Citation: Baguma, G.; Bamanya, G.; Gonzaga, A.; Ampaire, W.; Onen, P. A Systematic Review of Contaminants of Concern in Uganda: Occurrence, Sources, Potential Risks, and Removal Strategies. Pollutants 2023, 3, 544–586. https://doi.org/10.3390/ pollutants3040037 Academic Editor: Annabel Fernandes Received: 5 September 2023 Revised: 7 November 2023 Accepted: 15 November 2023 Published: 4 December 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). Review A Systematic Review of Contaminants of Concern in Uganda: Occurrence, Sources, Potential Risks, and Removal Strategies Gabson Baguma 1,2,* , Gadson Bamanya 2, Allan Gonzaga 3, Wycliffe Ampaire 2 and Patrick Onen 4 1 Department of Civil and Environmental Engineering & Construction, University of Nevada Las Vegas, 4505 S. Maryland PKWY, Las Vegas, NV 89154, USA 2 Department of Physical Sciences, School of Natural and Applied Sciences, Kampala International University, Kampala P.O. Box 20000, Uganda; gadsonbamanya@gmail.com (G.B.); ampairewycliffe@gmail.com (W.A.) 3 Department of Biological and Environmental Sciences, School of Natural and Applied Sciences, Kampala International University, Kampala P.O. Box 20000, Uganda; isiagiallan@gmail.com 4 Department of Chemistry, University of Kerala, Thiruvananthapuram 695581, India; patrickonen1995@gmail.com * Correspondence: bagumagabson@gmail.com or baguma@unlv.nevada.edu; Tel.: +1-(725)-278-8773 Abstract: Contaminants of concern (CoCs) pose significant threats to Uganda’s ecosystems and public health, particularly in the face of rapid urbanization, industrial expansion, and intensified agriculture. This systematic review comprehensively analyzed Uganda’s CoC landscape, addressing imminent challenges that endanger the country’s ecosystems and public health. CoCs, originating from urban, industrial, and agricultural activities, encompass a wide range of substances, including pharmaceuticals, personal care products, pesticides, industrial chemicals, heavy metals, radionu- clides, biotoxins, disinfection byproducts, hydrocarbons, and microplastics. This review identified the major drivers of CoC dispersion, particularly wastewater and improper waste disposal practices. From an initial pool of 887 articles collected from reputable databases such as PubMed, African Journal Online (AJOL), Web of Science, Science Direct, and Google Scholar, 177 pertinent studies were extracted. The literature review pointed to the presence of 57 pharmaceutical residues and personal care products, along with 38 pesticide residues and 12 heavy metals, across various environmental matrices, such as wastewater, groundwater, seawater, rainwater, surface water, drinking water, and pharmaceutical effluents. CoC concentrations displayed significant levels exceeding established regu- lations, varying based on the specific locations, compounds, and matrices. This review underscores potential ecological and health consequences associated with CoCs, including antibiotic resistance, endocrine disruption, and carcinogenicity. Inefficiencies in traditional wastewater treatment meth- ods, coupled with inadequate sanitation practices in certain areas, exacerbate the contamination of Uganda’s aquatic environments, intensifying environmental and health concerns. To address these challenges, advanced oxidation processes (AOPs) emerge as promising and efficient alternatives for CoC degradation and the prevention of environmental pollution. Notably, no prior studies have explored the management and mitigation of these contaminants through AOP application within various aqueous matrices in Uganda. This review emphasizes the necessity of specific regulations, improved data collection, and public awareness campaigns, offering recommendations for advanced wastewater treatment implementation, the adoption of sustainable agricultural practices, and the enforcement of source control measures. Furthermore, it highlights the significance of further research to bridge knowledge gaps and devise effective policies and interventions. Ultimately, this compre- hensive analysis equips readers, policymakers, and regulators with vital knowledge for informed decision-making, policy development, and the protection of public health and the environment. Keywords: contaminants of concern; Uganda; ecological impacts; public health; legacy contaminants; sustainable agriculture; environmental management Pollutants 2023, 3, 544–586. https://doi.org/10.3390/pollutants3040037 https://www.mdpi.com/journal/pollutants https://doi.org/10.3390/pollutants3040037 https://doi.org/10.3390/pollutants3040037 https://creativecommons.org/ https://creativecommons.org/licenses/by/4.0/ https://creativecommons.org/licenses/by/4.0/ https://www.mdpi.com/journal/pollutants https://www.mdpi.com https://orcid.org/0000-0002-2095-9193 https://orcid.org/0000-0002-2458-9388 https://doi.org/10.3390/pollutants3040037 https://www.mdpi.com/journal/pollutants https://www.mdpi.com/article/10.3390/pollutants3040037?type=check_update&version=1 Pollutants 2023, 3 545 1. Introduction Environmental pollution, with its multifaceted dimensions, is a growing concern worldwide, with developing countries often facing the brunt of its consequences [1–4]. This issue has escalated due to the rapid industrialization, urbanization, and modernization processes taking place across the world [1,2]. These processes have led to the release of a diverse array of pollutants into various environmental compartments, giving rise to the concept of “contaminants of concern (CoCs)” [5]. These CoCs, often originating from new technologies, industrial processes, and urban activities, have the potential to pose significant ecological and human health risks [6,7]. CoCs encompass a wide array of substances, including emerging contaminants (Ecs) and legacy contaminants, both raising heightened environmental and public health con- cerns. Ecs include previously unidentified or underrecognized substances, such as in- dustrial byproducts, pharmaceutical residues, pesticides, personal care products, flame retardants, polycyclic aromatic hydrocarbons (PAHs), polychlorinated compounds (PCBs), mycotoxins, and microplastics, whose presence and potential environmental implications were not widely known, necessitating ongoing investigations [8–11]. In contrast, legacy contaminants are well-established and regulated, with documented adverse consequences for ecosystems and public health. This category comprises familiar contaminants such as heavy metals and persistent organic pollutants (POPs) [4,12–14]. Notably, many of these CoCs, particularly Ecs, currently lack established regulatory standards, demanding continuous monitoring due to their bioaccumulation potential, and persistence in various environmental compartments [15]. Understanding their presence, sources, distribution, and potential impacts is essential for sustainable environmental man- agement and public health protection [16]. However, the scarcity of data regarding their occurrence, transport, and fate, and the absence of standardized detection methods are significant challenges. Advanced analytical chemistry and instrumentation have played a pivotal role in revealing these substances, with the ability to detect them at minute concentrations, often in parts per trillion (ppt) or even parts per quadrillion (ppq). These substances enter water bodies, soil, and the atmosphere through various pathways, includ- ing industrial discharges, agricultural runoff, improper waste disposal, and atmospheric deposition as illustrated in Figure 1, where they persist, accumulate in organisms, and potentially cause adverse effects [4,5,17–19]. Uganda, renowned for its rich biodiversity and stunning landscapes, faces mounting challenges with the rise of CoCs. These pose significant threats to the country’s ecosys- tems, public health, and socio-economic development [4,20,21]. Uganda’s contribution to the continent’s overall contaminant pollution is estimated to be between 6–8%, primarily resulting from rapid urbanization, industrial growth, importation of electric waste, and intensified agricultural practices, all contributing to the release of various contaminants into the environment [21]. These developments have triggered concerns regarding the long-term sustainability of the region [21–23]. Furthermore, the status of ambient air quality in Uganda presents alarming figures, with PM2.5 mass concentrations exceeding the US 24 h PM2.5 National Ambient Air Quality Standards (NAAQS; 35 µg/m3) and the WHO air quality guidelines (25 µg/m3) by three to four times, highlighting a dangerous level of air pollution, particularly detrimental to susceptible populations such as children and the elderly [24]. The impacts of these contaminants can be profoundly detrimental to both the environment and human health. They have been associated with ecosystem disruption [25], biodiversity loss, hormonal imbalances in wildlife, and reproductive im- pairments [3,20,26,27]. In humans, exposure to these pollutants has been linked to various health issues, including endocrine disruption, developmental abnormalities, neurological disorders, and increased risks of certain cancers [28,29]. Despite considerable efforts to monitor and regulate legacy contaminants, the knowledge about different types of CoCs and their impact on Ugandan ecosystems and public health remains limited. The persis- tence and potential adverse effects of CoCs raise significant concerns as these substances are characterized by their diverse behavior and sources of production, making their de- Pollutants 2023, 3 546 tection and characterization challenging. Some CoCs, previously identified as “legacy persistent organic pollutants”, have been restricted under the Stockholm Convention due to their environmental persistence, wide distribution, bioaccumulation potential, and tox- icity to humans and wildlife [15]. The detection of these CoCs necessitates the use of sophisticated analytical techniques capable of detecting trace levels of these compounds in environmental matrices. Pollutants 2023, 3, FOR PEER REVIEW 3 Figure 1. Sources, pathways, and distribution of CoCs in different environmental compartments in Uganda. Uganda, renowned for its rich biodiversity and stunning landscapes, faces mounting challenges with the rise of CoCs. These pose significant threats to the country’s ecosys- tems, public health, and socio-economic development [4,20,21]. Uganda’s contribution to the continent’s overall contaminant pollution is estimated to be between 6–8%, primarily resulting from rapid urbanization, industrial growth, importation of electric waste, and intensified agricultural practices, all contributing to the release of various contaminants into the environment [21]. These developments have triggered concerns regarding the long-term sustainability of the region [21–23]. Furthermore, the status of ambient air qual- ity in Uganda presents alarming figures, with PM2.5 mass concentrations exceeding the US 24 h PM2.5 National Ambient Air Quality Standards (NAAQS; 35 µg/m3) and the WHO air quality guidelines (25 µg/m3) by three to four times, highlighting a dangerous level of air pollution, particularly detrimental to susceptible populations such as children and the el- derly [24]. The impacts of these contaminants can be profoundly detrimental to both the environment and human health. They have been associated with ecosystem disruption [25], biodiversity loss, hormonal imbalances in wildlife, and reproductive impairments [3,20,26,27]. In humans, exposure to these pollutants has been linked to various health issues, including endocrine disruption, developmental abnormalities, neurological disor- ders, and increased risks of certain cancers [28,29]. Despite considerable efforts to monitor Figure 1. Sources, pathways, and distribution of CoCs in different environmental compartments in Uganda. Several studies in Uganda have investigated the sources, presence, and concentrations of CoCs in various environmental systems, revealing a range of compounds, including phar- maceutical residues, personal care products, pesticides, industrial chemicals, microplastics, and heavy metals. However, concentrations vary depending on the sampling location, environmental matrix, and analytical techniques employed. Several researchers have em- ployed various analytical methods, including liquid chromatography-mass spectrometry (LC-MS), gas chromatography-mass spectrometry (GC-MS), and high-performance liquid chromatography (HPLC), to assess the presence and concentrations of CoCs in different en- vironmental compartments [30]. The diverse nature of CoCs necessitates a comprehensive investigation of their occurrence in various matrices, including surface water bodies (lakes, rivers, and wetlands), groundwater, sediments, soils, air, and biota (aquatic and terrestrial Pollutants 2023, 3 547 organisms). Understanding the distribution and concentrations of CoCs in various environ- mental compartments is crucial for assessing their potential risks and designing effective management strategies. Several studies conducted in Uganda have investigated the sources, presence, and concentrations of CoCs in various environmental systems, including water bodies [31,32], sediments [31,33], surface waters [34–36], food crops [37,38], edible insects [39], breast- milk [40], and fish [34]. These studies have identified a range of compounds, including pharmaceutical residues like antibiotics and analgesics [30,41,42], personal care products like fragrances and UV filters [43], pesticides like herbicides and insecticides [31,39,44,45], industrial chemicals like flame retardants and plasticizers [40,43,46], microplastics, and heavy metals [32,47,48]. The reported concentrations of these CoCs exhibit variation de- pending on the sampling location, environmental matrix, and analytical techniques used. For example, antibiotics have been detected in surface waters at concentrations ranging from 1 ng/L to 5600 ng/L, highlighting the potential ecological impact of pharmaceuti- cal pollution [30,42]. However, there is limited information on healthcare professionals’ disposal methods and adherence to disposal guidelines in Uganda, particularly for phar- maceutical waste [42]. This lack of data, combined with the absence of robust national guidelines and low compliance with existing protocols, heightens the risk of environ- mental contamination and the ingestion of toxic pharmaceutical waste by humans and animals. Likewise, various chemicals, including pesticides [31,49], perfluorinated alky- lated substances (PFAS) [50], personal care products [43], and persistent organic pollutants (POPs) [40], have been observed in surface waters, occasionally exceeding regulatory limits, indicating potential threats to agricultural productivity and human health [23,42,51]. The contamination of surface waters by these emerging contaminants poses a considerable public health concern, similar to the concerns raised in previous studies [42]. In addition, wastewater treatment plant (WWTP) effluents have been identified as significant sources of contamination in Uganda, with some compounds poorly degrading due to a lack of specific treatment methods for organic pollutants [41,42,51–53]. The role of hospitals and households in the pharmaceutical contamination of WWTPs is concerning [30,54]. Urban discharges, including separate or combined sewer overflows, can impact receiving waters in Uganda, similar to other regions. Urban stormwaters contain a variety of contaminants, such as polycyclic aromatic hydrocarbons (PAHs), alkylphenols, and pesticides, contribut- ing to the pollution of surface waters in urban areas [21,41,42,50–52,55]. Furthermore, Uganda faces challenges related to the importation and management of electronic waste (E-waste) due to its poor recycling infrastructure, reliance on informal sectors with crude dismantling, and artisanal recycling techniques [56–59]. As a result, Uganda’s soil, water, and air are contaminated with substances such as brominated flame retardants, non-dioxin- like polychlorinated biphenyls (PCBs), PAHs, polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PBDFs), and dioxin-like polychlorinated biphenyls (DL- PCBs) [35,40,43,46,60,61]. The crude activities involved in E-waste management, including waste dumping in agricultural farmlands and water bodies, further exacerbate environ- mental pollution in Uganda [56,59]. Beyond the context of Uganda, various African regions, covering approximately 17 percent of the continent’s countries, have also reported the presence of CoCs. Notably, 59 percent of these occurrences stem from studies conducted in South Africa, with contribu- tions of 9 percent each from Tunisia and Nigeria, along with 7 percent from Kenya [62–65]. The documentation of CoCs extends throughout the African landscape, including sedi- ments, sludge, treated drinking water, surface water, wastewater, groundwater, and solid deposits. However, limited knowledge about contaminant sources, pathways, properties, and analytical detection techniques hampers the systematic inclusion of CoCs in ground- water monitoring and protection policies. Improper disposal practices further exacerbate Uganda’s CoC issues [28,53,58]. The improper disposal of expired medications and elec- tronic waste presents additional risks to the environment and human health [58,66]. The indiscriminate disposal of pharmaceutical waste and the lack of adequate protocols for drug Pollutants 2023, 3 548 disposal contribute to potential water and soil contamination. The improper recycling and open burning of electronic waste introduce substances such as brominated flame retardants, polycyclic aromatic hydrocarbons, and dioxins into the environment, polluting soil, water, and air [35,67]. This systematic review aimed to provide a holistic understanding of the status, sources, and impacts of CoCs in Uganda. It offers valuable insights for policymakers, researchers, and stakeholders, ultimately guiding the development of evidence-based interventions and fostering sustainable practices that protect Uganda’s natural resources and promote a healthier environment for future generations. Importantly, this review article serves as a critical resource for raising awareness about the prevalence and implications of CoCs in Uganda. It underscores the urgency of addressing these pollutants’ sources and effects, both in Uganda and across Africa. By shedding light on the multifaceted challenges posed by contaminants of emerging concern, this article equips readers with essential knowledge for implementing effective management and mitigation strategies. It provides a foundation for informed decision-making, the development of sustainable environmental policies, and the protection of public health, ecosystems, and the country’s long-term socio-economic development. 2. Materials and Methods 2.1. Study Design This review followed a comprehensive and structured approach to assess the state of CoCs in Uganda. The review was guided by the established methodologies for systematic reviews, including a systematic search strategy, data extraction, and quality assessment of selected studies. 2.2. Search Strategy A systematic search of relevant literature was conducted to identify studies on CoCs in Uganda. Multiple electronic databases, such as PubMed, Scopus, Web of Science, and Google Scholar, were searched using appropriate keywords and Boolean operators. The search terms included combinations such as “contaminants of concern, Uganda”, “emerging contaminants in Uganda”, or “Emerging pollutants in surface water, Uganda”, “Emerging contaminants in soils, Uganda”, or “Emerging contaminants in the air, Uganda”, or “Emerg- ing contaminants in wastewater, Uganda”, and related terms. The search was limited to studies published in English up until the cutoff date of this review (September 2023). 2.3. Study Selection The inclusion and exclusion criteria were predefined to ensure the selection of studies relevant to the topic. Studies that focused on the identification, characterization, and assessment of CoC concentrations in Uganda were included. Both peer-reviewed articles and grey literature, such as reports and conference proceedings, were considered. Studies that did not specifically address CoCs in Uganda or lacked sufficient data were excluded. 2.4. Data Extraction Data was extracted from the selected studies using a standardized data extraction form. The information collected included study characteristics (e.g., authors, year of publication), study design, sampling methods, analytical techniques, types of CoCs investigated, pollu- tant sources and concentrations, and any reported impacts or observations. The extracted data were organized comprehensively for further analysis and synthesis. 2.5. Quality Assessment The quality and reliability of the selected studies were assessed to ensure the inclusion of robust and valid data. Quality assessment criteria were developed based on established guidelines for systematic reviews. The criteria included study design, sample representa- tiveness, data collection methods, analytical techniques, and reporting clarity. Each study Pollutants 2023, 3 549 was independently evaluated by two reviewers, and any discrepancies were resolved through discussion and consensus. 2.6. Data Analysis and Synthesis The extracted data was analyzed and synthesized to provide a comprehensive overview of the state of CoCs in Uganda. The data were summarized descriptively, highlighting key findings regarding the nature, sources, distribution, and potential impacts of the identi- fied pollutants. Where applicable, quantitative data were synthesized using appropriate statistical methods. The results were presented in tables, figures, and narrative summaries. 2.7. Limitations The review had potential limitations including the inclusive consideration of English- language studies, which may introduce language bias. Additionally, the review was limited to the available literature only until September 2023, possibly overlooking newer studies. Challenges in data synthesis and comparison may arise due to variations in methodologies and data reporting across different studies. Notably, being a literature review, ethical approval was not required; however, all selected studies were conducted adhered to ethical guidelines, and obtained appropriate ethical clearance where applicable. 3. Results and Discussion In this review, a comprehensive analysis of 177 articles was conducted to investigate the presence and concentrations of CoCs in Uganda. Employing the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flowchart facilitated the study selection process, providing a transparent overview of the search and screening procedure (see Figure 2) [68]. We initially identified 887 articles from various electronic databases. After the elimination of duplicate entries, 859 articles remained in the pool. Subsequently, we screened the titles and abstracts of these articles for relevance, leading to the exclusion of 214 articles that did not meet the inclusion criteria. Following the elimination of irrelevant articles, we sought the retrieval of the remaining 645 articles, while 305 articles could not be retrieved. We then carefully assessed the full texts of the remaining 340 articles for eligibility. After a meticulous evaluation, we excluded an additional 163 articles due to inadequate data or irrelevance, which ultimately resulted in the inclusion of 177 studies in the systematic review. A detailed summary of the characteristics of the included studies can be found in Table 1. This summary provides information such as author names, publication year, the classes of pollutants investigated, the areas of detection, sources, and concentrations in different environmental systems. The selected studies utilized a wide range of research approaches, including laboratory analyses, field studies, and monitoring programs. This systematic review successfully identified more than 194 CoC in Uganda, which were subsequently categorized into 12 major classifications, as illustrated in Figure 3. These classifications encompass pharmaceuticals, pesticides, persistent organic pollutants (POPs), personal care products, heavy metals, hydrocarbon compounds, biotoxins, radionuclides, electromagnetic radiations, microplastics, disinfection byproducts, and particulates, with detailed information provided in Tables 1 and 2. Pollutants 2023, 3 550 Pollutants 2023, 3, FOR PEER REVIEW 7 305 articles could not be retrieved. We then carefully assessed the full texts of the remain- ing 340 articles for eligibility. After a meticulous evaluation, we excluded an additional 163 articles due to inadequate data or irrelevance, which ultimately resulted in the inclu- sion of 177 studies in the systematic review. A detailed summary of the characteristics of the included studies can be found in Table 1. This summary provides information such as author names, publication year, the classes of pollutants investigated, the areas of detec- tion, sources, and concentrations in different environmental systems. The selected studies utilized a wide range of research approaches, including laboratory analyses, field studies, and monitoring programs. Figure 2. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow di- agram for the literature survey. This systematic review successfully identified more than 194 CoC in Uganda, which were subsequently categorized into 12 major classifications, as illustrated in Figure 3. These classifications encompass pharmaceuticals, pesticides, persistent organic pollutants (POPs), personal care products, heavy metals, hydrocarbon compounds, biotoxins, radio- nuclides, electromagnetic radiations, microplastics, disinfection byproducts, and particu- lates, with detailed information provided in Tables 1 and 2. The findings from these studies yield valuable insights into the state of CoCs in Uganda, shedding light on their potential implications for both human and environmental health. This diversity underscores the complex nature of pollution sources, arising from urbanization, industrial activities, agricultural practices, and improper waste manage- ment, highlighting the pressing need for comprehensive monitoring and assessment pro- grams to better understand their occurrence, behavior, and potential risks to the Figure 2. PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) flow diagram for the literature survey. Table 1. Major groups of CoCs; their descriptions, components, and properties, detected in Ugandan environmental systems. Category of CoC Description Components Persistence and Bioaccumulation Pharmaceuticals Medicinal compounds, including prescription and over-the-counter drugs, enter the environment through human excretion and wastewater. Antibiotics, Analgesics, Hormones, Antidepressants, Beta-Blockers, Diuretics, Antihypertensive, Fibrate, and Antiparasitic Low to Medium Persistence, some are bioaccumulative in zoobenthos Pesticides Chemical substances used to control pests in agriculture can leach into soil and water, impacting non-target organisms. Insecticides, Herbicides, Fungicides, and Rodenticides Medium to High Persistence, some are bioaccumulative such as the cases of Dichlorodiphenyl- trichloroethane (DDT) Persistent Organic Pollutants (POPs) Organic compounds that resist degradation, such as certain pesticides and industrial chemicals, with potential long-range transport effects. Polychlorinated Biphenyls (PCBs), Dioxins, and Furans, among others High persistence and Bioaccumulative Pollutants 2023, 3 551 Table 1. Cont. Category of CoC Description Components Persistence and Bioaccumulation Personal Care Products Chemicals found in cosmetics, shampoos, soaps, and perfumes can be washed into water bodies and contribute to water pollution. Fragrances, UV Filters, Preservatives, and Surfactants Low to Medium Persistence Heavy metals Metallic elements like lead, mercury, cadmium, and chromium can accumulate in the environment and pose health risks to living organisms. Lead (Pb), Mercury (Hg), Cadmium (Cd), Chromium (Cr), Nickle (Ni) among others Medium to High Persistence, some are bioaccumulative Hydrocarbon Compounds Organic compounds derived from petroleum, including polycyclic aromatic hydrocarbons (PAHs), are often associated with oil spills. Polycyclic Aromatic Hydrocarbons (PAHs), and Benzene Low to Medium Persistence, Bioaccumulative Biotoxins–Mycotoxins Toxins are produced by organisms like fungi (mycotoxins) and harmful algae, which can contaminate water and food sources, posing health risks. Aflatoxins, Ochratoxins, and Fusarium Toxins Low Persistence, bioaccumulative in humans and animals Radionuclides and Electromagnetic radiations Radioactive elements and non-ionizing electromagnetic radiation that can impact human health and the environment. Uranium (U), Thorium (Th), 40-K and Radon (Rn), Radiofrequency (RF), Microwaves, Electromagnetic Fields, Low to High persistence Other Contaminants of concern Various emerging contaminants, like flame retardants and nanomaterials, whose impacts on the environment and health are under investigation. Flame Retardants, and Nanomaterials, Persistent and highly Bioaccumulative, atmospheric deposition Microplastics Tiny plastic particles result from the breakdown of larger plastic waste, which can be ingested by organisms and enter the food chain. Microplastic particles, and Microfibers, Low to Medium Persistence, atmospheric deposition Disinfection byproducts Chemical compounds formed when disinfectants like chlorine react with organic matter in water, potentially leading to health risks. Trihalomethanes (THMs) Low to Medium Persistence Particulates Tiny solid particles or liquid droplets suspended in the air can have adverse health effects when inhaled by humans and animals. PM2.5 (Fine Particulate Matter), PM10 (Coarse Particulate Matter), Gases, Sulphur dioxide (SO2), Ozone (O3), and Nitrogen dioxide (NO2) Low Persistence Pollutants 2023, 3 552 Pollutants 2023, 3, FOR PEER REVIEW 8 environment and human health. One prominent category revealed in the reviewed stud- ies is the pharmaceutical compounds. Antibiotics, analgesics, hormones, and antidepres- sants have been detected in various environmental matrices such as water bodies and soils. These compounds enter the environment primarily through wastewater discharge and improper disposal of unused medications, raising concerns about ecological impacts and antibiotic resistance [30,42]. Figure 3. Major groups of CoCs detected in Ugandan environmental systems. Table 1. Major groups of CoCs; their descriptions, components, and properties, detected in Ugandan environmental systems. Category of CoC Description Components Persistence and Bioaccumulation Pharmaceuticals Medicinal compounds, including pre- scription and over-the-counter drugs, enter the environment through human excretion and wastewater. Antibiotics, Analgesics, Hormones, Antidepres- sants, Beta-Blockers, Diuret- ics, Antihypertensive, Fi- brate, and Antiparasitic Low to Medium Persis- tence, some are bioaccu- mulative in zoobenthos Pesticides Chemical substances used to control pests in agriculture can leach into soil and water, impacting non-target organ- isms. Insecticides, Herbicides, Fungicides, and Rodenti- cides Medium to High Persis- tence, some are bioaccu- mulative such as the cases of Dichlorodiphe- nyltrichloroethane (DDT) Figure 3. Major groups of CoCs detected in Ugandan environmental systems. The findings from these studies yield valuable insights into the state of CoCs in Uganda, shedding light on their potential implications for both human and environmental health. This diversity underscores the complex nature of pollution sources, arising from urbanization, industrial activities, agricultural practices, and improper waste management, highlighting the pressing need for comprehensive monitoring and assessment programs to better understand their occurrence, behavior, and potential risks to the environment and hu- man health. One prominent category revealed in the reviewed studies is the pharmaceutical compounds. Antibiotics, analgesics, hormones, and antidepressants have been detected in various environmental matrices such as water bodies and soils. These compounds enter the environment primarily through wastewater discharge and improper disposal of unused medications, raising concerns about ecological impacts and antibiotic resistance [30,42]. Pollutants 2023, 3 553 Table 2. Sources and occurrence of different categories/classes of detected concentrations of CoCs in Ugandan environmental compartments. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Pharmaceuticals Antibiotics Sulfamethoxazole Pharmaceutical Wastewater Effluents, Sediments, Soil, Surface Waters 1–5600 ngL−1 Murchison Bay on L. Victoria and Bugolobi wastewater treatment plant, Kampala, Uganda 2020–2022 [30,41,42] Trimethoprim Pharmaceutical 1300–22,600 ngL−1 Sulfamethazine Pharmaceutical 2.4–50 ngL−1 Sulfacetamide Pharmaceutical 0.8–13 ngL−1 Tetracycline Pharmaceutical 3–70 ngL−1 Erythromycin Pharmaceutical 10–66 ngL−1 Carbamazepine Pharmaceutical 5–72 ngL−1 Oxytetracycline Pharmaceutical 17–300 ngL−1 Tetracycline Pharmaceutical 2.7–70 ngL−1 Erythromycin Pharmaceutical 10–66 ngL−1 Azithromycin Pharmaceutical 14–60 ngL−1 Ciprofloxacin Pharmaceutical 2.0–41 ngL−1 Levofloxacin Pharmaceutical 1.8–29 ngL−1 Norfloxacin Pharmaceutical 1.9–26 ngL−1 Enoxacin Pharmaceutical 5.9–51 ngL−1 Ampicillin Pharmaceutical Wastewater Effluents, Ground Water, Runoffs 1350 ngL−1 Bwaise Wobulenzi city suburbs, Kampala, Uganda 2013–2022 [42,69,70] Chlortetracycline Pharmaceutical 394 ngL−1 Ciprofloxacin Pharmaceutical 340 ngL−1 Enrofloxacin Pharmaceutical 17 ngL−1 Metacycline Pharmaceutical 17 ngL−1 Nalidixic acid Pharmaceutical 2340 ngL−1 Oxytetracycline Pharmaceutical 17 ngL−1 Penicillin G (benzylpenicillin) Pharmaceutical 800 ngL−1 Sulfathiazole Pharmaceutical 140 ngL−1 Tetracycline Pharmaceutical 47.3 ngL−1 Analgesic/Anti- inflammatory Ibuprofen Pharmaceutical Wastewater treatment plant (WWTP) Effluents, Runoffs, sewer channel wastewater 5.9–780 ngL−1 Nakivubo sewer channel, Murchison Bay on L. Victoria and Bugolobi wastewater treatment plant, Uganda 2020 [30,41] Diclofenac Pharmaceutical 100–500 ngL−1 Acetaminophen Pharmaceutical 1.6–27 ng/L Antiepileptics/ antidepressant Carbamazepine Pharmaceutical 200–1300 ngL−1 346.496 µgL−1 *CEC Pollutants 2023, 3 554 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Beta-Blockers Atenolol Pharmaceutical Wastewater treatment plant (WWTP) Effluents, Runoffs, sewer channel wastewater 24–380 ngL−1 Nakivubo sewer channel, Murchison Bay on L. Victoria and Bugolobi wastewater treatment plant, Uganda 2020 [30,41] Metoprolol Pharmaceutical 0.4–21 ngL−1 Diuretics Furosemide Pharmaceutical 160–1300 ngL−1 Hydrochlorothiazide Pharmaceutical 230–1350 ngL−1 Antihypertensive Losartan Pharmaceutical 100–160 ngL−1 Fibrate Gemfibrozil Pharmaceutical 190–800 ngL−1 Antiparasitic Pyrimethamine Pharmaceutical 8.4–14.0 ngL−1 Pesticides Organochlorine pesticides (OCPs) Endosulfan sulfate Herbicide, insecticides and fungicides Air, sediment, and surface water samples 0.82–5.62 µg kg−1 d.w. (Banned for all users in 2011) Murchison, Waiya, Thurston Bays, and Napoleon Gulf on the Ugandan side of L. Victoria 2004–2022 [23,31,34,39, 45,49,52,71– 74] Aldrin Herbicide, insecticide 0.22–15.96 µg kg−1 d.w (MRL = 0.1 mg kg−1) (Banned for all users in 2001) Dieldrin Soil insecticide and for control of mosquitoes. 0.94–7.18 µg kg−1 d.w (MRL = 0.1 mg kg−1) (Banned for all users in 2001) Lindane Insecticide 7–11.4 µg kg−1 d.w. (MRL = 0.5 mg kg−1) Chlordane Insecticide 3.82–35.6 pgm−3 (Banned for all users in 2001) Hexachlorocyclohexanes Insecticide 3.72–81.8 pg m−3 (Banned for all users in 2009) Heptachlor Insecticide 0.81 µg kg−1 d.w. (Banned for all users in 2001) Heptachlor epoxide Insecticide. Used for fire ant control in power transformers 3.19 µg kg−1 d.w. (Banned for all users in 2001) p, p′- dichlorodiphenyldichloroethy- lene (DDE) Insecticides 0.11–3.59 µg kg−1 d.w. (Banned for all users in p, p′-DDD 0.38–4.02 µg kg−1 d.w. (Banned for all users in p, p′- dichlorodiphenyltrichloroethane (DDT) 0.04–1.46 µg kg−1 d.w. (Banned for all users in Pollutants 2023, 3 555 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Pesticides Organochlorine pesticides (OCPs) o, p′-DDE Insecticides Air, sediment, and surface water samples 0.07–2.72 µg kg−1 d.w. Murchison, Waiya, Thurston Bays, and Napoleon Gulf on the Ugandan side of L. Victoria 2004–2022 [23,31,34,39, 45,49,52,71– 74]o, p′-DDT 0.01–1.63 µg kg−1 d.w. Total Endosulfan Isomer of Endosulfan. Insecticide and acaricide 12.3–282 pg m−3 (Banned for all users in 2011) Air and water samples of Lake Victoria Northern shore watershed, areas of Kakira and Entebbe, Uganda 2006–2022 [31,45,49,69, 72,73,75–78]Total DDT-related compounds Insecticide used in agriculture 22.8–130 pg m−3 (Banned in 2001, production for the specific uses) Endosulfan sulphate Insecticide and acaricide 0.82–5.62 µg kg−1 d.w. (Banned for all users in 2011) α-Endosulfan 7.59 and 6.00 µg kg−1 (MRL = 0.1 mg kg−1) (Banned for all users 2011) Napoleon Gulf on L. Victoria, Uganda 2004–2022 [34,49,73,79] p, p′-1,1-dichloro-2,2-bis-(4- chlorophenyl) ethylene (p, p′-DDE) Insecticide Air, Surface waters, Fish Tissues 6.10 and 3.44 µg kg−1 Napoleon Gulf on L. Victoria, Uganda 2006–2010 [31,45,77] p, p′-1,1,1-trichloro-2,2-bis-(4- chlorophenyl) ethane (p, p′-DDT) 7.34 and 4.30 µg kg−1 (MRL = 0.1 mg kg−1) ∑DDTs 503.6 µg kg−1 d.w. Abandoned pesticide store in Masindi district in western Uganda 2020 [78] Endosulfans 1.55 µg kg−1 d.w. (Banned for all users in 2011) p, p’DDE 125 mg/kg Kampala and Iganga districts in Uganda 1996–2011 [44,80] Dieldrin 123 mg/kg p, p’DDD 24 mg/kg p, p, DDT 13 mg/kg o, p’DDT 23 mg/kg α-hexachlorocyclohexane (HCH) 54 mg/kg (Banned for all users in 2009) β-HCH 10 mg/kg (Banned for all users in 2009) Total Dichlorodiphenyl- trichloroethane (ΣDDTs) 22.8–130 pg/m3 Kakira and Entebbe, northern shore of L. Victoria, Uganda 2016 [73] Total hexachlorocyclohexanes (ΣHCHs) 3.72–81.8 pg/m3 Total Endosulfan (ΣEndo) 12.3–282 pg/m3 Pollutants 2023, 3 556 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Pesticides Carbamates Carbofuran Insecticide Air, Surface waters, Fish Tissues 83.3 pg/m3 Air samples from Kakira and Entebbe, northern shore of L. Victoria, Uganda 2010–2019 [72,78,81]Organophosphates (OPPs) Chlorpyrifos 93.5 ng/m3 Chlorthalonil Fungicide <0.10–24.0 pg m−3 Metribuzin Herbicide <0.02–0.53 ng m−3 Trifluralin 0.02–0.32 pg m−3 Malathion Insecticide <0.08–193 pg m−3 Persistent organic pollutants (POPs) Brominated Flame Retardants polybrominated diphenyl ethers (PBDEs) Are used as coolants and lubricants in transformers, capacitors, and other electrical equipment Sediment samples 9.84 pg g−1 dry weight (Banned for all users in 2001) Napoleon Gulf and Thurston Bay on the northern shore of L. Victoria, Uganda 2013 [46] Chlorinated Flame Retardants Dioxin-like polychlorinated biphenyls (PCBs) 136 pg g−1 dw (Banned for all users in 2001) 2006–2021 [40,46,60,82] polychlorinated dibenzo-p-dioxins/furans (PCDD/Fs) 44.1 pg g−1 d.w. 0.07–5.53 pg Toxic Equivalent Factors (TEQ) g−1 d.w. (Banned for all users in 2001) 2006–2021 [40,60,82] polychlorinated dibenzofurans (PCDFs) 0.07–5.61 pg g−1 d.w. 0.01–0.23 pg TEQ g−1 d.w. (Banned for all users in 2001) 2006–2021 [40,60,82] Organochlorine pesticides Pymetrozine Pesticide Edible Insects 0.02 pg g−1 d.w. Ugandan districts 2022 [39] Methabenzthiazuron 0.08 pg g−1 d.w. Metazachlor 1.4 ± 0.03 pg g−1 d.w. Fenimorph 0.04 ± 0.03 pg g−1 d.w. Fludioxonil Fungicide 0.29 pg g−1 d.w. Metalaxyl 0.01 ± 0.01 pg g−1 d.w. Organophosphorus flame retardants (OPFRs) Tricresyl phosphate Used as a plasticizer Waters, sediments, and soil samples 25–8100 ngL−1 Napoleon gulf, Murchison, Waiya, Entebbe, and Thurston bays, Uganda 2006–2021 [31,43,44,49, 72,74,76–78] Tris-(2-chloroethyl) phosphate (TCEP) Widely used as a plasticizer, fire retardant, and solvent 24–6500 ngL−1 Triphenyl phosphate (TPP) 54–4300 ngL−1 Tris-(2-ethylexyl) phosphate (TEHP) 4300 ngL−1 2-Ethylhexyl diphenyl phosphate (EHDPP) 7.7–730 ngL−1 Tricresyl phosphate (TCP) 8100 ngL−1 Pollutants 2023, 3 557 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Persistent organic pollutants (POPs) Tris-(2-chloroisopropyl) phosphate (TCPPi) Used as plasticizers and antifoam agents Waters, sediments, and soil samples 25–600 ngL−1 Napoleon gulf, Murchison, Waiya, Entebbe, and Thurston bays, Uganda 2006–2021 [31,43,44,49, 72,74,76–78]Tributyl phosphate (TBP) 29 ngL−1 Triethyl phosphate (TEP) 9.6–500 ngL−1 Phthalate ester plasticizers (PEP) Dibutyl phthalate (DBP) Are added to polymers to ease processing and to enhance flexibility and toughness of the final product Waters, sediments, and soil samples 350–16,000 ngL−1 Napoleon gulf, Murchison, Waiya, Entebbe, and Thurston bays, Uganda 2021 [43] Bis-(2-ethylhexyl) phthalate (DEHP) 210–23,000 ngL−1 Dimethyl phthalate 6.8–400 ngL−1 Diethyl phthalate (DEP) 38–1100 ngL−1 N-butyl benzenesulfonamide (NBBS) 7.5–200 ngL−1 Bis-(2-ethylhexyl) adipate (DEHA) 12–6100 ngL−1 Personal Care Products Antimicrobial Triclosan Antibiotics in soaps, toothpaste, detergents Wastewater Effluents 89–1400 ngL−1 Napoleon gulf, Murchison, Waiya, Entebbe, and Thurston bays, Uganda 2021 [43] Organic sunscreens Benzophenone Protect the products from UV light 36–1300 ngL−1 4-methylbenzylidine camphor Organic UV filters 21–1500 ngL−1 Phenolic antioxidants Butylated hydroxytoluene Used as an antioxidant in cosmetic product formulations 14–750 ngL−1 Synthetic musk fragrances Musk ketone Used in cleaning and washing agents, surface treatments, lubricants and additives 7.3–460 ngL−1 Preservatives Chlorophene Used to be applied as a preservative and disinfectant in personal care products 21–310 ngL−1 Masking agent Acetophenone Covers the unpleasant scents of other ingredients 2.2–100 ngL−1 3-methylindole It is used as a flavoring ingredient 1.8–130 ngL−1 Insect repellents N, N-diethyltoluamide Is an active ingredient in many insect-repellent products 3.9–98 ngL−1 Pollutants 2023, 3 558 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Personal Care Products Preservatives 3-tert-butyl-4-hydroxy anisole Is used as an antioxidant and preservative Wastewater Effluents 7.3–100 ngL−1 Napoleon gulf, Murchison, Waiya, Entebbe, and Thurston bays, Uganda 2021 [43] Antioxidant 2,6-di-tert-butyl-phenol They are used as stabilizers, free-radical scavengers, and antioxidants 66 ngL−1 Heavy metals Post-transition metals Pb Battery assembling, in gasoline Water, sediments, dairy, and beef product samples 79–138.18 mg/kg Nakivubo channelized stream sediments and in Kampala markets, Uganda 2009–2021 [32,34,47,48, 83–94] Transition metals Cd Find applications in batteries, alloys, coatings (electroplating), solar cells, plastic stabilizers, and pigments Water, sediments, Roadside soils, surface films, and selected vegetable weeds 0.84–1.04 mg/kg Transition metals Cu Find applications in electrical wiring, roofing, plumbing, and industrial machinery. Sludge waste, dairy and beef products, soil, food crops, groundwater, Industrial effluents, Herbal medicine, rainwater, sediments, food items, water sediments, dumpsites 28.84–38.01 mg/kg Nakivubo stream, Southwestern Uganda, Kilembe copper mines, Jinja steel rollings and Osukuru phosphate mines, Kampala markets, L. Victoria 2006–2021 [32,33,36,47, 86–90,94–102] Trace element Zn Smelting and galvanization Roadside soils, surface films, and selected vegetable weeds 177.89–442.40 mg/kg Kampala city roads, Uganda 2017–2022 [47,83,89,101, 102] Transition metals Mn Welding, making structural alloys Food crops, 363.47 mg/kg Kampala City, Uganda 2004–2019 [33,48,52,71] Transition metal Fe Making alloy steels Groundwater, soils, stream sediments, and food crops. 30,085.33–5835.00 mg/kg Nakivubo stream, Kilembe copper mines, southwestern Uganda areas 2004–2021 [33,91,92,95, 99,103] Transition metal Ni Use in alloying such as in armor plating Soils, surface water, herbal medicines, and food items 2.2–9.40 ppm Jinja steel rolling mills, areas of southwestern Uganda, and Kampala markets 2015–2020 [87,98,99] Metalloid As Used as an allowing agent as well as in making glass, pigments, textiles, and both metal and wood adhesives Up and Downstream waters, soil, surface water, and plant tissues 0.5–4.6 ppm Roofings rolling mills, steel and tube industries in Nakawa Industrial area and areas of Kilembe copper mines, Uganda 2007–2022 [47,87,91,92] Pollutants 2023, 3 559 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Heavy metals Transition metals Co Making alloys, find applications in magnets and is also used as a catalyst in petroleum industries. Surface water, vegetables, and medicinal herbal samples 0.233 g/mL River Nyamwamba areas in Kasese, southwestern Uganda parts, and Soroti district 2010–2020 [33,86,98] Transition metals Hg Find applications in gold extraction and also used in manometers Soils, Food samples, Surface waters 0.05 ± 0.01 ppm Kampala, Wakiso and Busia districts, Uganda 2009–2022 [34,47,103] Transition metals Cr Applied in the manufacture of steel as well as hardening steel Soils, Dairy products, Herbal samples, Food samples 156.9 ppm Steel and Tube industrial area, Roofings rolling mills area, Kampala and Soroti districts, Uganda 2010–2022 [32,104] Transition metal Fe Making alloy steels Sediments, Soils, Surface Waters, 64.05–147.40 mg/Kg Industrial effluents in Kampala and Soroti districts, Nakivubo stream, and Osukuru phosphate mines areas, Uganda 2007–2022 [87,91,92] Hydrocarbon Com- pounds High and Low molecular Polycyclic aromatic hydrocarbons (PAHs) Acenaphthene Used to prepare naphthalene dicarboxylic anhydride, which is a precursor to dyes Leachates and Groundwater samples 1020 ng/L Bwaise and Wobulenzi towns in Kampala district, Uganda 2013–2021 [67,69,105] Acenaphthylene Used to make electrically conductive polymers 92 ng/L Anthracene Used in the manufacture of red dye alizarin, wood preservation, insecticide, coating of material 340 ng/L Benzo[a]pyrene No known uses 405 ng/L 1.1 ng/L Benzo[k]fluoranthene Majorly used for research purposes 180 ng/L 226 ng/L Chrysene Used to make some dyes. 102 ng/L 224 ng/L Fluoranthene No found uses but is produced by some plants. 550 ng/L 580 ng/L Fluorene Used to make dyes, plastics, and pesticides. 480 ng/L 240 ng/L Pollutants 2023, 3 560 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Hydrocarbon Com- pounds High and Low molecular Polycyclic aromatic hydrocarbons (PAHs) Naphthalene Industrial solvent Leachates and Groundwater samples 570 ng/L 258 ng/L Bwaise and Wobulenzi towns in Kampala district, Uganda 2013–2021 [67,69,105] Phenanthrene Used to make dyes, plastics and pesticides, explosives and drugs 220 ng/L 1050 ng/L Pyrene Used to produce dyes, plastics, and pesticides. 40–687 ng/L BTEX compounds Benzene Industrial solvent 86.7 ng/L Ethylbenzene Industrial solvent 5–960 ng/L Xylene Industrial solvent 410 ng/L Low and High Molecular Polycyclic aromatic hydrocarbons (PAHs) Naphthalene Naphthalene Sediments and Fish tissues 184–239 ng g−1 d.w. The White Nile environment near melt oil fields, South Sudan, Uganda Napoleon Gulf, and Murchison Bays 2017–2021 [67,105,106] Acenaphthylene Used to make electrically conductive polymers 16–20.5 ng g−1 d.w. Fluorene Used to make dyes, plastics, and pesticides. 148–156 ng g−1 d.w. Anthracene Used in the artificial manufacture of red dye alizarin, wood preservation, insecticide, coating of material 79.3–112 ng g−1 d.w. Fluoranthene No found uses and is said to be produced by some plants. 2.46–8.73 ng g−1 d.w. Pyrene Used to produce dyes, plastics, and pesticides. 2.09–5.7 ng g−1 d.w. Benzo[a]anthracene Can be found in coal tar, roasted coffee, smoked foods, and automobile exhaust and is used in research laboratories 0.5–1.3 ng g−1 d.w. Chrysene Used to make some dyes. 8.4–25 ng g−1 d.w. Benzo[b]fluoranthene Research purpose 2.7–9.3 ng g−1 d.w. Benzo[k]fluoranthene Research purpose 0.6–6.5 ng g−1 d.w. Benzo[a]pyrene No known use 0.02–1.06 ng g−1 d.w. Dibenzo [a, h] anthracene Is used only for research purposes to induce tumorigenesis 1.0–1.9 ng g−1 d.w. Pollutants 2023, 3 561 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Hydrocarbon Com- pounds Chlorinated aromatic chemicals Polychlorinated dibenzo-p-dioxins (PCDDs) Applicable in chemicals, notably herbicides Sediments 44.1 pg g−1 dry weight (d.w.) Napoleon Gulf and Thurston Bay on the northern shore of L. Victoria, Uganda 2017–2021 [67,105,106]Polychlorinated dibenzofurans (PCDFs) 5.61 pg g−1 dry weight (d.w.) Dioxin-like Polychlorinated biphenyls (di-PCBs) 136 pg g−1 d. w. Biotoxins– Mycotoxins Aflatoxins Aflatoxin B1 (AFB1) Exert inhibitory effects on biological processes including DNA synthesis, DNA-dependent RNA synthesis, DNA repair, and protein synthesis Food Samples 16.0 ± 3.6 µg/kg Kitgum district 2006–2010 [107–110] 1.9 ± 0.9 µg/kg Kitgum and Lamwo districts, Uganda 2021–2022 [101,110–113] 2.9 ± 1.2 µg/kg 4.3 ±1.5 µg/kg 2.4 ± 1.1 µg/kg 3.5 ± 2.9 µg/kg 16.0 ± 3.6 µg/kg Fish Tissues 148 ± 46.9 µg/kg Lake Victoria Basin, Uganda Fish Tissues 110 ± 39.9 µg/kg Lake Victoria Basin, Uganda 2006–2016 [107,108] Aflatoxin B2 (AFB2) Food Samples 0–540 µg/kg Mubende, Uganda 2006–2016 [107,108]10.5 ± 6.15 µg/kg Iganga markets, Uganda 7.3 ± 4.98 µg/kg Mayuge markets, Uganda 11.5 ± 0.43 µg/kg Southwestern Uganda markets 2010–2021 [110,114] Food Samples 15.2 ± 0.20 µg/kg Southwestern Uganda markets 2016–2018 [86,108] 14.0 ± 1.22 µg/kg Southwestern Uganda markets 2010 [110] Aflatoxin G1 [AFG1] 16.0 ± 1.66 µg/kg Southwestern Uganda 2010–2016 [108,110] 18.6 ± 2.40 (µg/kg) Southwestern Uganda [110] 0–540 µg/kg Kampala markets, Uganda [101,107] 9.6 ± 4.20 µg/kg Mubende markets, Uganda [110,114] 10.1 ± 3.10 µg/kg Ibanda markets, Uganda 2010–2020 [108,113,115]9.1 ± 4.35 µg/kg Jinja markets, Uganda 2010–2020 11.0 ± 3.01 µg/kg Hoima markets, Uganda Pollutants 2023, 3 562 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Biotoxins– Mycotoxins Aflatoxins Aflatoxin G2 (AFG2) Exert inhibitory effects on biological processes including DNA synthesis, DNA-dependent RNA synthesis, DNA repair, and protein synthesis Food Samples 10.6 ± 1.63 µg/kg Mayuge markets, Uganda 2010–2020 [108,113,115] 6.5 ± 0.60 µg/kg Buikwe markets, Uganda 3.8 ± 1.30 µg/kg Mpigi markets, Uganda 7.2 ± 1.99 µg/kg Masindi markets, Uganda 8.5 ± 2.56 µg/kg Bugiri markets, Uganda 2021 [114] Aflatoxin M1 (AFM1) Aflatoxin M1 is usually present in the fermentation broth of Aspergillus parasiticus and is a metabolite of aflatoxin B1 in humans and animals Food Samples 60.3 ± 27.99 µg/kg Kalerwe markets, Uganda 2010–2017 [101,110] 40.5 ± 12.82 µg/kg Bukoto markets, Uganda 10.3 ± 3.54 µg/kg Nakawa markets, Uganda 2010–2017 [101,115] 143.1 µg/kg Owino markets, Uganda 2017 [101] 5.8 ± 12.3 µg/kg Bugiri markets, Uganda 2010 [115] Food Samples 2.9 ± 6 µg/kg Bulambuli markets, Uganda 2010 [115] 0.7 ± 0.3 µg/kg Bundibugyo areas, Uganda 1.0 ± 0.9 µg/kg Gulu markets, Uganda 290.7 µg/kg Hoima areas, Uganda 2.4 ± 4.0 µg/kg Iganga markets, Uganda 145.5 µg/kg Kabale markets, Uganda 1.0 ± 0.7 µg/kg Kapchorwa areas, Uganda 1.7 ± 0.5 µg/kg Kasese markets, Uganda 1.7 ± 0.5 µg/kg Kiryadongo areas, Uganda Food Samples 6.87 µg/kg Northern Uganda 2010–2020 [108,112,113, 115] 6.77 µg/kg Northern Uganda 1.46 µg/kg Northern Uganda 10.24 µg/kg Northern Uganda Pollutants 2023, 3 563 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Biotoxins– Mycotoxins Ochratoxins (OTA) OTA-A, B, and C Can benefit humans by their use as antibiotics (penicillins), immunosuppressants (cyclosporine), and in control of postpartum hemorrhage and migraine headaches Food Samples 4.4 ± 0.8 n Kitgum markets, Uganda 2019–2021 [112,113,115, 116] 3.5 ± 0.7 ng/g Lamwo Markets, Uganda 2010–2020 3760 ng/g Kitgum markets, Uganda 0.3 ± 0.1ng/g Lamwo Markets, Uganda 1.1 ± 0.3 ng/g Kitgum markets, Uganda 1.0 ± 0.3 ng/g Lamwo Markets, Uganda 1.5 ± 0.3 ng/g Kitgum markets, Uganda 1.4 ± 0.2 ng/g Lamwo market, Uganda s 4.89 ng/g Northern Uganda 0.37 ng/g Northern Uganda 1.32 ng/g Northern Uganda 7.44 ng/g Northern Uganda Fumonisins A, B, C, and P-series Are usually esterified with propane tricarboxylic acid to provide a hydrophobic/hydrophilic dichotomy that is unique among the mycotoxins Fish Tissues 0.3 ± 0.19 µg/kg Lake Victoria Basin, Uganda 2011–2021 [113,117–119] 0.2 ± 0.24 µg/kg Lake Victoria Basin, Uganda 2021 [113] Food Samples 80.2–0.6 µg/kg Kampala markets 2016 [108] 1.19 µg/kg Northern parts of Uganda’s markets 2000–2021 [113,115,120] 19.4–99.8 µg/kg 2011–2021 [113,117–119]0.76 µg/kg 4.402 µg/kg Trichothecene Vomitoxin/Deoxynivalenol Is used as a mycotoxin to induce cytotoxicity in porcine jejunal epithelial cells and study the protective effects of Saccharomyces cerevisiae on the cell viability of host cells. Food Samples 0.153 µg/kg Northern parts of Uganda’s markets 2011–2021 [113,117–119] 0.92793 µg/kg 0.153 µg/kg 0.823 µg/kg Pollutants 2023, 3 564 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Radionuclides and electro- magnetic radiation Primordial radionuclides (naturally occurring noble gases) Radon (226Ra) Uranium-238. Used in making nuclear weapons as a ‘tamper’ material. Plant Tissues and Food samples 8.06 Bq/kg Osukuru phosphate factory areas, Tororo District, Uganda 2020–2021 [121,122] 7.08 Bq/kg 3.55 Bq/kg 9.14 Bq/kg 5.34 Bq/kg 4.35 Bq/kg 10.02 Bq/kg 4.88 Bq/kg 2.99 Bq/kg Tororo cement factory area 18 ± 3 Bqm−3 Dormitories at Adwari S.S., Uganda 2014–2020 [98,121–123] 31 ± 3 Bqm−3 Dormitories at Ogor Seed S.S., Uganda 26 ± 3 Bqm−3 Dormitories at Okwang S.S., Uganda 26 ± 2 Bqm−3 School Dormitories at Orum S. S, Uganda 49 ± 5 Bqm−3 Dormitories at Otuke S.S., Uganda Tororo mining area 97 ± 5 Bqm−3 Tororo district Chemical Laboratory tests 96 ± 4 Bqm−3 Eastern Uganda 2014–2022 [95,121–123] Steel company area 72 ± 3 Bqm−3 Steel Works in Eastern Uganda Hospital area 51 ± 2 Bqm−3 Hospitals in Eastern Uganda Hotel 28 ± 1 Bqm−3 TLT Hotel in Eastern Uganda Residential houses 92 ± 4 Bqm−3 Residential houses (closed) in Eastern Uganda Homesteads 45 ± 1 Bqm−3 Houses (Far away) in Eastern Uganda Pollutants 2023, 3 565 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Radionuclides and electro- magnetic radiation Primordial radionuclides (naturally occurring noble gases) Thorium (232Th) Used in making lenses for cameras, scientific instruments, high-temperature crucibles, and electrical equipment Soil mine tailings 119.3–376.7 Bq kg−1 Mashonga Gold Mine, Uganda 2016 [124] 211.7 ± 17.3 Bq kg−1 Kikagati Tin mine, Uganda 244.4 ± 10.9 Bq kg−1 Butare Iron ore mine, Uganda Food Samples 18.60 Bq/kg Medicinal plants in Osukuru, Tororo District, Uganda 15.51 Bq/kg 7.67 Bq/kg 11.26 Bq/kg 11.57 Bq/kg 5.98 Bq/kg 13.28 Bq/kg 7.37 Bq/kg 3.00 Bq/kg 2.24 Bq/kg Air 181.2 ± 66.8 nGy h−1 Mashonga Gold Mine, Uganda 2016 [124]167.2 ± 43.0 nGy h−1 Kikagati Tin mine, Uganda 191.6 ± 29.6 nGy h−1 Butare Iron ore mine, Uganda 40K (Potassium-40) Acts as a signaling molecule in a wide variety of processes Food Samples 350.17 Bq kg−1 Osukuru mines, Tororo District, Uganda 2021 [121] 141.0–1658.5 Bq kg−1 365.35 Bq/kg 297.81 Bq/kg 437.92 Bq/kg 419.72 Bq/kg 343.78 Bq/kg 379.21 Bq/kg 363.99 Bq/kg Pollutants 2023, 3 566 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Radionuclides and electro- magnetic radiation Primordial radionuclides (naturally occurring noble gases) 40K (Potassium-40) Acts as a signaling molecule in a wide variety of processes Food Samples 275.86 Bq/kg Osukuru mines, Tororo District, Uganda 2021 [121]361.07 Bq/kg Soil mine tailings 391.5 ± 46.3 Uranium (238U) Used in making nuclear weapons as a ‘tamper’ material. Soil mine tailings 35.5–147.0 Bq kg−1 Southwestern Uganda 2016 [124] 58.7 ± 8.8 Bq kg−1 Mashonga Gold Mine, Uganda 49.7 ± 3.1 Bq kg−1 Kikagati Tin mine, Uganda 57.6 ± 2.9 Bq kg−1 Butare Iron ore mine, Uganda Other emerging CoC Per- and poly-fluoroalkyl substances (PFASs) Perfluorooctane sulfonic acid (PFOS) Food package material, stain- and water-repellent fabrics, non-stick products (e.g., Teflon), polishes, waxes, paints, cleaning products, fire-fighting foams, industrial facilities (e.g., chrome plating, electronic goods, and oil recovery), Landfill wastewater treatment plant, and living organisms (e.g., fish, animals, and humans) due to the accumulation and persistence over time Wastewater effluent 1.3–2.4 ng L−1 Nakivubo wetland area, downstream of Bugolobi WWTP and upstream of L. Victoria, Uganda 2018–2021 [50,51] Soils 600–3000 pg g−1 (Banned in 2009, production for specified uses) Perfluorooctanoate (PFOA) Surface water 1.5–2.4 ng L−1 Soils 480–910 pg gL−1 d.w. (Banned in 2019, production for specified uses) Perfluoroheptanoate (PFHpA) Plant tissues 0.65–0.67 pg gL−1 d.w. Perfluorohexanoic acid (PFHxA) Soils 210–460 pg gL−1 d.w. (Banned in 2022 for all users) Average Perfluoroalkane sulfonates (∑PFSAs) Urban runoffs 8.5–14 ngL−1 Wetland soil 4200–5300 pg g−1 d.w. Nakivubo Wetland, Uganda 2018–2021 [50,51]Sugarcane soil 3000–7900 pg g−1 d.w. Maize soil 1600–4900 pg gL−1- d.w. Microplastics Microplastics <1 mm size Plastic materials utilized by communities Surface water 0.69–2.19 particles/m3 Surface water of northern L. Victoria, Uganda 2020 [125] Disinfection byproducts Trihalomethanes Chloroform Uses as an extraction solvent Drinking water 23.07 µg/L Ggaba water treatment plant and water distribution lines, Uganda 2022 [126] Bromodichloromethane Was formerly used as a flame retardant but now is used as a reagent or an intermediate in organic chemistry. 10.5 µg/L Total trihalomethane (TTHM) Used in the treatment of water to kill disease-causing microorganisms. 32.89 µg/L Pollutants 2023, 3 567 Table 2. Cont. Categories of CoC Classes CoC (s) Use/Application Sampling Matrix Detected Levels Place of Study Detection Periods References Particulates Particulate matter PM2.5 Help in the implementation of effective pollution control measures and public health interventions to protect people and improve air quality Air samples 152.6 µg/m3 Kampala, Jinja, Mbarara, kyebando, and Rubindi districts, Uganda 2010–2022 [24,102,127– 129] Long-term particulate matter PM10 208 µg/m3 Gas Phase Pollutants NO2 Used in the production of nitric acid, lacquers, dyes, and other chemicals 24.9 µg/m3 SO2 Used in the preparation of sulfuric acid, sulfur trioxide, and sulfites 3.7 µg/m3 O3 Is extensively applied for decontamination purposes 11.4 µg/m3 CEC—Critical Environmental concentration values [42]. MRL—Maximum residue limits. Pollutants 2023, 3 568 4. Challenges of CoCs in Uganda 4.1. Sources, Occurrence, Fate, and Transport of CoCs in Uganda Several studies conducted in Uganda have identified and quantified various classes of CoCs in different environmental matrices, including WWTP and industrial effluents, surface and groundwater, food items, air, sediments, edible insects, and soil. Surface waters were identified with the highest pollution levels (58%) for all the detected CoC in Uganda as illustrated in Figure 4. In addition, pharmaceutical residues, pesticides and POPs were the mostly detected CoC in all the available literature as illustrated in Figure 5. Furthermore, this review unveiled the distribution patterns and sources of CoCs in Uganda, shedding light on areas with substantial pollution loads. Urban areas, industrial zones, and agricultural regions emerged as the most prominent sources of both legacy and ECs in Uganda. Rapid urbanization sweeping across the country, coupled with inadequate waste management practices, are identified as the biggest contributors of most CoC that find their way into various environmental compartments in Uganda, contaminating both surface and groundwater resources [28,71,130]. Industrial activities on the other hand, are identified as the biggest contributors of multitudes of chemical byproducts into the various environmental matrices [41,48,50,87], followed by agricultural practices characterized by the application of pesticides and fertilizers, leading to significant soil and water pollution [69,77,78,81]. Additionally, the uncontrolled municipal waste disposal, WWTP effluents, and urban center runoffs are identified as the main drivers for the presence of most CoC in different matrices. Pollutants 2023, 3, FOR PEER REVIEW 29 waters were identified with the highest pollution levels (58%) for all the detected CoC in Uganda as illustrated in Figure 4. In addition, pharmaceutical residues, pesticides and POPs were the mostly detected CoC in all the available literature as illustrated in Figure 5. Furthermore, this review unveiled the distribution patterns and sources of CoCs in Uganda, shedding light on areas with substantial pollution loads. Urban areas, industrial zones, and agricultural regions emerged as the most prominent sources of both legacy and ECs in Uganda. Rapid urbanization sweeping across the country, coupled with inade- quate waste management practices, are identified as the biggest contributors of most CoC that find their way into various environmental compartments in Uganda, contaminating both surface and groundwater resources [28,71,130]. Industrial activities on the other hand, are identified as the biggest contributors of multitudes of chemical byproducts into the various environmental matrices [41,48,50,87], followed by agricultural practices char- acterized by the application of pesticides and fertilizers, leading to significant soil and water pollution [69,77,78,81]. Additionally, the uncontrolled municipal waste disposal, WWTP effluents, and urban center runoffs are identified as the main drivers for the pres- ence of most CoC in different matrices. Figure 4. Percentage contaminations of different matrices from the conducted studies in Uganda. 58% 10% 3% 4% 2% 2% 3% 0% 2% 15% 0% 1% Surface waters WWTP effluents Ground water Soil Sediments Runoffs Air Food items Dumpsites Drinking water Herbal plants Food items 0 10 20 30 40 50 60 70 80 90 100 Pe rc en ta ge o cc ur en ce (% ) CoC in Uganda Herbal plants Drinking water Dumpsites Food items Air Runoffs Sediments Soil Ground water WWTP effluents Surface waters Figure 4. Percentage contaminations of different matrices from the conducted studies in Uganda. Considering all the 82 articles related to the occurrence of CoCs in Uganda out of 177 articles selected for this study, a total of 194 contaminants were detected in 121 districts out of the 136 in the five regions of the country and in different environmental matrices. Central Uganda which hosts the country’s capital city—Kampala emerged with the greatest pollution indices, attributed to the industrial growth and urban activities, this is followed by eastern Uganda where most of the industrial parks are located, then western Uganda renowned for agricultural activities, southern, and finally northern parts of Uganda with the least pollution indices as illustrated in Figure 6a. Pollutants 2023, 3 569 Pollutants 2023, 3, FOR PEER REVIEW 29 waters were identified with the highest pollution levels (58%) for all the detected CoC in Uganda as illustrated in Figure 4. In addition, pharmaceutical residues, pesticides and POPs were the mostly detected CoC in all the available literature as illustrated in Figure 5. Furthermore, this review unveiled the distribution patterns and sources of CoCs in Uganda, shedding light on areas with substantial pollution loads. Urban areas, industrial zones, and agricultural regions emerged as the most prominent sources of both legacy and ECs in Uganda. Rapid urbanization sweeping across the country, coupled with inade- quate waste management practices, are identified as the biggest contributors of most CoC that find their way into various environmental compartments in Uganda, contaminating both surface and groundwater resources [28,71,130]. Industrial activities on the other hand, are identified as the biggest contributors of multitudes of chemical byproducts into the various environmental matrices [41,48,50,87], followed by agricultural practices char- acterized by the application of pesticides and fertilizers, leading to significant soil and water pollution [69,77,78,81]. Additionally, the uncontrolled municipal waste disposal, WWTP effluents, and urban center runoffs are identified as the main drivers for the pres- ence of most CoC in different matrices. Figure 4. Percentage contaminations of different matrices from the conducted studies in Uganda. 58% 10% 3% 4% 2% 2% 3% 0% 2% 15% 0% 1% Surface waters WWTP effluents Ground water Soil Sediments Runoffs Air Food items Dumpsites Drinking water Herbal plants Food items 0 10 20 30 40 50 60 70 80 90 100 Pe rc en ta ge o cc ur en ce (% ) CoC in Uganda Herbal plants Drinking water Dumpsites Food items Air Runoffs Sediments Soil Ground water WWTP effluents Surface waters Figure 5. Percentage occurrences of CoCs in different matrices in Uganda. Pollutants 2023, 3, FOR PEER REVIEW 30 Figure 5. Percentage occurrences of CoCs in different matrices in Uganda. Considering all the 82 articles related to the occurrence of CoCs in Uganda out of 177 articles selected for this study, a total of 194 contaminants were detected in 121 districts out of the 136 in the five regions of the country and in different environmental matrices. Central Uganda which hosts the country’s capital city – Kampala emerged with the great- est pollution indices, attributed to the industrial growth and urban activities, this is fol- lowed by eastern Uganda where most of the industrial parks are located, then western Uganda renowned for agricultural activities, southern, and finally northern parts of Uganda with the least pollution indices as illustrated in Figure 6a. (a) (b) Figure 6. (a) Percentage numbers of CoCs investigated in the available literature in Uganda; (b) percentage levels of CoCs in different regions of Uganda from the conducted studies. Furthermore, these CoCs from different sources eventually find their way into vari- ous environmental compartments, including soil, rivers, lakes, air, and even drinking wa- ter where they accumulate. Pharmaceutical residues have the highest accumulation rate (21%), followed by the pesticides (17%) and the least is observed in microplastics from the available literature as illustrated in Figure 6b [131,132]. The introductions and accumula- tion of these compounds can have detrimental consequences for ecosystems and eventu- ally humans. The fate and persistence of these contaminants are strongly influenced by the physicochemical properties of the environmental compartments they interact with as illustrated in Figure 7. The primary processes that dictate the fate of CoCs in the environ- ment include their biodegradation rate, photodegradation rate, and sorption kinetics [4,133]. Humans and animals may consume these contaminants for diverse reasons, such as for medical or recreational purposes, including veterinary drugs in the case of animals or pesticides and herbicides used in agriculture. Upon ingestion, biotransformation pro- cesses occur, leading to the release of drug residues and metabolites into the environment. These substances, which can end up in water bodies or sewage systems, can adversely affect various organisms, from humans to large mammals and other life forms [134,135]. 21% 17% 14%6% 7% 14% 7% 2% 3% 1% 2% 6% Pharmaceuticals Pesticides POPs Personal care products Heavy metals Hyrocarbons Biotoxins-Mycotoxins Radionuclides Other emerging CoC Plastics DBPs Particulate matter 57% 22% 11% 7% 3% Central Eastern Western Southern Northern Figure 6. (a) Percentage numbers of CoCs investigated in the available literature in Uganda; (b) per- centage levels of CoCs in different regions of Uganda from the conducted studies. Furthermore, these CoCs from different sources eventually find their way into various environmental compartments, including soil, rivers, lakes, air, and even drinking water where they accumulate. Pharmaceutical residues have the highest accumulation rate (21%), followed by the pesticides (17%) and the least is observed in microplastics from the avail- able literature as illustrated in Figure 6b [131,132]. The introductions and accumulation of these compounds can have detrimental consequences for ecosystems and eventually humans. The fate and persistence of these contaminants are strongly influenced by the physicochemical properties of the environmental compartments they interact with as illus- trated in Figure 7. The primary processes that dictate the fate of CoCs in the environment include their biodegradation rate, photodegradation rate, and sorption kinetics [4,133]. Humans and animals may consume these contaminants for diverse reasons, such as for medical or recreational purposes, including veterinary drugs in the case of animals or pesticides and herbicides used in agriculture. Upon ingestion, biotransformation processes occur, leading to the release of drug residues and metabolites into the environment. These substances, which can end up in water bodies or sewage systems, can adversely affect various organisms, from humans to large mammals and other life forms [134,135]. Pollutants 2023, 3 570Pollutants 2023, 3, FOR PEER REVIEW 31 Figure 7. Flow of CoCs across various environmental compartments, following their introduction; these substances transform, giving rise to secondary contaminants that have the potential to impact human health. This dynamic interplay suggests that human beings play a dual role as both sources and recipients of these contaminants. Sewage, which contains waste from residential, industrial, and clinical sources, is usually mixed in waste stabilization ponds, contributing to the chemical burden. This wa- ter is then reused in agriculture and aquaculture, and sludge, laden with active chemicals, is used as fertilizer. This reinserts active chemicals into the soil, ultimately leading to their presence in food crops. The consequence of this cycle is that active chemicals find their way into the food chain, taken up by plants and algae, leading to bioaccumulation in aquatic ecosystems. This can subsequently result in bioconcentration and biomagnifica- tion as they move through the food chain, as established by previous studies. This dy- namic interaction between active chemicals, ecosystems, and human consumption high- lights the need for comprehensive monitoring and assessment programs to understand their occurrence, behavior, and potential risks. Additionally, it underscores the im- portance of adopting measures to manage and mitigate the introduction and proliferation of these contaminants throughout the environment. The coalescence of these findings pro- vides a holistic view of the sources and environmental fate of CoCs in Uganda, Figure 7. Flow of CoCs across various environmental compartments, following their introduction; these substances transform, giving rise to secondary contaminants that have the potential to impact human health. This dynamic interplay suggests that human beings play a dual role as both sources and recipients of these contaminants. Sewage, which contains waste from residential, industrial, and clinical sources, is usually mixed in waste stabilization ponds, contributing to the chemical burden. This water is then reused in agriculture and aquaculture, and sludge, laden with active chemicals, is used as fertilizer. This reinserts active chemicals into the soil, ultimately leading to their presence in food crops. The consequence of this cycle is that active chemicals find their way into the food chain, taken up by plants and algae, leading to bioaccumulation in aquatic ecosystems. This can subsequently result in bioconcentration and biomagnification as they move through the food chain, as established by previous studies. This dynamic interaction between active chemicals, ecosystems, and human consumption highlights the need for comprehensive monitoring and assessment programs to understand their occurrence, behavior, and potential risks. Additionally, it underscores the importance of adopting measures to manage and mitigate the introduction and proliferation of these contaminants throughout the environment. The coalescence of these findings provides a holistic view of the sources and environmental fate of CoCs in Uganda, emphasizing the Pollutants 2023, 3 571 urgency of regulatory measures and sustainable practices to safeguard both ecosystems and human health. 4.1.1. CoCs in Ugandan Surface Waters From the available literature, this review identified that about 58% of the surface waters are contaminated with a widespread CoC across Uganda. One prominent category revealed in the reviewed studies is the pharmaceutical compounds. Antibiotics, analgesics, hormones, and antidepressants, have been detected within various environmental ma- trices, particularly within water bodies. The concentration levels, for instance, ranging from 1–5600 ngL−1 in surface water samples at Murchison Bay of Lake Victoria strongly underscore their classification as CoC [30,42]. These compounds carry the potential for detrimental effects on aquatic organisms and ecosystems, with implications extending to the development of antibiotic resistance and disruption of endocrine systems [41,136]. Furthermore, numerous studies highlighted the widespread use of pesticides in Ugan- dan agriculture. These studies have identified multiple classes of pesticides, including insecticides, herbicides, and fungicides, in soil and water samples [49,78,81]. The detection of pesticide residues not only poses risks to human health but also bears environmental consequences, thus emphasizing the critical importance of adhering to proper pesticide management practices and promoting the adoption of sustainable agricultural methods [44]. Moreover, the presence of microplastics within various water bodies, including lakes and rivers, and their occurrence within fish species consumed by humans, has been emphasized by several studies [125]. The ubiquitous distribution of microplastics in the environment raises concerns about their impact on aquatic ecosystems, further raising concerns about human ingestion through the food chain. In addition to pharmaceuticals, pesticides, and microplastics, the presence of personal care products within water sources and aquatic ecosystems has been noted in multiple studies [30,73,77]. These products, which often contain substances like fragrances, UV filters, and preservatives, are commonly used in cosmetics and personal care items and find their way into the environment through various pathways. Detecting these chemicals in the environment highlights the imperative role of rigorous wastewater treatment practices, which are vital for preventing their release into water bodies. The potential consequences of these substances finding their way into water bodies include ecological impacts and potential human health concerns, making proper wastewater treatment a priority for mitigating these effects. 4.1.2. Urban Runoffs and Wastewater Treatment Plants (WWTP) Effluents as Sources of CoCs Wastewater has emerged as a significant source of CoCs in Uganda [43,52,137]. In WWTP effluents, a troubling array of substances, including pharmaceuticals, personal care products, and various chemical compounds, has been identified. Specifically, industrial and municipal wastewater originating from Kampala city, coursing through the Nakivubo chan- nel, and emanating from the Bugolobi WWTP, have exhibited notable contamination [43]. A compelling example of this contamination includes the presence of 89–1400 ngL−1 of triclosan, an antibiotic found in soaps, toothpastes, and detergents detected in the effluents from Bugolobi WWTP [43]. Furthermore, the detection of 0.84–1.04 mg/kg of cadmium, a toxic heavy metal, in both the water and sediments of the Nakivubo channel, points to the detrimental impact of untreated industrial effluents on this drainage channel [33]. This worrisome trend can be attributed to inadequate wastewater treatment infrastructure and practices, especially prevalent in urban areas and regions characterized by high population densities. The presence of these emerging CoCs in wastewater underscores the immedi- ate necessity for improved treatment technologies and the implementation of stringent regulatory measures. These measures are imperative to ensure the removal or reduction of these contaminants before their discharge into the environment, thereby preventing further pollution and safeguarding aquatic ecosystems. Additionally, the effluents from Pollutants 2023, 3 572 the Bugolobi Wastewater Treatment Plant have been found to contain a concentration of 100–500 ngL−1 of diclofenac, a common pharmaceutical compound [41,42]. The presence of such pharmaceutical compounds within wastewater effluents is typically a result of improper disposal of unused medications and their discharge into the wastewater systems. This situation raises serious concerns about the potential ecological impacts and the devel- opment of antibiotic resistance, as well as the disruption of endocrine systems [30,42]. It is crucial to recognize that these contaminants, once present in wastewater, ultimately enter aquatic environments and ecosystems. In such environments, these substances can have adverse effects on aquatic organisms and ecosystems, potentially leading to the develop- ment of antibiotic resistance and disruption of endocrine systems, further emphasizing the urgency of addressing this issue comprehensively and effectively [41,136]. 4.1.3. CoCs in Sediments Sediments serve as a sink for pollutants, accumulating various contaminants of con- cern over time. The comprehensive review identified the presence of heavy metals [32], pesticides [31], and microplastics [55] in sediment samples from different water bodies in Uganda. The sources of sediment pollution were traced back to industrial activities, mining, and runoff from agricultural operations [104]. Of note, a study conducted by [33] detected substantial concentrations of lead, ranging from 79 to 138.18 mg/kg within both the water and sediments of the Nakivubo channel. The persistence of these contaminants in sediments raises significant concerns regarding potential long-term impacts on benthic organisms and the potential for their re-entry into the water column. Consequently, the implementation of effective sediment management strategies, including remediation efforts and the adoption of best management practices within industrial and agricultural sectors, becomes vital. Such measures are critical for minimizing the consequences of emerging CoCs on sediments and the ecosystems they are a part of. Moreover, the systematic review unveiled reports detailing the occurrence of persistent organic pollutants, such as polychlorinated biphenyls (PCBs), dioxins, and furans, in the Ugandan environment [35,40]. These toxic compounds, renowned for their resistance to degradation, were identified within both sediments and aquatic organisms, raising consid- erable concerns regarding potential health effects on humans consuming contaminated fish and other aquatic products. In another context of this systematic review, there was a focus on the examination of heavy metal contamination in Uganda, focusing on metals like lead (Pb), mercury (Hg), cadmium (Cd), and chromium (Cr) [32,33,47]. Elevated concentrations of heavy metals were attributed to industrial activities, mining, and urbanization. The accumulation of heavy metals within the environment can lead to adverse health effects on humans and contribute to ecological disruptions. 4.1.4. Ambient Air as a Transport Medium for CoCs in Uganda Hydrocarbon compounds, including polycyclic aromatic hydrocarbons (PAHs) and benzene, were detected in soil and air samples across Uganda [67,69]. These compounds originate from various sources such as vehicle emissions, industrial processes, and the burning of biomass, highlighting the potential carcinogenic and toxic effects of hydrocarbon compounds. This emphasizes the importance of robust air quality management and the implementation of emission control measures. Furthermore, the systematic review brought to light the occurrence of biotoxins, particularly mycotoxins, in agricultural products and food items. Aflatoxins and other fungal toxins were detected in crops such as maize and groundnuts [101,114,115,138]. Consuming mycotoxin-contaminated foods can pose significant health risks, including liver damage and cancer. The review also identified reports on natural radionuclides such as uranium and tho- rium in soil and water samples [121,124]. Additionally, concerns were raised regarding po- tential exposure to electromagnetic radiations, including radiofrequency and microwaves, Pollutants 2023, 3 573 emanating from sources like mobile communication towers [56,58,66]. It is important to note that some CoCs can also be transported through the air. Airborne particles and gases can carry pollutants, including persistent organic pollutants (POPs) and microplastics, over long distances, leading to their deposition in ecosystems, including water bodies and soils. For instance, a study conducted by [24,128] measured 152.6 µg/m3 of PM2.5 and 208 µg/m3 of PM10 in air samples around the districts of Kampala, Jinja, and Mbarara in Uganda. Despite limited research on airborne emerging contaminants of concern, it is essential to consider the industrial growth, vehicular emissions, and open burning practices prevalent in specific regions, warranting further investigation into the potential presence and impacts of such contaminants in Uganda. The review identified reports on disinfection byproducts, such as trihalomethanes (THMs), in drinking water supplies [126]. In addition, particulate matter, including fine and coarse particulates (PM2.5 and PM10), was also a subject of investigation in air quality studies [24,102,128]. 4.1.5. CoCs Detected in Various Food Items Grown in Uganda Although this comprehensive review primarily focused on the distribution of CoCs in various environmental matrices, it is crucial to address the potential transfer of these CoCs into the food chain. Contaminated water, soil, and sediments can contribute to the accumulation of contaminants in crops, aquatic organisms, and livestock. For example, processed peanuts contained 0.5–4.6 ppm of arsenic [101], and raw bovine milk and herbal medicines in the Kampala and Wakiso districts in Uganda were found to have 156.9 ppm of chromium. Such contamination poses risks to human health through the consumption of tainted food products, potentially leading to various health issues. The presence of pesticides, heavy metals, and pharmaceutical residues in food items can lead to acute or chronic health effects, such as pesticide toxicity or the introduction of antibiotic-resistant bacteria. To ensure food safety and minimize consumers’ exposure to these emerging contaminants of concern, the implementation of robust monitoring programs and adherence to good agricultural practices are imperative. This systematic review provides valuable insights into the nature, sources, distribution, and potential impacts of these contaminants in the country. The discussion of the results delves into key findings, and their implications, and offers recommendations for future research and policy interventions. The transfer of these contaminants into food crops and the subsequent effects on human health should be a subject of ongoing research to comprehensively address the broader implications of emerging pollutants in Uganda. Understanding the pathways and consequences of these contaminants in the food chain is vital for developing strategies to ensure food safety and protect human health. The reviewed studies underscore the environmental impact of CoCs on ecosystems and biodiversity. These pollutants, including pharmaceuticals, personal care products, heavy metals, and pesticides, have been identified in surface waters, posing significant risks to both human and aquatic organisms as shown in Figure 7. They have the potential to disrupt endocrine systems and reproductive processes Figure 8 [30,32,33,42,61]. Pesticide residues in soils can adversely affect soil health, microbial communities, and non-target organisms, contributing to ecological imbalances, as shown in [73,77]. Waterborne exposure to CoCs through drinking water sources can have lasting conse- quences, including antibiotic resistance and endocrine disruption [30,40,42]. Contaminants accumulating in biota can propagate risks through the food chain, potentially causing acute toxicity, chronic health conditions, and further endocrine disruption [4,32,139]. Moreover, occupational exposure to these contaminants, particularly among workers in agriculture and waste management sectors, has been linked to various acute and chronic health effects. In addition to these well-documented health effects, it is critical to consider the poten- tial association of CoCs with cancer risks in Uganda. Emerging evidence from epidemio- logical studies suggests a concerning link between environmental exposures to CoCs and cancer incidence rates in Uganda, estimated to be around 109.9 and 99.9 per 100,000 in Pollutants 2023, 3 574 males and females [140]. Specifically, certain CoCs, such as persistent organic pollutants (POPs), heavy metals, and specific pesticides, have been implicated in increasing the risk of cancer among exposed populations as illustrated in Table 3. Prolonged exposure to these substances through contaminated water sources, agricultural practices, and other routes could potentially elevate the cancer risk within the Ugandan population, emphasizing the urgency of comprehensive risk assessment and mitigation strategies. The complex interplay between CoCs and cancer risks requires further research and attention to safeguard the well-being of Ugandan communities. Table 3. Toxic effects of different categories of CoCs, and their ecological and human health effects. Category of CoC Ecological Effect Human Health Effects Pharmaceuticals Altered aquatic ecosystems due to bioaccumulation of pharmaceutical residues. Antibiotic resistance, endocrine disruption Pesticides Soil health and microbial community disruption, non-target organism harm, ecological imbalances Acute and chronic toxicity, reproductive and endocrine disruption, carcinogenicity Persistent Organic Pollutants (POPs) Bioaccumulation, endocrine disruption, harm to aquatic life, disruption of food chains. Cancer, developmental and reproductive disorders, immunotoxicity, neurotoxicity Personal Care Products Environmental toxicity to aquatic organisms, ecological disruption, contamination of water resources Skin and eye irritation, allergies, hormonal disruptions Heavy metals Soil and water contamination, impact on aquatic life, potential bioaccumulation, disruption of aquatic food chains Potential health issues from exposure include: neurological damage, kidney damage, cardiovascular issues, developmental problems, cancer risks Perfluorinated compounds Bioaccumulation in fish and fish products Accumulates primarily in the serum, kidney, and liver, potentially diverse effects on developmental, and reproductive systems and other damaging outcomes. Biotoxins–Mycotoxins Harm to aquatic organisms, food chain disruption, and ecological imbalance. Acute poisoning, mycotoxicosis, neurotoxicity Radionuclides and Electromagnetic radiations Genetic and ecological impacts due to radiation exposure, potential harm to organisms and ecosystems Increased cancer risk, radiation sickness, tissue damage, genetic mutations Engineered nanoparticles Toxicity in plants, fish, earthworms, and bacteria (growth, mortality, reproduction, gene expression) Cytotoxicity, oxidative stress, inflammatory effects in lungs, genotoxicity, carcinogenic effects, granulomas, thickening of alveolar walls, and augmented intestinal collagen staining Microplastics Accumulation in ecosystems, potential harm to marine life, potential disruption of the food chain Health effects from potential ingestion, respiratory problems, skin irritation, potential carcinogenicity Disinfection byproducts Potential harm to aquatic life, impact on water quality, aquatic ecosystem disruption Carcinogenic risk, skin and eye irritation, potential reproductive and developmental effects Particulates Air quality deterioration, potential harm to the respiratory health of ecosystem organisms Respiratory issues, cardiovascular diseases, decreased lung function, cancer risks The presence of pharmaceuticals and personal care products in Lake Victoria, a pri- mary source of drinking water in Uganda, raises concerns about antibiotic resistance development and water resource contamination [30,73,77]. In agricultural areas like Kakira and Entebbe, pesticide residues have been identified in soils, surface waters, and crops, signifying ecological disruption and human exposure risks [31,73,77]. Urban areas have reported the presence of microplastics in various environmental compartments, including water bodies, soils, and the air, suggesting potential impacts on human health and the Pollutants 2023, 3 575 environment [125]. Addressing these emerging CoCs is essential to safeguard ecosystems, biodiversity, and human health in Uganda. These risks are not confined to aquatic environ- ments. Airborne emerging contaminants of concern, including volatile organic solvents, different particles like microplastics and engineered nanoparticles, and bio-aerosols, can infiltrate the human body through inhalation, dermal contact, or ingestion, leading to a range of health issues [3,4,17,141]. Waterborne CoCs, primarily stemming from agricultural, industrial, and domestic activities, can contaminate surface water, groundwater, municipal wastewater, and drinking water sources [5,17]. Microplastics, a notable emerging pollutant in water, accumulate various contaminants as they traverse the food chain, amplifying the risk [5,55,125,142]. The contamination of surface waters, including rivers and lakes, with CoCs like pesticides, pharmaceuticals, perfluorinated alkylated substances, and personal care products, has become a growing concern due to its potential harm to freshwater resources and public health. Furthermore, CoCs can also jeopardize groundwater quality, which serves as a critical source of fresh water for various purposes. While traditional pollutants are well- regulated, the emergence of new substances with uncertain immediate effects presents a substantial challenge to groundwater protection. Pollutants 2023, 3, FOR PEER REVIEW 36 Figure 8. Health effects of some CoCs on human body systems (adapted from [143]). Table 3. Toxic effects of different categories of CoCs, and their ecological and human health ef- fects. Category of CoC Ecological Effect Human Health Effects Pharmaceuticals Altered aquatic ecosystems due to bioaccumula- tion of pharmaceutical residues. Antibiotic resistance, endocrine disruption Pesticides Soil health and microbial community disruption, non-target organism harm, ecological imbalances Acute and chronic toxicity, repro- ductive and endocrine disruption, carcinogenicity Persistent Organic Pollutants (POPs) Bioaccumulation, endocrine disruption, harm to aquatic life, disruption of food chains. Cancer, developmental and repro- ductive disorders, immunotoxicity, neurotoxicity Personal Care Products Environmental toxicity to aquatic organisms, eco- logical disruption, contamination of water re- sources Skin and eye irritation, allergies, hormonal disruptions Heavy metals Soil and water contamination, impact on aquatic life, potential bioaccumulation, disruption of aquatic food chains Potential health issues from expo- sure include: neurological damage, kidney damage, cardiovascular is- sues, developmental problems, can- cer risks Perfluorinated compounds Bioaccumulation in fish and fish products Accumulates primarily in the se- rum, kidney, and liver, potentially diverse effects on developmental, and reproductive systems and other damaging outcomes. Biotoxins–Mycotoxins Harm to aquatic organisms, food chain disrup- tion, and ecological imbalance. Acute poisoning, mycotoxicosis, neurotoxicity Figure 8. Health effects of some CoCs on human body systems (adapted from [143]). 5. Current Monitoring and Regulation Efforts in Uganda In Uganda, a concerted effort has been made to monitor and assess emerging con- taminants of concern, seeking to understand their presence, concentrations, and potential risks to the environment and public health. Collaborative initiatives with institutions like the National Environment Management Authority (NEMA) have played a crucial role in environmental management and hotspot identification [144]. The Ministry of Water and Environment, particularly the Directorate of Water Resources Management, conducts routine water quality assessments, extending their scope to encompass emerging CoCs in surface waters, groundwater, and drinking water sources. Furthermore, academic and research institutions, including universities and research centers, actively contribute to Pollutants 2023, 3 576 monitoring by evaluating these contaminants in various environmental compartments and providing valuable scientific insights to inform policymaking. While Uganda has made significant progress in monitoring contaminants of con- cern, challenges persist in their effective regulation and management. Existing regulatory mechanisms, spearheaded by NEMA, establish a foundation for addressing these pollu- tants through environmental regulations, guidelines, and standards [144,145]. However, opportunities for improvement exist, particularly in the formulation of comprehensive, targeted regulations dedicated to CoCs and improved data collection and accessibility. Constraints in monitoring capacity and resource availability hinder the implementation of comprehensive, routine monitoring programs. Therefore, there is a pressing need to expand research efforts to deepen our understanding of the prevalence, fate, and impacts of contaminants of concern. Access to comprehensive data is pivotal for the development of effective mitigation strategies. It is imperative to strengthen technical expertise and monitoring capabilities regarding CoCs, necessitating the use of advanced analytical techniques and fostering collaboration between research institutions and regulatory bodies. Additionally, refining regulatory frameworks to specifically address CoCs, including the formulation of guidelines and standards, is vital. Raising awareness among the public, policymakers, and industries is also imperative and can be achieved through educational and outreach programs that promote responsible practices and sustainable alternatives. By addressing these gaps and challenges, Uganda can significantly enhance its monitoring, regulation, and management of contaminants of concern. 6. Mitigation Strategies and Future Directions for Addressing Risks Posed by CoCs Addressing the risks posed by CoCs, both in Uganda and on a global scale, is a complex challenge requiring effective approaches and advanced technologies. In the Ugandan context, upgrading wastewater treatment systems is paramount, and this can be achieved through the implementation of advanced technologies such as advanced oxidation, activated carbon adsorption, and membrane filtration, which have demonstrated their effectiveness in removing a wide range of CoCs, including pharmaceuticals, personal care products, and other emerging pollutants [4,146–148]. Furthermore, promoting sustainable agricultural practices is essential in mitigating CoC risks. Techniques like integrated pest management (IPM) and organic farming offer promising avenues to reduce pesticide usage, a common source of contamination. Implementing source control measures and improving waste management practices can effectively prevent the release of CoCs. Encouraging the adoption of green chemistry principles and developing eco-friendly alternatives are key steps in minimizing the generation and release of CoCs. While these strategies are well-established globally, it is noteworthy that there has been a lack of studies conducted in Uganda regarding the mitigation, prevention, or remediation of CoCs. However, based on the removal efficiencies provided in Table 4, AOPs stand out as the most promising option, with treatment efficiencies ranging from 95 to 99%. On a global scale, the management of CoCs also presents a