Mold Assessment and Management
You will prevent problems by controlling moisture, responding quickly to leaks or complaints, and relying on qualified specialists.
IN the aftermath of Hurricane Katrina, mold has been receiving substantial press, and for good reason. Many health conditions have been attributed to mold exposure; as a result, there have been more than 10,000 mold-related lawsuits in the United States and the coining of the term "toxic mold."
Numerous medical studies have confirmed that, while mold is generally not a significant health hazard for most healthy individuals, some individuals can experience negative effects. Effects can be divided into three categories: 1) allergic reactions, 2) infectious conditions, and 3) toxic effects.
According to the American College of Occupational and Environmental Medicine, about 10 percent of the population has allergic antibodies to fungal antigens, and half of those individuals will show clinical symptoms. Common symptoms, especially in asthmatics who are sensitive to mold, may include eye and respiratory tract irritation, congestion, sneezing, the worsening of asthmatic conditions, and skin rash. Furthermore, continuous and/or repeated exposure to high levels of airborne molds can cause some individuals to become sensitized, such that the immune system begins to increasingly overreact to exposures. Hypersensitivity pneumonitis is an example of one condition caused by prolonged occupational exposure. Immune-compromised individuals can present serious infectious conditions.
Some species of molds also produce microbial volatile organic compounds (MVOCs). These compounds are released directly into the air and are the responsible for the objectionable "moldy" smell that can be observed in areas where mold growth or amplification has occurred. Individuals sensitive to mold exposure often perceive their conditions to be worse when MVOCs are observable.
Toxic effects to mold exposure are observed less frequently. Some molds produce substances known as mycotoxins. Because mycotoxins have the potential to cause serious health effects and some are carcinogenic, molds capable of producing mycotoxins have achieved celebrity status (e.g., Aspergillus and Stachybotrys). The mere presence of mold in a building, however, does not indicate significant concentration of mycotoxins is present or airborne. Concentrations of mycotoxins and exposure pathways typically found in buildings are not considered likely to cause toxic effects.
CDC and IOM Research, Recommendations
One of the largest and more recent studies was commissioned by the Centers for Disease Control and Prevention and performed by the Institute of Medicine (IOM) of the National Academies. The IOM report, "Damp Indoor Spaces and Health," was released in 2004. Based on the review, the IOM reported finding "sufficient evidence of an association" to link numerous health conditions (such as upper and lower respiratory tract symptoms) to damp indoor environments and mold.
The IOM did not find sufficient evidence to support the claims of "toxic mold syndrome," but the IOM and CDC advise against prolonged exposure to damp conditions because of a variety of inherent factors that could negatively affect health.
CDC recommends that all people strive to reduce their exposure to molds, especially those with suppressed immune systems. Although there are no health-based standards or recommended exposure limits for indoor airborne concentrations of mold, several organizations have published guidance documents regarding means of limiting exposure during mold cleanup. Assessment, exposure, and remediation guidelines are available from the Environmental Protection Agency, CDC, OSHA, and various trade organizations including the American Conference of Governmental Industrial Hygienists. Additionally, the Institute of Inspection, Cleaning and Restoration Certification (IICRC) published the third edition of the "Standard for Professional Water Damage Restoration, IICRC S500" in 2006.
Methods of preventing exposure to mold include: 1) avoiding exposure, 2) use of environmental controls, 3) use of personal protective equipment, and 4) following proper decontamination procedures.
Avoiding exposure is difficult because molds and fungi are ubiquitous in the environment. They can appear anywhere conditions are conducive for growth. In fact, there may be up to a quarter million species of known fungi.
Molds reproduce by forming and releasing small spores that spread throughout the environment. Due to the extremely small size (a range of 1 to 20 microns), spores can spread profusely, but not all spread in the same manner. For example, some spores become airborne relatively easily (such as Cladosporium), while others (such as the Stachybotrys) are relatively more sticky and not easily released into the air.
Conditions required for growth vary (e.g., the degree of light present) depending upon the species, but the basic growth requirements include favorable temperature ranges, a suitable nutrient base to serve as a growth medium, and the presence of sufficient moisture. Because all three factors exist in most buildings, a variety of molds are commonly found in our homes and work environments.
The one controllable limiting factor to growth is the availability of moisture. Moisture in the form of water and water vapor can be utilized by mold to support growth. Under normal conditions, excessive mold growth can be limited or precluded entirely in buildings by maintaining indoor relative humidity levels below 55 percent and by preventing moisture intrusion. A common mistake made by building owners/managers is being too slow to address moisture intrusion issues. Ongoing roof leaks or leaks in the building skin are perfect examples. Once water is trapped behind drywall or under carpeting, it is extremely difficult to extract without special equipment such as commercial-grade dehumidifiers or desiccators. Moisture will generally take an extensive period to naturally evaporate, but mold growth can occur within as little as 24 hours (with visible colonies within 48 to 72 hours). Consequently, responding quickly to water line breaks and roof leaks is extremely important.
How do you know if you have a mold problem? Common indicators include a history of moisture intrusion issues or a substantial release of water, "moldy" or "musty" odors, frequent headaches and allergy symptoms experienced by occupants, higher absenteeism because of respiratory infections, and visual evidence of growth. CDC guidelines stipulate assuming that any structure not thoroughly dried within 48 hours probably will be contaminated by indoor mold.
Hiring Competent Help
Initial response steps are numerous and multifaceted. As a first step, seek to determine the type, size, and seriousness of the problem and whether any response action is appropriate. If it appears a mold problem does exist, consider hiring an environmental consultant who has significant experience dealing with mold assessments and remediation, preferably one who has received specialized training based upon industry-recognized guidelines. If the problem appears to be serious, having a certified industrial hygienist or toxicologist consulting on the project may be prudent.
One of the most common mistakes is hiring an insufficiently qualified consultant who addresses all mold investigations the same way--by merely collecting air and bulk samples. Typically, several other assessment approaches should be employed before sampling. Visual and olfactory observations are two of the first means of investigation. The inspection should include crawl spaces, areas above ceiling tiles, and any areas that could be affected by water intrusion, water leaks, or flooding. A hand-held borescope can be used to view inaccessible areas.
A moisture meter is commonly used for identifying moisture-affected materials and tracking progress in drying building materials. This is a hand-held device that, when applied to the surface of a building material such as wood, provides a reading of relative percent moisture content. An infrared camera can be another invaluable tool. These highly sensitive cameras reveal temperature differentials in building materials by sensing the amount of infrared light being emitted by the source's surface area.
Some inspection companies are using specially trained dogs, referred to as "mold dogs," to identify inaccessible affected materials. Inspectors using mold dogs in conjunction with infrared cameras reportedly can quickly and accurately locate mold growth that is hidden from observation.
Several types of sampling practices can be employed when performing mold assessments. They range from collecting surface samples of visible growth with a swab, a "tape-lift" or merely a bulk sample, or performing sampling for airborne concentrations of mold spores and fungal structures.
The most commonly employed air sampling techniques are spore-traps and impactor plates used to identify and count non-culturable and culturable mold-related materials. Non-culturable spore-trap samplers draw air into the sampling device on which both viable and non-viable structures can be counted. Culturable air samples involve collection of air drawn into a sampling device that contains a Petri dish with a growth medium. The spores that are viable and find the growth medium to their liking grow, form colonies, and are subsequently counted and identified.
Use air sampling with caution. EPA and other authorities agree such sampling can be misleading because of the unpredictability of mold sporulation and other variables. If air sampling is performed, consider some of the following recommendations, in addition to following standard protocols:
* Be sure that outdoor background samples are collected for comparison to indoor values.
* Avoid collecting air samples on windy or rainy days and during winter months in regions that experience freezing temperatures.
* For culturable samples, ask for speciation of colonies.
* For non-culturable air samples, ask the lab to differentiate like species and report them separately.
* Collect culturable samples in pairs using different growth mediums, one that is favored by "xerophilic" molds (such as Aspergillus and Penicillium), and one favored by more "mesophilic" and "hydrophilic" organisms (such as Cladosporium and Stachybotrys).
* If possible, determine the time of day, season, and weather conditions during which occupants have posted complaints, if any. Collect samples under similar conditions to the extent possible.
Keys to Successful Abatement of Mold Problems
Abatement of mold problems generally involves removal of mold-contaminated porous materials and the use of chlorinated cleaning products to kill the mold on non-porous surfaces. Abatement will not be successful in resolving a mold growth problem unless the source of moisture intrusion is first eliminated and all materials that contain increased amounts of moisture are either dried or removed from the area.
Most areas of the country do not require licensing of abatement contractors, but the use of an appropriately trained contractor certified in mold abatement has generally become an industry standard practice.
In sum, unabated mold growth can cause serious health problems, but it can be prevented in most cases. With steps in place, such as controlling relative humidity and moisture intrusion, responding promptly to water leaks and occupant complaints, and relying upon qualified specialists, managing mold growth will keep buildings (and their inhabitants) healthy.
This article appeared in the May 2006 issue of Occupational Health & Safety.
This article originally appeared in the May 2006 issue of Occupational Health & Safety.