J. Hicks, P. Rey, Exponent Inc., Oakland, CA; H. Granger, HP Environmental, Santa Fe, NM.
Frequently, the most practical and efficient method for repairing mold-impacted gypsum wallboard is removal and replacement. However, from time to time, circumstances are encountered where removal and replacement of drywall is not physically or economically feasible. In these cases, an alternative method for repair is necessary. This presentation describes one such case. During construction of a large public building, installed drywall suffered water damage that produced visible mold growth. Physical constraints resulted in projection of exorbitant costs for removal and replacement of the damaged drywall, thus compelling formulation and consideration of alternative methods. The method selected for repair was surface cleaning followed by treatment and encapsulation. The efficacy of this repair was initially verified by laboratory and field studies. Procedures were subsequently specified and the repair was performed on 1000 ft/2 of damaged drywall. On completion, the repaired drywall was visually examined, and various surface and air samples were collected to demonstrate the effectiveness of this repair and the quality of the final indoor environmental condition.
J. Krause, Indoor Air Solutions, Tallahassee, FL; Y. Hammad, University of South Florida, Tampa, FL.
This research examined the effects of fungal growth on a commonly used fiber glass ductboard insulation that was treated with antimony trioxide flame retardant. We demonstrated that growth of Aspergillus versicolor reduced antimony trioxide levels by 25% to 43% at varying rates over the course of 1 to 29 weeks. Fungal degradation of building materials that contain antimony trioxide has been demonstrated to greatly increase the rate of its release. In the indoor environment, mobilization and accumulation of antimony in building dust could result in occupant exposures and adverse health effects. Poor maintenance of heating, ventilation, and air conditioning (HVAC) systems or episodic water damage can lead to severe fungal growth on fiber glass ductboard used in HVAC systems. Mold growth on fiber glass ductboard has been documented in numerous studies. Certain brands of fiber glass ductboard are treated with the flame retardant antimony trioxide (CAS 1309-64-4; Sb2O3). The toxic and carcinogenic properties of antimony trioxide have been well documented and are recognized by the Environmental Protection Agency, Consumer Product Safety Commission, U.S. Geological Survey, and International Agency for Research on Cancer. However, the extensive use of antimony trioxide as a flame retardant on consumer products, textiles, and building materials has been allowed because of its presumed immobility and presumed low risk of human exposure. A handful of laboratory studies have previously demonstrated that antimony can be released from substrates containing Sb2O3 via biomethylation, a process demonstrated by many bacteria and fungi. Researchers have consistently raised concerns that hazardous exposures to antimony compounds could result from microbial degradation of flame retardant-treated materials in indoor environments.
T. Pearce, C. Calvert, C. Coffey, NIOSH, Morgantown, WV; N. Williams, Savannah State University, Savannah, GA; J. Ham, J. Wells, NIOSH, Morgantown, WV.
Measuring mold-produced volatile organic compounds (mVOCs) in indoor air is sometimes used as an indicator of hidden mold in buildings. However, there is limited evidence that mVOCs reach detectable levels in such buildings. This laboratory-based project assessed the growth of Aspergillus versicolor and Stachybotrys chartarum and mVOC levels produced by them after inoculation on 1 s.f. sections of potato dextrose agar and wetted gypsum board. Blank (control) and mold-inoculated substrates were sealed within 10-L teflon bags for incubation at 21ºC and 100% relative humidity. Headspace air samples for total volatiles and mVOCs were collected in 6-L evacuated canisters on days 0, 4, 7, 10, 14, 17, and 21, and directly introduced to a gas chromatograph-mass spectrometer. Each mold covered approximately 90% of the agar surface (day 4) and 10% of the gypsum board (day 21). Volatile compounds were detected in air samples from above blank and mold-inoculated substrates, and they were higher in samples from above agar than from above gypsum board. A. versicolor on agar produced mVOCs that comprised approximately 10% of total volatiles; mVOCs types and amounts varied across sampling days with 1,3-octadiene and 2-methyl furan present at detectable levels on all days. A. versicolor mVOC production on gypsum board was highest on day 14, with mVOCs comprising approximately 10% of the total volatiles. No difference in total volatile concentration across sampling days was found between air samples from above blank and S. chartarum-inoculated agar or from above blank and S. chartarum-inoculated gypsum board; no mVOCs were identified. Direct measurement allowed quantification of mVOCs produced by A. versicolor but not by S. chartarum. The study demonstrated that agar and wetted gypsum board without mold releases volatile compounds. Recommendations were formulated for improvements in mVOC measurement methodology.
L. Lee, M. Berkheiser, University of Texas, Houston, TX.
Nosocomial invasive aspergillosis is an increasing problem for immunocompromised patients. This study evaluated the association between Aspergillus species, which can be transmitted via air and water, and housekeeping practices, airflow direction, and seasonality. Between April and October 2004, 2897 air, water, surface, and spore trap samples were collected in 209 cleaned and uncleaned patient rooms on two floors of a large cancer center hospital. Rooms were sampled prior to (uncleaned) and following (cleaned) a terminal cleaning. Of the 627 bioaerosol samples analyzed, 88 were collected outdoors while the rest were from 72 patient rooms. Analyzed surface samples (1258) were from 73 patient room sink and shower drains, showerheads, and air grilles. According to univariate analyses, there was no evidence that environmental contamination with Aspergillus species in patient rooms was associated with room-cleaning status (p = 0.55), airflow direction (p = 0.55), or the floor on which the room was located (p = 0.50). The outdoor Aspergillus secies contamination rate was much higher (60.2%) than indoor samples (7.3%, p < 0.0001). The univariate analyses showed the Aspergillus rate was 6.1% in cleaned rooms compared with 8.6% in uncleaned rooms (p = 0.058). Contamination rates in room (11%) and shower areas (9.1%) were much higher than in toilet areas (1.9%, p = 0.0002). Forty-six samples from 26 patient rooms revealed Aspergillus species. Among the rooms contaminated, uncleaned rooms were found to have lower Aspergillus density than cleaned rooms (GM ratio = 0.33, 95% confidence interval [CI]: 0.16-0.69, p = 0.0057). Sample location is significantly related to Aspergillus density found in bioaersol samples. Patients are more likely to encounter Aspergillus in outdoor air than inside properly controlled hospital environments. However, infection control practices should be in place inside patient rooms and surrounding areas to reduce physical transport of mold spores.
J. Millar, B. Shelton, PathCon Laboratories, Norcross, GA.
Mycobacteria-contaminated cutting fluids are a documented cause of occupational hypersensitivity pneumonitis (“machinist’s lung”). More recently, mycobacteria in the waters of hot tubs have been shown to cause hypersensitivity pneumonitis, greatly expanding the potential environmental sources of disease from mycobacteria. Because their discipline is expert in the assessment of exposure and environmental intervention, industrial hygienists (IHs) have a critical role to play in prevention and control of all diseases caused by environmentally transmitted microbial agents, including mycobacteria. Speed plays a crucial role in the initiation of preventive interventions. Fortunately, the availability of newer laboratory technologies, which can produce a quantitatively accurate preliminary result in less than a day, promises a new era of effective responsiveness in prevention. While such technologies have limitations with regard to microbial agents, including the lack of differentiation between living and dead organisms, the rapid availability of a quantitative result in conjunction with culture is a major asset to prevention. IHs should be armed with a general idea of both the utility of these technologies in preventing mycobacterial diseases and how to appropriate them.
H. Burge, Environmental Microbiology Laboratory Inc., San Bruno, CA; I. Botvinnik, Sharper Image Design, Novato, CA.
Room air cleaners are used to remove airborne contaminants, including viruses. The most effective of these are often cumbersome and noisy. We have tested a new electrostatic precipitator produced by the Sharper Image (Hybrid), which accelerates air using nearly soundless fans and which charges, captures, and/or kills microorganisms on charged plates. We aerosolized phage specific for Escherichia coli in our room-sized chamber, and sampled onto agar plates preseeded with a lawn of E. coli. We collected samples at 5-min intervals for 20 min with the Hybrid on high during half the trials, and off during the other half. We calculated the clean air delivery rate (CADR) and the power usage. Phage levels fell from an average of 1000 to 100 within 7 min and were near zero at 15 min. Slopes of lognormal decay curves with no cleaner operating were 7.0 (range 6.4-7.2, n=5). With the air cleaner, slopes were 17.4 (15.8-18.7, n=5). These slopes approximate the air exchange rate (ACH) in the room as indicated by bacteriophage decay. Background ACH was 7.0 (0.5 from the ventilation system, and 6.5 from natural death of the virus). With the air cleaner on, the ACH was 17.4 (7 from background), resulting in a net increase in the ACH of 10.4. The CADR was 175 for dust; the input power 11 W. This Hybrid electrostatic air cleaner collected viral particles efficiently and effectively. It produced 175 CADR/W on the high setting and 20 CADR/W on the low setting, compared with 3.3 CADR/W for the best of the competitors. The unit is quiet enough for continuous operation and should provide a useful alternative to noisier and more power-hungry air cleaners.
S. Cho, G. Ramachandran, A. Ryan, L. Aberly, J. Adgate, University of Minnesota, Minneapolis, MN; J. Grengs, Pace Analytical Services Inc., Minneapolis, MN.
To characterize within-home and between-home variance components of allergen concentrations and to examine seasonal variation as well as residential characteristics associated with the concentrations of indoor allergens (dust mites, cat, cockroach, and fungi), we measured the concentrations of indoor allergens six times over a one-year period in the floor dust of 47 inner-city households in Minneapolis, Minn. A longitudinal analysis of allergen concentrations was carried out using mixed-effect models. Dust mite allergens (Der f 1 and Der p 1) showed significant seasonal variation; however, seasonal variability had a smaller effect on dust mite concentrations than the variability associated with housing type, with houses having higher dust mite levels than apartments. Seasonal variation of cat (Fel d 1) and cockroach (Bla g 1) allergens was negligible compared to variability due to residential characteristics such as race/ethnicity, family income, and the presence of cats. Fungal concentrations showed seasonal variation that outweighed the variability associated with residential characteristics. Cockroach allergen concentrations were higher in Spanish- and Somali-speaking households than in English-speaking households, while English-speaking households had higher cat allergen concentrations compared to the other language groups. The ratios of within-home to between-home variance for fungal, dust mite, cockroach, and cat allergen concentrations were 2.54 1.91, 0.55, and 0.24, respectively. Consequently, the within-home correlations over time for fungal, dust mite, cockroach, and cat allergen concentration were 0.28, 0.34, 0.64, and 0.81, respectively. We conclude that a single measurement of cat and cockroach allergens is a reasonable surrogate for annual average exposure since repeated measurements over time were highly correlated. In contrast, dust mites and fungal allergens will require repeated measurements for rigorous assessment of annual exposure. Repeated measurements of fungal and dust mite allergens will be needed to characterize room-to-room or within-home variability because of low correlations in fungal measures.
R. Morse, Morse Zehnter Associates, Troy, NY; P. Haas, D. Zehnter, Morse Zehnter Associates, West Palm Beach, FL.
It is not surprising that the airborne spore levels were extremely high in the New Orleans area after buildings and vegetation were moisture saturated during the 2005 hurricanes. This study presents a longitudinal study of airborne spore levels experienced for several months after the hurricane as measured by Air-O-Cell samples. It was found that mold spore levels varied with weather and the activities of reconstruction. Clearance sample data from remediated building areas will be presented. Spore counts in these clearance samples were generally much lower than outdoor levels. This indicates that the work area isolation and remediation measures were successful in creating a clean microenvironment despite a high overall level of contamination within the hurricane stricken area. The nature of the remediation practices used will be described.
R. Morse, Morse Zehnter Associates, Troy, NY; P. Haas, D. Zehnter, Morse Zehnter Associates, West Palm Beach, FL.
In 2005, Hurricane Katrina drove moisture into buildings in New Orleans, causing extensive water and mold damage to many structures. The problems obviously continue to this day and will continue into the foreseeable future, with a tremendous impact on the industrial hygiene community. Some types of construction resisted becoming wet, or they dried out before mold could grow. Hurricanes provide an acid test of the ability of different types of construction to avoid moisture intrusion and mold damage. This session will look at several structures in New Orleans that were impacted by Hurricane Katrina. In some instances these buildings did not develop mold problems; in other cases, extensive mold contamination followed the wetting. The sensitivity of different construction types will be described.