H. Perez, N. Zimmerman, Purdue University, West Lafayette, IN.
While it is known that airborne fungi and their spores are associated with hay fever, asthma, and hypersensitivity pneumonitis, a universally accepted method to accurately detect and quantify this contamination is lacking. The purpose of this research was to develop a method of evaluating building HVAC filters for viable fungal contamination levels. This evaluation was performed through (1) the loading HVAC filters with known concentrations of fungal spores, (2) the extraction and quantification of these previously loaded fungal spores, and (3) the comparison of the estimated number of spores loaded with the estimated number of spores recovered. A ventilation test chamber consisting of a length of 2’ x 2’ square ducting was used to load the filters evaluated in this research. Filters were loaded with a fungal spore aerosol generated through the use of respiratory therapy nebulizers. The nebulizers were filled with an Aspergillus niger spore suspension. The concentration of viable spores in the suspension was determined through serial dilution. The quantification method used to determine the fungal load on the filters involved the removal of small samples from the filter, the immersion of these samples in sterile saline, the shaking of the filter/saline combinations, and the subsequent plating of aliquots of the shaking solution onto potato dextrose agar.
The results of this research indicate that the generation of fungal spore aerosols of known concentrations through the use of respiratory therapy nebulizers may become a very useful method in bioaerosol research. The results also indicate that viable fungal particle recovery and quantification from HVAC filters is possible and may become a useful method for the evaluation and comparison of building areas served by separate HVAC systems. This method may also be a useful tool for the evaluation of a single building or building area before and after remediation efforts.
D. Kahane, Forensic Analytical, Hayward, CA.
Industrial hygienists are routinely called upon to make recommendations regarding mold investigations. These decisions are based on a combination of quantitative and qualitative data about the environment including sampling results, visual observations, and occupant/building history. Often times, sampling or budget constraints limit the hypothesis testing approach to data assessment, and the amount of quantitative airborne data that can be gathered on suspect environments. The use of quantitative real-time PCR (QPCR) may greatly increase the hypothesis testing approach for airborne data by lifting many of the constraints of the present sampling schemes in use, as well as for its notable benefits of rapid speciation and instrumental traceability.
For airborne interpretations to be useful, data regarding airborne sample repeatability using QPCR-based sampling and analysis should be known. Specifically, spore-equivalent loading on air sample media may play a large role in sample repeatability, and may dictate target loading and thus sampling times industrial hygienists should consider.
A previously reported study (AIHce 2003) discussed general qualitative/quantitative conclusions from a field study involving a comparison of molecular methods and commonly used optical methods. The initial study suggests that comparisons between airborne sampling methods are unlikely to correlate with one another, and are better used independently of one another in IH investigations. To better address the nature of precision between paired QPCR data suggested by the first study, a second study involving both field and laboratory generated samples was performed. Data from this analysis will be presented describing spore-equivalent loading issues and recommended sampling times to achieve appropriate limits of quantification and detection for airborne samples. Further, the research study suggests that for QPCR to be useful in airborne data evaluations, the industrial hygienist must factor in the sampling and analysis variability QPCR needs from the variability associated with the environments under investigation.
C. Feigley, A. Fox, W. Harley, D. Salzberg, University of South Carolina, Columbia, SC; A. Sebastian, L. Larsson, University of Lund, Lund, Sweden.
Muramic acid (Mur) is found in bacterial peptidoglycan (PG), whereas 3-hydroxy fatty acids (3-OH FAs) are found in Gram-negative bacterial lippopolysaccharide (LPS). Thus Mur and 3-OH FAs can serve as markers to assess bacterial levels in indoor air. A previous study from a single school found that dust, PG, and LPS (pmol/m3) were each much higher in occupied rooms than in the same rooms when unoccupied, suggesting that the higher levels resulted from the presence of children. Similar findings from two additional schools suggest that this finding is widespread. The concentrations of both Mur and LPS in dust (pmol/mg) were also shown to be higher in occupied rooms in schools 2 and 3; however, the increase in LPS was less dramatic than that of Mur. The results indicate that the concentration of Gram-positive bacteria increases with occupancy, but the Gram-negative bacteria remains fairly constant. Examination of four individual 3-OH FAs showed that the C12:0 and C14:0 3-OH FAs were consistently higher for occupied classrooms versus unoccupied classrooms, and C10:0 and C16:0 3-OH FAs were consistently lower for occupied classrooms. This suggests a shift in the Gram-negative species present. The results show that airborne dust found in occupied and unoccupied rooms is quite distinct in bacterial content. Also, the airborne particle size distributions in occupied rooms differed markedly from those in unoccupied rooms; occupied rooms had many more large dust particles (>1 to 20 µm in diameter) and unoccupied rooms had more small dust particles (0.3–0.5 µm). Thus, it appears that airborne dust in unoccupied rooms is of environmental origin, whereas children are the primary source in occupied rooms.
J. Bird, IHI Environmental, Salt Lake City, UT; F. DeRosso, Rocky Mountain Environmental Consultants, Salt Lake City, UT; D. Lillquist, G. White, S. Alder, University of Utah, Salt Lake City, UT.
Mycotoxins are non-volatile, relatively low molecular weight, secondary metabolic products of fungi. They have been shown to have adverse health effects when inhaled or ingested by humans. Identifying and quantifying airborne levels of mycotoxins in water-damaged/mold-contaminated buildings is the critical first step in identifying the potential health hazards these chemical compounds pose to building occupants and mold remediation workers. Inexpensive, accurate, and reproducible field measurement and/or biomarker techniques must be developed to advance the evaluation of fungal toxins in occupational settings. This research compared the capabilities of two different air sampling media used in mycotoxin collection. A preliminary study compared the recovery and stability of a specific mycotoxin, Ochratoxin A, on three types of filter materials (glass fiber, polycarbonate, and polyvinyl chloride). In this follow-up study, an aerosol generator was used to create a uniform concentration of particulate contaminated with Ochratoxin A inside an exposure chamber. Air samples were collected simultaneously with polyvinyl chloride and polycarbonate filters. The data from the exposure chamber sampling indicated that the collection and recovery of the Ochratoxin A from the polycarbonate and polyvinyl chloride filters was not statistically different. Therefore, it appears either polycarbonate or polyvinyl chloride filters may be applicable for airborne sampling of Ochratoxin A.
T. Brasel, J. Martin, M. Larranaga, S. Wilson, D. Straus, Texas Tech University, Lubbock, TX.
The presence of fungi in indoor environments and the role they play in adverse human health effects is an expanding field of research. Specifically, Stachybotrys chartarum has become a main focus of indoor air quality (IAQ) investigations. S. chartarum is a known producer of simple and macrocyclic trichothecene mycotoxins. These compounds actively inhibit protein synthesis and are highly toxic in vitro and in several animal models. Currently, no data exist that effectively demonstrate the presence of airborne mycotoxins in the indoor environment, thereby weakening an elucidation of the relationship between these mycotoxins and human health effects. A major reason for this is that currently accepted techniques for IAQ investigations (viable and non-viable impactors, filtration, liquid impingers, etc.) are relatively slow and do not allow for efficient collection of high volumes of air for identification and quantification of mycotoxins. In addition, at any given time in a native mold-contaminated environment, the concentration of airborne mycotoxins is expected to be low. Therefore, a sensitive and specific means of sample testing is required. Through the use of a novel high volume liquid impaction bioaerosol sampler (SpinCon PAS 450-10) and a sensitive enzyme-linked immunosorbent assay (ELISA) specific for macrocyclic trichothecenes, we were able to demonstrate the presence of airborne trichothecenes in one controlled and six native S. chartarum-contaminated environments over a sampling time as short as 10 minutes. Based on standards, estimated toxin concentrations ranged from 0.45 ng/m3 to over 1.0 ng/m3 of sampled air. Six environments considered negative (no obvious S. chartarum growth) were tested similarly and demonstrated significantly lower levels of trichothecene mycotoxins that could be attributed to non-specific ELISA reactivity. Our data suggest that airborne macrocyclic trichothecenes from S. chartarum exist in contaminated indoor environments and future IAQ investigations should incorporate a means to collect and identify these potential occupant health threats.
B. Kollmeyer, S. Yaussy-Chua, Forensic Analytical, Rancho Dominguez, CA; D. Kahane, D. Cox, Forensic Analytical, Hayward, CA.
Situation: This case study involves fungal remediation of 2600 rooms in a large hotel where post-remediation assessment was to be completed within a stringent timetable and in consideration of budget constraints.
Problem: Spore trap sampling is the most commonly used method when making rapid decisions in a post-remediation setting; however, this method still introduces significant time delays and costs. It has been suggested that direct-reading particle counters can be used in lieu of fungal spore sampling or as a screening tool prior to spore sampling in order to expedite the clearance process and reduce sampling and analysis costs. Unfortunately, industrial hygienists are faced with a paucity of data that considers the relationship between particulate concentrations and fungal spore concentrations in a post-remediation setting. The fundamental questions are (1) whether or not particle counts are predictive of spore concentrations, and (2) what particle counts represent reliable clearance or screening criteria.
Resolution: In this case study, particle count and fungal spore data were collected simultaneously following remediation efforts in each of the 2600 rooms. Airborne particulate data was collected using a six-channel optical particle counter and airborne spores were collected using a spore trap cassette. Data was then analyzed to characterize the correlation between particulate counts and spore concentrations and to develop particle count-based decision criteria.
Benefit: The data and lessons learned from this case study will help hygienists to better understand the relationship between particle concentrations and spore concentrations in post-remediation settings. As the dynamics of this relationship are better characterized, hygienists will be better equipped to make sound decisions in a shorter time frame and at reduced cost.
Posted May 30, 2004