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Biocontaminant Control

Our strategy is to work cooperatively with experts to enhance the scientific understanding of indoor air biocontaminants and to develop prevention and control techniques for mitigation of indoor air pollution by biocontaminants. This can be accomplished by

The current emphasis of our research is on fungi, endotoxins, and allergens. Laboratory experiments are being conducted to investigate the sources and causes of indoor air biocontamination. Laboratory experiments provide a controlled environment so that reproducible data can be generated by which critical parameters that promote or discourage the germination, growth, dispersion, and death of indoor biocontaminants can be isolated and identified. The critical parameters identified provide a scientific base for evaluation and development of effective prevention and control techniques to reduce the risk of exposure to indoor biocontaminants.

Evaluation of Fungal Growth on Fiberglass Duct Materials
Under a cooperative agreement, Research Triangle Institute is using a newly developed static chamber test method to evaluate the impact of moisture, soil, use, and temperature on the fungal growth potential of fiberglass duct materials. Fiberglass duct materials are commonly used in both residential and commercial heating, ventilation, and air-conditioning systems to provide the needed thermal insulation and noise control. Many building investigations have documented biocontamination of those materials, and the appropriateness of their use in high-humidity locations has come into question. A series of experiments, were conducted in static environmental chambers to assess some of the conditions that may impact the ability of a variety of fiberglass materials to support the growth of a fungus, Penicillium chrysogenum. The ultimate outputs from this project include: 1) fungal growth data on various fiberglass duct materials; and 2) test methods to measure the fungal resistance of duct materials. Critical parameters determining the fungal growth on fiberglass duct materials can be identified by analyzing the fungal growth data. Pollution prevention and mitigation techniques and guidelines can be developed by controlling those critical parameters. The test methods can be used by duct-material manufacturers to assist the development of fungal-resistant products. Both static and dynamic chamber experiments will be utilized using new and used building materials with and without antimicrobial treatment and encapsulants/sealants.

Biological Particulate Matter Research
Emphasis in studying the relationship between indoor and outdoor pollutants has acknowledged fine particulate matter as being equal in importance to gaseous contaminants. Detrimental health effects associated with indoor aerosols were previously believed to come primarily from tobacco smoke. However, the new concern over ambient particles is based on several relatively new epidemiological studies that indicate that adverse health effects occur at ambient particle concentrations lower than previously believed.

While indoor environments are not presently covered by ambient standards, it is widely recognized that, on the average, Americans spend 21 hours per day indoors and, consequently, receive a significant fraction of their exposure from that environment. Exposures from indoor environments (microenvironments) are a major issue for evaluating total long-term personal exposures to the fine fraction (<2.5 µm) of particulate matter (PM), originating from ambient and indoor sources. One approach to distinguish between indoor and outdoor sources will be to evaluate the mechanisms by which ambient particles penetrate into the indoor environment. A mathematical model will be developed by EPA/IEMB, to predict the concentration of particles entering from the outdoors. Once a model describing the mechanisms of particle penetration as a function of particle size and air exchange has been validated in laboratory experiments, the model will be applied to particle entry into a real house (IEMB's research house).

Bacteria and fungi are important components of outdoor or atmospheric aerosols in addition to being important components of indoor aerosols. The size range of airborne bacteria is from 0.5 to 2.0 µm (Bacillus spp., Pseudomonas spp., Xanthomonas spp., and Arthrobacter spp.), while many of the mold spores are in the 1.0 to 2.5 µm size range (Aspergillus spp., and Penicillium spp.). Desiccated non-viable fragments of organisms are also common. These fragments can remain toxic or allergenic depending upon the specific organism, or organism component. These organisms or organism components can cause allergic, asthma-like reactions or pulmonary disease upon exposure. Although these bioaerosols have been identified, they have not been quantitatively studied for their prevalence of PM with time or their affinity to penetrate indoors.

Biological Contamination and Indoor Air Quality
It is widely accepted in the indoor air quality research community that biocontaminants are one of the important indoor air pollutants. Major indoor air biocontaminants include fungi, bacteria, dust mites, viruses, and protozoa. Under favorable conditions, biocontaminants are able to grow and multiply by themselves on a variety of building materials and indoor surfaces. Once the biocontaminants or their metabolites become airborne, indoor air quality could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, allergic, infectious, and chemical responses in exposed individuals.

Little information is available that quantifies the relationship between indoor and outdoor levels of bioaerosols. Although it is well established that outdoor levels influence indoor levels, the mechanisms are not understood. Outdoor levels of bioaerosols are affected by a number of factors, including seasonal variation, environmental or climatic influences, and activity in the area. As in the study of PM, penetration transfer mechanisms for bioaerosols from outdoors include infiltration, ventilation flows, and mechanical transport on apparel. Over some period of time, indoor levels are thought to be dependent upon outdoor levels when indoor sources are minimized. Bioaerosols have been identified outdoors and indoors without any study of the relationships, transport properties, PM associations, sources, or optimal ambient control.

Data on the performance of various methods for prevention and control of indoor air biocontamination, are scarce and fragmented. The understanding of the indoor ecology of biocontaminants and the effects of various prevention and mitigation measures are largely anecdotal. There is significant uncertainty about the soundness of the basic principles used by some of the control techniques. A lack of scientific data plus the lack of standard testing methods make it almost impossible to evaluate the effectiveness of various prevention, cleaning, and mitigation techniques sold in the marketplace.

IEMB's biocontaminant research goals for this cooperative research include development of testing methods and procedures to provide standardized tools and protocols for biocontaminant research and evaluation, studies of the relationship between environmental conditions, substrate properties, and biocontaminant growth and death. The data generated by this cooperative research are to be used as a basis for guidance, criteria, and development of control techniques, and development of effective engineering control methods for prevention and mitigation of indoor air biocontamination. Research objectives include 1) quantifying the relationship between outdoor and indoor levels of bioaerosols and 2) determining the fraction of ambient and indoor PM that is biological.

Research Objective
The overall objective of the proposed research is to contribute to a better understanding of the sources and causes of indoor air PM/biological contamination and to enhance the ability to prevent and control indoor air pollution by PM/biological contaminants. For example: 1) establish standardized test methods and procedures for evaluation and development of techniques and equipment for prevention and mitigation of indoor air PM/biological contamination; 2) evaluate factors controlling building penetration and distribution of PM/biological contamination; 3) identify sources and evaluate amplification factors of biological agents and antimicrobial treatments in the indoor environment to develop guidance for climate control, material selection, and cleaning and maintenance to minimize the possibility of indoor air biocontamination; and 4) evaluate the dynamics of emission and dissemination of PM, biological aerosols, and volatile compounds from indoor environmental reservoirs to develop strategies to reduce human exposure to indoor air contaminants.

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