Mold is a non-scientific term for many types of unwanted fungi found both indoors and outdoors. Active mold growth requires moisture. Actively-growing mold damages the material it lives on, thereby impairing structural integrity. In addition, mold is associated with some untoward health effects in humans, including allergies and infections.

Mold is a non-scientific term for many types of fungi - unwanted, unappealing patches of black, brown, yellow, pink, green, smelly, fuzzy growths. Countless species of mold are found both indoors and outdoors.

"Mold" and "fungus" have many connotations, most of them unpleasant: musty odors, damp basements, moldy carpets, water leaks, soggy drywall, athlete's foot, and poisonous mushrooms, among others. On the positive side, molds are also responsible for penicillin and blue cheese; yeasts are fungi (plural of fungus) used to make bread, beer, and wine; and some types of mushrooms are considered edible delicacies. And without fungi to break them down, the world would be buried in leaves, trees, grass, and garbage.

Although mold and its spores are literally everywhere, active mold growth requires moisture. Whether on visible surfaces or hiding behind drywall, in attics, or under carpets, indoor mold grows in the presence of excessive dampness or water. Also found in damp indoor environments are:

• bacteria;
• dust mites;
• break-down products of bacteria and molds, such as proteins, cell-wall particles (glucans) and volatile organic compounds (the actual cause of the musty odor associated with mold);
• airborne chemicals, gasses, and particulate matter caused by destruction of materials by growing molds.

Indoor mold may be unsightly and smelly, but the potential problems are more serious than that. By definition, actively-growing mold damages the material it lives on, thereby impairing structural integrity. In addition, mold is associated with some untoward health effects in humans, including allergies and infections. (Some health effects attributed to mold may in fact be caused by bacteria, dust mites, etc., found in mold-colonized environments. So-called "toxic mold" has been claimed as the cause of "toxic mold disease"; this syndrome remains undefined and "toxic mold" as a cause remains unproven. "Toxic mold" is also unproven as a cause of the various symptoms associated with "sick building syndrome".1,2)

Mold growth in homes, schools, and businesses should be eliminated for the sake of human health, structural integrity, and quality of life. Cleaning up small amounts of mold can be done by homeowners. Eliminating mold from large areas requires expertise and protection both for the removal specialists and occupants of the affected space.

Fungus and mold

Fungi comprise a vast world of organisms, perhaps as many as 300,000 species. The U.S. Environmental Protection Agency defines funguses, or fungi, as "types of plants that have no leaves, flowers or roots."3 Fungi include such seemingly unrelated substances as poisonous and non-poisonous mushrooms; organisms that can cause athlete’s foot, fingernail infections, and some types of pneumonia; molds found in cheese, peanut butter, mulch, hay, grains, and spoiled foods; and the black material growing in bathroom grout.

Fungi reproduce by means of spores which are spread through the air but land and survive on surfaces. Many spores can remain dormant for long periods under dry conditions, but typically develop into fungi in the presence of moisture.

Outdoors, fungi break down organic matter, including leaves, grass clippings, and dead trees. The fungi themselves constitute a large mass of material with many types of spores. These spores vary with the material on which they are found, the season, and the weather. At any given time, the same types of spores are found indoors because they enter through doors and windows and on clothing and shoes.

Molds are fungi. Homes and structures often provide many opportunities for mold spores to grow, even in the absence of frank water leaks: seepage through foundation walls and cellar floors, dehumidifiers and air conditioners, window condensation, defective plumbing, damp bathrooms, air filters, and potted plants.4 Different types of mold spores thrive on different surfaces; for example, the "yellow slime" found on hardwood mulch won’t be found growing in a tiled bath enclosure.

Common indoor mold species include Aspergillus, Alternaria, Acremonium, Cladosporum, Dreschslera, Epicoccum, Penicillium, Stachybotrys, and Trichoderma.2  Specific types of molds can be tested for and identified. This allows comparison of indoor and outdoor mold species at a given location and time. If the two don't correlate, at least roughly, it is possible that indoor mold colonies have developed. Even if they're not in a visible location, such molds can release spores and other material into the indoor air.

The presence of molds or mold metabolites does not necessarily correlate with human illness, though. Tests identify the presence of these substances at a moment in time, and not necessarily the time frame in which individuals are exposed and illness develops. Also, the presence of these substances does not necessarily mean exposure: the fact that they are present doesn't necessarily mean they were inhaled.5

Note that identification of specific mold spores is not necessary when cleaning up indoor mold colonies. It may or may not be useful when treating health effects of mold exposure, depending on the circumstances. In any case, the role of testing for indoor mold is undefined, because as yet there are no standards for interpreting these tests.6

Health effects associated with exposure to indoor damp spaces and mold

Molds and other fungi grow easily in damp indoor environments. People who spend time in such environments sometimes complain of respiratory effects, headaches, and other physical symptoms. In addition to visible or hidden mold, damp spaces likely harbor mold break-down products, dust mites, bacteria, and chemicals, gasses, and particulate matter released from the materials on which molds are growing. Given the difficulties in testing for all of these elements, hard evidence of precise cause-and-effect can be elusive.

In an extensive 2004 report, the Institute of Medicine (IOM) did not find enough evidence to identify health effects which were definitely caused by spending time in damp indoor spaces. However, the experts found that being in damp indoor spaces seemed related to respiratory illnesses: nose and throat [upper respiratory] symptoms, cough, wheeze, and asthma symptoms. They also found limited evidence that these environments can be associated with shortness of breath, the development of asthma in people who did not previously suffer from it, and lower respiratory symptoms (coughing, wheezing, chest tightness, and shortness of breath) in healthy children. Based on available research, IOM was not able to substantiate claims of numerous other symptoms such as skin irritations, fatigue, cancer, lung disease, or respiratory infections. There was enough evidence of health effects overall, though, that IOM identified damp indoor spaces as a public health problem that needs to be addressed.7

Publications in 2007, 2010, and 2011 did not substantially change those findings.8,9,10,11They reiterate that there is evidence to support an association between damp spaces, indoor mold, and respiratory illnesses. Therefore, whether the precise cause is mold or an accompanying indoor contaminant, spending time in places damp enough to support the growth of mold is a potential cause of ill health. Whether or not mold is actually seen, finding and fixing the sources of excess moisture are important for health and to keep the structure from being further damaged. Researchers note that, if dampness and mold could be confirmed as a cause of ill health, controlling these conditions would make a substantial contribution to public health.

However, some authors state definitively that mold exposure is capable of causing illness in humans. For example:

• Bush and colleagues summarize three mechanisms: harmful immune responses, e.g. allergies or the uncommon occurrence of hypersensitivity pneumonitis; infections; and irritation from mold by-products.5
• Some authors discount the role of mold in irritant responses but add toxicity to the list of acknowledged responses to mold exposure.11
• Yet others include all four mechanisms as possible causes of adverse health effects.9
• Terr describes four known types of allergy caused by inhaling mold spores, including asthma and a type of sinusitis.1

Fisk and colleagues reviewed thirty-three studies to assess the risk of health effects in individuals who spent time in damp, moldy environments. Subjects were adults and children. They found that upper respiratory tract symptoms, cough, wheeze, and asthma were more frequent in people who spent time in damp spaces.8

In a review of studies of children from ten countries, aged six to twelve, Antova and colleagues found that mold in the household correlated with a variety of respiratory disorders, including wheezing, coughing at night, and allergic symptoms and hay fever.12

Park and colleagues reported an increase in new-onset asthma among employees working in a water-damaged office building. There was a correlation between the onset of asthma and mold levels in the building's dust.13

Karvonen and colleagues studied a group of 396 children for the first eighteen months of life and found that wheezing was more common in children whose homes had moisture damage in the kitchen and visible mold in the primary living areas.14 Different findings were published by Dales and colleagues. They studied a group of 357 children for the first two years of life and found no correlation between respiratory illness and mold.15

Many of the above authors stated the need for standardized assessments of environmental mold coupled with clinical evaluation of the patients in question, including diagnosis of illness (particularly allergy and asthma) based on objective findings. In 2011, Reponen and colleagues published a study of 176 children followed from birth through age seven. A research tool developed and being evaluated by the Environmental Protection Agency (EPA)16 was used to assess the children's homes. The children themselves were evaluated for the presence of asthma at age one and again at age seven. It was found that children who lived in homes with higher levels of mold at age one were more likely than other children to have asthma by the age of seven. (Other risk factors for asthma included living without air conditioning and having a parent with asthma.) This still does not prove that molds cause asthma, but it does provide evidence that reducing the amount of mold in infants' homes is a useful strategy to pursue. Footnote 1; Reference 17

Allergies and Asthma

As suggested above, there are hundreds of studies reaching a variety of conclusions. It can be difficult or impossible to assess all types of molds, spores, fungal fragments, chemicals from destruction of mold-colonized materials and second-hand smoke, and other airborne matter indoors at any given time. Though numerous studies associate the presence of dampness and mold with respiratory allergies and asthma, it can be equally difficult or impossible to establish the presence of these substances as the definitive cause of illness in particular patients.

Even so, it is possible to assess and treat individuals who have symptoms of respiratory allergies and asthma. Khalili and colleagues emphasize that determining whether respiratory symptoms are related to mold exposure involves a process of elimination. Before mold is considered the likely cause of respiratory symptoms and infections, patients must be evaluated for the possible presence of pre-existing illness or the recent onset of an illness that happens to coincide with mold exposure. Once other possible causes of respiratory symptoms have been ruled out, patients can be assessed for the possibility of mold-induced illness.18

In a lengthy document, Storey and colleagues identify three groups of patients to be assessed for mold exposure: those who present with symptoms often associated with wet spaces and mold; those whose symptoms occurred at the time of a presumed exposure to mold or damp spaces; and patients concerned about exposures to mold even though they have no symptoms.2

In any case, a medical diagnosis is needed. For example, does the person have an allergy, asthma, or an infection? There are established methods for diagnosing these and many other conditions. Diagnosis is related to the disease process, not a specific trigger. For example, it is possible to test people for allergies to molds, but positive results do not necessarily correlate with symptoms. A sizeable percentage of the U.S. population will test positive for mold allergens but have no symptoms; estimates range from 3 percent to more than 90 percent.9 And, generally speaking, treatments will not differ if the cause is mold exposure versus other triggering conditions.

One issue is whether to undertake environmental assessments for the presence of mold or other airborne substances found in damp homes, schools, and workplaces. If someone does develop respiratory conditions in a given location only, an environmental assessment may be indicated if there are no other known triggers. These conditions include asthma (either newly diagnosed or worsening of existing asthma), the lung conditions called interstitial lung disease and hypersensitivity pneumonitis, sarcoidosis, and recurring cold-like symptoms, sinus infections, and hoarseness.2

Hypersensitivity pneumonitis is a lung disease sometimes called "farmer's lung" as it is associated with overwhelming exposure to fungi found in feed and grain. Hypersensitivity pneumonitis also has been associated with bird droppings in pigeon breeders and exposure to molds in homes and hot tubs.19

If mold and related substances seem to be causing adverse health effects, removal from the damp place is a necessary part of prevention and treatment. Storey and colleagues provide several case studies of people who developed allergies, bronchitis, and asthma when spending time in damp spaces. Avoiding those places decreased symptoms and re-exposure caused symptoms to recur.2 Unquestionably, removing people from those environments until dampness was controlled and mold removed was indicated in those cases, even if the precise cause of illness could not be determined.

Infection

Spending time in damp and moldy buildings seems to increase the risk of bronchitis and respiratory infections, but is not proven to do so. If it is a cause of these infections, bacteria or chemical emissions are likely to be responsible.10

There are well-known fungal infections, but they are not typically a result of exposure to indoor molds. Examples include:

• Allergic bronchopulmonary aspergillosis. Although Aspergillus is a fungus found indoors and outdoors, people who develop this condition usually suffer from asthma, cystic fibrosis, or immune deficiency. The illness is related to the anatomy of the lung, not exposure to indoor molds.5,20
• Athlete's foot and thrush are among many fungal infections that are not related to the presence of indoor mold.21,22

Pulmonary hemorrhage

In the 1990s, several children in Cleveland, OH, developed pulmonary hemorrhage (bleeding in the lungs). One of those children died. A preliminary study identified exposure to mold, particularly mycotoxins from Stachybotrys chartarum, as a possible cause of these illnesses.23,24 On further review, however, the U.S. Centers for Disease Control and Prevention (CDC) determined that the earlier analyses were in error and that the cause remained unknown. CDC also noted that a similar cluster of cases in Chicago was not associated with mold exposure and that pulmonary hemorrhage was not consistent with what is known of exposure to this fungus.25

"Toxic Mold Syndrome"

The original publication about pulmonary hemorrhage fueled concerns and speculation about the health effects of Stachybotrys chartarum, or "black mold". "Black mold" is indeed unsightly, but has not been identified as a cause of human illness.

"Toxic mold syndrome" is a legal construct, rather than a medical diagnosis, involving unidentified disease processes, a constellation of disparate symptoms, and reports of illness uncorroborated by a physical examination of the patients or a professional examination of their surroundings. Although "black mold" or "toxic mold" has been identified in litigation as a cause of human illness, there is no established cluster of symptoms or physical findings associated with this alleged disease. There are neither diagnostic criteria nor any valid scientific publications establishing Stachybotrys or other molds as a cause of these diverse symptoms.Footnote 2;Reference 1

There are many practitioners who advertise themselves on web sites as experts in "treating" victims of "toxic mold disease", an entity which does not exist. For large sums of money, they will advise on numerous supplements and restrictive diets to "extract" mold from people. Since mold is not retained within human organs, it is pointless to spend money on such processes.

"Sick Building Syndrome"

The Environmental Protection Agency defines "sick building syndrome" as "situations in which building occupants experience acute health and comfort effects that appear to be linked to time spent in a building, but no specific illness or cause can be identified". Those effects might include headache, fatigue, and irritation of skin, eyes, or throat, among others. Most often, these symptoms are linked to indoor air quality problems when a building is insufficiently ventilated or maintained.

It is possible for mold to be an indoor air contaminant, for example in heating ducts or other areas where moisture can accumulate and stagnate. Any number of other contaminants may be responsible for symptoms, though; a lengthy list ranges from bacteria, to body odors, plumbing exhaust, copy machine fumes, cleaning agents, pesticides, bird droppings, carpeting, and furniture.26

Preventing and eliminating indoor mold

Mold spores are literally everywhere; controlling moisture is the key to preventing their growth. Sources within homes, businesses, and schools include leaks through roofs, walls, and basements; condensation on windows and in bathrooms; standing water in drains, on floors, and in heating, cooling, and dehumidifying equipment; heating/cooling ducts; and wet floors and carpets. Preventing mold growth requires preventing leaks, removing standing water, venting areas prone to condensation (especially bathrooms and kitchens), and immediately drying or removing damp carpets and furniture. Mold-inhibiting paints can be used indoors, and air conditioners and dehumidifiers can be used in humid weather.27

If mold is present or suspected, it is possible to assess the building for mold and mold spores. However, there are no nationwide standards for mold inspectors, testing methods, normal amounts of mold, or reporting formats. This makes it difficult to interpret test results and their potential implications.6,27 A process developed by EPA identifies DNA of some molds in indoor spaces, even if the mold is hidden; this testing method is being used experimentally.16

If mold is clearly present, as determined by visual inspection or a reputable inspector, it should be removed because it can destroy the materials it grows on and is associated with human health problems. Small amounts of mold on hard surfaces can be removed with commercial mold and mildew removers, or with a solution of bleach and water (one cup bleach to one gallon water).27 Follow product instructions carefully to avoid breathing fumes, irritating skin, or splashing chemicals in the eyes.

Large amounts of mold require specialized removal techniques and personal protective equipment. The U.S. Environmental Protection Agency described the necessary steps in a document entitled "Mold Remediation in Schools and Commercial Buildings". However, this document is applicable to mold removal in homes as well.28

Summary

Moisture is required for indoor mold to grow. Indoor mold damages or destroys whatever substances it grows on. That, plus associated odors, causes diminished quality of life in people who spend time in such spaces.29There is considerable disagreement in the scientific community about whether adverse health effects are actually caused by indoor mold, though most seem to agree that spending time in damp/moist environments can contribute to such respiratory illnesses as allergy, asthma, cough, runny nose, and sinus conditions. Whether these illnesses are caused by mold, mold by-products, dust mites, chemicals emitted from deteriorating surfaces, or indoor air pollution, remains a subject for further research.

This may seem like scientific hair-splitting to an average person who simply wants to live and work in nuisance-free environments. Whether or not scientists agree on the cause of illnesses that might occur in damp places, or even the definition of dampness, there are abundant reasons to keep indoor environments clean and dry. This process begins with determining the source(s) of excess moisture, taking necessary steps to eliminate those sources, getting rid of mold that may already be in place, and keeping the area dry afterwards to minimize the potential for further growth of mold.

People who feel they are ill should seek medical care to establish a diagnosis and course of treatment, rather than relying on self-appointed "experts" who advertise unfounded "cures" on the internet.

Take-Home Messages:

Mold is a non-scientific term for many types of fungi - unwanted, unappealing patches of black, brown, yellow, pink, green, smelly, fuzzy growths. Countless species of mold are found both indoors and outdoors.

Although mold and its spores are literally everywhere, active mold growth requires moisture. Whether on visible surfaces or hiding behind drywall, in attics, or under carpets, indoor mold grows in the presence of excessive dampness or water. Also found in damp indoor environments are:

• bacteria;
• dust mites;
• break-down products of bacteria and molds, such as proteins, cell-wall particles (glucans) and volatile organic compounds (the actual cause of the musty odor associated with mold);
• airborne chemicals, gasses, and particulate matter caused by destruction of materials by growing molds.

Indoor mold may be unsightly and smelly, but the potential problems are more serious than that. By definition, actively-growing mold damages the material it lives on, thereby impairing structural integrity. In addition, mold is associated with some untoward health effects in humans, including allergies and infections. (Some health effects attributed to mold may in fact be caused by bacteria, dust mites, etc., found in mold-colonized environments. So-called "toxic mold" has been claimed as the cause of "toxic mold disease"; this syndrome remains undefined and "toxic mold" as a cause remains unproven. "Toxic mold" is also unproven as a cause of the various symptoms associated with "sick building syndrome".) Mold growth in homes, schools, and businesses should be eliminated for the sake of human health, structural integrity, and quality of life. Cleaning up small amounts of mold can be done by homeowners. Eliminating mold from large areas requires expertise and protection both for the removal specialists and occupants of the affected space.

Rose Ann Gould Soloway, RN, BSN, MSEd, DABAT emerita
Clinical Toxicologist

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