Given the potential for human exposure to silver nanoparticles from spray disinfectants and dietary supplements, we characterized the silver-containing nanoparticles in 22 commercial products that advertised the use of silver or colloidal silver as the active ingredient. Characterization parameters included: total silver, fractionated silver (particulate and dissolved), primary particle size distribution, hydrodynamic diameter, particle number, and plasmon resonance absorbance. A high degree of variability between claimed and measured values for total silver was observed. Only 7 of the products showed total silver concentrations within 20% of their nominally reported values. In addition, significant variations in the relative percentages of particulate vs. soluble silver were also measured in many of these products reporting to be colloidal. Primary silver particle size distributions by transmission electron microscopy (TEM) showed two populations of particles - smaller particles (<5nm) and larger particles between 20 and 40nm. Hydrodynamic diameter measurements using nanoparticle tracking analysis (NTA) correlated well with TEM analysis for the larger particles. Z-average (Z-Avg) values measured using dynamic light scattering (DLS); however, were typically larger than both NTA or TEM particle diameters. Plasmon resonance absorbance signatures (peak absorbance at around 400nm indicative of metallic silver nanoparticles) were only noted in 4 of the 9 yellow-brown colored suspensions. Although the total silver concentrations were variable among products, ranging from 0.54mg/L to 960mg/L, silver containing nanoparticles were identified in all of the product suspensions by TEM.

The utilization of silver nanoparticles (AgNPs) in consumer products has significantly increased in recent years, primarily due to their antimicrobial properties. Increased use of AgNPs has raised ecological concerns. Once released into an aquatic environment, AgNPs may undergo oxidative dissolution leading to the generation of toxic Ag + . Therefore, it is critical to investigate the ecotoxicological potential of AgNPs and determine the physicochemical parameters that control their dissolution in aquatic environments. We have investigated the dissolution trends of aqueous colloidal AgNPs in five products, marketed as dietary supplements and surface sanitizers. The dissolution trends of AgNPs in studied products were compared to the dissolution trends of AgNPs in well-characterized laboratory-synthesized nanomaterials: citrate-coated AgNPs, polyvinylpyrrolidone-coated AgNPs, and branched polyethyleneimine-coated AgNPs. The characterization of the studied AgNPs included: particle size, anion content, metal content, silver speciation, and capping agent identification. There were small differences in the dissolved masses of Ag + between products, but we did not observe any significant differences in the dissolution trends obtained for deionized water and tap water. The decrease of the dissolved mass of Ag + in tap water could be due to the reaction between Ag + and Cl − , forming AgCl and affecting their dissolution. We observed a rapid initial Ag + release and particle size decrease for all AgNP *

The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small (< 5 mm and > 100 nm) plastic particles known as 'microplastics' (MPs). These particles are thought to pose greater risks than larger plastic debris as they are more likely to be ingested by many species. Their widespread presence may pose a threat to marine organisms globally. Contamination of freshwater and terrestrial systems also has been reported, and more recent studies indicate the presence of even smaller (≤ 100 nm) plastic particles, termed 'nanoplastics' (NPls), that may have unique risks due to their nanoscale. Most of the nano and microplastic (N&MP) pollution in marine environments is assumed to originate from land-based sources, but their sources, transport routes, and transformations are uncertain. Information on freshwater and terrestrial systems is lacking, and data on NPl pollution is particularly sparse. The shortage of systematic studies of freshwater and terrestrial systems is a critical research gap because estimates of plastic release into these systems are much higher than those for oceans. As most plastic pollution originates in urban environments, studies of urban watersheds, particularly those with high population densities and industrial activities, are especially relevant with respect to source apportionment. Released plastic debris is transported in water, soil, and air. It can be exchanged between environmental compartments, adsorb toxic chemicals, and ultimately be carried long distances, with potential to cause both physical and chemical harm to a multitude of species. Unfortunately, these processes are not well understood. Measurement challenges and a lack of standardized methods has slowed progress in determining the environmental prevalence and impacts of N&MPs.An overall aim of this project is to report the sources and abundances of N&MPs in urban watersheds. Their fate, transport, transformations, and potential impacts are discussed.Monitoring methods and their limitations also are reviewed, knowing that identifying N&MPs Pinto, Madhav Machavaram, and Raghuraman Venkatapathy, for their input and support.Finally, I wish to thank my family, especially my mother, Dr. M. Eileen Birch, to whom I am eternally grateful for her tremendous input and motivation throughout this project. The love and support they provided me cannot be overstated.

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A commercially-available, 3D printer nanocomposite filament of carbon nanotubes (CNTs) and acrylonitrile-butadiene-styrene (ABS) was analyzed with respect to its VOC emissions during simulated fused deposition modelling (FDM) and compared with a regular ABS filament. VOC emissions were quantified and characterized under a variety of conditions to simulate the thermal degradation that takes place during FDM. Increasing residence time and temperature resulted in significant increases in VOC emissions and oxygen content of the reaction gas influenced the VOC profile. In agreement with other studies, the primary emitted VOC was styrene. Multiple compounds are reported in this work for the first time as having formed during FDM, including 4vinylcyclohexene and 2-phenyl-2-propanol. Our results show that printing 222.0 g of filament is enough to surpass the reference concentration for inhalation exposure of 1 mg/m 3 according to the EPA's Integrated Risk Information System (IRIS). The presence of CNTs in the filament influenced VOC yields and product ratios through three types of surface interactions: 1) adsorption of O 2 on CNTs lowers the available O 2 for oxidation of primary backbone cleavage intermediates, 2) adsorption of styrene and other VOCs to CNTs leads to surface-catalyzed degradation, and 3) CNTs act as a trap for certain VOCs and prevent them from entering vapor emissions. While the presence of CNTs in the filament lowered the total VOC emission under most experimental conditions, they increased the emission of the most hazardous VOCs, such as α-methylstyrene and benzaldehyde. The present study has identified an increased risk associated with the use of CNT nanocomposites in 3D printing.