Microbial Volatile Organic Compounds (MVOCs) and Health Consequences

Clients often tell us that they smell mold and it's causing adverse health symptoms. However, they are confused when an air sample sent to the laboratory shows little to know spore activity in the areas of concern. Does this mean there is no mold and not to worry? No, what they are actually smelling is decay off-gassing from biological growth which includes molds, bacteria and biofilm. These odors contain microbial volatile organic compound (MVOC). People may compare this odor to a dank locker room, old cheese, dirty socks, or wet dog.

Microbial Volatile Organic Compound Overview:
The dank musty odor signifies the presence of microbial volatile organic compounds (MVOCs). Traditional volatile organic compounds (VOCs) are mainly industrial made chemicals with low molecular weights, high vapor pressure and low water solubility. MVOCs are released from metabolic processes of decay agents like fungi, bacteria and biofilm. The off gassing of MVOCs include a wide range of alcohols, ketones, aldehyde, esters, carboxylic acids, lactones, terpenes, aromatic hydrocarbons, sulfur and nitrogen compounds.

MVOCs produced during primary fungal metabolism include: Ethanol, 1-octen-3-ol, 2-octen-1-ol, and benzyl cyanide. MVOCs produced during secondary metabolism include 2-methyl-isoborneol, geosmin (1-10-dimethyl-trans-9-decalol) and terpenes.

Significance:
The perception of MVOC's is an indication that microbial growth is occurring. In the indoor environment, exposure to MVOC's has been blamed for headaches, nasal irritation, dizziness, fatigue, and nausea. Information on MVOCs produced in indoor settings and health effects is limited. The specific toxic properties and concentrations of MVOC's needed to produce symptoms are still unknown.

Recommendations:
Prudent and preventative measures should be taken to eliminate or reduce musty odors and associated MVOCs. These measures include but are not limited to:

• Professional HVAC system and air duct cleaning
• Disengage any built in humidification devices within the HVAC system
• Control humidity below 45% year round 
• Replace carpeting with a more synthetic floor system 
• Remove water damaged building materials 
• Improve airflow in the home or building by encouraging fresh air with windows open or with an air recovery system (HRV/ERV)

Basement Carpeting Leads To Poor Air Quality

More and more people are looking to finish their basements to increase overall property value and expand their space. It is still a common practice to finish a basement with carpeting, but this is not the best course of action. Carpeting and basement simply don’t mix. Just as you wouldn’t want carpeting at the base of a shower, you should avoid carpeting in your basement because of increased moisture. Carpeting is prone to mold through a moisture wicking process called capillary action that occurs in all basement foundations. As moisture wicks up from the foundation, it evaporates, hence the reason why basements maintain higher humidity than elsewhere in the home. Once a carpet, area rug or a pad is placed on top of the cement foundation, it will begin absorbing this excess moisture. When excess organic matter such as dirt, dust, skin cells, and pet dander are added to the mix mold growth occurs. Carpet manufactures sell the concept that the fibers are mold resistant, which many are, but it’s the imbedded organic matter that promotes biological growth. Furthermore, basements without proper dehumidification will exasperate the issue when the relative humidity exceeds 55%. Hidden moisture within the carpeting will cause foul odors. These odors are actually a chemical or microbial volatile organic compound (MVOC). The mal-odor results from off-gassing during the biological processes causing eye, nose and throat irritation. These harmful MVOCs are a clear indicator that there is an indoor air quality issue which can cause adverse health effects even without the presence of elevated mold spores. This issue becomes significantly more serious when pathogenic spores are present, as they lead to acute or chronic diseases. If the mold and bad odors aren’t enough to discourage you from carpeting a basement, consider the inevitable dust mite explosion and bacterial proliferation within the fibers. IndoorDoctor recommends a synthetic floor system like a soft tile or laminate to decrease the ultrafine particulates and toxic mold spores. Be sure to control the humidity throughout the basement below 45% with supplemental dehumidification. For most New England basements a typical 60 pint dehumidifier sold at a hardware store is insufficient to sustain low humidity during summer months. The larger dehumidifiers like the Santa Fe, Sani-Dry or Wet Basement models are much more effective at controlling the overall humidity throughout the basement. Ventilation systems like E-Z Breathe (www.ezbreathe.com) will further assist with humidity, odor, radon and spore reduction without any added maintenance. When retrofitting your basement be safe and consider the air you and your family will breathe.