FAQ About Mold and Public Health

Mold can be a confusing and scary thing to see in your home after the news stories and medical reports we’ve all heard and read throughout the years. Here are a few of the most frequently asked questions when it comes to what mold is, how it begins to grow in your home, whether you should be concerned about it, and how we take care of it:

Q: What are molds – plants or animals?
A: Neither. Molds are members of a unique kingdom called fungi. Other common fungi are yeasts and mushrooms.

Q: Are molds only found in wet environments?
A: Mold grows everyplace on Earth (the water planet), in all climates and environmental conditions. Fungi have an absolute requirement for water but exhibit a wide range of tolerance in relation to water availability. Fungi can survive over a broad temperature range; however, optimum growth tends to be found in the range of 54-84 degrees Fahrenheit.

Q: What are the main sources of water and moisture for mold growth?
A: Common indoor moisture sources include humidifiers, cooking and dishwashing, bathing, plumbing leaks, house plants, firewood storage indoors, improper venting of clothes dryer / indoor clothes line, and combustion appliances. Common outdoor sources of moisture include roof leaks, flooding, rain or snowmelt, seasonal high humidity, ground moisture, and wet building materials.

Q: What is the source and cause of “musty” or distinct odor associated with wet or damp environments?
A: The odorants are organic (carbon based) compounds excreted from bacteria and fungi. They are often referred to as VOCs (volatile organic compounds), but more accurately they should be identified as gas-phase organic compounds derived from biodegradation (the process by which organic substances are decomposed by micro-organisms, mainly aerobic bacteria, into simpler substances such as carbon dioxide, water, and ammonia).

Q: What is the most likely human response to mold by way of exposure to air?
A: The most likely human response by way of air exposure is allergic reaction to mold spores when in a sufficient high concentration.

Q: Who is most at risk when exposed to mold and mold spores?
A: The very young, the very old, those with weakened immune systems, and asthmatics.

Q: What is the most effective way to manage mold?
A: The most effective way to prevent mold growth is to keep materials clean and dry; if they get wet, dry them quickly before mold growth can start.

Q: How can we best get rid of mold spores?
A: Do not let mold grow to begin with. Keep the environment clean and dry. If mold does grow, contain the growing mold along with its wet food source (i.e., wrap it in plastic and get it outside) before spores are released into the air. If spores are released, remember that they settle onto surfaces hours after activities end in the exposure area. Vacuuming and damp wiping of walls and hard surfaces and vacuuming of fabrics (including carpet) is effective in the removal of mold spores before they can get put back into the air.

Q: How do we manage fungal spores in the air?
A: Properly designed airflow across a source of mold spores carries airborne contaminants into the air filtration device where they are trapped. This principle can be applied to vacuum cleaners and air filters. HEPA vacuums, or any other vacuum that can filter particles down to one micron or less, if applied consistently, will remove large amounts of mold spores from an indoor environment.

Q: Can biocides be used to effectively manage mold?
A: Biocides are useful poisons designed to kill microorganisms. However, biocides are not recommended for the management of mold primarily because they will only slow the mold problem down, they will not correct the problem. To correct the problem, in addition to cleaning and/or removing the affected materials, the environmental conditions that support mold growth must be changed by removing the water and organic food sources.

Q: How should we manage environmental quality in the face of demolition or mold-damaged material removal?
A: Demolition procedures on a restoration project should be performed in such a way as to minimize and control dust, mold spores, and other biopollutants. Controls applicable to mold management include source containment before removal, minimization of air activity prior to containment, containment, and negative air pressurization of contaminated areas.

Q: Can we see mold spores indoors?
A: No. The size of mold spores is between 2 and 100 microns. The vast majority are under 20 microns. A micron is one millionth of a meter. We cannot see objects of less than 40 microns without optical magnification.

Q: What about the size of mold spore and bacteria, is size important?
A: Particles of all size ranges are important. They can enter the cranial cavity, be ingested, enter the upper or lower regions of the lung, or come in contact with the eyes or skin. Particles smaller than 2.5 microns are especially hazardous because they are small enough to be inhaled into the gas exchange portion of the lung, the alveoli (air sacs). When alveoli are damaged, lung function is permanently impaired.

Q: What about the color of mold, is back mold more dangerous than other species?
A: The risk potential of mold cannot be judged by its color. There are literally thousands of species of mold and a large number of them appear black to the human eye after the mold colony has grown large enough to see.

Q: Are there any safe molds as far as allergic response goes?
A: In the face of uncertainty, it is prudent to suspect that all mold spores are allergens to some degree. In high enough concentrations and sufficiently long exposure times, regardless of species, mold spores can, in theory, trigger a reaction. Some molds trigger allergic reactions even at lower exposure levels.

Q: What species of mold should be of most concern?
A: Penicillium, Aspergillus, and Stachybotrys are hazardous species in the sense that humans tend to have more of an allergic reaction to these. Although hazards by themselves do not guarantee harm, we should be very concerned when any of these three species are the source of the dominant spore concentration found indoors.

Q: What is the leading cause of serious deadly illness indoors?
A: Bacteria and viruses, not mold, are the most “pathogenic” (disease causing) organisms commonly found indoors.

Q: If mold has been around for millions of years, why all of a sudden are people concerned for complaining about mold?
A: Several reasons: 1) People are more aware about environment and its relation to human health than at any time in history. People are learning that microorganisms, biopollutants, and biocontaminants, not chemicals, are the biggest health risks indoors. 2) Humans tend to react to risks that are exotic and invisible and that affect their children and those they protect, like elderly parents. Living, colorful mold, growing in a Petri dish is exotic especially in the mind of someone who has never taken a biology class. 3) Modern dwellings tend to trap dirt and moisture. Little water leaks are often unnoticed and not attended to. If we do not keep an indoor environment dry and clean, mold is going to grow, always.

Excerpted from the Institute of Inspection Cleaning and Restoration Certification’s “The Journal of Cleaning, Restoration, & InspectionDecember 2015 Issue, pgs. 28-29, “Frequently Asked Questions About Mold in the Interest of General Public Health Education” within the article “Basic Principles for Managing Mold” by Michael A. Berry, Ph.D.

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