Health Issues and Symptoms
Molds are very common in nature and are to some extent always present in both indoor and outdoor air. Humans have a natural tolerance to molds and most individuals will not suffer adverse health effects from exposure to background levels of mold spores. Mold growth indoors can cause indoor levels to increase to elevated levels, a condition called mold amplification. Inhalation of a large number of mold spores can overwhelm the body’s natural defenses causing adverse health effects.
Allergic responses are the most common health problems associated with exposure to elevated levels of mold spores. These reactions may be similar to those of hay fever or exposure to high levels of pollen, such as headaches, sinus problems, congestion, sore throats, or coughing. These effects may be seasonal in nature. Many people experience allergic responses to molds in the fall when outdoor levels of molds are typically high.
Molds can also produce mycotoxins, which are chemicals associated with growth, digestion, and self-defense. Mycotoxins can be toxic to other organisms. Antibiotics like penicillin are made from mycotoxins that kill bacteria. Some mycotoxins can be toxic to humans and can cause very serious health problems. Mycotoxins can enter the body via inhalation, skin absorption, or ingestion. These chemicals are found on the surface of the spores and can be hazardous even if the mold spore is dead. Different mold species produce different mycotoxins, which can cause various reactions in exposed individuals. One mold called Aspergillus versicolor produces trichothecene toxins that are believed to cause neurological problems, such as memory loss, mood changes, constant headaches and trouble concentrating.
Exposure to mold spores and their mycotoxins can lead to a variety of non-specific health problems such as:
- Sinus problems
- Respiratory problems (wheezing, coughing, difficulty breathing)
- Cold and flu-like symptoms (fever, muscle aches, fatigue)
- Sore throats
- Eye irritation
- Frequent bloody noses
The types of health problems that develop depend on a variety of factors such as the length and amount of exposure and the mold growth conditions. Health symptoms may develop from chronic exposure and the mold growth conditions. Health symptoms may also develop from chronic exposure at slightly elevated levels over a long period of time, or from acute term exposure at very high levels, like those that occur during mold abatement. The growth conditions of the mold, such as the organic content of the food source, temperature, and the amount of moisture present affects the production of mycotoxins, which in turn affects exposure to the toxins.
The greatest factor affecting the development of health problems is individual sensitivity. Some people are naturally more sensitive to the molds than others. When a family is living in a home with elevated levels of mold spores, often only one or two family members will suffer any health problems while the other family members experience no ill effects. Individuals that are most susceptible include children, the elderly, and the immune-compromise patients, such as those undergoing chemotherapy or suffering from liver problems.
Mold exposure may be especially hazardous to young infants. It is believed that the Stachybotrys mold may have caused the death of 12 infants and the hospitalization of 37 infants in the Cleveland area of Ohio. These infants all came from homes that had suffered recent flood damage and had signs of Stachybotrys in their home. The Centers for Disease Control is currently reviewing the data and has said that the association is not conclusive.
In most cases, the mold induced health symptoms will diminish upon removal from the affected environment. Many doctors, however, believe that people having been exposed to high levels of molds have an increased sensitivity to them, so in the future it takes less exposure to molds to develop the same symptoms. In some cases, exposure to high levels of molds can lead to scarring of the lungs or the development of asthma, especially in children, which can have long-term effects.
If a person suspects that they are being or have been exposed to high levels of molds and they are concerned about health problems, they should consult a qualified physician familiar with respiratory problems. If they have had testing done and have any laboratory data, they should bring the data with them to the doctor. While there are many molds that have the potential to be hazardous, only a physician can decide if mold is causing a particular individual’s health symptoms or determine if the mold exposure may have any long-term effects.
Mold growth over a large area on the windowsill or on sheet rock next to or below the windowsill is a more serious problem, as these surfaces are more likely to support the more hazardous molds, like Stachybotrys. Growth under or next to a windowsill may be the result of a construction defect or a flashing problem allowing water intrusion around the window. If water is allowed to intrude into a wall space, the paper backing on the sheet rock (a food source for molds) and the dark, stagnant air spaces create a perfect environment for mold growth to occur. If mold growth is visible on sheet rock inside a room, there may be a larger colony of mold growing on the other side of the sheet rock inside the wall space. If mold growth is suspected inside a wall space, drilling a small hole through the wall can collect an in-wall air sample.
Mold Sampling & Analysis
Air sampling involves drawing a known volume of air over a slide or petri dish with a growth medium. Air sampling can be one of the most effective ways to sample for the presence of mold because it provides quantitative data that can be used to evaluate exposure. It is a measure of the number of mold spores present in the air and an indication of the level of mold spores that is being inhaled into the lungs. Air sample results are given as a colony forming units or spores per cubic meter. Air sampling can often detect hidden mold problems, such as growth in carpeting, HVAC systems or inside wall spaces. Air sampling will generally report more species of molds than surface sampling. Surface samples often report between one and four species of molds on each sample, depending on the type of mold growth. Air sample results can detect as many as 30 different types of molds. Whereas a surface sample may miss some species of molds growing over a large surface, these molds will usually show up as elevated in an air sample, as any visible mold growth will usually release spores into the air. Air samples can also be collected from inside wall spaces without any destruction to the wall surfaces.
Surface sampling can be used to determine what kind of mold growth, if any, is growing on a surface. Surface sampling is relatively simple and inexpensive and is effective in identifying the species or genus of visible mold growth. Surface sampling will determine the relative density of each of the mold species present on the surface with a rating of 1+ to 4+ with 4+ denoting the highest number of mold spores. This data can often be misleading without information on the sampling location and the surface area covered by the mold growth. A square foot area on a wall with 2+ levels of a mold species is much more serious than a dime size area with a 4+ level. One of the disadvantages of surface sampling is that it is a check of only one particular area. Often if mold growth covers a large surface area, several different types of molds are present and different species are predominant in different areas. It may be necessary to collect multiple samples from several locations to identify all the molds present, especially if trying to determine if Stachybotrys is present. Surface sampling also does not provide any information on exposure to airborne spores.
Dust sampling is a relatively new sampling technique that is believed to be a way to evaluate long-term levels of airborne mold spores. Airborne mold spores settle and become a natural part of dust.
Dust sampling involves the collection of dust using a modified vacuum to vacuum a section of carpet or from the air intake filter for the HVAC system. The dust is weighed at the laboratory and then plated onto a growth medium to culture the mold.
This technique is still being evaluated for its effectiveness in determining long-term airborne mold levels. One problem with this technique is that there is no way to correspondingly measure the outdoor mold levels to use for comparison. Another drawback is that the samples can only be analyzed using viable analysis methods, which is discussed in the next section.
In general, sampling using a combination of different sampling methods is the best way to investigate a potential mold problem inside a building.
The first step in mold removal is to find and eliminate the source of mold. The mold-impacted materials including flooring, sheet rock, insulation, and any other materials with visible mold must be removed and disposed of. It is always safer to remove all the infected material than to try to treat and risk the mold returning, especially if mold is growing on porous materials like sheet rock or wood. For substantial mold growth, this may require removing interior walls and/or siding to expose the framing as shown in the photo.
Any surface that is not easily removed, like wood framing, may remain provided it is not severely impacted with mold growth, is structurally sound, and is thoroughly treated to kill the mold and remove the dead spores. Current technology has us cleaning these areas with an anti-microbial designed for this purpose.
The removal work depends on the types of molds present. Stachybotrys can be especially difficult to eradicate and sometimes require more extensive treatments. With other molds, once the source is removed and the surfaces treated, it is acceptable to still have background levels of spores in the indoor air since these molds are very common outdoors and indoors.
Stachybotrys is not normally found outside and should not be present in indoor air samples at all. The spores are also sticky so they will stick to furniture and can become dormant, but germinate later if conditions are favorable. Thus, when conducting mold abatement with Stachybotrys, it is necessary to fully remove all of the airborne spores as well as the physical growth from the building. This requires additional air filtering and air exchanges during abatement.
When conducting abatement it is necessary to limit the amount of spores that become airborne and prevent cross contamination of spores to clean rooms. This involves sealing off affected areas with plastic, sealing off and/or limiting use of the HVAC system, and using vacuums and air filtering devices with HEPA filters.
Abatement zones should be kept under a negative pressure with engineered controls. Personal protective equipment (PPE) should be used and all personnel should go through decontamination. After the abatement is completed, it is also a good idea to have the HVAC system fully cleaned.
Mold abatement can be extremely hazardous if proper precautions are not taken. Mold spores are found on the surface of mold and become airborne when disturbed. During abatement or cleanup activities mold levels will increase from 10 to 10,000 background levels. It is very important that PPE be worn when doing any kind of mold cleanup. At the very minimum, gloves, goggles, and a dust mask should be worn. Personnel trained in the proper handling of hazardous materials should complete mold abatement of large areas of mold growth. For these jobs, level C PPE is required which includes gloves, full coveralls, and a full-face respirator.
It is very important that all moisture intrusion issues be resolved after the abatement is completed. The mold will return if all moisture sources are not eliminated!
Confirmation testing should also be completed after the abatement work is completed to verify the success of the abatement work. Samples should include viable surface samples of treated surfaces and air samples in all treated areas. If mold growth is reported from any viable surface samples, additional treatment is necessary. If airborne levels are higher than background levels for any mold species, additional treatment of the surfaces and/or air may be necessary.
[The National Institute of Environmental Health Sciences (nieh) website release, “Mold and Mildew Awareness/Mold Awareness and Inspection]