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Environmental Sciences
Potentially toxic elements (PTEs) are metallic chemicals with densities that are higher than that of water. Water pollution by PTEs due to the discharge of untreated pharmaceutical industrial effluents is a risk to human health and ecological integrity.
- potential toxic elements
- pharmaceutical effluents
- pathways
- health risk assessment
- advance treatment
1. Introduction
There has been increasing concern in recent years regarding water treatment and reuse which necessitates the toughest standards due to the increasing demand for high-quality water worldwide, be it for drinking, sanitation, agriculture, or industrial usage [1]. Increased industrial activities have caused a number of water bodies to become contaminated with pollutants that go above what is permitted for effluent [2]. Among the different contaminants, potential toxic elements have posed the major concerns for environmental and human health due to their non-biodegradability and great accumulation capability [3]. Potentially toxic elements (PTEs), otherwise known as heavy metals, are metallic chemicals with a density that is higher than that of water. These metals are very toxic to people and can hurt them if they go beyond what is considered normal [4].
Priority metals are naturally present in groundwater, and while some of them are necessary for life, higher concentrations of these metals can actually be quite detrimental. These vital resources of life, such as water and land, are becoming pressured as a result of industrialization, poor water and land use practices, farming techniques, and population growth [5]. Waterbody contamination has become a global issue that has grown in both developed and developing countries, impeding economic growth and negatively harming public health [6]. Both the condition and the features of our finite freshwater resources are being negatively impacted by the discharge of toxic metal ions into the environment. The uncontrolled release of contaminants is threatening the sustainability and availability of drinking water, and this is becoming a worldwide public concern [7]. Due to their bioaccumulative nature, potential hazardous metals have raised health concerns even in minute quantities [8]. Many of these elements, including arsenic (As), cadmium (Cd), chrome (Cr), nickel (Ni), lead (Pb), and zinc (Zn), are non-biodegradable, and the Environmental Protection Agency has designated them as priority contaminants to be controlled [9].
Several industrial processes are discharging PTEs, and pharmaceutical industrial effluents have proven to be a major discussion point. International organizations such as the World Health Organization (WHO) and the United Nations Environmental Programme (UNEP) have comprehensively reviewed the health consequences related to several toxic elements. Over the years, PTEs have been discovered, and their intensely detrimental impacts on human health are well documented, but currently the use of PTEs has greatly increased, giving rise to their discharge into the environment and thus provoking sudden symptoms in the body [10].
2. Sources and Entry Pathways of Potential Toxic Elements
Toxicity can be explained as the tendency of a substance to cause harm to a living organism. It is also the degree to which a chemical substance can exert a harmful influence on the life span, development, and replication of living things. Several studies have demonstrated that certain toxic metals have been identified as substances that alter normal body functions, leading to developmental malformations commonly known as cancer and genetic mutations in organisms based on the exposure rate to those metals and the amount taken at a particular time, which affects both humans and animals. The following sections describe the primary sources of pharmaceutical effluents and their end products in the environment [11,12,13].
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Pharmaceutical manufacturing generates effluents containing human drugs, suspension drugs, and solid wastes containing animal drugs in the form of boluses, and storm water runoff carries finely ground drugs.
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Consumers and clients also dispose used and untreated drugs into water bodies, which pollute the ecosystem and affect human health. Furthermore, numerous households also release wastes through excretion into the wastewater without any precautionary methods.
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Health centers and clinics discharge wastewater and pharmaceutical wastes down the drain.
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Agricultural residues and drugs administered to animals such as fowl, sheep, and cold-blooded animals; discharge of dissolved fertilizers and antibiotics mixed with farm animal feed and water.
3. Routes of Uptake
Living things can be exposed to PTEs through the respiratory organs such as lungs, skin, and the process of taking in food [15,16]. There are three (3) ways in which these priority metals are taken up by humans and animals, as discussed below:
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Ingestion: This is the process of swallowing foodstuffs or other substances such as coffee, water, and juice that are polluted by the PTEs.
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Skin or dermal adsorption: Skin adsorption is a process by which the harmful substance meets the body through the skin or gills.
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Inspiration (inhalation): Living things breathe in poisonous gases or vapor as dust fumes in this process.
4. Potentially Toxic Metals in Ground and Surface Water
Potentially toxic elements such as Cr, Pb, and Cd can harm living organisms, in addition to long-lasting organic pollutants such as pesticides and polychlorinated biphenyls (PCBs), which are some of the pollutants found in pharmaceutical effluent discharges. These elements are highly harmful to marine animals, even at trace amounts, because they change the morphology of the organisms’ cells [18].
The evaluation of the influence of point-source contaminants on the sustainability of water bodies is becoming particularly crucial. The study of the risk of chemicals in rivers and the effects of adulteration on the freshness of streams is important because these sources of water play significant functions. The society ends up paying a heavy cost for inappropriate pharmaceutical sewage discharge because contaminated water is primarily used for both household and specific purposes by residents living near groundwater and surface water [19].
In 2015, according to the World Health Organization, 8.8 million cancer deaths occurred globally. The accumulation of harmful metals above legal limits in bodies of water is among the main reasons people die because these metals affect the central nervous system. The physiology of living tissues in the body is severely affected when foodstuffs or potable water comprising potentially harmful metals surpass their optimum threshold level [21]. The immunological and blood systems in humans and livestock are also harmed when they are exposed to metal combinations.
5. Classifications of Potentially Toxic Metals
Several scholars (e.g., [23,24] have discovered that pollutants in groundwater are harmful metals. These harmful components are divided into four classes due to their health implications.
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Essential: These are metals that play a biological role in living organisms but become hazardous when they exceed their permitted limits; examples are manganese, copper, iron, and zinc.
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Less toxic: These are metals that are less toxic to human health; examples include tin and bismuth.
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Highly toxic: These are known as metalloids such as cadmium, lead and arsenic.
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Non-essential: These are metals that do not have a biological role in human beings; examples include aluminum and lithium.
6. Pharmaceutical Industrial Effluents
Pharmaceutical effluents are liquid waste produced by drug companies during the development of new drugs; pharmaceutical effluent mainly contains the largest proportion of organic and inorganic compounds, animal drugs, and antibacterial drugs. During their synthesis, administration, and disposal, active pharmaceutical ingredients (APIs) are discharged into the surroundings, and there is an indication that API exposure in the environment has adverse implications on living organisms [27,28]. Potentially harmful metals have heavily contaminated the surroundings and their components. The biosphere is the most significant region of the ecosystem since it houses living things.
7. Selected Potentially Toxic Metals
7.1. Lead (Pb)
Pb is among the most common elements in nature all over the world. Due to its elemental physical and chemical properties, it has numerous industrial applications. It ranks as the fifth most widely used metal in the world as a result of increased industrial applications; it is used in over 900 industries, including oil refineries, drug manufacturing, and quarrying. There is a rise in the metal ion concentration in industrial effluent due to an increase in outflow from firms operating close to rivers.
7.2. Arsenic (As)
Arsenic is a substance that is found in nature and is broadly distributed across the atmosphere. It is widely distributed in nature because it can exist as a synthetic or natural compound and has variable oxidation states of −3, −1, 0, +3, and +5. It can be found in environmental matrices such as soil, air, water, and natural food sources. Arsenic is sometimes referred to as the “King of Poisons” due to its potent toxicity [33]. Arsenic is exceedingly hazardous in nature; studies have shown that its potential adverse health effects are linked to its exposure, which has gotten a lot of attention in the last two decades [34,35]. P
7.3. Cadmium (Cd)
Cadmium exposure has been reported to be associated with fertility problems because it impairs sperm and lowers pregnancy outcomes. It is a cancer-causing agent and appears to play a role in heart disease and high blood pressure [37]. Cadmium destroys the gastrointestinal system, reduces renal antioxidant activities, and alters chemical fluid in the body, resulting in reproductive organ malfunction. The cognitive function of the brain is affected when Cd is present [38]. Cadmium is hazardous to tissues due to its ability to remove vitamins C and E from their metabolically active locations.
7.4. Nickel (Ni)
Nickel is among the most common metals on earth and is present in a wide range of metal alloys used in the steel industry, as well as in colorants, taps, and dry cells. Nickel can end up in water bodies due to its presence in wastewater streams [41]. Respiratory illness, lung fever, hypersensitivities, cardiovascular disease, skin irritation, and mishaps are all caused by the excessive absorption of Ni by humans. There is a high risk of developing prostate cancer, nasal cancer, and laryngeal cancer due to human exposure. Ni is only found in trace amounts in the environment, but food plants grown in contaminated soils can accumulate large quantities.
7.5. Chromium (Cr)
Chromium is essential for glucose and fat breakdown, as well as lipoprotein consumption. Its biological function is intertwined with that of insulin, and most Cr-enhanced processes are insulin dependent. An excessive amount, on the other hand, could be harmful [42]. In soils treated with wastewater, toxic levels are typical. Over 7.5 million tons of chromium are thought to be produced annually on an international scale. In the presence of chromium ions, the discharge of collagen-type I, which aids in the repair of broken bones, is reduced. Nose ulcers, pneumonia, and genetic mutation in humans, as well as the destruction of red blood cells and urinary damage, are caused by chromium. While Cr (VI) is associated with a variety of anomalies and disorders, Cr (III) acts as an endocrine activator and is required in trace amounts for appropriate fat and amino acid metabolism [43,44,45].
8. Human Health Risk Assessment of Pharmaceutical Industrial Effluents in the Environment
8.1. Health Risk Assessment
Human health risk assessment is a method of calculating the potential health consequences associated with the exposure of people to chemical hazards.
In the risk assessment process, there are four basic steps:
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Hazard identification,
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Assessment of exposure,
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Toxicity/dose–response assessment, and
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Characterization of risk.
8.1.1. Hazard Identification
The purpose of hazard identification is to look at the contaminants that are present in a given area, their level of accumulation, and their diffusion rate.
8.1.2. Assessment of Exposure
The purpose of the assessment of exposure is to determine the magnitude, reoccurrence, duration, or timing of individual exposure to pollutants (i.e., PTEs). The average daily dose (ADD) of the toxic elements discovered by consumption and skin contact in the population was calculated to assess exposure.
8.1.3. Toxicity/Dose–Response Assessment
Dose–response analysis determines the toxicity of PTEs based on their exposure strengths. The two critical toxicity indices used are a carcinogen intensity factor called the cancer slope factor (SF) and a non-carcinogenic level termed the reference dose (RfD).
8.1.4. Characterization of Risk
Risk characterization aids in predicting the potential cancerous and non-cancerous health hazards that the vast majority of the population in the research area is vulnerable to; this is done by combining all the data obtained to create statistical evidence of exposure to cancer and the threat proportion [45]. The sudden rise in pollution of priority metals [46] can have disastrous health repercussions on communities and habitats, disrupt crop productivity, and make animal and human drinking water unsafe. Toxic metal, in particular, can build up inside important organs, causing short- and long-term damage. Metals are commonly encountered in corrosive effluents, where water forms electrostatic dipolar ion interactions with priority metals [47].
9. Advanced Treatment of Pharmaceutical Industrial Effluents
9.1. Coagulation and Flocculation
Coagulation is a chemical water treatment process used to remove solids by adding coagulant agents and modifying the electrostatic charges of suspended particles in water to form large flocs, which then settle down as sludge. For improved treatment of industrial effluents, it is essential to squeeze and remove bound water from around hydrophilic colloids. As a result, determining the coagulation impact is heavily dependent on the flocculant nature. Polymers and metal salts are frequently used as flocculants. This procedure is effective for removing chromaticity as well as hazardous organic materials [52].
9.2. Flotation
Excluding sedimentation, flotation can eliminate dissolved particles from secondary effluents. The technology creates a large number of tiny bubbles by introducing air into effluent, creating floating floc with a lower density than the wastewater. It can also float to the top of the effluent to separate it. Ion flotation could be a suitable option for removing hazardous metal ions from industrial effluents. Ion flotation is based on the application of surfactant to make ionic metal species in effluent hydrophobic, followed by the removal of these hydrophobic species by gas bubbles [53].
9.3. Activated Carbon Adsorption
Activated carbon offers several benefits as an adsorbent: it features a large surface area, a multi-level pore volume, adsorption ability, and a constant chemical property. As a result, it is commonly utilized as an adsorbent to eliminate contaminants [54]. Activated carbon is used in the treatment of water and wastewater, including hazardous and difficult-to-meet discharge standards pharmaceutical wastewater. This is also a significantly advanced treatment method for industrial wastewater. There are two different types of activated carbon adsorption: chemical and physical. There is no adsorption selectivity, and physical adsorption is reversible.
9.4. Photocatalytic Oxidation
Ultraviolet photocatalytic oxidation, also known as photochemical oxidation, is a way of combining ultraviolet radiation as a catalyst with a UV-sensitive oxidant. When exposed to ultraviolet light, the breakdown of oxidants produces free radicals with a higher oxidative ability, allowing them to oxidize more and more difficult-to-decompose organic pollutants using only oxidants. Based on the kinds of oxidants used, photochemical oxidation can be classified as UV/O3, UV/H2O, UV/H2O2/O3, etc.
9.5. Electrochemical Oxidation
The electrochemical approach is well recognized for the removal of poisonous and hazardous pollutants in water and wastewater. In the field of water treatment, electrochemistry is a novel approach. The technique works on the following principle: during the electrochemical reaction, the reactant loses electrons and is oxidized at the anode surface. The chemical at the cathode surface, on the other hand, will lose electrons and get reduced. In particular, the oxidation of the anode causes the elimination of refractory organic materials.
9.6. Ultrafiltration (UF)
The ultrafiltration process is utilized in the tertiary treatment of water and wastewater for additional cleaning and treatment. The difference in pressure between the membranes on either side is what propels the movement; the membrane for ultrafiltration serves as the filtering medium. When a fluid travels through the surface of the membrane under a specific amount of pressure, water, inorganic ions, and tiny molecules pass through, while other components are prevented from crossing the membrane barrier.
9.7. Reverse Osmosis (RO)
Reverse osmosis efficiently removes metal ions from water, making it suitable for drinking [60,61]. RO membranes can be classified as either cellulose ester or aromatic polyamide. A variety of organic materials and dissolved inorganic salts can be removed using RO methods. It also has a high rate of water recycling and salt extraction efficiency.
9.8. Electrodialysis (ED)
Electrodialysis (ED) is among the new techniques for removing and recovering metals. Recently, metal-contaminated water has been treated using the emerging technique of electrodialysis [62]. The electrodialysis process (ED) combines electrolysis with dialysis. The dissolved salts in the wastewater are subsequently transported to the anode and the cathode by the direct current electric field.
10. Management of Potentially Toxic Elements in Pharmaceutical Industrial Effluents
Waste management and sewage treatment have recently become major issues for humans. Pharmaceutical metabolites have been found in the water cycle in the past 10 years, which has caused policy makers, water distributors, and communities at large to worry about the potential implications for human well-being. The World Health Organization (WHO) and the Environmental Protection Agency (EPA) both support a significant risk management strategy called the “water quality approach”. It implies that, to avoid any associated danger, particularly health problems, pharmaceutical effluents should be managed to a level that meets precise water quality guidelines [64].
If there is no landfill leachate collection, pharmaceuticals improperly disposed of in domestic waste wind up in landfills, where they may eventually be transmitted into water bodies [67]. Regarding the known and conceivable threats to humans and ecosystems, the presence of pharmaceuticals in surface water has sparked alarm among freshwater suppliers, policy makers, and the general public. It has been established that several pharmaceutical effluents have unfavorable impacts on ecosystems, including abnormalities, behavior, fertility, and death. Due difficulties faced in biodegrading toxic metals, which are naturally present in the earth’s crust, these materials have contributed to a significant number of environmental pollutants [5,51]. To stop environmental deterioration, the regulatory bodies for the pharmaceutical companies must demand constant supervision and the application of regulations governing the proper discharge of pharmaceutical pollutants. The World Health Organization has listed the issue as among the top ten potential health risks [68].
This entry is adapted from the peer-reviewed paper 10.3390/su15086974
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