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MOLD
Mold spores are fungal reproductive cells of about the same size as pollen grains. They can occur in various colors and shapes, such as round, spheroid, banana-shaped, or tadpole-shaped. They can occur in enormous quantities, and at all times of the year. Mold spores can be found and generated at serious levels indoors, as well as out. Fungi can invade healthy individuals and can cause a variety of effects. The most common response is allergies (runny nose, sneezing, sinus congestion, and skin rashes). Allergies result from inhaling mold spores. When environmental conditions become conducive, many molds develop fungal hyphae, small appendages containing spores. These spores are analogous to plant seeds and can be spread by the billions when air currents pass over the hyphae. Even dead fungi are capable of causing allergic symptoms. Mold spores can be airborne, and get indoors through doors, windows or cracks and crevices, or be carried in from the outdoors on shoes and clothing. Building materials that were left outside before use can harbor viable (living) mold spores for many years. Indoor environments are never entirely free of molds. As a general rule of thumb, in a "healthy" building the concentration of spores and the mix of mold species tend to be similar to outdoor environment levels. If buildings are air-conditioned, or windows and doors are kept closed in summer, the concentration of spores within should even be lower than outside levels. High moisture (above 70.0% relative humidity) in a building will invariably lead to mold, mildew, or other microbial growth. This growth requires four things: a nutrient source (found in most building materials), proper temperature (usually found indoors), mold spores (ubiquitous in ambient air), and water. Some molds also produce toxins (poisons) which are thought to be useful in killing competing molds in their vicinity. These toxins can also have deleterious effects on humans when ingested, inhaled or in contact with the skin. The fungi that produce toxins are known as toxigenic fungi. Many fungi produce secondary toxic metabolites which can produce adverse health effects (mycotoxicoses) in animals and human. These metabolite are collectively known as mycotoxins. The latest World Health Organization (WHO) publication on mycotoxins, available in 1990, indicated that there are more than 200 mycotoxins produced by a variety of common fungi. Historically, mycotoxins are a problem to farmers and food industries and in Eastern European and third world countries. However, many toxigenic fungi, such as Stachyhotry.v chartarum (also known as Stachybotrys atra) and species of Aspergillus and Penicillium, have been found to infest buildings with known indoor air and building-related problems. Many indoor air quality related problems have been traced to the growth of fungus in buildings. Almost without exception, these buildings have usually had chronic water or moisture problems. In addition to mycotoxins, volatile organic compounds (moldy odors) released from actively growing fungi may also pose a health risk. Fungi occur in nature and as such are always present in air at
ambient levels. Although these levels vary
considerably, depending on the locale and current prevailing environmental conditions,
most individuals won't suffer adverse health effects except possibly allergic responses at
these levels. However, in buildings,
conditions can be favorable for fungal growth (e.g. moisture problems) resulting in
increasing the levels of airborne fungal spores by several orders of magnitude. Inhalation of such elevated levels of airborne
spores can result in allergenic or toxic responses. Although
infection can even occur in an otherwise healthy individual occasionally, high levels of
fungi in indoor environments are of particular concern with infants, elderly, and immune
compromised individuals who are much more susceptible to fungal infections. Health effects from exposure to fungi can be
divided into four general categories: infection, toxicosis, allergy and irritation. Infection Many fungi are purely saprophytic, using dead or decaying organic
matter for food. However, there are now over 100 species that are known to cause infection
in humans. There are three classifications of infection caused by fungi: systemic,
opportunistic and dermatophytic. 1. Systemic Infection: Systemic fungal infections include:
Histoplasmosis, Coccidioidomycosis, Blastomycosis and Paracocidioidomycosis. In most cases
infection is initiated when spores are of the fungi that cause these diseases are inhaled.
A large majority of these infections are self-limiting and produce minimal or no symptoms.
However immune suppressed individuals may develop chronic localized infections or the
disease may disseminate throughout the body, which generally proves fatal. 2. Opportunistic Infection: Opportunistic infections are
generally limited to individuals with impaired immunological defenses, where infection is
secondary to a primary disease or condition. The opportunistic fungi are facultative
parasites, meaning they can use both living and dead substrates for nutrients. Common
opportunistic fungi include species of Aspergillus, Candida, Cladosporium, Mucor, Rhizopus
and Cryptococcus. 3. Dermatophytes: Dermatophytes are a group of fungi that infect the
hair, skin and nails. Infection usually occurs through direct contact with an infected
individual or indirectly by sharing clothes, grooming utensils, towels, etc. Transmission
to humans from an environmental source is extremely rare, although outbreaks from soil
have been reported. Toxicosis Many fungi produce toxic metabolites called mycotoxins. The health effects from exposures to the levels of
mycotoxins that may be encountered in contaminated indoor environments are not yet
completely known. However, dramatic toxic and
carcinogenic effects have been recorded for animals and humans exposed to high levels of
mycotoxins in laboratory studies or agricultural situations. Some of the more commonly known mycotoxins are
aflatoxin, sterigmatocystin and ochratoxin,
produced predominantly by Aspergillus and Penicillium species, and T-2 toxin, vomitoxin,
fumonisin, zearalenone, satratoxins and other tricothecene mycotoxins produced by Fusarium
and Stachybotrys species. There are numerous other mycotoxins produced by a fungi, of
which the health effects remain unknown. Generally mycotoxins are nonvolatile and
inhalation exposure usually occurs only after disturbance of a contaminated source.
Symptoms of exposure to mycotoxins may include cold and flu like symptoms,
headache, nose
bleeds, dermatitis and immune suppression. Many mycotoxins are highly carcinogenic. Allergy Allergy is the most common symptom associated with exposure to
elevated levels of fungal spores or mycelial fragments. Any fungus can be allergenic,
producing antigenic proteins and polysaccharides that can cause allergic reactions in
sensitive individuals. Symptoms include
conjunctivitis, rhinitis, bronchitis, asthma and hypersensitivity pneumonitis. The first step in the allergic process is sensitization, which occurs
from an initial exposure to an antigen. During the sensitization process there may be no
symptoms, however, the body's immune system produces antibodies to the antigen. Following
each additional exposure the antibodies react with the antigen resulting in a release of
histamine and other inflammatory response agents. All people produce antibodies, however,
certain people with genetic predisposition to allergy, produce significantly greater
quantities, which continues for years after an encounter with an allergen. Irritation Fungi produce volatile organic compounds during degradation of substrates that cause the "moldy" odor associated with fungal contamination. These compounds can be irritating to mucous membranes, causing headaches and other symptoms.
Cladosporidium sp.: From Aerotech's IAQ Tech Tip #24 Back
to the Top Fungal Fact #1: Fusarium graminearum is a fungus with worldwide distribution. It is isolated from soil and from plants belonging to the grass family, where it can also act as a parasite. It attacks seeds of cereals, particularly barley and corn. Massive growth in water-damaged carpets in schools has been reported. Optimum temperature for growth is 25 degrees Celsius; toxin production is optimum at lower temperatures. (Microfungi, ISBN: 87-16-11436-1, Page 112)
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