Document Type
Dissertation
Date of Award
12-2023
School/College
College of Science, Engineering, and Technology (COSET)
Degree Name
Ph.D. in Environmental Toxicology
Committee Chairperson
Momoh A. Yakubu
Committee Member 1
Sunny Ohia
Committee Member 2
Erica Cassimere
Committee Member 3
Mario Hollomon
Keywords
Emerging contaminants, Endocrine disruptors, Heavy metal contamination, Pharmaceuticals and personal care products, Rat pituitary cell lines, Urban watersheds
Abstract
Rapid industrialization and urbanization within the Greater Houston area have driven a surge in anthropogenic activities that affects the burgeoning population. This region stands as one of the most densely inhabited metropolises in the United States, experiencing a substantial population growth of 9.8% from 2010 to 2020, with the population expanding from 5.92 million to 7.14 million. This population boom has been accompanied by an increased reliance on modern conveniences, leading to escalated production and utilization of chemicals such as personal care products, pharmaceuticals, pesticides, and heavy metals, all of which pose potential threats to the environment. Although these products are discharged daily in minimal concentrations, there exists a possibility of their interaction with our food sources and biological systems, potentially inducing adverse health effects. Consequently, there is a growing awareness and concern regarding their impact. The primary recipients of these contaminants are the tributaries that flow into the Galveston Bay/Gulf Coast, significantly influencing water quality in the region. The potential adverse effects of these contaminants on humans, the human environment, and the ecosystem encompass a spectrum from acute to chronic and merit significant attention. Given the complex network of bayous draining the Greater Houston area, this study assessed the concentrations of heavy metals and selected Pharmaceuticals and Personal Care Products (PPCPs) within nine bayous and Galveston Bay. The study zones encompass the Buffalo Bayou Watershed, San Jacinto River Watershed, Clear Creek River Watershed, Galveston Bay, and other areas featuring parks and reserves utilized for recreational activities. The study aims include (1) characterizing the presence of commonly used PPCPs, as well as heavy metals in water, sediment, and fish samples obtained from the study areas; (2) evaluating the potential risks associated with the presence of these contaminants; and (3) investigating the effects of these contaminants at environmentally relevant concentrations on biomolecular regulation in rat pituitary cells. All samples were systematically collected from the identified watersheds, carefully stored, and processed in accordance with EPA standard protocols, with minor adjustments as needed. Heavy metal analysis was conducted using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), while the analysis of PPCPs was performed using Liquid Chromatography-Mass Spectrometry/Mass Spectrometry (LC-MS/MS). Following quantification, comprehensive cellular studies using rat pituitary cells in culture were carried out, using the detected concentrations of PPCPs over a specified duration. Subsequent assays were performed to scrutinize dysregulated parameters and the mechanisms of dysregulation. The result of this study shows the presence of heavy metals both in water and sediment samples, with the exceptions of Cr and Zn in a few locations. Of particular concern is the presence of As at concentrations ranging from 0.90 ± 0.04 to 2.74 ± 0.17 μg/L in all water samples, surpassing the EPA criteria for human health protection of 0.02 μg/L. PPCPs like antibiotics and antihypertensive drugs were detected at significantly higher concentrations compared to other PPCP classes in all sample matrices, because of their widespread usage. In the health risk assessment, Cr exhibited noncancer and cancer risk values exceeding acceptable limits for oral and dermal exposure to sediment from many locations, with a particular focus on the vulnerability of children. The assays conducted using rat pituitary cell lines revealed intricate and time-dependent effects of PPCPs on cell proliferation and cytotoxicity were observed, emphasizing the importance of considering exposure duration and compound-specific responses. Furthermore, PPCPs displayed variable effects on key hormone levels within rat pituitary cells, with adrenocorticotropic hormone (ACTH) exhibiting dose and time-dependent dysregulation. The effects of these chemicals on cyclic adenosine monophosphate (cAMP) levels in the cells revealed substantial dysregulation of this second messenger, particularly evident in studies involving endocrine disrupting chemicals. These results highlight the intricate characteristics of newly emerging contaminants in interacting with biological systems, emphasizing the pressing requirement for robust regulatory and environmental management approaches. These measures are crucial for safeguarding public health and minimizing the detrimental impacts of contamination in these ecosystems.
Copyright
Copyright © for this work is retained by the author. Any documents and information presented are protected by copyright under US Copyright laws and are the property of the author. All Rights Reserved. For permission to use this content please contact the author or the Graduate School at Texas Southern University (graduate.school@tsu.edu).
Recommended Citation
Atobiloye, Sekinat Oluwakemi, "Occurrence Of Emerging Contaminants In Greater Houston Watersheds, Risk Assessment, And Toxicological Effects" (2023). Dissertations (2016-Present). 79.
https://digitalscholarship.tsu.edu/dissertations/79