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The Hidden Dangers of Microbial Volatile Organic Compounds (mVOCs)

July 3, 2024

mvocs at office

The musty odor you smell is decay off-gassing from biological growth, which includes molds, bacteria, and biofilm. These odors contain microbial volatile organic compounds (mVOCs). People may compare this odor to a dank locker room, old cheese, dirty socks, or wet dog. Many of my clients may experience immediate and longer-term health effects from mVOC exposure.

What are Microbial Volatile Organic Compounds (mVOCs)?

Microbial volatile organic compounds (mVOCs) are a subset of volatile organic compounds (VOCs) produced by microorganisms such as molds, bacteria, and biofilms. Unlike traditional VOCs, which are often industrial-made chemicals, mVOCs are byproducts of microbial metabolic processes. These compounds are typically characterized by their low molecular weights, high vapor pressure, and low water solubility.

Composition of mVOCs

mVOCs encompass a diverse range of chemical compounds, including:

  • Alcohols: e.g., ethanol
  • Ketones: e.g., 1-octen-3-ol
  • Aldehydes: e.g., 2-octen-1-ol
  • Esters: e.g., ethyl acetate
  • Carboxylic Acids: e.g., acetic acid
  • Lactones: e.g., γ-hexalactone
  • Terpenes: e.g., limonene
  • Aromatic Hydrocarbons: e.g., benzene derivatives
  • Sulfur Compounds: e.g., dimethyl sulfide
  • Nitrogen Compounds: e.g., amines

Health Impacts of mVOCs

Exposure to mVOCs can lead to a variety of health effects. Common symptoms include:

  • Headaches
  • Nasal and throat irritation
  • Dizziness
  • Fatigue
  • Nausea

The specific toxic properties and concentrations of mVOCs needed to produce symptoms are still not fully understood. However, individuals with multiple chemical sensitivity (MCS) are often more reactive to mVOCs, experiencing heightened symptoms at lower exposure levels compared to the general population.

Causes of mVOCs

mVOCs are produced during both primary and secondary metabolic processes of microorganisms. Primary fungal metabolism can produce compounds such as ethanol, 1-octen-3-ol, and benzyl cyanide. Secondary metabolism can result in the production of 2-methyl-isoborneol, geosmin, and various terpenes.

Testing for mVOCs

Advanced sampling techniques are essential for detecting and quantifying mVOCs. Two primary methods include:

  1. Sorbent Tubes: Air samples are collected using tubes filled with sorbent materials, which adsorb the mVOCs from the air. These samples are then analyzed in a laboratory.
  2. Mass Spectrometry: This technique is used to identify and quantify the specific mVOCs present in the samples. It provides detailed information on the chemical composition and concentrations of mVOCs.

mVOCs and Mold Odors Without Mold Spores

It’s possible to have mVOCs and mold odors without the presence of mold spores. This can occur because mVOCs are gaseous byproducts that can permeate the air even when mold spores are not airborne. This makes it crucial to address the source of mVOCs rather than relying solely on mold spore counts for indoor air quality assessment.

Recommendations to Reduce mVOC Exposure

To minimize exposure to mVOCs and their associated health risks, consider the following measures:

  1. Professional HVAC System and Air Duct Cleaning: Regular cleaning can remove accumulated mold and bacteria.
  2. Disengage Built-In Humidification Devices: These devices can contribute to excess moisture, promoting microbial growth.
  3. Control Humidity: Maintain indoor humidity levels below 45% year-round to inhibit mold growth.
  4. Replace Carpeting: Opt for synthetic flooring materials that do not retain moisture as easily as carpets.
  5. Remove Water-Damaged Materials: Promptly address and remove any materials that have been exposed to water damage.
  6. Improve Airflow: Increase ventilation by opening windows or using an air recovery system (HRV/ERV).
  7. Use Air Purifiers: Invest in a medical-grade air purifier with activated carbon to capture and neutralize mVOCs.


The presence of microbial volatile organic compounds (mVOCs) is a significant concern for indoor air quality. These compounds, produced by molds, bacteria, and biofilms, can lead to various health issues, especially in individuals with multiple chemical sensitivity (MCS). Understanding the sources, health impacts, and testing methods for mVOCs is crucial for creating a healthier indoor environment. By implementing preventative measures and improving ventilation, you can significantly reduce the presence of mVOCs and their associated health risks.


These references provide comprehensive information on mVOCs, their health impacts, and the importance of proper ventilation and air purification to mitigate exposure.

  1. Agency for Toxic Substances and Disease Registry (ATSDR)
  2. Environmental Protection Agency (EPA)
    • Volatile Organic Compounds (VOCs)
    • EPA VOCs
  3. National Institute for Occupational Safety and Health (NIOSH)
  4. World Health Organization (WHO)
  5. National Institutes of Health (NIH)
  6. American Lung Association
    • Indoor Air Pollution
    • American Lung Association Indoor Air Pollution
  7. Environmental Health Perspectives
  8. Centers for Disease Control and Prevention (CDC)
  9. American Industrial Hygiene Association (AIHA)
    • Recognition, Evaluation, and Control of Indoor Mold
    • AIHA Indoor Mold
  10. Journal of Occupational and Environmental Hygiene
    • Characterization and Health Effects of mVOCs
    • Journal of Occupational and Environmental Hygiene
  11. Science of the Total Environment

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