Browsing by Subject "Indoor air"
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Item The bacterial and fungal microbiome of retail stores(2013-05) Hoisington, Andrew James; Kinney, Kerry A.; Siegel, Jeffrey A.Microorganisms found in the indoor environment of retail stores are not well studied, despite potentially serious human exposure implications. In this study, filters from central heating, ventilation, and air-conditioning (HVAC) units were used to collect a time-integrated sample of the airborne indoor microbiome in 14 U.S. retail stores. The microbial communities recovered from the filter dust samples were analyzed with pyrosequencing to characterize the fungal and bacterial microbiome present. The objectives of this work were to: (1) characterize the microbial communities present in retail stores, (2) delineate relationships between the indoor microbiome and building or environmental parameters, and (3) evaluate the use of HVAC filter dust as a sample location for indoor microbial investigations. The microbiome in retail stores was observed to be diverse with 4,771 and 1,577 unique operational taxonomic units for bacteria and fungi, respectively. The diverse microbial community detected over time in the same store could not be fully explained by seasonal trends. That indicates that even when utilizing a long-term sampling approach like HVAC filter samples, the indoor microbiome cannot be completely characterized by a single sampling event. The bacterial community in retail stores was influenced by the outdoor microbiome and microbiota commonly associated with human skin. Physical location of the retail stores had some influence on the bacterial microbial community present and strongly impacted the fungal community recovered. Air exchange rate did not influence the observed bacterial or fungal communities. In a comparison to five other indoor air samplers, passive samplers including HVAC filter dust and settled dust captured a higher diversity of the microbial community. The collection of a more diverse sample may allow detection of potentially pathogenic microorganisms. However, there was significant difference in the microbial community structures recovered between samplers in the same sampling event which suggests sampling methodology has an impact on the inferred microbiome recovered. The overall results from this study indicate that retail stores harbor a diverse microbial community that varies over time.Item Inhalation exposures during cleaning activities(2013-05) Earnest, Clive Matthew, Jr.; Corsi, Richard L.Studies show that the use of cleaning products is related to adverse respiratory health effects ranging from irritation to asthma. Yet exposure to these chemicals is poorly understood. This dissertation summarizes the current state of knowledge of inhalation exposure to toxic chemicals in consumer cleaning products. An improved two-zone model that treats personal air space as distinct from bulk room air is presented. The model accounts for air exchange between the two zones, dynamic source characteristics (i.e., the time-varying liquid concentrations and emission rates of pollutants within a mixture), and the characteristics of chemical use (e.g., how frequently a cleaning chemical is applied to a new area). To assess exposure to cleaning products and validate the improved two-zone model twenty-three experiments, encompassing six cleaning scenarios, were completed in an environmentally-controlled chamber with a thermal mannequin. Then, the model was used to predict exposure for four hypothetical cleaning scenarios and compared against other models. The model's applicability is restricted by limited data available for parameterization. At low air exchange rates gas-phase experimental results show concentrations in the breathing-zone of the mannequin exceeded concentrations predicted by the well-mixed model by factors up to 2.1. Breathing-zone concentrations also exceed those measured at centralized room monitors by factors up to 6.1. Thus, studies that use the centralized room monitors or the well-mixed model as a surrogate for breathing-zone concentrations could potentially underpredict exposure at low air exchange rates. The two-zone model provides the best prediction of exposure to cleaning tasks, at low air exchange rates. The next best model is the well-mixed model with an exponentially decreasing emission rate, followed by the well-mixed model with a constant emission rate. At high air exchange rates the well-mixed assumption appears to be valid. The inner-zonal volume and inter-zonal air exchange were independent of fresh air ventilation rate. But both were dependant on the mannequin's body position, with standing having the highest inner-zonal volume and lowest intra-zonal air exchange rate of the three body positions investigates (standing, bent over 45°, and hands and knees).Item Phthalates and polybrominated diphenyl ethers in retail stores(2012-12) Urquidi, Jorge Rodolfo; Xu, Ying (Assistant professor); Siegel, JeffreyRetail stores are an environment with a rich diversity of toxic chemicals typically found in consumer products. Among these chemicals, semi-volatile organic compounds (SVOCs) are an important class with great health concerns. Phthalates and polybrominated diphenyl ethers (PBDEs) are high production volume SVOC chemicals pervasively used in plastics and other consumer products. Exposure to them may cause serious adverse health effects, including endocrine disruption. They, however, have not been widely studied in retail environments. In this study, indoor air samples were collected from 15 retail stores in Austin, TX and University Park, PA. Some of these stores were revisited on different temperate seasons to account for weather variability. Indoor concentrations of the most ubiquitous pollutants were correlated with several building characteristics, including retailer type, temperature, and building use characteristics. Collected data shows a wider variety of phthalates and PBDEs, as well as higher indoor airborne concentrations for large department stores as compared to grocery stores, which typically have fewer sources in comparison.Item Removal of formaldehyde from indoor air : enhancing surface-mediated reactions on activated carbon(2013-08) Carter, Ellison Milne; Katz, Lynn E.; Speitel, Gerald E.Formaldehyde is a ubiquitous and hazardous indoor air pollutant and reducing concentrations in indoor environments is a public health priority. The goals of this doctoral work were to advance analytical methods for continuous monitoring of formaldehyde at very low concentrations (sub-20 ppb[subscript v]) and to improve fundamental, mechanistic understanding of how structural and chemical properties of activated carbon influence removal of formaldehyde from indoor environments. To achieve these goals, emerging sensor-based technology was evaluated for its ability to detect and quantify ppb[subscript v]-level formaldehyde concentrations on a continuous basis at relative humidity levels characteristic of residential indoor environments. Also, a combination of spectroscopic and selective titration techniques was employed to characterize molecular-level structural and chemical properties of traditional and chemically treated granular activated carbon (GAC). In addition to selecting two different commercially available GACs for study, design and preparation of a laboratory-prepared, chemically treated GAC was pursued to create nitrogen-doped GAC with desirable surface chemical properties. Performance of all GACs was evaluated with respect to formaldehyde removal through a series of packed bed column studies. With respect to continuous formaldehyde monitoring, a method detection limit for emerging sensor technology was determined to be approximately 2 ppb[subscript v], and for relative humidity levels characteristic of indoor environments (> 40%), quantitative, continuous formaldehyde measurements less than 10 ppb[subscript v] were robust. The two commercially available GACs tested were both capable of removing formaldehyde; however, the GAC with greater density of basic surface functional groups and greater electron-donating potential (Centaur) removed twice as much formaldehyde (on a GAC mass basis) as the less basic GAC (BPL). A laboratory-prepared GAC (BPL-N) was successfully created to contain pyridinic and pyrrolic nitrogen, which was associated with increased surface density of basic functional groups, as well as with increased electron-donating potential. BPL-N exhibited better removal capacity for formaldehyde than BPL and Centaur. Furthermore, packed bed column studies of BPL-N and BPL formaldehyde removal performance yielded evidence to support the hypothesis that electron-donating potential, especially nitrogen functional groups at the BPL-N surface, promote catalytic removal of gas-phase formaldehyde via oxidation.