Mold: Health and Building Effects

What Mold Is and Why It Matters

Mold is a type of fungus that occurs naturally and exists indoors and outdoors. Mold spores are microscopic and travel through air; when they land on wet or damp surfaces, they can grow and multiply. Because mold needs moisture to thrive, it is a strong indicator of water intrusion or elevated humidity in a building. Environmental Protection Agency

For official information on the basics of mold, moisture control, and indoor environments, see the EPA mold page:
https://www.epa.gov/mold Environmental Protection Agency

Health Effects of Mold Exposure

Exposure to mold and damp indoor environments has been associated with a range of health effects, especially in sensitive individuals (e.g., people with allergies, asthma, or compromised immune systems):

• Allergic reactions and asthma symptoms: Mold spores and fragments can trigger hay‑fever‑like symptoms such as sneezing, nasal congestion, itchy or watery eyes, and coughing. Asthma sufferers may experience worsened symptoms. CDC+1

• Respiratory irritation: Even individuals without allergies may experience irritation of the eyes, nose, throat, or lungs when exposed to mold or elevated moisture. CDC

• Hypersensitivity pneumonitis and other immune responses: In some cases, repeated or high exposure can contribute to immune‑mediated lung inflammation. CDC

• Mycotoxin concerns: Some molds can produce potentially toxic substances (mycotoxins). Although the role of airborne mycotoxins in general occupant health remains complex and under study, avoiding unnecessary exposure is recommended by public health authorities. Environmental Protection Agency

The World Health Organization’s Guidelines for Indoor Air Quality: Dampness and Mould summarize global evidence showing that indoor dampness and mold are linked to increased respiratory symptoms, allergies, asthma, and immune system perturbations. Persistent dampness and microbial growth should be minimized to protect health. World Health Organization

For more on mold and dampness health effects from WHO, see:
https://www.who.int/publications/i/item/9789289041683 World Health Organization

Effects of Mold and Moisture on Buildings

Mold doesn’t just impact health—its growth reflects underlying moisture issues that can damage building materials:

• Degradation of structural and finish materials: Mold digests organic material (wood, drywall, paper), causing rot, staining, and weakening of structural components. Environmental Protection Agency

• Moisture indicators: Persistent condensation, leaks, and high indoor humidity create environments favorable for mold growth. Detecting and addressing these conditions early prevents widespread mold colonization and the associated damage. Environmental Protection Agency

• HVAC contamination: Moist or damp HVAC components and ductwork can harbor mold and distribute spores and fragments throughout a building. CDC

Guidance on Evaluation and Remediation

Public health authorities emphasize that moisture control is key to preventing and controlling indoor mold. It is not possible to eliminate all mold spores from indoor air; the focus should be on eliminating conditions that allow mold growth. Environmental Protection Agency

The CDC/NIOSH also notes that thorough visual inspection, assessment of moisture and dampness, and remediation of water problems provide more reliable information about the severity of a mold problem than short‑term airborne spore counts alone. CDC

The EPA provides practical guidance on moisture control and mold cleanup in homes:
https://www.epa.gov/mold/brief-guide-mold-moisture-and-your-home Environmental Protection Agency

Authoritative Resources

• EPA Mold Information & Resources
  https://www.epa.gov/mold Environmental Protection Agency

• NIOSH Mold and Dampness Guidance
  https://www.cdc.gov/niosh/mold/index.html CDC

• World Health Organization Indoor Air Quality Guidelines: Dampness and Mould
  https://www.who.int/publications/i/item/9789289041683 World Health Organization