Molds are microscopic organisms found virtually everywhere, indoors, and outdoors. Mold spores are tiny, lightweight, and easily detached by airflow, vacuuming, walking on a carpet or sitting on a couch. In indoor environments, they grow in
air-conditioning ducts, carpets, pots of household plants, etc. They produce and release millions of spores, which are small enough to stay airborne threatening to invade the human respiratory system. Mold growths can often be seen in the form of discoloration, ranging from white to orange and from green to brown and black. In large quantities, molds can cause
allergic symptoms similar to those caused by plant pollen. In order for mold to grow, it needs food sources (such as leaves, wood, paper, or dirt), a source of moisture, and a place to grow.
Different Types of Mold
molds are normally not dangerous in low amounts, but they can cause allergenic or asthmatic symptoms such as wheezing or runny nose. These molds can be abated safely with the assistance of gloves and a disposable particulate-removing respirator.
Mycotoxic molds can cause serious health effects in humans and animals. Health effects range from short-term irritation to immunosuppression to cancer and even death. If any toxic molds are identified, it is suggested that you seek advice from an Industrial Hygienist or other mold professional for guidance. The average homeowner should NOT attempt the abatement of these types of mold.
Pathogenic molds can cause serious health effects in persons with suppressed immune systems, those taking chemotherapy, those with HIV/AIDS, or autoimmunity disorders. If any pathogenic molds are identified, it is suggested you seed the advice of an Industrial Hygienist or other mold professional for guidance. The average homeowner should NOT attempt the abatement of these types of mold.
Hyphae & hyphal
elements refer to single, unidentifiable fragments of mold. Although they may not be traceable to a specific mold species, the fragments themselves may be responsible for allergic reactions in some people and may indicate previous or current growth event. Smut spores are agricultural spores from outside sources. Ascospores and basidiospores are clusters of spores that may not be easily identified as per specific species, but may still represent f mold problem in the home.
How do you come in contact with mold?
Mold spores are found in all homes and offices, and grow rapidly from excess humidity. The following are some sources of indoor moisture that may cause mold problems in a home or office: flooding, leaky roofs, humidifiers, damp basements or crawl spaces, constant plumbing leaks, house plants, steam from cooking, shower/bath steam and leaks, wet clothes, bathroom towels, pets, sweaty sneakers indoors, dirty HVAC systems, spilled liquids on carpeted surfaces and clothes dryers vented indoors.
What can mold do to you?
Exposure to mold is not healthy for anyone but the following individuals are at a higher risk for adverse health effects: infants, children, elderly, immune compromised patients, pregnant women, and individuals with existing respiratory conditions. When inhaled, even in small amounts,
mold can cause a wide range of health problems including respiratory problems (wheezing), nasal and sinus congestion, watery and red eyes, nose and throat irritation, skin irritation, aches and pains, fevers, and in some cases even death.
Causes of Indoor mold Growth
High moisture is the major contributor to indoor microbiological activity (mold growth) . This is due to nutrients for spore germination and growth being readily available in most household constituents. These household constituents can be dirt, dust, wood, paper, adhesives, acoustical fiber, paint textiles, stored material, carpets, floors, and much more.
Why Test for Mold?
Mold, the hitchhiker, is being aggressively spread throughout the world by humans’ traveling and living patterns. We have created millions of square feet of pristine living conditions for molds and we pick up mold spores and bring them home with us every day. All houses will harbor molds and some houses are friendlier to molds than others. All houses need to be monitored for mold growth as part of the maintenance procedures for the house. When any mold or mildew is present, more will come. Only through inspection and testing can it be determined if molds are present and if the subject property is showing signs of mold and mildew friendliness.
Allergies and sickness due to indoor air quality issues are increasing dramatically. More than 5% of all construction lumber manufactured each year in the United States is used to replace wood that has decayed in service. Allergies and sickness due to indoor air quality, damage to wood-frame buildings by mildew, mold, staining fungi, and decay fungi is entirely preventable. The first step in prevention is inspection and testing.
Mold is a competitive species for real estate, molds live and prosper in the same environment as we do. The houses we live in are wonderful environments for mold. All houses need regular inspections for mold along with other periodic preventative maintenance inspections. Before fungi can colonize, four requirements must be met: air, livable temperature, moisture, and food.
Humidity and water leaks are the cause of most mold infestations. Leaks being the easiest to spot are the first indications that mold may be present, however unusual activities may upset the humidity averages in the house and mechanical spaces and allow mold to establish itself.
The Most Common Mold...Known as Black Mold
Stachybotrys Chartarum is a greenish-black fungus found worldwide that grows particularly well in high-cellulose material, such as straw, hay, wet leaves, dry wall, carpet, wall paper, fiber-board, ceiling tiles, thermal insulation, etc. The fungus (mold), before drying, is wet and slightly slimy to touch. There are about 15 species of Stachybotrys, with a world-wide distribution. The toxic mold grows in areas where the relative humidity is above 55%. This type of fungus does not grow on plastic, vinyl, concrete products, or ceramic tiles. It is not found in the green mold on bread or the black mold on the shower tiles.
INTRODUCTION The toxic mold environmental risk may be one of the next major real estate “due diligence” concerns, especially in property development areas where major flooding has occurred. The problem is that this not only includes known residential and commercial flood areas incidents, but also numerous minor water releases due to plumbing failures, conductive condensation, house water leaks and accidents. The toxic mold concern could also be a problem where fires occurred at residential properties.
The second major concern is that one might not be able to permanently eliminate the entire toxic mold from the structure. There also remains a great propensity for future reoccurrence. The health risk/hazard could be back again. Therefore, we must recommend that great care be exercised to remove and dispose of all products, which have been contaminated by the toxic mold contaminated. This recommendation is supported by the Department of Health Administrations in many states. The third concern is that States’ Health Departments will consider ambiguous and genetic disposition as a response to the publics’ inquiries. There will be some people, especially children, that will exhibit more adverse reactions, including death, lung tissue damage, and memory loss, than other persons exposed to the toxic mold. This may depend on the chemical sensitivity, genetic disposition, predisposing health history (such as allergies, asthma, smoking, etc.). For some, the exposure to the toxic mold spores may just be a “health risk” and to others, it may be a real “health hazard” (potential life-threatening and loss of “quality of life”.) Whether a potential liability concern is a risk or hazard will be paramount in defining the critical level of due diligence and disclosure response by responsible parties. There are already several major lawsuits concerning toxic mold exposure in residential and commercial buildings throughout the United States.
Currently, most health organizations consider exposure to Stachybotrys mold as a health hazard. Also, keep in mind that most responses leading to testing, investigations, and abatement of the Stachybotrys toxic mold are due directly to occupant complaints or documented detrimental health effects. Stachybotrys mold may evolve to a point where it is regarded with the same cautions, response and liability concerns as those attributed to lead-base paint and asbestos. Health hazards and risks associated with concern to exposure to Stachybotrys are currently considered as short-term effects. Exposure to radon gas in houses is considered a long-term health risk and is not considered a short-term hazard.
Stachybotrys produces a mycotoxin that causes animal and human mycotoxicosis. This type of mold is thought to be a possible cause of the “sick building syndrome”. In May 1997, the Journal of the American Medical Association carried a news article titled “Floods carry potential for toxic mold disease”. Children’s exposure to air-borne Stachybotrys spores is thought most likely to cause pulmonary hemosiderosis (bleeding in the lungs). Please be aware that there is no threshold dangerous spore exposure level by the U.S. EPA or any other health administrations. There are ongoing new epidemiology studies being conducted. There is reference information related to a 1994 incident in Cleveland, Ohio where 45 cases of pulmonary hemorrhage in young infants occurred. Sixteen of the infants died. In addition, many state’s department of health administrations as well as the Center for Disease Control (CDC) list the following as symptoms associated with exposure to Stachybotrys mold spores:
1) Respiratory problems, such as wheezing, and difficulty in breathing
2) Nasal and sinus congestion
3) Eyes-burning, watery, reddened, blurry vision, light sensitivity
4) Dry, hacking cough
5) Sore throat
6) Nose and throat irritation
7) Shortness of breath
8) Chronic fatigue
9) Skin irritation
10) Central nervous system problems (constant headaches, memory problems, and mood changes)
11) Aches and pains
12) Possible fever
14) Possible hemosiderosis
15) Immune suppression
VISUAL DETECTION AND HOMEOWNER DISCLOSURES 1) The Stachybotrys fungi cannot be identified by a routine visual inspection. Remember all black mold is not necessarily Stachybotrys. It could be non-toxic black mold. The only method to determine the type of mold present is by sample analysis by an accredited laboratory. Also, it is important to keep in mind that the mold is only a toxic risk or hazard if a person breathes or comes into contact with the spores. Wet mold is not an indoor air quality health risk, but there is a significant potential for the mold to dry and released into the air. 2) There may be visual appearance of black mold in a visible water damage area, but be aware that there may be areas of water damage and mold that can be hidden (behind dry wall, under organic thread carpets). 3) The home inspector may notice or note water damage areas, but the majority of home inspectors are not aware of the water-damage environment and toxic mold relationship or concern. 4) Perhaps a question should be added on the homeowner disclosure which related to any water damage, water leaks, or flooding in the house or around the structure 5) Historical records of flooding in that geographic area may be used. 6) The standard ERC inspection form should perhaps contain an addendum, which would note any evidence of water, mold or mildew in or around the structure.
The Toxic Effects Of Fungal Exposure
Once one is tested and diagnosed with mycotoxicosis, one should begin to try to assess the extent of the fungal infection and how impaired, if any, one may be. This is exceptionally important as most physicians are inexperienced in dealing with this illness, and finding out as much as one can would possibly most helpful in describing symptoms and effective treatments.
Fungi have long been known to affect human well being in various ways, including disease of essential crop plants, decay of stored foods with possible concomitant production of mycotoxins, superficial and systemic infection of human tissues, and disease associated with immune stimulation such as hypersensitivity pneumonitis and toxic pneumonitis. The spores of a large number of important fungi are less than 5 µm aerodynamic diameter, and therefore are able to enter the lungs. They also may contain significant amounts of mycotoxins. Diseases associated with inhalation of fungal spores can include toxic pneumonitis, hypersensitivity pneumonitis, tremors, chronic fatigue syndrome, kidney failure, and cancer.
Exposure to molds has become a significant health risk to an increasing number of workers in various occupations throughout the nations. Fungal antigens are able to cause occupational asthma, rhinoconjunctivitis, hypersensitivity pneumonitis and organic dust toxic syndrome(ODTS). In recent years, an increasing incidence of mold-induced diseases has been encountered in moldy contaminated water-damaged buildings. This has occurred both in homes and workplaces. Symptomatic persons occupying moisture problem buildings may develop asthma, rhinitis, ODTS and HP.
The Symptoms of Fungal Exposure
Mold toxicity is often the end result with constant exposure to mold of a toxic substance. A common misconception among allergists who are untrained in this type of toxicity levels in humans, which is technically not their area of expertise unless they have trained specifically in environmental medicine with their background in immunology, is to do general allergen testing. Most tests usually come back unequivocal, a 2+ or less. This induces some physicians to order allergy shots, regardless. These shots are absolutely worthless to a person who has been heavily exposed to these mycotoxins as they are already in a state of toxicity. If anything, this could exacerbate the problem. Because many doctors are not trained in this field, they may try to "guess" at a diagnosis.
In laymen's terms, some molds produce mycotoxins. These substances although unseen by the naked eye, are ingested and enter the body through the skin and airways. Once inside the body, mold has it requirements to colonize and live. In doing this, it compromises the immune system and damages everyday processes of the body. Mold and yeast are interchangeable only in their dimorphic state, which is often a big misconception, although both are fungi.
The following are a list of the most common symptoms of fungal exposure (bear in mind, most people never fit
all of this criteria). Most people with mycotoxicosis meet at least ten (recent symptoms) of the following criteria:
- Respiratory distress, coughing, sneezing
- Difficulty swallowing, choking, spitting up (vomiting) mucous
- Burning in the throat and lungs
- Asthmatic signs; wheezing, shortness in breath, coughing, etc.
- Diarrhea, nausea, piercing lower abdominal pains, vomiting
- Bladder, liver, spleen, or kidney problems
- Dark urine
- Strange taste in mouth, coated tongue
- Memory loss; short term memory; brain fog
- Vision problems
- Swollen lymph nodes
- Slurred speech
- Ringing in ears, balance problems, dizziness
- Chronic fatigue
- Intermittent face flushing; almost always systemic (called the
- Numbness in face and limbs, intermittent twitching
- Night sweats and hot flashes (especially around the head)
- Elevated blood pressure and triglycerides, heart palpitations
- Nose bleeds
- Bruising easily
- Rash/hives, bloody lesions all over the body
- Reproductive system; infertility, changes in menstrual cycles
- Sudden weight change
- Hair loss
- Joint pains; swelling
- Heart attack
- Inadvertent facial movements or extremity jerking
- Anaphylaxis upon re-exposure to mycotoxic molds
- Death in some cases
This site is not intended to give medical advice. Seek the advice of a professional for medication, treatment options, and complete knowledge of any illness. The opinions expressed here are exclusively my personal opinions do not necessarily reflect my peers or professional affiliates. The information here does not reflect professional advice and is not intended to supercede the professional advice of others.
Is Mold Contamination a Health Threat?
The Fungus Among Us
Molds, a subset of the fungi, are ubiquitous on our planet. Fungi are found in every ecological niche, and are necessary for the recycling of organic building blocks that allow plants and animals to live. Included in the group "fungi" are yeasts, molds and mildews, as well as large mushrooms, puffballs and bracket fungi that grow on dead trees. Fungi need external organic food sources and water to be able to grow.
Molds can grow on cloth, carpets, leather, wood, sheet rock, insulation (and on human foods) when moist conditions exist). Because molds grow in moist or wet indoor environments, it is possible for people to become exposed to molds and their products, either by direct contact on surfaces, or through the air, if mold spores, fragments, or mold products are aerosolized.
Many molds reproduce by making spores, which, if they land on a moist food source, can germinate and begin producing a branching network of cells called hyphae. Molds have varying requirements for moisture, food, temperature and other environmental conditions for growth. Indoor spaces that are wet, and have organic materials that mold can use as a food source, can and do support mold growth. Mold spores or fragments that become airborne can expose people indoors through inhalation or skin contact.
Molds can have an impact on human health, depending on the nature of the species involved, the metabolic products being produced by these species, the amount and duration of individual’s exposure to mold parts or products, and the specific susceptibility of those exposed.
Health effects generally fall into four categories. These four categories are allergy, infection, irritation (mucous membrane and sensory), and toxicity.
The most common response to mold exposure may be allergy. People who are atopic, that is, who are genetically capable of producing an allergic response, may develop symptoms of allergy when their respiratory system or skin is exposed to mold or mold products to which they have become sensitized. Sensitization can occur in atopic individuals with sufficient exposure.
Allergic reactions can range from mild, transitory responses, to severe, chronic illnesses. The Institute of Medicine (1993) estimates that one in five Americans suffers from allergic rhinitis, the single most common chronic disease experienced by humans. Additionally, about 14 % of the population suffers from allergy-related sinusitis, while 10 to 12% of Americans have allergically-related asthma. About 9% experience allergic dermatitis. A very much smaller number, less than one percent, suffer serious chronic allergic diseases such as allergic bronchopulmonary aspergillosis (ABPA) and hypersensitivity pneumonitis. Allergic fungal sinusitis is a not uncommon illness among atopic individuals residing or working in moldy environments. There is some question whether this illness is solely allergic or has an infectious component. Molds are just one of several sources of indoor allergens, including house dust mites, cockroaches, effluvia from domestic pets (birds, rodents, dogs, cats) and microorganisms (including molds).
While there are thousands of different molds that can contaminate indoor air, purified allergens have been recovered from only a few of them. This means that atopic individuals may be exposed to molds found indoors and develop sensitization, yet not be identified as having mold allergy. Allergy tests performed by physicians involve challenge of an individual’s immune system by specific mold allergens. Since the reaction is highly specific, it is possible that even closely related mold species may cause allergy, yet that allergy may not be detected through challenge with the few purified mold allergens available for allergy tests. Thus a positive mold allergy test indicates sensitization to an antigen contained in the test allergen (and perhaps to other fungal allergens) while a negative test does not rule out mold allergy for atopic individuals.
Infection from molds that grow in indoor environments is not a common occurrence, except in certain susceptible populations, such as those with immune compromise from disease or drug treatment. A number of
Aspergillus species that can grow indoors are known to be pathogens.
Aspergillus fumigatus (A. fumigatus) is a weak pathogen that is thought to cause infections (called aspergilloses) only in susceptible individuals. It is known to be a source of nosocomial infections, especially among immune-compromised patients. Such infections can affect the skin, the eyes, the lung, or other organs and systems.
A. fumigatus is also fairly commonly implicated in ABPA and allergic fungal sinusitis.
Aspergillus flavus has also been found as a source of nosocomial infections.
There are other fungi that cause systemic infections, such as
Coccidioides, Histoplasma, and Blastomyces.
These fungi grow in soil or may be carried by bats and birds, but do not generally grow in indoor environments. Their occurrence is linked to exposure to wind-borne or animal-borne contamination.
Mucous Membrane and Trigeminal Nerve Irritation
A third group of possible health effects from fungal exposure derives from the volatile compounds (VOC) produced through fungal primary or secondary metabolism, and released into indoor air. Some of these volatile compounds are produced continually as the fungus consumes its energy source during primary metabolic processes. (Primary metabolic processes are those necessary to sustain an individual organism’s life, including energy extraction from foods, and the syntheses of structural and functional molecules such as proteins, nucleic acids and lipids). Depending on available oxygen, fungi may engage in aerobic or anaerobic metabolism. They may produce alcohols or aldehydes and acidic molecules. Such compounds in low but sufficient aggregate concentration can irritate the mucous membranes of the eyes and respiratory system.
Just as occurs with human food consumption, the nature of the food source on which a fungus grows may result in particularly pungent or unpleasant primary metabolic products. Certain fungi can release highly toxic gases from the substrate on which they grow. For instance, one fungus growing on wallpaper released the highly toxic gas arsine from arsenic containing pigments.
Fungi can also produce secondary metabolites as needed. These are not produced at all times since they require extra energy from the organism. Such secondary metabolites are the compounds that are frequently identified with typically "moldy" or "musty" smells associated with the presence of growing mold. However, compounds such as pinene and limonene that are used as solvents and cleaning agents can also have a fungal source. Depending on concentration, these compounds are considered to have a pleasant or "clean" odor by some people. Fungal volatile secondary metabolites also impart flavors and odors to food. Some of these, as in certain cheeses, are deemed desirable, while others may be associated with food spoilage. There is little information about the advantage that the production of volatile secondary metabolites imparts to the fungal organism. The production of some compounds is closely related to sporulation of the organism. "Off" tastes may be of selective advantage to the survival of the fungus, if not to the consumer.
In addition to mucous membrane irritation, fungal volatile compounds may impact the "common chemical sense" which senses pungency and responds to it. This sense is primarily associated with the trigeminal nerve (and to a lesser extent the vagus nerve). This mixed (sensory and motor) nerve responds to pungency, not odor, by initiating avoidance reactions, including breath holding, discomfort, or paresthesias, or odd sensations, such as itching, burning, and skin crawling. Changes in sensation, swelling of mucous membranes, constriction of respiratory smooth muscle, or dilation of surface blood vessels may be part of fight or flight reactions in response to trigeminal nerve stimulation. Decreased attention, disorientation, diminished reflex time, dizziness and other effects can also result from such exposures.
It is difficult to determine whether the level of volatile compounds produced by fungi influence the total concentration of common VOCs found indoors to any great extent. A mold-contaminated building may have a significant contribution derived from its fungal contaminants that is added to those VOCs emitted by building materials, paints, plastics and cleaners. Miller and co-workers (1988) measured a total VOC concentration approaching the levels at which Otto
et al., (1989) found trigeminal nerve effects.
At higher exposure levels, VOCs from any source are mucous membrane irritants, and can have an effect on the central nervous system, producing such symptoms as headache, attention deficit, inability to concentrate or dizziness.
Adverse Reactions to Odor
Odors produced by molds may also adversely affect some individuals. Ability to perceive odors and respond to them is highly variable among people. Some individuals can detect extremely low concentrations of volatile compounds, while others require high levels for perception. An analogy to music may give perspective to odor response. What is beautiful music to one individual is unbearable noise to another. Some people derive enjoyment from odors of all kinds. Others may respond with headache, nasal stuffiness, nausea or even vomiting to certain odors including various perfumes, cigarette smoke, diesel exhaust or moldy odors. It is not know whether such responses are learned, or are time-dependent sensitization of portions of the brain, perhaps mediated through the olfactory sense, or whether they serve a protective function. Asthmatics may respond to odors with symptoms.
Molds can produce other secondary metabolites such as antibiotics and mycotoxins. Antibiotics are isolated from mold (and some bacterial) cultures and some of their bacteriotoxic or bacteriostatic properties are exploited medicinally to combat infections.
Mycotoxins are also products of secondary metabolism of molds. They are not essential to maintaining the life of the mold cell in a primary way (at least in a friendly world), such as obtaining energy or synthesizing structural components, informational molecules or enzymes. They are products whose function seems to be to give molds a competitive advantage over other mold species and bacteria. Mycotoxins are nearly all cytotoxic, disrupting various cellular structures such as membranes, and interfering with vital cellular processes such as protein, RNA and DNA synthesis. Of course they are also toxic to the cells of higher plants and animals, including humans.
Mycotoxins vary in specificity and potency for their target cells, cell structures or cell processes by species and strain of the mold that produces them. Higher organisms are not specifically targeted by mycotoxins, but seem to be caught in the crossfire of the biochemical warfare among mold species and molds and bacteria vying for the same ecological niche.
Not all molds produce mycotoxins, but numerous species do (including some found indoors in contaminated buildings). Toxigenic molds vary in their mycotoxin production depending on the substrate on which they grow. The spores, with which the toxins are primarily associated, are cast off in blooms that vary with the molds' diurnal, seasonal and life cycle stage. The presence of competitive organisms may play a role, as some molds grown in monoculture in the laboratory lose their toxic potency. Until relatively recently, mold poisons were regarded with concern primarily as contaminants in foods.
More recently concern has arisen over exposure to multiple mycotoxins from a mixture of mold spores growing in wet indoor environments. Health effects from exposures to such mixtures can differ from those related to single mycotoxins in controlled laboratory exposures. Indoor exposures to toxigenic molds resemble field exposures of animals more closely than they do controlled experimental laboratory exposures. Animals in controlled laboratory exposures are healthy, of the same age, raised under optimum conditions, and have only the challenge of known doses of a single toxic agent via a single exposure route. In contrast, animals in field exposures are of mixed ages, and states of health, may be living in less than optimum environmental and nutritional conditions, and are exposed to a mixture of toxic agents by multiple exposure routes. Exposures to individual toxins may be much lower than those required to elicit an adverse reaction in a small controlled exposure group of ten animals per dose group. The effects from exposure may therefore not fit neatly into the description given for any single toxin, or the effects from a particular species, of mold.
Field exposures of animals to molds (in contrast to controlled laboratory exposures) show effects on the immune system as the lowest observed adverse effect. Such immune effects are manifested in animals as increased susceptibility to infectious diseases. It is important to note that almost all mycotoxins have an immunosuppressive effect, although the exact target within the immune system may differ. Many are also cytotoxic, so that they have route of entry effects that may be damaging to the gut, the skin or the lung. Such cytotoxicity may affect the physical defense mechanisms of the respiratory tract, decreasing the ability of the airways to clear particulate contaminants (including bacteria or viruses), or damage alveolar macrophages, thus preventing clearance of contaminants from the deeper lung. The combined result of these activities is to increase the susceptibility of the exposed person to infectious disease, and to reduce his defense against other contaminants. They may also increase susceptibility to cancer
Because indoor samples are usually comprised of a mixture of molds and their spores, it has been suggested that a general test for cytotoxicity be applied to a total indoor sample to assess the potential for hazard as a rough assessment.
The following summary of toxins and their targets is adapted from Smith and Moss (1985), with a few additions from the more recent literature. While this compilation of effects does not describe the effects from multiple exposures, which could include synergistic effects, it does give a better idea of possible results of mycotoxin exposure to multiple molds indoors.
Vascular system (increased vascular fragility, hemorrhage into body tissues, or from lung, e.g., aflatoxin, satratoxin, roridins).
Digestive system (diarrhea, vomiting, intestinal hemorrhage, liver effects, i.e., necrosis, fibrosis: aflatoxin; caustic effects on mucous membranes: T-2 toxin; anorexia: vomitoxin.
Nervous system, tremors, incoordination, depression, headache, e.g., tremorgens, trichothecenes.
Cutaneous system : rash, burning sensation sloughing of skin, photosensitization, e.g., trichothecenes.
It should be noted that not all mold genera have been tested for toxins, nor have all species within a genus necessarily been tested. Conditions for toxin production varies with cell and diurnal and seasonal cycles and substrate on which the mold grows, and those conditions created for laboratory culture may differ from those the mold encounters in its environment.
Toxicity can arise from exposure to mycotoxins via inhalation of mycotoxin-containing mold spores or through skin contact with the toxigenic molds. A number of toxigenic molds have been found during indoor air quality investigations in different parts of the world. Among the genera most frequently found in numbers exceeding levels that they reach outdoors are
Aspergillus, Penicillium, Stachybotrys, and Cladosporium. Penicillium, Aspergillus
and Stachybotrys toxicity, especially as it relates to indoor exposures, will be discussed briefly in the paragraphs that follow.
Penicillium species have been shown to be fairly common indoors, even in clean environments, but certainly begin to show up in problem buildings in numbers greater than outdoors. Spores have the highest concentrations of mycotoxins, although the vegetative portion of the mold, the mycelium, can also contain the poison. Viability of spores is not essential to toxicity, so that the spore as a dead particle can still be a source of toxin.
Important toxins produced by penicillia include nephrotoxic citrinin, produced by
P. citrinum, P. expansum and P. viridicatum; nephrotoxic ochratoxin, from
P. cyclopium and P. viridicatum, and patulin, cytotoxic and carcinogenic in rats, from
Aspergillus species are also fairly prevalent in problem buildings. This genus contains several toxigenic species, among which the most important are,
A. parasiticus, A. flavus, and A. fumigatus. Aflatoxins produced by the first two species are among the most extensively studied mycotoxins. They are among the most toxic substances known, being acutely toxic to the liver, brain, kidneys and heart, and with chronic exposure, potent carcinogens of the liver. They are also teratogenic. Symptoms of acute aflatoxicosis are fever, vomiting, coma and convulsions.
A. flavus is found indoors in tropical and subtropical regions, and occasionally in specific environments such as flowerpots.
A. fumigatus has been found in many indoor samples. A more common aspergillus species found in wet buildings is
A. versicolor, where it has been found growing on wallpaper, wooden floors, fibreboard and other building material.
A. versicolor does not produce aflatoxins, but does produce a less potent toxin, sterigmatocystin, an aflatoxin precursor. While symptoms of aflatoxin exposure through ingestion are well described, symptoms of exposure such as might occur in most moderately contaminated buildings are not know, but are undoubtedly less severe due to reduced exposure. However, the potent toxicity of these agents advise that prudent prevention of exposures are warranted when levels of aspergilli indoors exceed outdoor levels by any significant amount.
A. fumigatus has been found in many indoor samples. This mold is more often associated with the infectious disease aspergillosis, but this species does produce poisons for which only crude toxicity tests have been done. Recent work has found a number of tremorgenic toxins in the conidia of this species. Ochratoxins damage the kidney and are carcinogenic.
Stachybotrys chartarum (atra)
Stachybotrys chartarum (atra) has been much discussed in the popular press and has been the subject of a number of building related illness investigations. It is a mold that is not readily measured from air samples because its spores, when wet, are sticky and not easily aerosolized. Because it does not compete well with other molds or bacteria, it is easily overgrown in a sample, especially since it does not grow well on standard media. Its inability to compete may also result in its being killed off by other organisms in the sample mixture. Thus, even if it is physically captured, it will not be viable and will not be identified in culture, even though it is present in the environment and those who breathe it can have toxic exposures. This organism has a high moisture requirement, so it grows vigorously where moisture has accumulated from roof or wall leaks, or chronically wet areas from plumbing leaks. It is often hidden within the building envelope. When
S. chartarum is found in an air sample, it should be searched out in walls or other hidden spaces, where it is likely to be growing in abundance. This mold has a very low nitrogen requirement, and can grow on wet hay and straw, paper, wallpaper, ceiling tiles, carpets, insulation material (especially cellulose-based insulation). It also grows well when wet filter paper is used as a capturing medium.