems or who may be more susceptible than the general population to infection.

What Are The Gaps In Our Knowledge About Mold Exposure And The Health Effects Of Mold Exposure?

The etiology of infectious fungi is relatively well understood. Conversely, mechanisms responsible for allergic sensitization, contact dermatitis, hypersensitivity pneumonitis, and inhalation fevers vary from incompletely characterized to entirely unknown. Predisposing host factors, presumably under genetic control, influence individual susceptibility to environmental exposures. The psychogenic/psychosocial contribution to mold-related illness remains elusive. Chief among our knowledge gaps are: (1) defining how mycotoxins affect human health and (2) the health risks associated with mycotoxin, microbial volatile organic compound, allergen, and glucan exposures, particularly the proposed response to Stachybotrys mycotoxins associated with hemosiderosis.

The lack of meaningful threshold limit values for most indoor air quality contaminants is a major obstacle to establishing regulatory standards for individual exposure to airborne contaminants. The same is certainly true for molds. Until microbiological methods for demonstrating mold concentrations in the environment are standardized and reproducible, epidemiological studies necessary to determine dose-response can only suggest association, not cause and effect, with respect to mold exposures and health effects.