Indoor Air Problems – Emissions From Mold And Fungus May Be The Culprits
Metabolic gases emitted from molds and fungi growing inside buildings may be a significant source of airborne volatile organic compounds
that can cause indoor air quality problems known collectively as the "Sick Building Syndrome," a new study suggests.
Indoor air quality problems have long been blamed on a variety of causes, including emissions from particleboard partitions, paints, carpets and
cleaning supplies. The new research suggests that control measures prescribed for sick buildings may need to be altered to address microbial problems
as well as building materials.
Dr. Charlene Bayer analyzes emissions from mold and fungi in a study of the role they may play in causing indoor air problems.
"As molds and fungi grow, they give off metabolic gases that contain VOC emissions," said Dr. Charlene Bayer, principal research scientist
and director of the Georgia Institute of Technology's Indoor Environment Research Program. "Some of the volatile compounds that we are finding are primary solvents, and we think some of the manufacturers are being blamed for emissions from their products when the emissions may actually
be coming from the microbes. Because the VOCs have usually been attributed to other types of sources, the source control may be incorrect."
In research funded by the Georgia Environmental Technology Consortium, a division of the Georgia Research Alliance, Bayer and biologist Sidney Crow at Georgia State University investigated a number of "sick" buildings in the Southeast, collecting fungi samples from buildings afflicted with microbial contamination. The samples were allowed to grow in the laboratory, and the VOCs released from the microbial broths were collected and identified. These VOCs were then compared to those detected in the ambient air within the buildings.
"Many of the volatile compounds produced by the cultured fungi are identical to those originating from solvent-based building materials and cleaning
supplies," Bayer explained. "These VOCs included hexane, methylene chloride, benzene, and acetone."
The microbial VOCs may contribute heavily to the overall level of ambient VOCs in buildings, Bayer says. In one building the researchers investigated,
for example, the microbial contamination was clearly evident on the walls, the carpets, and other locations.
"The concentration of hexane -- a solvent commonly used in cleaning fluids, paints, and adhesives -- was extremely high," said Bayer, "but no source of the hexane could be found. The microbiological contamination could have been the source of the hexane."
Cladosporium, Penicillium, and Aspergillus are among the host of commonly occurring microbes that can infest homes, schools, and offices. Usually,
the first indication of their presence is a foul, musty odor. When growth runs rampant, then the headaches, itchy eyes, rashes, and respiratory
Conditions favorable for microbial growth include heat and moisture, says Bayer. In the Southeast's semi-tropical climate, buildings are prime targets for microbial contamination.
Molds and fungi are not particular about what they eat. They will happily devour just about any organic material, including the dirt and dust trapped within ventilation systems. What can be done to lessen the risk of microbial contamination? First of all, look for ways to reduce the necessary nutrient base.
"Under ideal conditions, a building's ventilation system should filter
out both the microbes and the dirt they feed upon," added Bayer. "Unfortunately, however, many homes, schools, and small office buildings use cheap, throwaway filters in their ventilation systems."
Cheap furnace filters are merely "boulder catchers," Bayer notes. "They only catch the big stuff, they don't catch the fine dust particles and
they don't catch the microbes. So, they really don't do anything to help human health."
Bayer's advice: simply throw away the cheap filters and replace them with more efficient, albeit more expensive, filters.
But, the bigger the building, the bigger the problems with ventilation systems become. In larger office buildings, fiberglass-lined ductwork is often used for noise control, says Bayer. The fibers tend to trap dirt, and that provides a rich nutrient base for microbes.
"Add a little moisture, and you can have a mold garden growing in your ductwork," Bayer explained. "The microbes grow and multiply, and then get blown all over the building to infest other areas."
Moisture control is extremely important in preventing microbial contamination, says Bayer. When the humidity goes up, microbial growth can skyrocket.
"Many buildings erected in the Southeast simply were not designed to handle the heavy humidity loads we have, particularly during our hot,
muggy summers," Bayer noted. "And most building owners don't run their ventilation systems continuously."
Schools typically turn their systems off during the summer months, and most office buildings cycle their systems over nights and weekends, often
resulting in an unpleasant "Monday morning cocktail" for the workers. Such intermittent operation allows the humidity to increase and the molds to multiply.
Preventive maintenance involves proper filtration, correct moisture control, and periodic cleaning of the entire ventilation system -- including the humidifier assembly on residential furnaces.
"Typical reservoir humidifiers are little mold factories," says Bayer. "They are just pools of standing, stagnant water throughout much of the
year that allow mold to grow and infiltrate the ducts. They should be cleaned regularly."
A great deal of research remains to be done, including identifying individual metabolic gases and their respective odors, and acquiring a better understanding of the microbes that are producing them. Once a knowledge base is developed in these areas, the human response to molds and fungi and the sources of complaints in buildings can be better understood.
"Ultimately, we want to identify the microbial contamination on the basis of the odors which are present," says Bayer. "That way, we will be able
to identify the source much more quickly and accurately, and deal with the problem faster and more effectively...before it becomes a major problem requiring expensive remediation."
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Mark Hindley contributes and publishes news editorial to http://www.fresh-air-purifiers.com.
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