The Challenges of Mold Growth in Indoor Environments

Most people breathe in mold spores every day without significant health effects. After all, mold is ubiquitous and naturally found living both indoors and outdoors. The main issue is – although we can expect to find mold spores floating around in the indoor air in numbers and types that are similar to those found outdoors, we don’t want mold growing indoors. When water intrusion occurs and mold grows indoors in damp or water-damaged buildings, it can cause a variety of adverse health and safety effects on both the occupants and buildings.

How Does Mold Begin to Grow?

For molds to grow, they need a food source (e.g., organic material such as dust, paper, drywall, wood) and moisture.  Because molds grow by digesting organic material, they will eventually destroy whatever they grow on.  Moisture intrusion caused by flooding, condensation, and plumbing or roof leaks provide the next ingredient.  It can often grow out of sight and unnoticed. Even when the moisture source is removed, if mold had begun growing on a building surface, the spores will remain there and potentially cause allergic reactions or other health effects until they are physically removed.

Incentives Involved with the Control of Indoor Mold

There are overwhelming incentives involved with managing moisture intrusion and mold indoors. Mold remediation and building repairs associated with moisture intrusion and structural damage can cost a facility tens to hundreds of thousands of dollars.  Exposure to elevated levels of airborne mold have been directly attributed to adverse health effects in water damaged buildings, as well as healthcare associated infections (HAIs) in healthcare settings.  Not only is treatment and management costly but unfortunately, research has shown that some HAIs have resulted in patient deaths.  Taking these consequences into consideration, water-damaged facilities are well incentivized to effectively and proactively manage the impact of mold in their buildings.

Several agencies such as state health departments, the Institute of Medicine (IOM), the Center for Disease Control (CDC), and the World Health Organization (WHO), among other professionals, all agree that dampness and mold cause adverse health effects.  These may include:

  • Upper respiratory symptoms: sore/irritated nose or throat, and congested nose or sinuses
  • Lower respiratory symptoms: difficulty breathing, cough, shortness of breath, and wheezing
  • Respiratory infections: acute bronchitis
  • Asthma attacks in those with asthma and causation of new asthma
  • Allergic rhinitis (runny or congested nose, sneezing)
  • Eye irritation: reddening, burning and watering
  • Skin rashes, irritation, and eczema

While certain molds are considered toxigenic and can produce “mycotoxins”, not all molds produce these toxins.  Individuals with suppressed immune systems or underlying lung disease, such as those in healthcare facilities, are more susceptible to fungal infections and exposure to certain types of pathogenic molds can result in health complications.  Aspergillus for example is found everywhere, indoors and outdoors, and their transmission occurs through inhalation of airborne conidia.  According to an article by NCBI, invasive aspergillosis (IA) is a leading cause of infection-related death in immunocompromised patients.

Control and Prevention Efforts

It is crucial to focus on control and prevention efforts.  Buildings have a large number of spaces that include large wall and ceiling cavities where mold can grow undetected, along with extensive plumbing and HVAC systems that provide the final ingredient needed – moisture.  Facility professionals must constantly be on the lookout for signs of moisture on ceilings, walls, under sink cabinets, and floors.

Regular inspections should be conducted to ensure all areas are inspected, no matter how insignificant they may seem. These affected areas can be inside ductwork or hidden within wall and ceiling cavities. Care should be taken when removing or replacing any water-damaged building material to prevent releasing mold spores and to protect occupants from unnecessary exposure.

It is not suggested to rely on sampling and culturing alone to determine your level of health risk because either by the type or amounts of mold present, effects on people can vary greatly.  On that note, you generally do not need to know the type of mold growing indoors to determine whether or not remediation is necessary, because no matter the type (or color), mold impacted building materials must be addressed.

To date, no federal or state policies have set safe exposure limits to airborne mold or quantify the health risks from indoor dampness and mold growth in buildings (e.g., OSHA, NIOSH, EPA).  However, scientific research on the relationship between mold exposures and health effects is ongoing and certain codes exist to increase awareness and reduce exposure to these hazards.  The Department of Public Health (CDPH) for example, states that it “agrees with other building and health professionals that indoor dampness, water intrusion, or fungal growth should always be eliminated in a safe and efficient manner”.  Several other states require mold licensing or regulate mold businesses in some way or another and may impose civil penalties.

For details on addressing mold and moisture intrusion, credible resources can be found by the: EPA, OSHA, AIHA, New York City Department of Health, IICRC, and CDC.

Consult with an Industrial Hygienist (IH)

If known or suspected water intrusion is reported, a qualified IH should be consulted to help assess whether or not an indoor mold growth source is suspected.  This is generally accomplished through visual investigations, moisture content measurements, the reported history of moisture intrusion and associated drying efforts, and (sometimes) the collection of airborne mold spore samples.  The steps described in the assessment above (at the least) should all be considered.  The primary objectives of the investigation and response effort should at least include:

  • Finding/identifying the source(s) of moisture intrusion,
  • rapidly drying damp materials (within 24-48 hours),
  • making repairs to prevent future mold growth from recurring, and
  • performing mold remediation in accordance with generally accepted industry guidelines.

In general, porous materials that have been affected by mold growth such as drywall, moisture barrier paper, insulation, carpeting, and ceiling tiles should be removed under controlled conditions and discarded.  Cleanable non-porous and semi-porous surfaces such as wood, tile, stone, plastic, and metal, can be HEPA vacuumed and scrubbed clean with soapy water and a bristle brush.

Take Immediate Steps to Control the Source

In order to avoid costly remediation associated with water-damaged building materials, it is crucial that moisture intrusion issues are addressed timely. Every effort must be made to dry all affected building materials before mold growth begins to develop, which is generally within 24 to 48-hours.  Facility professionals should consult with an IH as soon as moisture intrusion occurs. Don’t wait! Drying efforts should be put into effect immediately. The IH should conduct an initial inspection, provide recommendations for remediation (with oversight if necessary), and perform post-remediation inspections and testing prior to build-back to help assess whether or not remediation efforts were effective.

Lastly, the investigation and subsequent remediation process is a team effort. To avoid potential conflicts of interest and to ensure a successful outcome, it is in the client’s best interest to keep the recommendation, oversight, and scope development process (performed by Industrial Hygienists) separate from actual remediation (performed by qualified remediation contractors). Hiring two separate entities to perform these services will control potentially costly follow-ups later on.

For questions, please contact Nicole Naggar, LEED GA, SFP at

Share on Socials!

Related Articles

Related Articles

OSHA issues guidance to employers on frequently cited COVID-19 standards

OSHA has issued guidance and an accompanying one-pager to help employers understand which standards are most frequently cited during coronavirus-related inspections. OSHA based these documents on data from citations issued, ...
Read More

Masks also protect the wearer, CDC announces

Wearing a mask protects you, not only those around you, the Centers for Disease Control and Prevention said Tuesday in a significant update to its guidance ...
Read More

5 takeaways on needlestick injuries and health care worker safety

The COVID-19 pandemic has highlighted the importance of health care worker safety. But while infectious disease outbreaks such as COVID-19 illustrate the gaps in protecting frontliners during emergency ...
Read More

Follow IHW!


Sign up to receive our industry publications for FREE!

Industrial Hygiene

Construction Safety