Publication Details

Mold: The New Hot Spore

Claims Magazine - April 27, 2003

For the plaintiff’s bar, mold is big business today. The media, ever attracted by the unusual and extreme, publish each unfounded and absurd claim, giving the impression that mold is a serious problem for the general population. In reality, the health threat from mold is more speculative than certain.

The issue might be little more than the stuff of cocktail conversation were not the legal and financial implications so broad and daunting. The good news is that careful investigation and analysis can ferret out the hypochondriacs and limit the costs of remediation.

The Toxicology of Mold

All molds have the theoretical potential to cause adverse health affects. Molds produce allergens, irritants, and, in some cases, toxins that may cause reactions in humans. The type and severity of symptoms depend, in part, on the types of molds present, the extent of exposure, the ages of the individuals, and their existing allergies or medical conditions. Claims of physical harm vary from mild hay fever complaints to allegations of serious injury.


Allergies are, by their nature, an exaggerated physical response to some antigen, typically a common environmental substance producing little or no response in the general population. Allergies are triggered by the release of histamine or histamine-like substances from injured cells. The allergic reaction involves various respiratory and dermatological symptoms, such as sneezing or itching.

Almost any protein may produce an allergic reaction in some, usually small, percentage of the population. Inhaling or touching mold or mold spores, which, like all living things, contain protein in various molecular forms, can cause allergic reactions in sensitive individuals. So-called hay fever-type symptoms (sneezing, runny nose, red eyes, and skin rashes) are the most common reaction. Live or dead mold spores, as well as mold fragments, can induce allergic reactions in sensitive individuals.

Given the enormous number of potential causes of allergies, the association of such symptoms with mold without proof of the presence of mold in excess of background levels is speculative.

Asthma and Other Severe Breathing Difficulties

Asthma is a disease process that is characterized by narrowing of the bronchi (lung passageways). Symptoms include wheezing, difficulty breathing (particularly exhaling), and tightness in the chest. Although the underlying bodily processes that lead to this medical condition are not fully understood, a number of highly effective treatment regimes exist.

Many factors seem to exacerbate asthma, including rapid changes in ambient temperature or humidity, exposure to an allergen, presence of an upper respiratory infection, exercise, stress, and cigarette smoke. As a potential allergen, mold may, in some circumstances, exacerbate asthma.

Severe re-actions to mold have been documented among workers exposed to large amounts of mold in occupational settings, such as farmers working around moldy hay. Reactions in such situations may include fever and shortness of breath, not unlike asthma.

Organic Dust Toxic Syndrome is an illness primarily noted in agricultural or manufacturing settings. Its flu-like symptoms are triggered by exposure to very high levels of glucans or dust mixtures containing glucans. Glucans are small pieces of cell walls of molds.

Hypersensitivity penumonitis, an uncommon reaction, has been documented. As the name implies, this subpopulation has a severe reaction, an inflammation of the lung tissue. Common symptoms include a cough with production of sputum or mucus, fever, chills, and shortness of breath.

Molds, along with bacteria, other fungi, and viruses, may be a threat to individuals with existing chronic illnesses. For example, persons with obstructive lung disease may develop mold infections in their lungs.

Pulmonary Hemorrhage in Infants

One of the recent allegations in the press has been that certain molds, which produce specific toxins, can cause bleeding of the lungs in exposed infants. As the Center for Disease Control has phrased it, “a causal link between the presence of toxic mold and these conditions has not been proven.”

Memory Loss

The same claim is being made relative to memory loss. That is, certain molds, which produce specific toxins, can cause memory loss in exposed individuals. Again, the CDC has found no causal link to the presence of toxic mold.

Irritant Effects

Molds produce irritants, which affect the eyes, skin, nose, throat, and lungs. A burning-like sensation may be created. As with allergies, such symptoms can be triggered by a wide variety of circumstances and substances.

By way of example only, the Environmental Protection Agency’s fact sheet on sick building syndrome recognizes a wide variety of potential causes for such irritation. Among these are inadequate ventilation, outdoor chemical contaminants (e.g., exhaust fumes from cars) that ooze into the structure, and a wide variety of biological organisms (including bacteria, molds, pollen, and viruses) that float or are brought inadvertently into a structure. Given the enormous number of potential causes of such irritant effects, associating such symptoms with mold without proof of the presence of mold in excess of background levels is speculative.

Opportunistic Infections

People with weakened immune systems may be more vulnerable to infections by molds (as well as bacteria, other fungi, and viruses) than the general population; they may also be more vulnerable to mold toxins. For example, Aspergillus fumigatus has been known to infect the lungs of immune-compromised individuals, and Trichoderma has been known to infect immune-compromised children. Treatment of such illnesses can be difficult and complex.


Some molds release microbial volatile organic compounds (mVOCs). These compounds may have strong or unpleasant odors, the smell of which may be commonly associated with mold. Exposure to mVOCs has been linked to symptoms such as headaches, nasal irritation, dizziness, fatigue, and nausea.

Solving the Problem

Molds are able to use a wide variety of substrates as nutrients, including wood, wood products, hardboard siding, drywall, carpet, and ceiling tiles. Thus, the key factor determining whether mold proliferates is the presence of water.

For at least the past 25 years in the state of California, the authors have noted that the quality of construction, particularly as it relates to multi-family developments, appears to have declined. A variety of design- and construction-related deficiencies abound in both residential and commercial structures. One of the most prominent deficiencies is increased pathways for water infiltration, the essential element for the growth of mold.

Water infiltration has been shown to occur through roofs, windows, hardboard siding, stucco, decks, balconies, landings, and every type of penetration made to the exterior envelope of any dwelling or building. As such, the parties who would be causes-in-fact for mold claims include virtually every trade involved in the construction of the home or building, with the possible exception of those dealing strictly with interior finishes.

Given water’s key role, any plan for investigation and remediation must begin with identifying the sources of water infiltration.

Typically, when signs of water infiltration show up on ceilings (for example, around windows, doors, along floors or baseboards), mold concerns arise. If the occupants are less than diligent in their housekeeping, visible signs of mold (e.g., dark spots or stains) may appear. Generally, any mold which is visually present in such locations poses no greater threat or risk than the mold that commonly appears in bathroom showers or tubs. The remedy for this condition is simple and involves nothing more than applying bleach or cleanser.

The real concern, however, is not what is visible within the living or working space, itself, but what is contained within the walls of the home or building. This concealed mold poses a potential threat of significant contamination to air quality and the contents of the home or building interiors.

The first step in any investigation is to make a preliminary assessment of the extent of the problem. For example, with multi-dwelling structures, it is important to know whether mold is being reported in 70 percent of the residences, or only 10 percent.

If the presence of mold is sufficiently widespread to warrant a large-scale investigation, the next step in the process is to identify, by species, those molds which are directly linked to the areas of water infiltration. It is important to bear in mind that while mold growth may be occurring within wall cavities, the spores and mycotoxins associated with this growth may not be appearing within the living space. Since the largest single cost associated with mold contamination is the remediation of the interior living spaces, evidence that the mold growth within the wall cavity is not contaminating those interior living spaces will dramatically reduce the remediation cost. Consequently, mold samples need to be obtained from within both wall cavities and living spaces, and then accurately analyzed and identified. This work is typically directed by an expert industrial hygienist.

In many instances, an investigator’s method of mold identification can be completely inadequate to the task. For example, one of the common methods for obtaining samples of mold is to use a tape lift. This method, however, often fails to allow for the identification of molds beyond the genus level. As there are more than 300 mold species in both the aspergillus and pennicullium genuses alone, the tape lift method fails to provide key information about the specimen within any given genus.

Once samples have been gathered from the air, wall cavities, and living spaces (including the contents therein), the comparison between the actual mold growth associated with the water infiltration and what is found within the living unit can go forward.

This information then allows an assessment to be made of the mold problem. For example, in a recent case we handled, the expert industrial hygienist determined that although the mold species within the wall cavity were similar to those found in the air and the contents of the living space, the level of mold was really no different than the background level. Consequently, we were able to argue successfully that the water infiltration, and any associated mold, had not resulted in contamination of the dwelling units.

It is important in any mold investigation to carefully monitor the testing techniques, apart from the method of collection discussed above. For example, in that same case, the industrial hygienist on the other side conducted aggressive air sampling, making every effort to stir up the mold found in the contents of the living space to artificially inflate the level of mold present in the air samples. Our expert discredited these results by noting the method used.

Similarly, any investigation must be careful to develop an acceptable database for any resulting mold remediation. For example, in that same case, the testing done by the other side was not random, but geared to a few of the more than two hundred units in the building which were deemed to be the worst-case units. Obviously, such an analysis would skew the results and call for a much more extensive mold remediation. Thus, an unbiased database, developed from random testing, must be established.


A remediation plan first must focus on stopping water infiltration. Typically, this involves correcting leaks found in roofs, windows, decks, balconies, and other penetrations. Depending on the length of time the water infiltration has occurred and its extent, the repairs may also involve replacement of the structural components.

Once the source of the water has been eliminated, and assuming that the interior of the living space is contaminated, repairs need to be assessed and then made. For example, the fact that the air quality of the living space is contaminated does not necessarily mean that the contents likewise are contaminated. Once again, the level of contamination must be determined both with air quality sampling and sampling of the contents to determine whether the contents themselves are contaminated over and above the background level.

Should both the air quality and the contents prove to be contaminated, the level of contamination must be established. If the level of contamination is low for the contents, on-site cleaning may be possible. For high contamination, contents, including carpets, may have to be removed and cleaned off-site.

The costs of remediation vary with the degree of contamination. It is not unusual for remedial costs to exceed $30,000 to clean all of the contents of a one-bedroom unit; additional costs may be incurred to address particular contents. There also will be additional costs to remove the occupants from the home during the cleaning process.

Mold, like all fungi, are ubiquitous. Their effects on people and property are very site- and fact-specific. In most cases, the impacts are minor. The press has greatly exaggerated the threat posed by such infestations.

The key to the control of mold is proper assessment of the problem, identification of the species of mold involved at a site, and elimination of the moisture which supports mold growth. The science and engineering of assessment and remediation is well understood.

Tom Clarke and Kevin Cody are partners at the California law firm Ropers Majeski Kohn & Bentley, where they concentrate on assessing and defending mold-related lawsuits.