Emerging Water Pollutants: Concerns and Remediation Technologies E-Book
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- Herausgeber: Bentham Science Publishers
- Kategorie: Fachliteratur
- Sprache: Englisch
This book examines a wide range of emerging sources of water pollution. It consists of thirteen chapters dedicated to the topic, giving readers comprehensive information about the types of contaminants involved and the solutions for their removal.
The first five chapters present an analysis of the emerging water pollutants, their toxicities, and the legislations available to monitor and regulate their emissions. This introduction is followed by 3 chapters that cover risk assessment of emerging pollutants, their fate and life cycle assessment. The last section of the book goes through the details of remediation technologies for wastewater treatment.
This reference is equally suitable for academia, industry professionals and students, presenting state-of-the-art learnings on emerging water pollutants and their remediation methods.
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Seitenzahl: 638
Veröffentlichungsjahr: 2002
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PREFACE
With the increasing population, industrial growth and consumer needs, water is getting adulterated with several new contaminants of concern. Nanomaterials, pharmaceuticals & personal care products, endocrine disrupting compounds, artificial sweeteners, surfactants, etc. are some of the emerging sources of water pollutants. Several of these emerging water pollutants introduce noxious effects on humans and the ecosystem. These emerging pollutants need to be removed from wastewater sources. Some of the most investigated technologies for the removal of emerging pollutants from wastewater include catalytic processes including oxidation, membrane process, adsorption, osmotic processes, integrated processes, etc. This book cincludes of thirteen chapters. The first five chapters discuss and analyze the sources of emerging water pollutants, their toxicities, and legislations available to monitor and regulate their emissions. The next three chapters (6-8) are on the risk assessment of emerging pollutants, their fate and life cycle assessment. The last five chapters are on the remediation technologies for wastewater treatment containing emerging pollutants. This book is equally good for academia, industry professionals and students for state-of-the-art learning on emerging water pollutants and their remediation methods.
Chapter 1 provides an extensive review on classification of various emerging pollutants reported worldwide along with their physio-chemical properties and potential environmental effects. Moreover, the legislative policy regulations formulated worldwide for the monitoring of various emerging pollutants are also discussed.
Chapter 2 discusses the state-of-the-art global applications of pharmaceuticals and personal care products, the mechanism of water pollution by pharmaceuticals and personal care products, possible biohazards, and negative impacts on the environment. Besides that, various types of pharmaceuticals and personal care products, the most applied chemical compounds in pharmaceuticals and personal care products have been discussed in this chapter. The chapter also presents a future perspective for reducing the pharmaceuticals and personal care products’ contamination of surface water with cutting-edge technologies along with wastewater treatment.
Chapter 3 focuses on the release of emerging pollutants from the food and packaging industries. This chapter interconnects the use of chemicals and fertilizers for the production and prevention of food crops and food. Also, the use of drugs for livestock and poultry for the food raw materials are highlighted. Furthermore, this chapter summarizes all aspects of emerging water pollutants from the food and packaging industry and highlights the source-sink relation of emerging water pollutants as well.
Chapter 4 introduces nanomaterials and their release to the environment and the relevant concerns. In addition, the effect of various nanomaterials in the aquatic environment is discussed, including the behavior and toxicity of nanomaterials to the aquatic ecosystem. It is important to identify, assess and reduce the environmental impact of these nanomaterials. The chapter further highlights environment-friendly and advantageous use of engineered nanomaterials for a sustainable world.
Chapter 5 highlights the industrial sources of emerging water pollutants, their possible routes to waterbodies, and their respective impacts on the environment and ecosystem. Furthermore, the concerns of emerging contaminants from industrial operations and processes have also been discussed. Furthermore, an insight into the challenges in minimizing water pollution is also focused on the shared benefit.
Chapter 6 discusses the risk assessment of the emerging water pollutants. The environmental risk assessment of emerging pollutants can help to indicate potential risks associated with these substances, highlighting the importance of the identification of their hazard, dose response, exposure assessment and finally their risk characterization. The chapter provides useful insights into the recent findings related to the pollutants’ effects and their assessment approaches.
The major focus of chapter 7 is the fate of emerging water pollutants. The chapter introduces emerging pollutants of concerns, and identifies their routes to sources where they end up. More importantly chapter highlights the end sink of pollutants with potential threats and risk evaluation for plants and human health through the end sink.
Chapter 8 briefs on the lifecycle assessment of emerging water pollutants. This includes the process of lifecycle assessment for various emerging pollutants, including the release and accumulation to examine the impacts and associated risks to water quality, the aquatic environment, and ultimately on the human beings. Furthermore, a deep insight into lifecycle has been provided that may help to understand the flow of pollutants in environment and fill the existing knowledge gaps.
Chapter 9 introduces various conventional wastewater technologies such as disinfection, desalination, coagulation, chemical precipitation, filtration, adsorption, etc. Some of these technologies have potential uses for the removal of emerging water pollutants. Furthermore, the chapter discusses the limitations of these processes and their advantages over the others.
Chapter 10 briefly describes advanced membrane processes for the removal of emerging water pollutants. Various membranes, such as nanofiltration, reverse osmosis, membrane bioreactors have been discussed and evaluated for the removal of emerging water pollutants in detail. Furthermore, challenges related to membrane technologies such as their efficiency, prevention from fouling, stability when using cleaning agents, permeability, cost, and energy reduction have been discussed as well.
Chapter 11 discusses osmotic and filtration processes for the removal of emerging water pollutants. A detailed account has been provided for the pressure driven membrane filtration processes including micro-filtration, nano-filtration, ultra-filtration, reverse osmosis, forward osmosis, osmotically driven membrane filtration processes such as pressure retarded osmosis, etc. Apart from their technicalities, the performance evaluation of these osmotic processes has also been given.
Chapter 12 brings a detailed account of various catalytic processes for the removal of emerging water pollutants. Some of these processes include ozonation, electrocatalysis process including electrocatalytic oxidation, electro-Fenton process, photoelectro-Fenton process, photocatalysis, reduction by hydrodehalogenation, etc. Moreover, the features, mechanisms, and potential applications of catalytic processes in the treatment of emerging water pollutants are discussed in detail.
List of Contributors
Emerging Water Pollutants, their Toxicities, and Global Legislations
Shoaib Ahmed1,6,Fahad Saleem Ahmed Khan1,Nabisab Mujawar Mubarak2,*,Yie Hua Tan1,Rama Rao Karri2,Mohammad Khalid3,Rashmi Walvekar4,Ezzat Chan Abdullah5,Shaukat Ali Mazari6,Sabzoi Nizamuddin7Abstract
Emerging pollutants (EPs) in the environment have become a significant source of pollution and cause of serious concern for the ecosystem and human health. Although during the recent decades, extensive research has been performed worldwide for the detection and analysis of EPs, continuous refinement, and development of specific analytical techniques; a great number of undetected EPs still need to be investigated in different components of the ecosystem and biological tissues. Therefore, this chapter provides extensive reviews of several emerging pollutants reported around the globe along with their physiochemical properties and potential ecological impacts. Moreover, formulated legislations and policy regulations for the monitoring of EPs are also discussed in this chapter.
INTRODUCTION
Over the recent years, owing to the uncontrolled progress in multiple human activities, such as transport, agriculture, industrialization, and urbanization, the world has experienced antagonistic consequences. The change in living standards and unsustainable consumer demand have enhanced the air pollution load, for example, particulate matter, SO2, NOx, greenhouse gases, and ozone. On the other hand, the water sources are adulterated with numerous manmade chemicals, heavy metals, nondegradable materials, oil spills, nutrients, landfill leachates, etc [1, 2]. Emerging contaminants include a variety of anthropogenic chemicals, for example, active pharmaceutical compounds, personal care products, pesticides, and numerous industrial chemicals, which are widely used in the world [3, 4]. It has been estimated that global production of anthropogenic chemicals between 1930 and 2000 reached from 1 million to 400 million tons per year [5]. Hence, increasing chemical demands and their uses have become a reason for several ecological impacts worldwide.
According to the environmental protection agencies, these EPs are newly detected in the environment. Therefore, their impacts are not completely determined. Thus, they are often considered un-regulated trace contaminants [6]. Moreover, conventional water and wastewater treatment facilities cannot completely remove these pollutants. Therefore, numerous studies reported their occurrence in drinking as well as surface and groundwater [5, 7, 8]. Furthermore, various metabolites and transformation by-products of EPs have also been reported by researchers, which are quite harmful and biologically active and become a reason for various adverse effects [9].
The majority of studies related to EPs occurrence and toxicities have been conducted in developed regions of the world. The circumstances are worse in developing countries where the occurrence and concentration of EPs are high owing to less efficient wastewater treatment plants, unskilled personnel, large population size, and disposal of international expired chemicals near rivers, etc [10]. The release of these chemicals into the river also pollutes the surrounding environment, including animals and aquatic life [11, 12]. Based on recent research studies, the improved administration and methodology must be formulated and implemented [13]. However, for precise regulations and monitoring of EPs to determine the permissible limit of these pollutants in the environment, there is a dire need for a complete understanding of fate and toxicities [14]. Ecotoxicology study is a major concern of the EPs because most pollutants are persistent and possess bioaccumulation [15].
The ecotoxicity of different emerging toxicants has been evaluated previously on sentinel species recommended by the U.S.-Environmental Protection Agency (USEPA) and the European Union (EU) for the safety potential of xenobiotics. To determine exposure limits of specific pollutants in the environment and decide the safety, various models and experimental protocols have been developed previously by researchers. The two widely used are whole organism battery tests and cell-lines decipher. The whole-organism battery test determines ecological exposure obtained by performing significant co-relation with realistic scenarios. At the same time, laboratory-based information obtained by cell lines deciphers certain limitations in extrapolating the adverse effects information regarding organisms of higher levels, such as humans, and is considered the bottleneck in ecotoxicity assessment.
Based on numerous emerging pollutants in an ecosystem, this chapter provides the classification of potential emerging contaminants, such as active pharmaceutical chemicals, personal care products, pesticides, and emerging industrial chemicals found in the environment. The knowledge of physicochemical properties of pollutants helps determine the fate and transport of specific pollutants, which are also discussed. Moreover, the ecotoxicological impacts of several EPs and available legislations formulated for the monitoring and handling of several EPs in the world are also discussed in this chapter.
PATHWAYS OF EPS IN THE ECOSYSTEM
EPs enter the ecosystem through different paths, including industrial/municipal wastewater, hospital wastewater, treated/partially treated effluent from the treatment plant, farmyard and agricultural runoff released into surface water, and application of sludge and biomass [16, 17]. For example, some pharmaceuticals are not completely metabolites by animals and humans and are released into the environment by urine and feces [8]. The classes of different EPs and their metabolites recently detected in other components of the environment around the globe are described in Table 1. Most of these pollutants are not completely removed by conventional water and wastewater treatment facilities. Therefore, when released into rivers, lakes, and coastal water, partially or untreated water pollute the water with trace concentration of EPs. Thus, when used for horticulture, irrigation, or other non-potable purposes, water from these natural sources intensifies the concentration of these pollutants from parts per trillion to parts per million, thus deteriorating the quality of surface water, groundwater, and soil [18]. Other possible sources of EPs pollution in the environment might include agricultural runoff, recreational activities, swimming, veterinary medicines, and the discharge of various disposable goods [19, 20]. Typical pathways of EPs pollution from different sources are described in Fig. (1).
CLASSIFICATION OF EMERGING POLLUTANTS
Emerging pollutants are broadly classified into 4 major groups: pharmaceuticals, personal care products, pesticides, and numerous industrial chemicals based on their sources and usage. The fate and transport of EPs are strongly dependent upon the physicochemical properties of the contaminants, including the octanal-water partition coefficient (Kow), distribution coefficient (D), water solubility, and dissociation constant (pKa), as well as the metabolic capability of microbes in the ecosystem. Various groups and subgroups of EPs and their physicochemical properties are described in Table 2.
Pharmaceutical Active Compounds
Pharmaceutical active compounds are an imperative class of emerging pollutants because of their widespread occurrence in water bodies, drinking water contamination, and toxic effects on human health and ecosystems [30]. In recent years, numerous countries have reported the presence of different subgroups of PhACs in finished drinking water, including antibiotics, analgesic and anti-inflammatory drugs, antiepileptic drugs, β-blockers Contrast, Harmons and others [29, 31]. Different pollutants of subgroups of pharmaceutically active compounds and physicochemical properties are described in Table 2. Most of these pollutants are reported at an elevated level in treated water based on the type of treatment facilitated [32-34]. A trace amount of a few pollutants (ng/l) such as carbamazepine, acetaminophen, ibuprofen, and clofibric acid has been found in treated drinking water in several countries. It is observed that the treatment system utilizing surface water shows a higher concentration of these contaminants than the system that uses groundwater [35]. Furthermore, it was also observed that a few of the drinking water treatment methods such as coagulation/flocculation, disinfection and filtration could efficiently remove the parent pollutants of some PhACs. Still, these pollutants sometimes react with disinfectants and form disinfection by-products (DBPs), which are difficult to remove [36, 37].
In addition to excessive use of pharmaceuticals by humans, they are also used in fish farming, livestock, and poultry. A wide range of drugs is frequently used for animals to reduce infection and diseases. Although around three thousand chemicals are used as pharmaceutical ingredients, only a few are investigated in the environment. Regulatory agencies and scientists are always questioned about the adverse effects of these contaminants on the ecosystem at minimum trace concentration (ng/l). Even though several pharmaceutical pollutants can potentially affect humans, animals and ecosystems adversely, most environmental concentrations are observed well below the lowest observed effect concentrations (LOECs). However, few PhACs such as diclofenac, ciprofloxacin, ethinylestradiol, carbamazepine, fluoxetine, and clofibric acid have been found in water at a level well above the LOECs [38].
Previously, the two major disasters occurred owing to the release of trace amounts of PhACs in the environment. First, about 40 million vultures died in Pakistan from consuming diclofenac, an anti-inflammatory drug from cattle carcasses [39]. This event was significantly surprising because about 90% of the vulture population was poisoned by diclofenac. Therefore, the event was named as “worst case of wildlife poisoning ever”. The second happened in Ontario, Canada, where the collapse and feminization of a wild fish owing to the release of trace concentration of estrone (5 to 6 ng/l) into lake water were investigated and found responsible [40].
Furthermore, hormones are also one of the most important subgroups of PhACs, owing to their potential androgenic and estrogenic effects on animals [41]. A wide range of synthetic and natural hormones are often released into the environment by wastewater treatment and agriculture runoff [32]. The U.S. environmental protection agency published a list of 9 widely reported hormones in the background in new CCL-4 (Ethinylestradiol, norethindrone, aquiline, estrone, equilenin, mestranol, 17β estradiol, 17α-estradiol) (UEPA, 2020).
Personal Care Products
Personal care products (PCPs) include various types of goods used in our daily life, such as surfactants, perfumes, insect repellents, sunscreens, UV filters, disinfectants, etc. Unlike pharmaceuticals, PCPs do not undergo any metabolic changes because these products are applied externally, therefore, released into the environment in their original forms [25]. The most widely detected PCPs and subgroups and physicochemical properties are described in Table 2. However, due to intense urbanization and excess use of these products, they are widely detected in surface and groundwater. Moreover, most of these pollutants are persistent and have bioaccumulation potential [42]. It is observed that when N, N-diethyle-m-toluamide, a widely used ingredient of insect repellent, is applied, only 20 percent of the total chemical is consumed by the screen, and the remaining 80 percent is discharged into water [43]. Polycyclic tonalide and galaxolide musk are the two most used ingredients in fragrance manufacturing. In Europe alone, around 5000 tons of these chemicals were produced in 2004. it has been reported that about 77 percent of used musk was released into water [25].
Furthermore, disinfectants such as triclosan are commonly used ingredients in toothpaste, shampoo, and soap and are often detected in the environment [44]. The use of this chemical was banned in Minnesota in 2017. Similarly, in Europe, the excess use of this chemical was recently limited (EU, 2014), and a ban on other use is being considered. In the United States, an extensive study was conducted in 2002 to investigate lakes and rivers affected by wastewater. About 50 percent of the samples were polluted with triclosan chemicals [45]. One of the major concerns of triclosan contamination is that it has characteristics of active contribution to antibiotic resistance. It is validated by one of the studies performed to identify triclosan resistance bacteria in the aquatic environment [46]. Triclosan contamination equally affects marine life, including crustaceans, algae, and fish. Moreover, this pollutant also has endocrine-disrupting, cytotoxic, and genotoxic properties. Additionally, it is also reported that triclosan may transform into hazardous by-products during water and wastewater treatment [47].
UV filters and sunscreens are another sub-group of personal care products widely used in manufacturing cosmetic products such as hairsprays, moisturizers, skincare, hair dyes, and lipsticks. These chemicals also manufacture non-cosmetic products such as furniture, washing powder, plastics, and carpet [48]. The most often used UV-filters are camphor, 4-methylbenzylidene, benzophenone-3, and homosalate etc [48]. These pollutants enter the aquatic environment through bathing, washing and swimming [20]. Human and animal exposure pattern to these contaminants overlaps through the food chain.
Pesticides
Due to rapid urbanization, the extensive use of various pesticides in agriculture, forestry, and amenities such as airports, sports grounds, public parks, and industrial sites increases [49]. The widely used sub-groups of pesticides include insecticides, herbicides, and fungicides to protect the crops from pests and disease [50]. When applied to the crops, these pesticides enter freshwater bodies by irrigation runoff water, spray drift, or wash water. Moreover, during the application of pesticides on crops, some amounts of chemicals reach the soil, eventually polluting the unground water after seepage [51].
Industrial Chemicals
The extensive use of different plasticizers, including bisphenol A, DBP, DEHP etc., for improving the rheology and plasticity of gypsum, clays, concrete, and plastics has created a variety of harmful pollutants. Among these pollutants, most plasticizers are a potential endocrine disruptor. For example, Bisphenol A, an ingredient of polycarbonate plastics, has been used in wide applications, including flame retardants, containers of beverages and foods, electronic components, paper coatings, eyeglass lenses, building materials and dental sealants. They are the highest manufactured chemicals around the globe, with an annual production of around 11.5 billion pounds in 2012 and are on the increase with a 4.6% annual rate and are expected to reach 10.6 million metric tons by 2022 [52]. This chemical enters the water cycle by releasing wastewater from industries, landfill leachates and other domestic waste [35]. According to the United States environmental protection agencies, around 1.5 lac pounds of BPA was released into the environment in 2010 (UEPA 2010).
Flame retardants are another subgroup of emerging industrial chemicals widely produced globally. The most commonly manufactured flame retardants include tri(chloropropyl) Phosphate and tri(2-chloroethyl) Phosphate [53]. These chemicals are used in various applications such as thermoplastics, thermostats, electronics and furniture coatings [54]. Owing to the hydrophobic properties, a trace amount of these chemicals are often found in sediments than in the aquatic environment [55]. Moreover, their persistent nature might transport them away from the point source for a long distance and uptaken by vegetables and marine life when released [56]. Therefore, various studies have reported their occurrence in food chains. Similarly, numerous other chemicals are widely detected, including different food additives and hydrocarbons.
Electronic Waste
Since the abrupt digitalization, the production of electrical and electronic products has increased significantly. The waste from electronic devices contains metals and organic and inorganic materials, some of which are toxic and hazardous. The valuable portion of the electronic waste is recovered and recycled. However, some of its portions still go into wastewater [57]. The major portion of electronic equipment is the metals, several of these metals and metalloids are reported to develop various forms of cancer. For example, As, Be, Cd, and Cr(VI) is reported by the International Agency for Research on Cancer (IARC) as carcinogenic to humans. Similarly, Pb, antimony trioxides, Co, organic Hg compounds, and Ni are suspected to be carcinogenic [58, 59].
TOXICITY AND ECOLOGICAL RISK OF EPs
Various EPs and their metabolites in the environment can pose a serious threat to human health, animals, and aquatic species, including non-targeted organisms such as bacteria, algae, and plants [82]. The unsustainable production of numerous synthetic pharmaceuticals and chemicals creates various pollutants in an aquatic environment, which becomes a reason for several adverse effects [83]. Over usage and release of ample amounts of antibiotics by humans and animals create numerous types of antibiotic resistance in the aquatic environment, posing a serious threat to public health. According to the data released by the Center for Disease Control and Prevention (CDC), particularly in the EU and U.S., about 25 thousand and 23 thousand deaths occurred due to the presence of antibiotic resistance, respectively. In addition, around 2 million individuals developed drug resistance in the U.S [84]. Some researchers predict that by 2050, 10 million deaths will be caused by exposure to these antibiotic resistances, and cancers as a leading cause of mortality globally [85]. The principal reason for this issue includes poor hygiene and sanitation, antibiotics prescriptions, and insufficient facilities in a laboratory for infection detection accurately and quickly [86]. Various health effects in humans due to different emerging pollutants in water are shown in Fig. (2). At the same time, the summary of ecotoxicology effects of widely reported emerging pollutants is described in Table 3.
Other problematic pollutants are the compounds of harmons, commonly prescribed these days, the leading cause of disease in animals and aquatic life. One of the studies performed to predict adverse health effects associated with widely reported harmons (Estrone, 17-β estradiol, 17-α ethinylestradiol) predicted the altered sexual development, presence of intersex species, changed mating behavior, etc. in marine life. Higher intersexuality was found in walleyes (Sander vitreus vitreus) and wild roach (Rutilus) in rivers [87]. Chronic exposure to 17-α ethinylestradiol results in the feminization of various fish species [40]. In addition, different health effects in other domestic animals are also reported in studies, such as shortness of teat length [88].
LEGISLATIONS
To develop a sustainable and protected environment for future generations, strict policy regulations are essential. It is evident from the previous practices that intense urbanization and industrialization created numerous harmful emerging pollutants in our environment, which are difficult to be removed. The studies on the occurrence of EPs in the ecosystem, their toxicities, and removal have been conducted worldwide. Yet, most studies include case studies in Europe, the United States, Canada, and some developed regions of Asia [111]. There is a lack of information about emerging pollutants in the aquatic environment [112]. Therefore, most policies and regulations are formed in developed regions [13]. Currently, available policy regulations for mitigating EPs are as follows:
EU water policy (Directive, 2000) has been framed to describe and prioritize the high-risk pollutants [113]33 priority compounds based on their ecological quality standards have been confirmed as per directive 2008/105/EPs [114]A watch list of chemicals of emerging concern for monitoring in Europe has been formulated in the field of water policy in a decision 2015/495/EU [115]Fate and occurrence of EPs in the watch list show fewer reports in the list, 27 examinations of transformation by-products, and the study of unspiked water matrices.In emerging pollutants, such as PhACs, PCPs, pastiches, and various industrial contaminants, fate and transport mechanisms are not discovered at diverse levels of biological organization for determining the effective risk assessment policies [49]. In some developed countries like the U.S., legislation for plastic beads was recently formulated to ban microplastics because of confirmed adverse effects on human health and the aquatic environment. Similarly, other developed countries like New Zealand, Canada, and Kenya also implemented strict regulations on plastic beads [116]. The United States’ drug and food administration center for drug evaluation and research regulates over-the-counter widely prescribed drugs, including genetic and therapeutics. In addition, this department also considers new drugs which are widely prescribed and used for humans and animals for policy formulation and safety efficacy.
Similarly, in Japan, to evaluate various pharmaceuticals used for veterinary and human health formulated, the Organization of Pharmaceuticals and Research worked under the umbrella of their ministry [117]. Furthermore, a trilateral (United States-Japan-EU) program was designed for the authorization of veterinary products and their marketing with technical and safety requirements (VICH). This program aimed to register veterinary products for their safe use [118].
In Europe, the European Medicines Agency (UMA) is formulated to evaluate and regulate pharmaceutical products used for animals and human health [119]. Despite the several international policies and regulating agencies, the regulation for monitoring various emerging water pollutants has not been completely formulated. Therefore, the concerned regulatory authorities and stakeholders must develop a strategic plan based on available scientific evidence and database. The developing countries face severe threats due to the lack of facilities and skilled personnel. Thus, there is a dire need for strict legislation at a regional level to formulate policies to overcome these alarming issues.
CONCLUSION
Emerging pollutants in the ecosystem have been recognized as an essential environmental issue. Many studies have reported the fate, occurrence, and ecotoxicity of numerous subgroups of EPs in river water, underground water, sediments, and effluent of wastewater treatment plants, in which trace concentrations range from nanograms per liter to milligram per liter. However, many EPs' fate and transport mechanisms are still not completely analyzed in the ecosystem. Moreover, the ecotoxicity of these EPs on different components of the environment and biological tissues is also not evaluated. Thus, there is a dire need for further exploration of various groups of undetected emerging pollutants in the environment along with their potential adverse impacts on the ecosystem.
Furthermore, a vast majority of legislative policies are designed and implemented in developed regions of the world. However, developing countries' condition is worse due to the lack of facilities, skilled personnel, and international waste disposal alongside freshwater resources. Hence, better policy regulations must be formulated at regional levels to regulate the occurrence of these pollutants in the environment.
CONSENT FOR PUBLICATION
Not applicable.
CONFLICT OF INTEREST
The author declares no conflict of interest, financial or otherwise.
ACKNOWLEDGEMENTS
Declared none.
