Introduction to Mold: A Primer
January, 2002
Mold is ubiquitous in outdoor environments. It grows naturally outdoors, and the spores that it produces are present in the outside air. The potential problem arises when mold moves indoors. Because molds proliferate in environments that contain an excessive amount of moisture, a leaky roof, broken pipe, or clogged drainage system can initiate the process of mold growth. After moisture is present, mold needs a nutrient source to develop and spread, and those nutrients are also present indoors. Wallpaper, cardboard, ceiling tiles, wood, and wood products all provide nutrients that may sustain mold growth.
Many molds are benign substances that simply make a wall or ceiling appear worn and deteriorated. However, some molds produce toxins harmful to human health. These are called mycotoxins. Mycotoxins are easily absorbed into the human body through the intestinal lining, airway paths, and skin. Human exposure to mold can be quite dangerous; however, different individuals often experience different symptoms, and some individuals do not exhibit symptoms at all. Mold exists in a variety of distinct forms. Following is a list of some of the more common molds, and the range of effects they may have on human health.
Alternaria:
Alternaria is known for its large spores, which are easily deposited in the nose, mouth, and upper respiratory tract. This mold has been associated with hypersensitivity and pneumonitis. Acute symptoms include edema and bronchiospasms; chronic cases may develop pulmonary emphysema.
Aspergillus:
The member molds of this genus, some of which are listed below, are known for their ability to initiate the onset of allergies in humans, as well as upper respiratory infections. This genus also produces mycotoxins that are known to be carcinogenic in animals, although evidence that the mycotoxins are carcinogenic in humans is still unknown.
Aspergillus candidus:
Aspergillus candidus has recently been associated with respiratory infections.
Aspergillus flavus:
Aspergillus flavus is capable of producing mycotoxins that have been proven to be carcinogenic in animals, although evidence suggesting these mycotoxins are carcinogenic in humans is limited. In humans, this mold strain is responsible for allergies, asthma, and other upper respiratory infections.
Aspergillus fumigatus:
Aspergillus fumigatus is known for producing aspergillosis, a pulmonary infection in humans that causes allergic-like symptoms. It is most common in humans with compromised immune systems.
Aspergillus niger:
Aspergillus niger is a close relative of Aspergillus fumigatus in that both initiate aspergillosis. Aspergillus niger is also known for causing fungal-related ear infections.
Aspergillus terreus:
Aspergillus terreus is able to produce a toxin called patulin which is known for its production of disease in both animals and humans. This fungus is also associated with aspergillosis of the lungs, as well as ear infections, and infections found in both finger and toe nails.
Basidiomycetes:
Basidiomycetes are fungal spores from mushrooms. These, and many other mushroom spores, are known to be allergenic in humans.
Bipolaris:
Bipolaris is a fungus with large spores that are typically inhaled and then deposited in the upper respiratory tract. This fungus produces a mycotoxin, sterigmatocystin, that has been shown in laboratory animals to produce liver and kidney damage.
Cladosporium:
Cladosporium is the most commonly identified outdoor fungus. Cladosporium is a common allergen in humans. This fungus is a common cause of extrinsic asthma, as well as edema, bronchiospasms, and sometimes pulmonary emphysema.
Fusarium:
Fusarium often produces intestinal problems in humans as it is found on a wide range of fruits and vegetables. In indoor environments, Fusarium is commonly found on humidifiers. It may cause allergies in humans, as well as eye, skin and nail infections.
Penicillium:
Penicillium represents a wide variety and number of organisms. Penicillium may cause hypersensitivity pneumonitis, as well as respiratory and skin allergies. Some species of Penicillium can produce mycotoxins. Acute symptoms from Penicillium include edema, bronchiospasms, and pulmonary emphysema.
Rhizomucor:
Rhizomucor is often linked to mucorosis in individuals with compromised immune systems. Sites of infection are commonly the lungs, nasal sinus passages, eyes and skin, and possibly the brain. Infections from Rhizomucor are often in multiple sites.
Stachybotrys:
Stachybotrys is the mold that has drawn the most attention for causing significant health effects in humans. Individuals who have experienced chronic exposure to Stachybotrys have reported cold and flu symptoms, sore throats, diarrhea, headaches, fatigue, dermatitis, localized hair loss, and generalized malaise. Stachybotrys is also capable of producing dangerous toxins that can suppress the human immune system. The Stachybotrys toxin when injected into laboratory animals has caused hemorrhage of the brain, spleen, intestines, lungs, heart, lymph nodes, liver, and kidneys.
Although allergies are clearly the most common effect that mold exposure has on humans, mold exposure has the potential to cause much more serious health problems. These health hazards are not permanent. Individuals who have suffered from mold exposure typically exhibit virtually no symptoms once removed from the environment, or after the mold has been remediated from the home or office. Since the health problems related to mold exposure are such a new area of study, much more research must be conducted to understand the extent of mold’s ability to affect human health. It is clear, however, that mold found in a home or office should be remediated soon after its discovery so as to avoid any associated health risks. •
Back to CM Report Special Report on Mold (2002) 2002 Winter Table of Contents
