G. Crawford, M. Cornwell, P. Morey, R. Rottersman, Boelter & Yates, Inc., Park Ridge, IL.
Many industrial hygienists have become proficient at anticipating, recognizing, and evaluating mold growth. Many have also become proficient in identifying sources of liquid water (leaks) in buildings. However, moisture problems often develop from water vapor and not from leaks. Tracking and diagnosing mold growth problems associated with water vapor migration is often difficult. An understanding of vapor drive and interactions with building materials is critical to the problem solving process. Case histories are presented to demonstrate how vapor drive can cause the growth of both xerotolerant and hydrophilic molds in buildings. Case studies show mold growth on the base of interior walls, in wall cavities, behind wallpaper and on subfloors. Construc-tion of the various exterior walls consisted of veneer brick over concrete masonry block (CMU), all brick or CMU alone. Review of the construction details in these case studies indicated that water vapor management provisions were either omitted or misplaced in these masonry walls. Rain will absorb into brick and CMU. The sun/heat causes the liquid water to form water vapor which migrates into the more porous block and/or interior wall cavity. During the cooling season the indoor to outdoor temperature gradient drives the moisture vapor inwards where it may condense or cause dampness, especially if water vapor impermeable materials are placed on the interior side of the wall or on the inner surface of interior walls. The team of an industrial hygienists and forensic architects identified the sources of moisture vapor and recommended effective remedial control measures. Failure to understand vapor drive and how it interacts with building components can result in wasted time searching for water leaks and recurrence of mold growth after remediation efforts.
T. Lee, S. Grinshpun, D. Martuzevicius, A. Adhikari, C. Crawford, T. Reponen, University of Cincinnati, Cincinnati, OH.
This investigation determined the viability of indoor and outdoor airborne fungi through 24-hour sampling. The inhalable fraction of fungal particles was collected with a Button Personal Inhalable Aerosol Sampler. The measurements were conducted during three seasons (spring, fall, and winter) in six Cincinnati area homes that were free from moisture damage or visible mold. Samples were analyzed by cultivation (culturable count) and microscopic counting (total count). The geometric mean concentration of indoor and outdoor culturable fungi were 88 and 102 CFU m-3, respectively, with a geometric mean of the indoor to outdoor (I/O) ratio equal to 0.66. Overall, 26 genera of airborne culturable fungi were recovered on MEA from the indoor and outdoor samples. For total fungal spores, the indoor and outdoor geometric means were 211 and 605 spores m-3, respectively, with a geometric mean of I/O ratio equal to 0.32. The total fungal spore analysis revealed 37 fungal genera/groups from indoor and outdoor samples. Indoor and outdoor concentrations of fungal spores showed significant correlations both for culturable count (r=0.655, p<0.0001) and total count (r=0.633, p<0.0001). The indoor and outdoor median viabilities of fungi were 55% and 25%, respectively, which indicates that indoor environment provides more favorable survival conditions for airborne fungi than outdoor air. Fall season showed the highest indoor and outdoor viability of fungi among the three seasons. Among predominant genera/groups of fungi Cladosporium had the highest median value of viability (38% and 33% for indoor and outdoor, respectively) followed by Penicillium/Aspergillus (9% and 2%). Increased viability of fungi inside the homes may have important consequences because of the potential increase in the release of allergens from viable spores and pathogenicity of viable fungi on individuals who have impaired or weakened immune system.
R. Rottersman, G. Crawford, Boelter & Yates, Inc., Park Ridge, IL; J. Shane, Environmental Microbiology Laboratories, Inc., Naperville, IL.
Carpet is often an accumulation site for mold amplification or contamination that may not be visually apparent. There are currently no standardized protocols for sample collection or analysis of mold levels in carpet. Two suggested methods for sample collection include dust extraction and tape lift samples. Analysis often consists of direct observation using optical microscopy, culture using dilution, and culture using direct plating. Does the method of analysis provide consistent or inconsistent conclusions when evaluating mold in carpets? Carpet sampling consisted of dust extract and tape lift from both heavy foot traffic and low foot traffic areas in: residential carpet, no history of water damage; office carpet, no history of water damage; and water-damaged residential carpet.
Bulk dust samples were submitted to an EMLAP-accredited laboratory for analysis using optical microscopy, dilution culture, and direct plating culture procedures. The tape lift sample was analyzed using microscopy. Results were reviewed by experts to determine whether or not similar conclusions would have been formed for each location based on method of analysis. Similar conclusions were found for dust samples regardless of whether or not they were analyzed using culture or direct microscopy. Penicillium was dominant in the samples from water damaged carpet and levels were relatively high. The residential carpet with no water damage had moderate fungal levels but a wide variety of genera were present indicating contamination but not amplification. Very low levels of mold were found in the office carpet. Findings were consistent regardless of foot traffic patterns. Surface lift samples did not identify mold in any of the samples. Findings from this method were not consistent with conclusions formed from dust samples. This was likely due to the methods inefficiency at extracting material entrained in the pile.
P. Morey, G. Crawford, Boelter & Yates, Inc., Park Ridge, IL; B. Prezant, Prezant Associates, Seattle, WA; R. Shaughnessy, University of Tulsa, Tulsa, OK.
Clearance air and surface microbial testing is often used to document that mold remediation has been effectively carried out. Historically, clearance air sampling for culturable or nonculturable molds was used along with physical inspection of the remediated area to document that the indoor environment was returned to a “normal condition” after mold remediation. Judging whether or not the indoor air or building surface is characterized by “normal condition” is difficult for even the most experienced investigators. In recent years, air and surface microbial sampling, in the opinion of the authors, has been overemphasized at the expense of other quality assurance documentation procedures for mold remediation. In 1992, the National Air Duct Cleaners Association published a guideline for objectively measuring the effectiveness of duct cleaning, namely, a limit for residual dust of 100 mg/m2 for nonporous surfaces. The 2001 AIHA Report of Microbial Growth Task Force document and the 2004 Health Canada–Fungal Contamination in Public Buildings Guide both comment that a 100 mg/m2 residual dust level can be reasonably achieved. We have found that the amount of residual dust on nonporous surfaces after mold remediation can be reduced to levels far below 100 mg/m2 (often <25 mg/m2) following mold remediation. Levels of residual dust <100 mg/m2 can be achieved for some porous surfaces. Measurement of residual dust on surfaces following mold remediation can be used as a quality assurance documentation procedure replacing microbial testing in some buildings. This paper will discuss the sampling methodology and practical experiences with its application.
S. Kim, J. Farnsworth, S. Goyal, P. Raynor, T. Kuehn, University of Minnesota, Minneapolis, MN.
A new bioaerosol sampling and monitoring method has been developed in which the filters in a building air handling unit (AHU) are used as high volume samplers. The method has been applied to estimate the background concentration of culturable bacteria aerosols in buildings. Method development included laboratory tests in which Bacillus subtilis, Mannheimia haemolytica, and Yersinia ruckeri, surrogates for human pathogens, were loaded onto test filter media by first spiking with suspensions of known concentration and later by loading media samples with bioaerosol in a small test facility. The microorganism recovery rate was measured for various filter media, eluents, and agitating methods. Two filter media were tested with anticipated bioaerosol collection efficiencies of 91.7% and 99.6%. Phosphate buffered saline (PBS) and 0.02% Tween 80 solutions were chosen as eluents for vegetative cells and Bacillus subtilis, respectively. Handshaking was determined to be the best agitation method. The bacteria recovery rates ranged from 31% to 109%. However, culturable vegetative bacteria were not recovered. The half-lives of Bacillus subtilis for the spiking and the nebulization tests were 8±1 day and 8±2 days, respectively. New full-size 2 ft x 2 ft HVAC filters were then challenged with Bacillus subtilis aerosols to simulate filter loading in building AHUs. The measured collection efficiency ranged from 95.1% to 96.7% and the recovery rates of culturable bacteria from the filters were 86.7% and 98.6%. Used HVAC filters were pulled from four AHUs serving a large building on two separate occasions. Bacteria were eluted from samples cut from the filter media and subsequently speciated using the MicroLog Microstation. The total average upstream culturable bacteria concentrations were computed to be 10 CFU/m3 indoors and 22 CFU/m3 outdoors without consideration of temporal losses of culturability. A total of 47 species were identified by this method.
D. Regelbrugge, F. Holcomb, J. Ruhl, G. Crawford, Boelter & Yates, Park Ridge, IL.
Floods and/or sewer system malfunctions can cause contaminated water or sewage to come into direct contact with building materials, personal belongings and equipment. Flood waters or sewage can contain a variety of pathogenic organisms, such as salmonella, tetanus, E.coli, hepatitis, etc. The Institute of Inspection Cleaning and Restoration Certification Standard and Reference Guide for Professional Water Damage Restoration (S-500) as well as other available guidelines call for most porous materials that had direct contact with flood waters or sewage (i.e., gray or black water) to be removed and disposed of as waste. What is less clear is what to do about adjacent porous building materials or personal belongings that may not have had direct contact with grey or black water and need to be cleaned. Floods and/or sewage system malfunctions also produce a need to decontaminate nonporous surfaces or fixtures that came into direct contact with the contaminated water. The industrial hygienist’s role in these projects is often to determine whether adjacent materials and belongings that have had direct or indirect contact with gray or black water have been successfully cleaned. A number of analytical procedures are available to assist in this effort including bacterial culture, coliform, and E.coli serotypes analysis. This presentation will describe the industrial hygienist’s role on at least two flood/sewage remediation projects from project planning through final testing. The presentation will discuss the difficulties encountered when using Gram negative bacterial culture and coliform analysis due to their prevalence in the environment and how E.coli absence/presence testing proved to be a better indicator of contamination. An overview of the significance of timely sample collection will also be addressed.
Posted May 30, 2006