In the past few years, "Sick Building Syndrome" has been blamed on a variety of causes, from particle board partitions to paints, from carpets to cleaning supplies. Recent research funded by a seed grant from the Georgia Environmental Technology Consortium, a division of the Georgia Research Alliance, indicates that these may be blamed when they are not the primary culprits, however.
The obnoxious emissions that congest our lungs and irritate our eyes may be coming from microbial infestations lurking in the floor beneath us, in the walls around us, and in the ceiling ahove us. Our buildings may be sicker than we thought.
Dr. Charlene Bayer, principal research scientist and director of Tech's Indoor Environment Research Program, and biologist Sidney Crow at Georgia State University have investigated a number of "sick" buildings. They believe that many of the indoor problems found in the Southeastern United States are caused by volatile organic compounds (VOCs) given off by molds and fungi.
Dr. Charlene Bayer of Georgia Tech Research Institute (shown) and biologist Sidney Crow of Georgia State University gather fungi from from buildings afflicted with microbial contamination, grow samples of the microbes, then identify the VOCs released. Their work will lead to healthier workplaces.
"As molds and fungi grow, they give off metabolic gases that contain VOC emissions," says Bayer. "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 he coming from the microbes. Because the VOCs have usually been attributed to other types of sources, the source control may be incorrect."
Bayer and Crow collected fungi samples from a number of buildings that were 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," says Bayer. "These VOCs included hexane, methylene chloride, benzene and acetone."
The microbial VOCs may contribute heavily to the overall level of ambient VOCs in buildings, says Bayer. 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," says 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 our 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 problems begin.
Conditions favorable for microbial growth include heat and moisture, says Bayer. In the Southeast, with its semi-tropical climate and high humidity, 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 our ventilation systems.
What can be done to lessen the risk of microbial contamination? First of all, you can 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," says 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," says Bayer. "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 higher quality, 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 a lot of dirt, and that provides a rich nutrient base for microbes.
"Add a little moisture, and you have a mold garden growing in your ductwork," says Bayer. "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," says Bayer. "And most building owners don't run their ventilation systems continuously."
Schools typically turn their systems off during the summer months (the prime time of year for microbial growth), 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 residental 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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