Moldy Smell

Some compounds produced by molds have strong smells and are volatile and quickly released into the air. These compounds are known as microbial volatile organic compounds (mVOCs). Because mVOCs often have strong or unpleasant odors, they can be the source of the "moldy odor" or musty smell frequently associated with mold growth. A moldy odor suggests that mold is growing in the building and should be investigated.

The health effects of inhaling mVOCs are largely unknown, although exposure to mVOCs has been linked to symptoms such as headaches, nasal irritation, dizziness, fatigue, and nausea. More research is needed to determine whether there are any human health effects from nonoccupational indoor exposures to mVOCs.

Toxic Molds

Some molds, such as Aspergillus versicolor and Stachybotrys atra (chartarum), are known to produce potent toxins under certain circumstances. Although some mycotoxins are well known to affect humans and have been shown to be responsible for human health effects, for many mycotoxins, little information is available, and in some cases research is ongoing. For example, some strains of Stachybotrys atra can produce one or more potent toxins. In addition, preliminary reports from an investigation of an outbreak of pulmonary hemorrhage in infants suggested an association between pulmonary hemorrhage and exposure to Stachybotrys chartarum. Review of the evidence of this association at CDC resulted in an a published clarification stating that such an association was not established. Research on the possible causes of pulmonary hemorrhage in infants continues. Consult the Centers for Disease Control and Prevention (CDC) for more information on pulmonary hemorrhage in infants.

Molds are fungi that are found virtually everywhere, indoors and outdoors. Mold can cause or worsen certain illnesses (e.g., some allergic and occupation-related diseases and infections in health care settings). No conclusive evidence exists, however, to associate mold exposure with a multitude of other health problems, such as pulmonary hemorrhage or memory loss. The Centers for Disease Control and Prevention conducts and supports activities to investigate the effect of mold on human health, to assist states in responding to concerns about mold, and to investigate concerns of employees and employers.

What are molds?
Molds are fungi that can be found both indoors and outdoors. No one knows how many species of fungi exist but estimates range from tens of thousands to perhaps three hundred thousand or more. Molds grow best in warm, damp, and humid conditions, and spread and reproduce by making spores. Mold spores can survive harsh environmental conditions, such as dry conditions, that do not support normal mold growth.

What are some of the common indoor molds?
Cladosporium
Penicillium
Alternaria
Aspergillus

How do molds affect people?
Some people are sensitive to molds. For these people, exposure to molds can cause symptoms such as nasal stuffiness, eye irritation, wheezing, or skin irritation. Some people, such as those with serious allergies to molds, may have more severe reactions. Severe reactions may occur among workers exposed to large amounts of molds in occupational settings, such as farmers working around moldy hay. Severe reactions may include fever and shortness of breath. Some people with chronic lung illnesses, such as obstructive lung disease, may develop mold infections in their lungs.

Where are molds found?
Molds are found in virtually every environment and can be detected, both indoors and outdoors, year round. Mold growth is encouraged by warm and humid conditions. Outdoors they can be found in shady, damp areas or places where leaves or other vegetation is decomposing. Indoors they can be found where humidity levels are high, such as basements or showers.

How can people decrease mold exposure?
Sensitive individuals should avoid areas that are likely to have mold, such as compost piles, cut grass, and wooded areas. Inside homes, mold growth can be slowed by keeping humidity levels between 40% and 60%, and ventilating showers and cooking areas. If there is mold growth in your home, you should clean up the mold and fix the water problem. Mold growth can be removed from hard surfaces with commercial products, soap and water, or a bleach solution of no more than 1 cup of bleach in 1 gallon of water.

If you choose to use bleach to clean up mold:

Never mix bleach with ammonia or other household cleaners. Mixing bleach with ammonia or other cleaning products will produce dangerous, toxic fumes.
Open windows and doors to provide fresh air.
Wear non-porous gloves and protective eye wear.
If the area to be cleaned is more than 10 square feet, consult the U.S. Environmental Protection Agency (EPA) guide titled Mold Remediation in Schools and Commercial Buildings. Although focused on schools and commercial buildings, this document also applies to other building types. You can get it free by calling the EPA Indoor Air Quality Information Clearinghouse at (800) 438-4318, or by going to the EPA web site at http://www.epa.gov/mold/mold_remediation.html. [external link]
Always follow the manufacturer’s instructions when using bleach or any other cleaning product.
Specific Recommendations:

Keep the humidity level in the house between 40% and 60%.
Use an air conditioner or a dehumidifier during humid months.
Be sure the home has adequate ventilation, including exhaust fans.
Add mold inhibitors to paints before application.
Clean bathrooms with mold killing products.
Do not carpet bathrooms and basements.

What areas have high mold exposures?
Antique shops
Greenhouses
Saunas
Farms
Mills
Construction areas
Flower shops
Summer cottages

I found mold growing in my home, how do I test the mold?
Generally, it is not necessary to identify the species of mold growing in a residence, and CDC does not recommend routine sampling for molds. Current evidence indicates that allergies are the type of diseases most often associated with molds. Since the susceptibility of individuals can vary greatly either because of the amount or type of mold, sampling and culturing are not reliable in determining your health risk. If you are susceptible to mold and mold is seen or smelled, there is a potential health risk; therefore, no matter what type of mold is present, you should arrange for its removal. Furthermore, reliable sampling for mold can be expensive, and standards for judging what is and what is not an acceptable or tolerable quantity of mold have not been established.

A qualified environmental lab took samples of the mold in my home and gave me the results. Can CDC interpret these results?
Standards for judging what is an acceptable, tolerable, or normal quantity of mold have not been established. If you do decide to pay for environmental sampling for molds, before the work starts, you should ask the consultants who will do the work to establish criteria for interpreting the test results. They should tell you in advance what they will do or what recommendations they will make based on the sampling results. The results of samples taken in your unique situation cannot be interpreted without physical inspection of the contaminated area or without considering the building’s characteristics and the factors that led to the present condition.

What type of doctor should I see concerning mold exposure?
You should first consult a family or general health care provider who will decide whether you need referral to a specialist. Such specialists might include an allergist who treats patients with mold allergies or an infectious disease physician who treats mold infections. If an infection is in the lungs, a pulmonary physician might be recommended. Patients who have been exposed to molds in their workplace may be referred to an occupational physician. CDC is not a clinical facility. CDC does not see patients, diagnose illness, provide treatment, prescribe medication, or provide referrals to health care providers.

My landlord or builder will not take any responsibility for cleaning up the mold in my home. Where can I go for help?
If you feel your property owner, landlord, or builder has not been responsive to concerns you’ve expressed regarding mold exposure, you can contact your local board of health or housing authority. Applicable codes, insurance, inspection, legal, and similar issues about mold generally fall under state and local (not federal) jurisdiction. You could also review your lease or building contract and contact local or state government authorities, your insurance company, or an attorney to learn more about local codes and regulations and your legal rights. CDC does not have enforcement power in such matters, nor can we provide you with advice. You can contact your county or state health department about mold issues in your area to learn about what mold assessment and remediation services they may offer. You can find information on your state’s Indoor Air Quality program at http://www.cdc.gov/nceh/airpollution/indoor_air.htm.

I’m sure that mold in my workplace is making me sick.
If you believe you are ill because of exposure to mold in the building where you work, you should first consult your health care provider to determine the appropriate action to take to protect your health. Notify your employer and, if applicable, your union representative about your concern so that your employer can take action to clean up and prevent mold growth. To find out more about mold, remediation of mold, or workplace safety and health guidelines and regulations, you may also want to contact your local (city, county, or state) health department.

You should also read the U.S. Environmental Protection Agency (EPA) Guidelines, Mold Remediation in Schools and Commercial Buildings, at http://www.epa.gov/iaq/molds/mold_remediation.html. [external link]

I am very concerned about mold in my children’s school and how it affects their health.
If you believe your children are ill because of exposure to mold in their school, first consult their health care provider to determine the appropriate medical action to take. Contact the school’s administration to express your concern and to ask that they remove the mold and prevent future mold growth. If needed, you could also contact the local school board.

CDC is not a regulatory agency and does not have enforcement authority in local matters. Your local health department may also have information on mold, and you may want to get in touch with your state Indoor Air Quality office. Information on this office is
Testing For Mold

MDH prepared this fact sheet to explain why it usually does not support mold testing as the first response to indoor air quality concerns and to help people better understand what mold testing can and cannot be expected to do. Contrary to much currently popular opinion, mold testing is often not an appropriate or effective way to answer many of the questions that lead people to ask for it. In a great deal of the cases that come to MDH’s attention, people seeking mold testing really need a thorough investigation into moisture problems and the damage it can cause – often times this is something they can do on their own.

Limitations of Mold Testing

There are many testing methods that can detect molds. They can be used to find mold particles suspended in air, in settled dust, or growing on surfaces of building materials and furnishings. Some methods can identify a portion of the types of live (viable) molds in a sampled environment, but these may also miss or undercount those are not live or won’t grow well on the nutrients used to incubate the sample. Other methods are better able to characterize the total amount of molds in a sample (including the non-living portion), but not very good for identifying the specific types of molds. Even tests that are done well only give a partial estimate of the amount and types of molds actually collected in a sample or in the sampled environment.

It is vital to appreciate that a test result only gives a “snap-shot” estimate for a single point in time and a single location – how well it represents other locations and times is uncertain since the amounts and types of mold in the environment is always changing. This variability can be especially large for airborne molds, with significant changes occurring over the course of hours or less. Caution must also be used in interpreting surface testing results, since mold growth or deposition may not be uniform over an area and may increase or decrease as time passes. Unless many samples are taken over a period of time and the investigator has been mindful of building operations and activities during the testing, the results might not be very representative of typical conditions. On the other hand, tests reflecting typical conditions may also miss evidence of problems that only occur infrequently.

Despite these limitations, there are situations where mold testing by skilled investigators may be valuable – for example, to “justify” remediation expenses or to document that cleanup has met expectations. In some cases, tests can also provide clues that may help find hidden mold, but the growth still has to be found by looking for it so that it can be removed. Experienced investigators should evaluate whether testing is warranted and if they are ethical, they should advise against testing whenever the problem can be corrected without it. Testing may be useful as part of an investigation, but it is never a substitute for a thorough visual inspection.

Doing mold testing well is often expensive. Consumers should recognize that if the testing is not needed or it is done poorly, their money is being wasted instead of being used to make repairs necessary to solve the problem. It is up to consumers to protect their own interests when they hire someone to perform mold testing. MDH advises people to attempt to investigate potential mold problems on their own first. The basic goals of any mold investigation are always twofold: 1) find the locations of mold growth, and 2) determine the sources of the moisture. If these can be answered by simpler or more cost-effective methods (see Finding a Mold Problem below or the Mold in Homes fact sheet), mold testing is probably not a wise use of resources.

What Testing Cannot Do

As described earlier, the commonly used testing methods are limited in what they can detect and measure. Skilled investigators are aware of these limitations and don’t rely on testing when it is not appropriate. However, many people have unrealistic expectations of what mold testing can do and they can be taken advantage of by those who perform testing poorly or for inappropriate reasons. Below are some impractical reasons commonly given for requesting mold testing.

Poor reason for testing #1 “To find out if there is mold”

A complex mixture of mold particles normally exists in all occupied indoor environments. If appropriate testing is done, it is expected that molds will be found. There is, however, an important distinction between the normal presence of mold particles, versus mold growth and accumulation indoors. Unfortunately, even when it is done well, testing may not be able to distinguish between “normal” and “problem” conditions and it may even give misleading results.

When mold is allowed to grow and multiply indoors, it poses a potential health risk and damages what it grows on. When mold growth is visible or mold odors can be smelled, it is common sense that there is a problem that should not be tolerated.

Poor reason for testing #2 “To identify what type of mold is present”

Some testing can be used to identify a portion of the live mold in a sample by growing it in the lab. This gives only a partial description of the total amount of molds, because those not present at the sampled time and location or those that didn’t grow in the sample are not “seen” by the analysis. Most importantly, nonliving molds will not be identifiable, but they can still contribute significantly to health complaints.

From a practical, health-protective perspective, knowing the types of molds is usually not very important because any indoor mold growth represents a problem. The problem should be corrected regardless of the types of molds that can be identified.

Poor reason for testing #3 “To learn if the mold is the toxic kind”

Many, if not all, molds may produce one or more substances broadly called “mycotoxins”. Molds that are known to be able to produce mycotoxins are referred to as “toxigenic”. Mycotoxins may harm living tissue if enough of the agent enters the body, but science does not yet know how much of the many mycotoxins that could be present are necessary to harm a person, especially by breathing it. It is simply safest to assume at this time that any molds may produce mycotoxins or other harmful substances in some circumstances and they ought to be removed.

Testing for mold is not the same as testing for mycotoxins. Since toxigenic molds may or may not be producing mycotoxins depending on the environmental conditions, their presence does not necessarily indicate that known mycotoxins are also present or that occupants will be harmed. Likewise, failing to detect molds that are currently recognized to potentially produce mycotoxins, does not mean that mycotoxins or other harmful substances are absent. MDH advises that any mold growth indoors should be safely removed regardless of whether toxigenic species have been found.

Poor reason for testing #4 “To find the cause of health complaints”

It can be very difficult to conclude if and how occupants may be impacted by a specific mold problem. For one thing, the full range of health effects caused by molds is poorly understood at this time. Whether health effects will occur depends, for each person, on how much mold gets into their body, the amount and potency of various substances that the mold mixture can contain, and the unique susceptibility of each person to the effects of these substances. Unfortunately, mold tests alone will not determine if a specific problem environment is causing a person’s complaints.

Even when mold contamination is found in an area where health problems are occurring, it is often difficult to conclude that the mold is the actual cause of an individual’s specific complaints since other contaminants commonly present in damp or water-damaged settings can also cause or contribute to the complaints associated with moldy environments. Indeed, focusing too heavily on mold alone can be a poor strategy if other potential causes of complaints are not also addressed. Nevertheless, such an association of complaints to evidence of mold contamination is reason enough to remove the mold and correct the underlying causes of excess moisture. One of the biggest problems related to mold testing happens when people misinterpret equivocal or negative findings. It is a common, yet serious error to conclude that a mold problem does not exist simply because tests failed to find evidence of it. Most mold testing simply cannot prove the absence of a problem, and it should never be used as the basis for dismissing complaints or to defend inadequate efforts to investigate or solve potential problems.

Poor reason for testing #5 “To determine if the environment is safe”

At this time, it is unknown what level of mold is “safe” or how much is necessary to cause health problems. Mold tests cannot measure all the molds in an environment or how much occupants are exposed to. Such testing can also miss evidence of problems and results may mislead or be misused. MDH recommends assuming that any visible amount of mold may potentially cause illness and advises that the best approach is to remove this potential threat as soon as it can be done safely. MDH also suggests that it is also reasonable to conclude that an area should be relatively safe with regard to mold, if all visible growth was removed, the surrounding areas thoroughly cleaned, and it remains dry and free of mold odors.

Poor reason for testing #6 “To decide how to correct a mold problem”

Knowing the specific types of mold does not change what ought to be done to clean up the mold or fix the moisture problem. All mold problems should be handled in the same general way, with safety precautions based mainly on the extent of the contamination and how likely the mold will be disturbed by removal activities. All visible mold growth, should be captured and physically removed to the greatest extent practical. In all cases, fixing the moisture problem is critical.

Poor reason for testing #7 “To make a party respond to the problem”

There is no legal requirement to correct a mold problem in most residential or occupational settings. Collecting mold test results does not change this fact. While common sense supports the importance of correcting indoor mold problems quickly and effectively, there is rarely any rule or law that requires a property owner to do so.

Private homeowners are responsible for deciding how they will respond to real or suspected mold problems. This includes owner-occupied condominiums and townhouses, although issues of preventive maintenance and liability may be more confusing when an association is involved. Their insurance company may or may not cover any related costs depending on the details of their policy and other factors. In occupational settings, mold and any related health concerns are solely the responsibility of the employer and/or the property manager. In leased space, terms of the lease agreement may or may not address responsibility for mold and air quality complaints.

In rental housing, tenants should promptly alert the property owner or manager to evidence of mold or moisture problems if they cannot fix the problem on their own. Tenants concerned about mold in rental properties may also ask their city or county housing officials for help. If and how local authorities address mold complaints in rental situations depends on the status of local codes or ordinances and what authority the local program has to deal with this issue.

Finding a Mold Problem

MDH does not recommend mold testing in many cases, especially as the first response to an indoor air quality concern. Instead, careful detailed visual inspection and recognition of moldy odors should be used to find problems needing correction. Efforts should focus on areas where there are signs of liquid moisture or water vapor (humidity) or where moisture problems are suspected. The investigation goals should be to locate indoor mold growth to determine how to correct the moisture problem and remove contamination safely and effectively