What is mold?

Mold is a fungal growth that forms and spreads on various kinds of damp or decaying organic matter. There are many different mold species that come in many different colors. Molds are sometimes referred to as mildew. They are found both indoors and outdoors in all climates, during all seasons of the year. Outdoors, molds survive by using plants and decaying organic matter such as fallen leaves as a source of nutrition. Indoors, molds need moisture to grow as well as a carbon source from building materials or building contents.

Excess moisture is generally the cause of indoor mold growth. Molds reproduce by releasing tiny spores that float through the air until landing in other locations. When they settle on wet or moist surfaces, the spores can form new mold colonies. Moderate temperatures and available nutrient sources make most office buildings ideal for mold growth.

Recent media attention has increased public awareness and concern over exposure to molds in the workplace. While this may seem to be a new problem, exposure to molds has actually occurred throughout history. In fact, the types of molds found in office buildings are not rare or even unusual. It is important to understand that no indoor space is completely free from mold spores – not even a surgical operating room. Molds are everywhere, making our exposure to molds unavoidable, whether indoors or outdoors, at home or at work.

Collage: old leaking pipe and mold on stairs/floor
“Toxic Mold” & Stachybotrys chartarum

Certain molds are toxigenic, meaning they can produce toxins (mycotoxins), but the molds themselves are not toxic, or poisonous. Hazards presented by molds that may produce mycotoxins, such as Stachybotrys chartarum, should be considered the same as other common molds which can grow in your house or workplace. Contradicting research results exist regarding whether toxigenic mold found indoors causes unique or rare health conditions such as bleeding in the lungs. Research is ongoing in this area.

Mold growing in buildings, whether it is Stachybotrys chartarum (Stachybotrys atra) or another mold, indicates that there is a problem with water or moisture. This is the first problem that needs to be addressed. For further information on Stachybotrys chartarum, go to the CDC mold website.

Remediation of dampness and mold contamination

First and foremost, determine the source of moisture and take appropriate measures to make repairs. Damp or wet building materials and furnishings as a result of leaks or flooding should be dried within 24 to 48 hours to prevent the growth of mold. Mold can be cleaned and removed from hard surfaces with detergent and water or a bleach solution of no more than 1 cup of bleach in 1 gallon of water. Never mix bleach with ammonia or other household cleaners. Mold in or under carpets typically requires that the carpets be removed. Once mold starts to grow in insulation or wallboard, the only way to deal with the problem is removal and replacement. For complete remediation guidelines go to the New York City Department of Health and Hygiene’s Guidelines on Assessment and Remediation of Fungi in Indoor EnvironmentsExternal Web Site Icon site.

I suspect mold in my workplace. How do I test for mold?

CDC does not recommend routine sampling for molds. Generally, it is not necessary to identify the species of mold growing in a building. Measurements of mold in air are not reliable or representative. If 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, 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.

Symptoms related to dampness and mold

A woman sneezing into a tissue.
Health problems associated with excessive damp conditions and mold include:


Allergic responses like those to pollen or animal dander are the most common types of health problems related to mold. Typical symptoms include sneezing; irritation of the nose, mouth, or throat; nasal stuffiness and runny nose; and red, itchy or watery eyes. Inhaling or touching mold or mold spores can cause a person who was not previously allergic to mold to become allergic to mold. For people with known allergies, molds can trigger asthma symptoms such as shortness of breath, wheezing, or cough. Irritation can also occur in non-allergenic (non-sensitized) people. Additionally, scientific studies indicate that exposure to molds in the workplace can make pre-existing asthma worse. Recent NIOSH investigations document that some damp buildings are associated with developing new asthma.

Hypersensitivity pneumonitis (HP) is a kind of lung inflammation that occurs in persons who develop immune system sensitization (similar to an allergy) to inhaled organic dust. It can be mistaken for pneumonia, but it does not get better with antibiotics for infection.

Symptoms of HP can vary. Some persons have shortness of breath, cough, muscle aches, chills, fever, night sweats, and profound fatigue. These symptoms usually first appear 2 to 9 hours after exposure and last for 1 to 3 days. Other affected persons have progressive shortness of breath and cough, as well as weight loss. Work-relatedness may only become apparent over long holidays if symptoms resolve and then recur on return to work. With continued exposure, the persistent lung inflammation of both kinds of symptoms can lead to scarring and permanent damage. The slow progression of symptoms and the persistence of symptoms away from work may result in delayed recognition of work-related lung disease by both workers and physicians.

HP has been referred to as Bird breeder’s lung and Mushroom picker’s disease in specific occupations with a risk of HP from biological dusts. HP has been documented in workers in buildings with mold and bacteria contaminated air-conditioners (including spray-water cooling systems), and contaminated ductwork and filters. This lung disease has also occurred in workers who worked in water-damaged buildings with roof leaks, plumbing leaks, poorly draining condensation pans, and high indoor relative humidity.

HP is not contagious and is due to a person’s immune system reaction to inhaled microorganisms, whether dead or alive. It is possible for workers to have both dampness-related HP and asthma at the same time. Additionally, workplaces that have workers with HP may also have workers with building-related asthma.

Asthma is a form of lung disease in which the airways develop inflammation and bronchospasm (reversible narrowing) in response to sensitizing or irritating exposure. Affected individuals can experience episodes of shortness of breath, cough, chest tightness, and wheezing. These symptoms occur after exposure to nonspecific irritating substances in the air or after exposure to substances to which an individual is allergic. Medical testing typically reveals evidence of bronchial hyperresponsiveness such as an abnormal methacholine challenge test or reversible airways obstruction on spirometry (a test of lung function). It is important for affected individuals to have a comprehensive asthma treatment plan and regular follow-up with their physician. Early diagnosis and removal from the impacted damp office environment can cure asthma caused by workplace exposures.

In approximately 15% of asthmatics, the illness may have been caused, or made worse, by workplace exposures. Some occupational exposures are well known risks for asthma development (e.g., western red cedar; isocyanates). Indoor environment research has identified evidence of an association between damp buildings and asthma symptoms in individuals with pre-existing asthma. There is also new evidence of an association between damp buildings and new-onset asthma. In an individual with new-onset asthma or worsening of stable pre-existing asthma, measurements of lung function made several times a day at work and at home over several weeks may reveal a pattern of changing lung function that suggests a workplace cause.

For individuals with new-onset asthma or worsening of stable pre-existing asthma that is suspected to be related to the indoor environment, controlling or eliminating the sources of indoor contaminants, along with optimal medical treatment, may lead to symptoms of improvement or resolution.
What workers can do

When workers suspect their health problems are caused by exposure to building-related dampness or mold, workers should:

Report concerns immediately to supervisors or those persons responsible for building maintenance.
See your doctor for proper diagnosis and treatment.
Ask your doctor whether you should be medically restricted from the affected environment.
What management and building owners can do

When health problems are believed to be caused by exposure to dampness or mold in the workplace, owners and managers should:

Always respond when occupant health concerns are reported.
Establish clear procedures for recording and responding to IEQ complaints to ensure an adequate and timely response.
Log all complaints or problem reports.
Collect information about each complaint.
Ensure confidentiality.
Determine a plan for response.
Identify appropriate resources for response.
Apply remedial action.
Provide feedback to building occupants regarding the complaint and response actions.
Follow-up to ensure that remedial action has been effective.
Regularly inspect building areas for evidence of dampness; take prompt steps to identify and correct the causes of any dampness problems found.
Conduct regularly scheduled heating, ventilating, and air-conditioning (HVAC) system inspections, and promptly correct any problems.
Prevent high indoor humidity through the proper design and operation of HVAC systems.
Dry any porous building materials that have become wet from leaks or flooding within 48 hours.
Clean and repair or replace any building materials that are moisture-damaged or show evidence of visible mold growth. Follow remediation guidelines such as the Environmental Protection Agency’s (EPA) Mold Remediation in Schools and Commercial Buildings.External Web Site Icon
Encourage occupants who have developed persistent or worsening respiratory symptoms while working in the building to see a health care provider.
Follow health care provider recommendations for relocation of occupants diagnosed with building-related respiratory disease.