Matching Items (2)
Description
In recent years, products advertised to contain nanosilver have become increasingly popular; however, while companies often advertise for nanosilver products, little regulation occurs to verify that these products actually contain silver nanoparticles. Furthermore, there currently exists much dispute regarding the safety and toxicity of silver nanoparticles. As more and more products incorporate nanosilver, the resolution of this dispute proves progressively important. The present study addressed these issues, with goals to synthesize silver nanoparticles, determine the solubility of the synthesized silver nanoparticles, and to evaluate leaching of nanosilver from commercially produced food storage containers. The silver nanoparticles were synthesized by a procedure devised by Leopold and Lendl, and subsequently evaluated for size and distribution by ICP-MS (Inductively Coupled Plasma Mass Spectrometry), SEC (Size Exclusion Chromatography), and DLS (Dynamic Light Scattering). The results indicated an average particle size of approximately 85 nm and a relatively monodispersed solution with a polydispersity value of 0.1245. The solubility of the nanoparticles was then examined using a dialysis experiment; however, the results of the dialysis experiments were inconclusive due to an aggregation that occurred which prevented the silver from diffusing out of the dialysis tubing. Lastly, commercially produced food storage containers advertised to contain silver nanoparticles were examined. These containers were digested using microwave assisted digestion, and subsequently analyzed using ICP-MS. It was determined that the containers contained between 7 .5 and 27 ug of silver per gram of container, and that the silver was not distributed uniformly throughout the container. While ICP-MS indicated the presence of silver, SEM (Scanning Electron Microscopy) failed to unambiguously identify silver nanoparticles in the container. The food storage containers were also examined for silver leaching under various conditions; it was found that the containers leached most greatly following exposure to an acidic solution and leached the least due to exposure to UV light. However, additional trials of the leaching experiments must be performed to validate the results obtained in these experiments.
ContributorsWilson, Amanda (Author) / Herckes, Pierre (Thesis director) / Westerhoff, Paul (Committee member) / McAllister, Chad (Committee member) / Barrett, The Honors College (Contributor)
Created2012-05
Description
Pathogens can proliferate in the built environment and can cause disease outbreaks if water and wastewater are not properly managed. Understanding pathogens that grow in engineered systems is crucial to protecting public health and preventing disease. Using dynamic computational models can reveal mechanistic insights into these systems to aid in understanding risk drivers and determining risk management strategies. The first research chapter of this thesis investigates tradeoffs for reducing the cost associated with Legionnaire’s Disease, hot water scalding, and energy use using a computational framework for evaluating an optimal water heater temperature set point. The model demonstrated that the optimal temperature set point was highly dependent on assumptions made regarding the dose response parameter for a common configuration of an electric water heater in a hospital setting. The optimal temperature was 55°C or 48°C for subclinical vs. clinical severity dose response, respectively, compared with current recommendations of 60°C to kill bacteria and 49°C to prevent scalding and conserve energy.
The second research chapter models the population dynamics of antibiotic-susceptible Escherichia coli (E. coli) and antibiotic-resistant E. coli with a population ecology-exposure assessment model in surface water to quantify the risk of urinary tract infection from recreational swimming activities. Horizontal gene transfer (HGT) was modeled in the environment and the human gastrointestinal tract for several scenarios. HGT was generally not a dominant driver of exposure estimates compared to other factors such as growth and dilution, however, the rank order of factors was scenario-dependent.
The final research chapter models pathogen transport from wastewater treatment plant (WWTP) exposures and assesses the risk to workers based on several exposure scenarios. Case studies were performed to investigate infection risk drivers across different scenarios, including adjustments for the timing of exposure and personal protective equipment. A web application was developed for use by WWTP risk managers to be used with site-specific data.
The proposed modeling frameworks identified risk drivers across several microbial risk scenarios and provide flexible tools for risk managers to use when making water treatment and use decisions for water management plans used for premise plumbing as well as for wastewater treatment practices.
ContributorsHeida, Ashley (Author) / Hamilton, Kerry (Thesis advisor) / Garcia, Margared (Committee member) / Muenich, Rebecca (Committee member) / Wilson, Amanda (Committee member) / Arizona State University (Publisher)
Created2023