Theses/Dissertations - Environmental Science
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Item A stepwise approach to understanding nanomaterial transformations under situationally relevant conditions.(2021-04-20) Mulenos George, Marina Rochelle, 1995-; Sayes, Christie M.Given the increasing use of nanomaterials in various consumer products and industrial processes, it is of the utmost importance to better understand potential mechanisms of adverse effects to ensure human health and safety when developing regulations and standard operating procedure with newly developed materials, like nanomaterials. Nanomaterials are materials with one or more dimensions in the nanoscale range that are produced to advance industrial processes, used as an additive in consumer products, and produce novel drug delivery carriers. Standardized toxicological studies focus on newly produced nanomaterial products before they reach the market; however, most of these studies exclusively investigate pristine engineered nanomaterials. The issue with testing pristine engineered nanomaterials is that most environmental and/or human toxicities are induced after nanomaterials undergo transformations, e.g. release of metal ions. The goal of this dissertation was to conduct a comprehensive study of increasingly complex situationally relevant environments on organic and inorganic nanomaterials to understand important insights into nanomaterial transformations and the associated toxicity after exposures in vitro. Situationally relevant conditions occur when nanomaterials are used in products or processes and interact with the surrounding environment, where they then may undergo transformations. These transformations may include distribution with biomolecules or natural organic matter, lipid membranes in cells, high ionic conditions, or changes in temperature, salt concentration, etc. In this study, important physicochemical characterization methods were established for organic and inorganic nanomaterials. Additionally, these nanomaterials were transformed under simulated conditions and examined in increasingly complex environments. Next, the transformed nanomaterials were incubated with an established in vitro liver model to elucidate the relationship between nanomaterial transformations and the associated toxicity after exposure. Finally, transformed nanomaterials were exposed to an in vitro model for steroidogenic disruption to investigate further into adverse effects nanomaterial transformations may have on human health. Ultimately, the aim of this work is to advance the field of toxicology by improving our understanding of nanomaterial transformation mechanisms and to aid in risk assessment and regulations.Item Accumulation of trifluralin and trinitrotoluene (TNT) in two aquatic invertebrates: formation and persistence of unextractable biotransformation products.(2008-06-09T13:12:51Z) Dudley, Melissa B.; Chambliss, C. Kevin.; Environmental Science.; Baylor University. Dept. of Environmental Science.Exposure to nitroaromatic compounds has been reported to result in unextractable residues, or residues not readily extracted by traditional techniques. However, limited information is available about the formation rate and biological half-life of unextractable residues in aquatic organisms. In this study, two aquatic invertebrates, Lumbriculus variegatus and Hyalella azteca, were exposed inaqueous media to ¹⁴C-labeled trinitrotoluene and trifluralin. Unextractable residues were formed in both organisms by both compounds. TNT formed a greater percentage of unextractable residues than trifluralin. L. variegatus accumulated more TNT-related unextractable residues compared to H. azteca, while the reverse was true for trifluralin. H. azteca eliminated unextractable residues moreefficiently than L. variegatus. Additionally, the biological half-life of unextractable residues was longer than that of the extractable residues. The presence and biological persistence of unextractable residues indicates that these compounds, and especially TNT, could cause subtle and chronic biological effectsand serve as indicators of exposure.Item Age matters : developmental stage of Zebrafish (Danio rerio) influences bioconcentration, and survival and behavioral photomotor response thresholds.(2017-08-03) Kristofco, Lauren A., 1989-; Brooks, Bryan W.Toxicology information for the tens of thousands of compounds in commerce is severely lacking, and with continual introduction of new substances, this global chemical space is only increasing in complexity. Thus, generating data pertinent to legislation, regulation and risk assessment has become paramount. Significant hurdles exist for the production of such data sets as traditional whole organism studies have exorbitant costs, are time intensive, and are low throughput. To meet these goals alternative methods have been developed that shift the focus from a traditional, high dose, apical endpoint, based study design to a higher throughput, systems-biology, based design, however, as this is realized, critical evaluations of the newly introduced methodologies are warranted. Transitioning to high throughput screening (HTS) and predictive methodologies will further require focused efforts to not only identify these assays but also their intrinsic uncertainties. This novel dissertation employed two of the proposed alternative methodologies, probabilistic environmental hazard assessment and the fish embryo toxicity (FET) test, and probed their efficacy with an understudied class of contaminant, antihistamines. In Chapter 2, global hazards of antihistamines in surface waters were assessed with a probabilistic environmental hazard approach (PEHA) to identify global trends in occurrence. Subsequently, the capacity of the FET method to examine mixture interactions with a comparative pharmacology and toxicology approach (Chapter 3), and to extend to include behavioral observations (Chapter 4), was evaluated. Finally, to further elucidate the applicability domain of the FET, Chapter 5 investigated the driver for the age specific shifts in sensitivity evidenced in Chapters 3 and 4. These observations demonstrate the utility of both methods, and underline the importance of method selection and application.Item Aquatic toxicology of salinity and silver in Daphnia magna : a comparative study of standardized chronic endpoints and progeny Phototaxis.(2011-12-19) Kolkmeier, Mark A.; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.Behavioral bioassays with the model freshwater cladoceran Daphnia magna have the potential to serve as nontraditional but sensitive endpoints of sublethal stress in the field of ecotoxicology. However, few studies have examined the comparative sensitivity of phototaxis perturbations to standardized endpoints in chronic toxicity testing protocols. D. magna 21 d chronic toxicity studies were conducted with model stressors of salinity (NaCl) and dissolved silver (Ag+). Phototaxis assays of progeny response to relative light changes in small water columns were conducted of each brood. Results indicated predominantly decreased phototactic behavior in comparison to control brood performance at common ecotoxicological thresholds. Phototaxis assays showed effects at treatment levels below the 21-d adult reproduction LOEC value in broods 2, 3, 5 and 6 in the salinity study and broods 2, 5, and 6 in the silver study. Future refinement of robust and potentially highly ecologically relevant behavioral assays such as phototaxis in combination with traditional and nontraditional endpoints may prove useful in characterization of assessment factors.Item Assessing interactions between nutrients and aquatic toxicity : influences of nitrogen and phosphorus on ionic silver toxicity to the aquatic macrophyte Lemna gibba.(2011-05-12T15:18:27Z) Bian, Jingyi, 1985-; Brooks, Bryan W.; Environmental Science.; Baylor University. Dept. of Environmental Science.Though nutrients and silver often co-occur in aquatic ecosystems, the combined effects of these environmental stressors on aquatic plants are poorly understood. Such coexposures are important because nanosilver is increasingly released to the environment, and recent studies indicate that the dissolved fraction of nanosilver appears to be more acutely toxic to aquatic life. The primary objective of this study was to understand the effects of nitrogen (N) and phosphorus (P) concentrations and N : P ratios on the toxicity of ionic silver toxicity to the model aquatic macrophyte Lemna gibba over 7-d study periods. The experimental results indicated that L. gibba were more sensitive to silver (e.g., lower EC50 values) when N and P concentrations were higher. In addition, greater ionic silver toxicity occurred under higher P-availability (e.g., lower N : P ratios) conditions. L. gibba frond number and fresh weight were also differentially affected and showed variable sensitivity to different nutrient x silver treatment combinations, which highlights the importance of considering site-specific nutrient conditions during the prospective and retrospective assessment and management of silver impacts to primary producers.Item Atmospheric concentrations of organophosphate esters in Delhi, India.(2018-04-27) Stephensen, Marie, 1992-; Usenko, Sascha.The rise of organophosphate esters (OPEs) as ubiquitous global air pollutants is in part associated with their high-production volume, physical and chemical properties, and heavy use in consumer products, including many electronics. The current study investigates the composition and seasonal variability of atmospheric OPEs in Delhi, India. Atmospheric PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5 microns) samples were collected from April to November 2009 in downtown Delhi. PM2.5 samples were extracted using pressurized liquid extraction and the extracts were analyzed for twelve OPEs, including TPhP, using gas chromatography-mass spectrometry. The sum of atmospheric OPE concentrations ranged from 2.71 to 61.4 ng m^-3 abd were up ~600 times that of concentrations reported in the US. Findings from a study were similar to those reported from e-waste recycling areas in Pakistan, where TPhP was the dominant OPE. This may suggest that e-waste recycling is a major source of atmospheric OPEs in Delhi.Item A baseline assessment of local mercury deposition from coal-fired power plants in Central Texas.(2006-10-02T15:11:58Z) Furl, Chad Van.; Lehr, Larry L.; Van Walsum, G. Peter (Gerard Peter), 1963-; White, Joseph Daniel.; Environmental Science.; Baylor University. Dept. of Environmental Science.Coal-fired power plants represent the largest source of anthropogenic mercury in the world. The Central Texas region as represented by the Heart of Texas Council of Governments contains two coal-fired power plants located in Freestone and Limestone Counties. A third plant, Sandy Creek, is currently being proposed for McLennan County. The primary objective of the study is to estimate the amount of mercury being deposited via wet deposition in 2003 from two existing power plants in Central Texas, Big Brown and Limestone, and predict deposition from a proposed plant, Sandy Creek. The Industrial Source Code Short-Term model was used to estimate wet deposition, and empirical data was collected to determine the mercury levels in environs near the plants. According to the research and statistical analyses, the Central Texas power plants studied appear to be having no impact on the water quality of area surface waters.Item Bioaccumulation of contaminants of emerging concern in dynamic ecosystems.(2018-11-14) Haddad, Samuel Perry, 1990-; Brooks, Bryan W.The aquatic environment includes complex systems on which society relies to provide ecosystem services and support biodiversity. In recent years, the demand for aquatic-ecosystem commodities has greatly increased due to rapid population growth and industrialization. This burgeoning population stresses the global water cycle in many ways including increased fossil-fuel consumption promoting climate change, altered snowpack decreasing instream flows, multiple cities utilizing the same waterways, and increased nutrient loading due to agricultural expansion. And poorly treated sewage Such alterations to aquatic systems leads to unique exposure scenarios of contaminants of emerging concern such as pharmaceuticals and cyanotoxins. Thus, an understanding of exposure, hazards, and bioaccumulation of contaminants of emerging concern in dynamic aquatic systems in necessary to support sustainable management of aquatic resources. In this dissertation, the first study examined bioaccumulation of diphenhydramine, an ionizable weak base pharmaceutical, across different life stages in an organism that demonstrated ontogenetic diet changes in an urban estuary. The findings of this study demonstrated that ontogenetic dietary shifts do not affect the bioaccumulation of diphenhydramine, but exposure difference in water does. The second study investigated whether ionizable weak base compounds with differing properties demonstrated trophic dilution within the food web of urbanizing rivers receiving runoff from snowmelt. This study observed that multiple ionizable weak base pharmaceuticals trophicly diluted with increasing trophic position and that inhalational uptake was the main driver of bioaccumulation in rainbow trout. The third study examined the spatial and temporal fate and transport of ionizable pharmaceuticals within a dynamic aquatic system that shifted from being influenced by spring snowmelt to effluent-dominated conditions. The findings of the third study reported decreasing concentrations with increasing distance downstream regardless of season and the presence of secondary inputs from onsite waste-water systems. The fourth study developed a novel analytical method and then investigated the bioaccumulation potential of various cyanobacterial toxins in a highly eutrophic Texas reservoir. The fourth study identified several novel methodological approaches to analytically identify cyanotoxins and reported the presence of cyanotoxins in Lake Waco, Texas, USA for the first time. These observations collectively provided novel environmental assessment approaches to support an advanced understanding of bioaccumulation within dynamic aquatic ecosystems.Item Biological responses from contaminants accumulated in seafood using an in vitro human intestinal and liver co-culture.(2019-06-10) Sutherland, Grace E., 1995-; Lavado, Ramon.In vitro bioassays have been useful in predicting mechanisms of toxicity; however, conventional cell-based assays grown in monolayers are unavoidably poor models for human tissues due to the lack of complexity and physiological interplay observed in vivo. To address these limitations, the present study utilizes a combination of human intestinal and hepatic cells in a co-culture model. The purposes of these projects are to evaluate the differences between mono- and co-culture systems related to cytotoxicity and enzyme activity, and apply the co-culture model in the screening of seafood samples collected from the Galveston Bay. It was observed that the co-culture model had greater antioxidant enzyme activity compared to that of the monoculture, suggesting that hepatocytes grown in co-culture may be better suited to facilitate the expression of enzymes in response to xenobiotic metabolism in intestinal cells. This emphasizes the importance of adequate model selection to facilitate assessment of risk.Item Community needs assessment among the Gujjars in Northern India.(2002) Dorrell, Janet C.; Alexander, Sara E.; Baylor University.The perceived needs of the Gujjars of northern India were investigated in the Gurdaspur District of Punjab, India. The purpose of this study was to provide baseline data on the Gujjars who migrate to and from the states of Punjab to Himachal Pradesh by assessing their basic human needs within Johan Holmberg's sustainable development framework. These baseline data were gathered using a Needs Assessment Survey that represents approximately seventy-five Gujjar families who suffer problems of under-representation and social, economic and geographic marginalization. The analysis encompassed in the approach, defined as advocacy anthropology, suggested that the Gujjars do perceive a need for development and advocacy, specifically in the areas of education, land distribution, medical access, freedom from exploitation, political empowerment, and relief from poverty.Item Designing quantitative structure activity relationships (QSAR) to predict specific toxic endpoints for polybrominated diphenyl ethers (PBDE) in mammalian cell culture systems.(2011-12-19) Rawat, Swati, 1984-; Bruce, Erica Dawn.; Environmental Science.; Baylor University. Dept. of Environmental Science.Polybrominated diphenyl ethers (PBDEs) are becoming increasingly known as effective flame retardants and have vast industrial application in products like plastics, building materials, and textiles. They are found to be structurally similar to thyroid hormones that are responsible for regulating metabolism in the body. Structural similarity with the hormones poses a threat to human health because once in the system, the PBDEs may change thyroid hormone transport and metabolism. This study is aimed at designing QSAR models for predicting toxic endpoints for PBDEs in mammalian cells. QSAR modeling uses the known chemicals’ activity, which serve as surrogates to study unknown chemicals belonging to the same family. This research is a threefold process including running in-vitro bioassays to collect data on the toxic endpoints, modeling the evaluated endpoints using QSARs and validating the models using compounds of interest from the same family (PBDEs).Item Detailed molecular and isotopic characterization of carbonaceous aerosols to assess air quality issues in urban areas : the San Francisco Bay Area and the Houston metropolitan area.(2020-07-20) Yoon, Subin, 1989-; Sheesley, Rebecca Jacobs.The objective of this dissertation is to provide detailed characterization of carbonaceous organic aerosols to better understand major sources of particulate matter (PM) and their atmospheric formation in an oxidizing and highly complex urban atmosphere. For this dissertation, optimized radiocarbon (14C) and source characterization techniques were applied to PM samples from the Houston Metropolitan Area and the San Francisco Bay Area. The San Francisco Bay area study was focused on identifying seasonal trends (winter and non-winter) and sources of elemental carbon (EC). The study required isolation of EC for 14C-based source apportionment. Chemical mass balance model (CMB) of EC and 14C-based total organic carbon (TOC; OC + EC) were also included for comparison of source apportionment methods and different carbonaceous aerosol fractions, respectively. Sources of EC and TOC were similar at most of the sites while a few sites (e.g. San Francisco and Napa) were distinctively more impacted by fossil fuel or contemporary/biomass burning sources. The winter season had significantly larger TOC concentration due to meteorological conditions and changes in emissions (e.g. increased residential wood smoke). Relatively good agreement between the 14C-EC- and CMB-EC- was observed for both seasons. The first and second Houston studies focused on identifying diurnal and temporal trends of aerosols using both fine and coarse PM and contribution of secondary organic carbon during periods of poor air quality (i.e. high ozone and PM), respectively. The largest concentrations of fine EC and BC concentrations occured during the mornings while periods of enhanced TOC was driven by an increase in the fine PM. Interestingly, a relatively large contribution of coarse EC was measured in Houston. Based on the 14C and CMB analysis, Houston’s carbonaceous aerosols are largely from secondary biogenic sources while secondary fossil contribution was highly variable. Furthermore, the poor air quality period in the Houston metropolitan area was driven by favorable meteorological conditions (i.e. Bay Breeze) providing stagnant atmospheric conditions, allowing for accumulation and photooxidation of fossil fuel emissions. Overall, the study results provided up-to-date characterization and source apportionment of less studied carbonaceous aerosols fractions at two major U.S. urban coastal regions.Item The fate of phosphate in the MixAlco process and its applicability to a Central Texas watershed.(2007-01-19T16:21:19Z) Doyle, Erin E.; Van Walsum, G. Peter (Gerard Peter), 1963-; Environmental Studies.; Baylor University. Dept. of Environmental Studies.The MixAlco process is proposed as a means to reduce phosphorus concentrations in dairy cow manure in order to help improve water quality in the Lake Waco watershed. Numerous dairy farms and intensive agricultural practices are located in this Central Texas watershed, and dairy manure is a major source of nutrients, particularly phosphorus. Nutrients, such as nitrogen and phosphorus, are the main causes of eutrophication. The MixAlco process, which can use dairy manure as a source of biomass to produce a mixed alcohol fuel, may reduce phosphorous levels in manure wastes. The dairy manure filtrate was analyzed for soluble reactive phosphorous (SRP) before and after the first two steps of the MixAlco process. An average reduction of 86 percent was observed from beginning to end. A reduction in SRP may ease the impact dairy manure has on eutrophication in the Lake Waco watershed to help improve water quality.Item Hydrology of non-riverine freshwater wetlands of the upper Texas coast.(2010-06-23T12:31:20Z) Clapp, Adam G.; Yelderman, Joe C.; Environmental Science.; Baylor University. Dept. of Environmental Science.Coastal Prairie Freshwater Wetlands (CPFWs) are characterized by depressions and flats that occur in the Galveston Bay area. Studies estimate that over 9,000 acres of CPFWs were lost between 1992 and 2002. The cumulative loss of water quality and flood storage function may have detrimental effects on water quality and flood attenuation. There are few quantitative data available to explain the hydrologic processes of palustrine (freshwater) wetlands. This study monitored six individual CPFWs with a combination of weirs, piezometers and rain gages; each with data loggers to record wetland, groundwater and nearby surface water levels. Data were collected for approximately 18 months with some gaps due to the effects of Hurricane Ike. Water budgets were calculated to evaluate storage volumes, discharge, and potential “nexus” with receiving waters. All the monitored wetlands discharged during the study, stored significant amounts of the annual water budget and were affected by seasons.Item Individual and interactive influences of low dissolved oxygen and calcium channel blockers in inland aquatic systems.(2018-08-31) Saari, Gavin N., 1988-; Brooks, Bryan W.Understanding and managing influences of multiple stressors represents a major water quality challenge, particularly in urbanizing regions. Because aquatic hazard assessments with chemical and nonchemical stressors can identify the global trends in occurrence and hazards of stressors for the protection of aquatic life, probabilistic aquatic hazard assessments were performed to examine whether water quality guidelines for dissolved oxygen (DO) are protective of aquatic life in inland waters. My analyses indicate that adverse effects of low DO to freshwater invertebrates and fish have been underestimated in inland waters. Additional low DO threshold information, including sublethal toxicity, for additional species such as warm water fish and mollusks across multiple life history stages is necessary to support environmental assessment and management of ecosystem protection goals. Similar techniques were used to examine the occurrence of calcium channel blockers (CCBs), a common class of vasodilators and cardio suppressants, in environmental matrices, and to predict hazards to non-target aquatic organisms in multiple environmental matrices and geographic regions. Whereas environmental occurrence of CCBs in freshwater and effluent have predominantly been reported from North America and Europe, data is lacking from many developing regions around the world and hazards and risks of CCBs to non-target biota remains poorly understood. Therapeutic hazard values (THVs), a comparative pharmacology and toxicology approach, employed during probabilistic hazard assessments with environmental exposure distributions revealed that amlodipine and verapamil in effluent and freshwater exceeded THVs 28% of the time. Diltiazem exceeded minimum human therapeutic thresholds in fish plasma ~18% of the time in surface waters. This approach demonstrated the utility of global assessments to identify specific CCBs and geographic regions where environmental assessments appear necessary. Subsequently, to understand adverse effects of individual and multiple stressors influencing cardiac function (DO, diltiazem, or DO x diltiazem), toxicity studies were performed using a comparative toxicology and pharmacology approach in fathead minnows (Pimephales promelas) across larval and adult life stages. DO x diltiazem toxicity studies with larval fish revealed acute lethality increased with decreasing DO levels and altered burst swimming behavior at DO water quality criteria levels deemed protective of aquatic life. In adult fathead minnows, low DO (3.0 mg DO/L) increased uptake of diltiazem and altered physiological responses (e.g., hematocrit, plasma lactate) at and above human therapeutic plasma levels. Failing to consider low DO influences with chemical exposure during toxicological studies of cardioactive medications and potentially other cardiotoxicants underestimates adverse outcomes in fish.Item Influences of nutrients and salinity on Prymnesium parvum elicited sublethal toxicity in two common fish models.(2018-07-12) Hill, Bridgett N., 1993-; Brooks, Bryan W.The magnitude, frequency, and duration of harmful algal blooms (HABs) are increasing worldwide primarily due to climate change and anthropogenic activities. Prymnesium parvum is a euryhaline and eurythermal HAB forming species that has expanded throughout North America resulting in massive fish kills. Previous ecotoxicological work supported an understanding of conditions resulting in HABs and fish kills; however, the primary endpoint selected for these studies was acute mortality. Whether adverse sublethal responses to P. parvum occur in fish are largely unknown. To begin to address this question, fish molecular and biochemical oxidative stress (OS) responses and behavioral alterations in two common fish models were investigated. Varying nutrient and salinity conditions influenced P. parvum related OS and fish behavioral responses of two common fish models, and these responses were heightened by conditions nonoptimal for P. parvum growth. Such sublethal observations present important considerations for future assessment and management of P. parvum.Item Influences of spatio-temporal variability during aquatic assessments of ionizable contaminants.(2019-04-16) Scott, William Casan, 1988-; Brooks, Bryan W.Urbanization and evolving land-use is challenging water management strategies in semi-arid regions of the United States, where stream flows are often dominated by treated wastewater effluent discharges. Effluent-dominated and dependent surface waters are becoming common in urbanized watersheds, where physical and chemistry factors can influence exposure and toxicity of many down-the-drain chemicals and contaminants of emerging concern (CECs). In these effluent-dominated systems, effective exposure increases when rate of chemical introductions to surface waters exceed chemical degradation rates in receiving systems. In fact, many consumer chemicals (e.g., pharmaceuticals) and other contaminants (e.g., ammonia, algal toxins) are ionizable across surface water pH. Here I examined aquatic biota in tidally influenced urban estuaries, where dynamic salinity and pH gradients may challenge prospective and retrospective risk assessments. In several of these urban systems, the ionizable pharmaceutical diltiazem was initially observed to exceed human therapeutic plasma doses in plasma from several fish species, which indicate risks to aquatic life in these dynamic systems. Dickinson Bayou, an urban estuary influenced by onsite (e.g., septic) and centralized effluent discharges, was then examined, in which influences of tides on spatiotemporal hazards of select ionizable contaminants were identified under conditions not typically included in routine surface water quality assessments. A third study employed the Gulf killifish, a common euryhaline species in the Gulf of Mexico, to define influences of salinity and pH conditions on uptake of representative ionizable weak bases (e.g., diltiazem, diphenhydramine) to fish plasma and body burden. Though pH, but not salinity, altered fish uptake, body burdens of diphenhydramine were elevated at low pH and apparent volumes of distribution were lower than studies with freshwater fish. The fourth chapter of this dissertation examined pH influences on toxicity of Prymnesium parvum, a harmful algal bloom (HAB) species in riverine and transition zones of a moderately saline inland reservoir. Combined with climatological and geological influences, anthropogenic changes in some Texas reservoirs support HAB of this typically estuarine alga, which appears to bloom in response to site-specific water chemistry, including pH and salinity. Observations suggest that fatty acid amides are not responsible for P. parvum related fish kills and identified locations of elevated risks for HABs of this emerging threat to water quality. Findings from these studies collectively, highlight the importance of characterizing site-specific influences on bioaccumulation and toxicity of ionizable contaminants, and integrating such information during prospective and retrospective risk assessments.Item Interactive effects of copper oxide nanoparticles and arsenic on rice (O.sativa japonica ’Koshihikari’) plant growth and development.(2019-05-02) Liu, Jing, 1987-; Cobb, George P.The emerging applications of nanomaterials (NMs) encompass a wide range of industries, including agriculture (e.g., as fertilizers, pesticides, and biosensors). NMs applied in the crop-field may influence plant growth and uptake of heavy metal(loid)s including arsenic (As). Being ubiquitous in the environment and readily bioavailable in aquatic system, As is taken up by rice plants, causes phytotoxicity and accumulates in rice grains. Classified as a Class I carcinogen and causing many diseases, As in rice grains potentially causes human health effects, particularly for infants who are eating rice to transition from breast milk to solid food, and Asian populations with regular daily rice consumption. Although As in water can be removed dramatically by copper oxide nanoparticles (nCuO) due to their high adsorption capacity for As, the interaction of nCuO and As has not been well elucidated on rice plant growth and As accumulation. This project was the first to investigate the interaction of nCuO and As on rice (Oryza sativa japonica’Koshihikari’) plant growth and development during a life cycle (from seed germination to seed maturation). The effects of nCuO and As were determined, individually and interactively, on rice seed germination and early seedling growth in sand and an artificial soil mixture of clay and topsoil. A greenhouse study on the life cycle growth of rice plants in the artificial soil mixture approximated the real agriculture scenario and identified the nCuO dependent acceleration of heading process of rice plants. Particularly, As accumulation in dehusked rice grains was decreased by nCuO to 128 ng/g, 36% lower than the WHO maximum safe concentration of As in white rice (200 ng/g) for humans. Arsenic distribution and speciation inside the plant growth were also affected by nCuO. Transgenerational effects of nCuO and As were also verified on seed germination and early seedling growth of rice plants in this project. These results contribute to the fundamental database of endpoint effects on rice plants, direct future research about wide-scale application of NMs in crop field as fertilizers or amendments, and provide insightful information to investigate the mechanism of the interaction between nCuO and As on plant growth.Item Investigating the efficacy of a novel therapeutic to mitigate traumatic brain injury : contributions of environmental exposures to overall healing.(2015-07-30) Yang, Peijin, 1987-; Bruce, Erica Dawn.Traumatic brain injury (TBI) is a leading cause of disability and premature death among both civilians and military. Morbidity and deaths are mainly caused by several secondary process that exacerbate brain dysfunction in the minutes to days following the primary injury when blood vessels and tissues are torn, stretched, or compressed. In previous studies, proper oxygen supply has been shown to help brain cells to grow and repair, remove the obstruction in blood flow, and alleviate brain edema to prevent secondary injury. OX-66, a novel therapeutic, potentially provides an efficient supply of oxygen to the cells. This therapeutic was investigated in this study to determine its cytotoxicity and potential mechanism of cellular repair in invitro-injured rat brain cells. The effects of exposure to polycyclic aromatic hydrocarbons (PAH) on TBI patients and the corresponding restorative influence of OX-66 were also evaluated.Item Metabolism and mechanistic toxicity of environmental pollutants in fish models : integrating in vitro and in vivo systems for ecotoxicological studies.(2021-09-15) Franco, Marco E., 1991-; Lavado, Ramon.The presence of legacy and emerging contaminants in the aquatic environment represents a significant threat to aquatic biota, often leading to significant declines of biodiversity. This issue is further aggravated by the influence of abiotic environmental factors, such as climate change, which could potentially modify organisms’ exposure and responses to pollution. Historically, ecotoxicological studies have relied on the use of live animals and endpoints such as mortality, growth, and reproduction to determine whether exposed organisms and populations are at risk. However, these approaches are often hindered by cost, ethic, and scientific limitations, making them unable to provide a thorough representation of exposure conditions and resulting adverse effects. Recently, significant research efforts have highlighted the need to understand pollutant-driven alterations at different levels of biological organization. In this context, new approach methodologies (NAMs), such as in vitro systems, have emerged as robust bioanalytical tools to mechanistically describe chemical-organism interactions, predict potential adverse effects from exposure, and support comprehensive assessments of risk, while reducing animal use. The scope of this dissertation relies on the applicability of NAMs, specifically cell-based bioassays, and their integration with more traditional approaches (e.g. in vivo systems) to address research gaps associated with the biotransformation of legacy compounds by fish populations with different exposure history, the endocrine disruption potential of wastewater effluents, and the description of mechanistic toxicity of natural and anthropogenic pollutants, while considering the influence of different environmental stressors. This work demonstrated that descriptions of adverse effects from exposure to pollutants are significantly facilitated by in vitro systems, but that overall characteristics of the species and areas of interest must be accounted for when selecting appropriate cell-based models, as their improper selection could significantly mislead observations and subsequent environmental management strategies. The integration of cell-based and whole-animal approaches showed that the sensitivity and specificity of in vitro systems are significant limitations for their implementation, and that their value in ecotoxicological studies relies on their integration with more complex experimentation through weight of evidence (WoE) approaches.
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