First of all, it is important to define exactly what molds are. Molds are filamentous fungi usually growing in damp areas. To put that in image, molds are the whitish or greenish fast growing stuff that you can sometimes observed on old fruit. It is interesting to note that wet grains can also be contaminated by mold. These microorganisms are also susceptible to grow indoors in homes or buildings, especially following water damage or leakage, flooding, or in case of an excessive level of moisture in the air. They are commonly observed in small quantities in homes, especially around windows and in the bathroom. However, in severe and rare cases, the indoor contamination may be more important. It is the case for example when drywall, wallpaper or carpet are contaminated by molds. In these cases, the contamination is usually visible by eyes on the walls for example and can be smelled. If the contamination is visible on walls and has a rotting smell, it is highly possible that the materials inside the wall are also contaminated and required extensive cleaning process (see Controlling molds).
It is interesting to note that molds are present everywhere at different levels. They propagate themselves by spore, a small structure resistant to unfavorable growing conditions and able to float freely in the air. Spores are susceptible to pass from outdoors to indoors by any place where air is susceptible to enter, such as doors, windows, ventilation systems, etc. Moreover, spores can also attach themselves to people or pet in order to get inside a house or any other building. Once inside, they can resume their growth if the right conditions are reunited, especially if there is enough moisture or dampness, as water availability is the main requirement for the growth of molds.
The most common molds observed indoors are composed of species from the genus Cladosporium, Penicillium, Aspergillus, and Alternaria. Stachybotrys chartarum, commonly known as black mold, is also observed in indoor contamination, although less common than the other ones. Even though this particular type of mold is called black mold, it is interesting to note that it has actually a bright greenish black color. The difficulties experienced by its spores to travel successfully within the air, as well as the relative difficulty to grow compared to the other types of mold explain why it is less commonly seen indoors. Stachybotrys chartarum is known to grow on high cellulose and low nitrogen substrates. Indoors, it means that it is more susceptible to grow on drywall, wallpaper and wood structures, as well as common objects such as papers and cardboard boxes. However, in contradiction with other fast-growing molds, Stachybotrys chartarum required that the materials are soaked in water for many days or even weeks before starting to grow. This particular mold is also associated with major construction defects, especially if it allows the building to have a high level of moisture in the air or if the building has water leakage. As Stachybotrys chartarum required water to be present for a long period before growing, it is very important to remediate quickly and effectively to any water damage or leakage in order to prevent its apparition (see Preventing molds).
It is interesting to note that Stachybotrys chartarum is kind of famous now, as many scientific studies and news articles have been written about it. However, this particular species is only one in the big family comprising 87 known species of Stachybotrys. In some profane reports, many symptoms and illnesses have been attributed to this particular mold, including the sick building syndrome, but no strong scientific evidences support these claims at the moment. The reason why this particular type of molds is so popular right now is because it is able to produce strong mycotoxins. However, the actual effects on health of these mycotoxins, especially in the context of indoor contamination, are still a matter of controversy and debates (see Mold effects on health).
Mold effects on health
Molds are contaminating homes and buildings, but are non-toxic in themselves for humans, meaning that they are not usually susceptible to cause by themselves an infection in human. However, it is interesting to note that people with weakened immune systems, mainly people suffering from AIDS, are susceptible to develop an opportunistic infection while inhaling spores of common molds. Opportunistic infections are defined as infections occurring in people with weakened immune systems with microorganisms that are not known to cause any infection in healthy people. Furthermore, people suffering from chronic lung diseases are also more susceptible to develop an opportunistic fungal infection in their lungs while exposed to indoor mold contamination. However, there is actually no report in the medical literature of any infection, opportunistic or not, caused by Stachybotrys chartarum or any other types of Stachybotrys in humans or in animals.
It is interesting to note that some molds, such as Stachybotrys chartarum, are nevertheless considered as toxigenic. Stachybotrys chartarum, for example, is able to produce around 30 different mycotoxins with proven toxic effects at different levels on humans and animals in laboratory studies. Clinical evidences also suggest that the ingestion of food contaminated with Stachybotrys chartarum mycotoxins, mainly grains stored in high moisture environment, is susceptible to provoke many symptoms, such as vomiting, diarrhea, hemorrhage, seizure, and even death. However, remember that the mold in itself is still considered as non-toxic. Furthermore, it is important to mention that only some strains (and not all) of Stachybotrys chartarum are able to produce dangerous mycotoxins.
Nevertheless, the Centers for Disease Control and Prevention, as well as the World Health Organization consider that indoors contamination with toxigenic molds is no more hazardous to the human health than the one with common non-toxigenic molds. In fact, even tough the ingestion of mycotoxins have been proven to cause many adverse health effects in humans and animals, there are actually not enough evidences linking inhalation of mycotoxins from Stachybotrys chartarum with any symptoms caused by indoor contamination. One of the hypotheses explaining this fact is that spores of Stachybotrys chartarum, containing mycotoxins or not, are not travelling well within the air. As such, more evidences are still needed in order to establish an actual link of causality between mycotoxins and potential adverse health effects experienced indoors. Consequently, the Centers for Disease Control and Prevention mention only rare exceptional reports of unique condition in humans potentially caused by these mycotoxins, such as memory loss and pulmonary hemorrhage, but the actual causal link between these and the presence of toxigenic molds have not been scientifically proven yet. As such, because of the lack of evidences suggesting otherwise, symptoms caused by the presence of the different types of mold indoors are thought to be the same regardless of the production or not of mycotoxins.
As mentioned earlier, a great number of different symptoms have been attributed to indoor contamination with molds. However, the links between many of these alleged symptoms and indoor contamination by molds have not been scientifically proven yet. Consequently, in the following paragraphs, I will talk about the symptoms that have been actually attributed to indoor contamination with molds following thorough scientific evidences.
The vast majority of the scientifically proven symptoms caused by indoor mold contamination affect the upper respiratory tract. However, these molds are not causing health problems in all the individuals. In fact, as the reaction to the presence of indoor molds contamination is mainly viewed as an allergic reaction, some people are considered as more sensitive to this exposure than others. The most common symptoms are often like the ones experienced by people suffering from hay fever and include nasal stuffiness, eye irritation, coughing and wheezing. According to some scientific evidences, exposed people are also more susceptible to acquire some respiratory infections than other people, mainly because of the state of chronic irritation experienced by their upper respiratory tract. Furthermore, some studies suggest that indoor mold contamination increase the risk of developing allergic rhinitis or asthma. Finally, skin irritation is also susceptible to occur when exposed to molds.
Evidences suggest that exposure to indoor mold contamination might also aggravate pre-existing conditions. For example, it is thought to increase asthma symptoms in people suffering from this disease. It is also thought to cause hypersensitivity pneumonitis, allergic alveolitis, chronic rhinosinusitis and allergic fungal sinusitis in people already susceptible to these conditions. However, there are no clinical evidences linking indoor mold contamination with the development of one of these conditions in otherwise healthy people.
The good news here is that these symptoms are usually reversible, meaning that the suppression of the indoor mold contamination is susceptible to greatly reduce or eliminate the symptoms. This is the reason why it is very important to control the propagation of mold in a house or in a building and to get the help of mold control professionals if the contamination level is too high (see Controlling molds).
Molds, even in small quantities, should be removed from the house or the building in order to prevent any adverse health effects or further propagation of the contamination. It is also important to clean and dry properly the affected area, as dead molds still have the potential to cause an allergic reaction in susceptible people. Furthermore, if the cleaned area remains wet, the molds are able to come back very quickly.
It is interesting to note that the same process is used to remove any mold regardless of the species involved. As such, formal identification of the contaminating species is not required and usually more time and resource consuming than helpful, as mold formal identification is considered to be complex. Furthermore, it is important to mention that there are no additional precautions to take while dealing with toxigenic molds, such as Stachybotrys chartarum.
Contaminated and at-risk hard surfaces, such as windows and bathroom, may be washed using water and soap. It is interesting to note that many commercial cleaning products are also specifically designed to fight mold contamination. Furthermore, the Centers for Disease Control and Prevention also suggest using a solution made of no more than one cup of bleach diluted in one gallon of water. It is important to respect these actual proportions, as they are the most effective ones to fight against molds. The organization also stresses the fact that this bleach solution should be used according to manufacturer’s specifications in well-ventilated areas (by opening windows and doors for example) and with protective gloves and goggles in order to ensure the safety of the users and inhabitants.
It is important to note that important contamination might require the help of experienced mold cleaning professionals in order to get rid effectively of the contamination. Furthermore, when the molds are growing on materials such as insulation, wallboard, as well as in or under a carpet, the only way to get rid successfully of the contamination is to get rid of them. As such, contaminated materials, such as drywall, tiles and carpets, might have to be thrown away and replace in case of mold contamination. In some very extreme and rare cases, the house might be so contaminated that the only solution to get rid of the contamination is to demolish it completely.
The best way to prevent the apparition of mold is to control the moisture inside the house or the building. In fact, the humidity level indoors should be below 50% at all times. To achieve this level, air conditioning or dehumidifier systems should be used. However, it is important to strictly follow the cleaning specifications for these systems according to the manufacturer’s specifications, as they accumulate water and are then susceptible to become contaminated by molds themselves. Furthermore, it is also recommended to make sure that the house is well ventilated, especially with exhaust fans in bathrooms and kitchen. Paints with mold-inhibitors and mold-killing cleaning products, especially intended for bathrooms, can also be used to reduce the occurrence of molds indoors.
Finally, as molds are growing rapidly in wet environment, it is very important to take care quickly and professionally of any damaged caused by water in a house or any other building. As such, professionals usually open the damaged walls and dry them completely using industrial fans. They also remove and replace water-soaked materials, such as carpets. Furthermore, it is very important to find and remediate to any water leakage in the building in order to prevent permanent wetness allowing the apparition of molds. These precautions are extremely important in case of damages caused by water because they can prevent the subsequent contamination by molds that are susceptible to cause many problems later, including the possible need to do major repairing to the house or building.