Karin Foarde

An Analytical Method for the Measurement of Nonviable Bioaerosols

ABSTRACT Exposures from indoor environments are a major issue for evaluating total long-term personal exposures to the fine fraction (<2.5μm in aerodynamic diameter) of particulate matter (PM). It is widely accepted in the indoor air quality (IAQ) research community that biocontamination is one of the important indoor air pollutants. Major indoor air biocontaminants include mold, bacteria, dust mites, and other antigens. Once the biocontaminants or their metabolites become airborne, IAQ could be significantly deteriorated. The airborne biocontaminants or their metabolites can induce irritational, allergic, infectious, and chemical responses in exposed individuals. Biocontaminants, such as some mold spores or pollen grains, because of their size and mass, settle rapidly within the indoor environment. Over time they may become nonviable and fragmented by the process of desiccation. Desiccated nonviable fragments of organisms are common and can be toxic or allergenic, depending upon the specific organism or organism component. Once these smaller and lighter fragments of biological PM become suspended in air, they have a greater tendency to stay suspended. Although some bioaerosols have been identified, few have been quantitatively studied for their prevalence within the total indoor PM with time, or for their affinity to penetrate indoors. This paper describes a preliminary research effort to develop a methodology for the measurement of nonvi-able biologically based PM, analyzing for mold and ragweed antigens and endotoxins. The research objectives include the development of a set of analytical methods and the comparison of impactor media and sample size, and the quantification of the relationship between outdoor and indoor levels of bioaerosols. Indoor and outdoor air samples were passed through an Andersen nonviable cascade impactor in which particles from 0.2 to 9.0 um were collected and analyzed. The presence of mold, ragweed, and endotoxin was found in all eight size ranges. The presence of respirable particles of mold and pollen found in the fine particle size range from 0.2 to 5.25 um is evidence of fragmentation of larger source particles that are known allergens.

Microbial Volatile Organic Compound Emission Rates and Exposure Model

This paper presents the results from a study that examined microbial volatile organic compound (MVOC) emissions from six fungi and one bacterial species (Streptomyces spp.) commonly found in indoor environments. Data are presented on peak emission rates from inoculated agar plates loaded with surface growth, ranging from 33.5 µg·m–2 per 24 h (Cladosporium sphaerospermum) to 515 µg·m–2 per 24 h (Rhodotorula glutinis). Furthermore, changes in MVOC emission levels during the growth cycle of two of the micro-organisms are examined. This report also includes a calculation of the impact of MVOC emissions on indoor air quality in a typical house and an application of an exposure model used in a typical school environment.

The Measurement of Ambient Bioaerosol Exposure

Monitoring of ambient bioaerosol concentrations through the characterization of outdoor particulate matter (PM) has only been performed on a limited basis in North Carolina (NC) and was the goal of this research. Ambient samples of PM 2.5 (fine) and PM 10−2.5 (coarse) were collected for a six-month period and analyzed for mold, endotoxins and protein. PM 2.5 and PM 10−2.5 concentrations of these bioaerosols were reported as a function of PM mass, as well as volume of air sampled. The mass of PM 2.5 was almost twice that of the PM 10−2.5 ; however, the protein and endotoxin masses were greater in the coarse than the fine PM indicating an enrichment in the coarse PM. The protein and mold results demonstrated a seasonal pattern, both being higher in the summer than in the winter. Except for an occasional excursion, the endotoxin data remained fairly constant throughout the six months of the study.

Testing Antimicrobial Efficacy on Porous Materials

The efficacy of antimicrobial treatments to eliminate or control biological growth in the indoor environment can easily be tested on non-porous surfaces. However, the testing of antimicrobial efficacy on porous surfaces, such as those found in the indoor environment (i.e., gypsum board, heating, ventilating and air-conditioning duct-lin er insulation, and wood products) can be more compli cated and prone to incorrect conclusions regarding re sidual organisms and non-viable allergens. Research to control biological growth using three separate antimicro bial encapsulants on contaminated duct-liner insulation has been performed in both field and laboratory testing. The results indicate differences in antimicrobial efficacy for the period of testing.

Increased personal respirable endotoxin exposure with furry pets

on the basis of our current knowledge. Care must be taken when interpreting association results of single genes, and when interpreting association studies with a candidate gene, other genes in the genomic neighbourhood that are possibly in linkage disequilibrium with that gene should be considered, too. This task should become much more feasible once the haplotype pattern and linkage disequilibrium islands of the genome are known (6). This project was supported by grants from the Deutsche Forschungsgemeinschaft (DFG HE 3123/3-1 and HE 3123/ 4-2). The recruitment of asthmatic children was partially supported by a grant from the NIH (NIH R01 HL66533-01).

An Evaluation of the Antimicrobial Effects of Gas-Phase Ozone

This project evaluated the effects of exposing a variety of microorganisms on porous and non-porous materials to elevated gaseous ozone concentrations ranging from 100 – 1000 ppm. Gypsum wallboard (porous) and glass slide (non-porous) building materials were used. Two fungi organisms, two bacteria organisms and two levels of relative humidity (RH) were tested. Increased humidity and non-porous surface exposure were found to increase the biocidal capability of high levels of ozone. The results of this study indicate that even at relatively high concentrations of ozone, it is difficult to get significant reductions of microorganisms on surfaces, especially on porous materials.