quality of indoor air has received and increasing amount of attention, including a large amount of discussion about sick building syndrome, which has been recognised since the 1970's. Certainly, most North Americans spend the majority of our lives indoors, and the quality of our indoor air environment has been shown to play a huge role on our health. A wide variety of indoor pollutants can have an effect on human health, including environmental tobacco smoke, volatile organic chemicals (VOCs) and biological pollutants. Biological indoor pollutants include dust mites, cockroaches, effluvia from pets like birds, rodents, dog and cats and mold.
Early investigations into sick building syndrome often gave a multi-factorial explanation for the symptoms of occupants. However, these investigations often could not explain the long duration of effects. Further, investigations into indoor air quality have historically ignored the problem of mold, and failed to give a clear history of water damage, or adequately document the presence of mold.
Certainly, mold falls into the category of biological pollutants that can affect human health. The statistics on the presence of mold in the indoor environment are compelling: one third to half of all buildings have damp conditions that can encourage the growth of biological pollutants like mold and bacteria.
The Center for Environmental Studies, University of Nevada, and Los Vegas was originally developed to deal with a wide variety of indoor issues. Interestingly, the UNLV centre had begun to focus primarily on mold, due to the large number of mold-related indoor air quality health complaints. The UNLV center investigated 72 cases in 1998, 92 in 1999, and a staggering 156 in 2002. The centre investigates complaints about the most common mold, stachybotrys, along with the other 300 kinds of aspergilli present. Of over 90 buildings investigated by UNLV in the Las Vegas Valley, over one third showed significant mold growth.
Interestingly, two of the highest-profile sick building cases in the United States have been traced back to excessive mold growth and exposure. These cases are the Grant Sawyer Building and the new UNLV Library in Las Vegas. When the Grant Sawyer building opened in 1995, the government workers employed there complained about a wide variety of allergic and respiratory symptoms, as well as headaches, chronic fatigue, and other illnesses.
When tests for infectious agents and chemicals turned up blank, the idea of mold exposure was investigated. Accordingly, the cause was eventually determined to stachybotrys mold spores from water-damaged ceiling tiles. The water damage occurred as a result of defective heating valves. When the ceiling tiles were replaced, and the heating valves were repaired, the clinical symptoms of the occupants improved significantly.
Molds are a subset of fungi, and one of the most ubiquitous forms of life on the planet Earth. They exist in almost all ecological niches, so it is likely no surprise that humans come into direct contact with molds on a constant basis.
Fungi are important in that they allow of the recycling of the basic organic matter of life. In other words, when a tree or animal dies, molds help decompose this organic matter. This organic matter can then be recycled, or reused, to help plants grow, thus continuing the cycle of life.
Fungi contain a large number of organisms from large mushrooms, bracket fungi that grow on dying trees, yeasts used to make bread and beer, and molds and mildews. Fungi are not photosynthetic, and require and external food source and water in order to grow and reproduce.
Specifically, molds can grow on almost any surface that provides water and adequate nutrients. They grow by using the surface they land on for nutrients, slowly "digesting" that surface. Molds can grow on leather, wood, paper, carpet, cloth, sheet rock, insulation, and human food when these conditions are met. Different molds have different requirements for moisture, nutrients, temperature and other environmental conditions for growth. Accordingly, molds can grow in almost any location with moisture and nutrients. As such, it is almost impossible to totally eradicate molds from our everyday life.
Given that molds can grow on almost any surface, it is impossible to totally prevent their growth. However, mold growth increases when there is excessive moisture or water that accumulates indoors. Specifically, if the moisture problem continues unchecked, the mold growth will escalate. In short, there is no guaranteed way to eliminate all mold and mold spores indoors; the only way to control the growth of mold indoors is to control the amount of moisture in the indoor environment.
People can be exposed to mold at home, at work, or basically in any indoor environment. Anywhere there is wetness or moisture in the indoor environment; it is possible to become exposed to molds or their products. Exposure to molds can occur through the direct contact of skin with surfaces containing mold, or by the air, if mold products, spores or even fragments of air are aerosolized. Simply, aerosolized refers to the process where a particle (like a mold spore, or a water droplet), becomes suspended in the air. When mold is suspended in the air, it becomes easy for humans to inhale.
Molds reproduce through spores, which are small, seed-like objects. A single mold can easily produce thousands of spores, and release them into the air. Mold spores are constantly floating in both indoor and outdoor air. If the spores land on a moist location, with adequate nutrients, they can germinate, and turn into a branching network of cells, called the hyphae.
Recently, the issue of the impact of molds on human health has received a great deal of attention. Certainly, molds can impact human health. This impact varies greatly, and depends on the nature of the mold species, they metabolic products that are created by the specific species. Further, the impact of mold on human health is dependent on individual considerations, including the duration and quantity of exposure to the mold, and individual susceptibility of the exposed individual.
Often, people assume that they have an allergic reaction, or a respiratory infection like a cold, when in fact, molds are causing the reaction. Interestingly, chemicals in mold called mycotoxins and glucans (a component of spore walls) may play a large role in mold-related health issues.
There are no widely available methods to measure mycotoxins and glucans. Allergan skin tests (commonly used to pinpoint allergies) are not reliable in diagnosing a sensitivity to mold. The diagnosis of mold-related health effects usually must be done clinically, and consider a wide variety of factors. Diagnosis of the cause, and removal from the environment are the most basic treatments for mold exposure.
There are a wide variety of major symptoms of mold exposure. There are four main categories of human health-related reactions to mold. Specifically, these are: 1) allergy, 2) infection, 3) toxicity, and 4) irritation (of the mucus membranes and sensory). The most common of these responses is the allergic response. An allergic response to mold often occurs when the skin or respiratory system is exposed to individuals who have become sensitized to mold. Sensitization can occur in almost all individuals who have sufficient exposure to molds.
Allergic reactions can be mild and short-lived, or severe, with a long duration. Interestingly, the Institute of Medicine estimated that 20% of Americans have allergic rhinitis, while 14% have allergy-related sinitus, and 10% have allergy-related asthma, and 9% have allergic dermatitis (where the skin reacts to the irritant). People working or living in a moldy environment commonly suffer from allergic fungal sinusitis. This may have both an infectious and an allergic component, however.
There are literally thousands of molds in indoor air, and purified allergen have only been identified for a few of these. As a result, the common alergen-based allergy skin test will not detect these allergies. As such, a negative result on an alergen-based allergy skin test does not rule out a mold-based allergy.
Infections that occur from molds in an indoor environment is not common. Mold based infections usually only occur in individuals with compromised immune systems, resulting from drug treatment or immune diseases like AIDS. In this population, a variety of Asperfillus species can be pathogens, including Aspergillus fumigatus, Coccidioides, Histoplasma and Blastomyces.
The third major indoor air health issue that is associated with mold is mucous membrane or trigeminal nerve irritation. This occurs from the volatile compounds produced by the fungus as it consumes its energy source, and engages in primary metabolic processes. The compounds produced can include alcohols, aldehydes and acidic molecules. Even in a low concentration, these can irritate the mucous membranes of the eyes and respiratory system.
Depending the mold's specific food source, pungent and unpleasant compounds can be released by the mold. Specifically, a mold can release toxic substances from the substrate they are ingesting. For example, a mold growing on wallpaper can release the highly toxic gas arsine from arsenic that is contained in the wallpaper. Molds also release secondary metabolites that are often identified as a "moldy" or "musty" odor by individuals.