We have done exhaustive review of literature to list out how many types of pollutants are affecting environment and to assess the risk of the pollutants present in environment impacting air, water bodies, soil and the living bodies dependent on it. Our review focuses on the percentage loss of natural resources all over the world due to various pollutants. It also involves the remedies and treatment to overcome the correspondence of pollutants in the environment.
a. Primary air pollutants
A primary pollutant is an air pollutant that is released into the atmosphere directly from a source. The source may be anthropogenic (caused by humans), such as industrial and car emissions, or it may be a natural event like sandstorms and volcanic eruptions (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans & International Agency for Research on Cancer, n.d.)
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Particulate matter: Particulate matter refers to the substances, whether they be solid or liquid, that are still floating in the air. The physical and chemical characteristics of air can be changed by these minute entities. Dust, smoke, pollen, and soot are a few examples of particulate matter.
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Carbon monoxide (CO): When a fossil fuel burns incompletely, carbon monoxide is produced, harmful and released by both businesses and vehicles.
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Sulfur dioxide (SO 2 ): Ore smelters and oil refineries both create sulphur dioxide. These gases build up in the environment, causing acid rain and numerous respiratory conditions in living things.
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Nitrogen oxide (NO and NO 2 ): Nitrogen oxide is released when fossil fuels are burned at high temperatures. Additionally, it contributes to acid rain and is detrimental to plant growth. It contributes to chronic heart and lung illnesses in people as well as skin ailments.
b. Secondary air pollutants
When ozone and peroxyacetyl nitrate (PAN) react together in the presence of UV light, smog is created. Photochemical smog is the cause of the brown and grey air in major cities. When primary and secondary contaminants are combined, photochemical smog is created. The followings are the secondary air contaminants that contribute to photochemical smog:
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Phenol: When main pollutants go through photochemical reactions, phenol is created in the atmosphere. In addition to spleen and lung failure, it damages the kidneys.
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Aldehyde: It develops when biomass and fossil fuels burn inefficiently. The respiratory and digestive tracts may get irritated by these secondary pollutants.
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PAN: It is generated by power plants, damages chloroplasts, and lowers plants' photosynthetic productivity. In humans, it is also to blame for eye discomfort.
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HNO 3 : Nitric oxide, which is the main pollutant, is oxidised to produce nitric acid. Acid rain is the result.
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H 2 SO 4 : Sulfuric acid is created when sulphur dioxide and water vapour are combined in the environment. Acid rain is one of its environmental effects. (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans & International Agency for Research on Cancer, n.d.)
c. Water pollutants
Sampling of river water and suspended sediment The Connecticut, Merrimack, and Thames watersheds' river water monitoring programmes were intended to record seasonal fluctuation but were not sufficiently thorough to record specific storm occurrences. A pole sampler was used to refill 1 L acid-washed high-density polyethylene bottles with river water in the field at a depth of around 50 cm that was at least 2 m distant from the shoreline. Before collection, bottles were rinsed with a river water sample and acid-washed with 10% trace metal-grade HNO3. Following USGS sampling guidelines was the water sampling. An insulated container was used to deliver water samples to the University of Massachusetts. Using vacuum filtering using 0.45-m cellulose membrane filters, suspended sediments from the water were removed from the samples, which were then frozen at 40°C, freeze-dried to eliminate moisture, and kept in a dark box at 4°C. The mass of suspended sediment per litre of river water was calculated using the term "bottle suspended sediment." (Tang et al., 2019).
Estuary areas
Estuary regions are highly urbanised and industrialised since they have historically been established as economic zones. Because of the lower flow velocity, the suspended solids transported by river streams are more likely to settle out in estuaries. This is because anthropogenically created organic contaminants are easily adsorbed on the surface of particulate matter in water. Nonylphenol was the most common component among the examined endocrine disrupting chemicals (EDCs) in marine sediments from the vicinity of submarine sewage outfalls (SSOs) along the So Paulo State Coast (Brazil). The variety of EDCs increased with an increase in people serviced by SSOs. (Tang et al., 2019)
Contaminants of emerging concern
a. Anthropogenic contaminants
Anthropogenic contaminants (ACs) are pollutants that humans have introduced into the environment (Rhind, 2009) and which may have a direct or indirect impact on living things. Many of these pollutants are now known to be endocrine disruptors and to be associated with dangers to human health, including hormonal imbalance, disorders of metabolism, neurological diseases, immunological disorders, and imbalances in the male and female reproductive systems (Gracia-Lor et al., 2017a), (Barrios-Estrada et al., 2018), (Bilal et al., 2019). Due to the volume and diversity of developing contaminants resulting from anthropogenic processes, ACs featuring wastewater treatment systems are therefore crucial.
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A brand-new class of man-made compounds that are classified as pollutants that are mostly present in trace amounts in the air, soil, water, food, and tissues of both humans and animals. These chemical substances are persistent in the environment and have the power to change the physiological properties of target receptors. (Bhandari et al., 2009);
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A brand-new class of man-made toxins, including unique metals and chemicals utilised in the electronics sector, nanoparticles, and innovative insecticides.
b. Pharmaceuticals and personal care products contaminants
PPCPs are utilised extensively over the globe (Demers et al., 2013), (Covelli et al., 2021). They are continuously released into home and industrial sewage systems, and traditional wastewater treatment facilities' (WWTPs') removal effectiveness is constrained. Due to their ubiquity, pseudo-persistence, and bioactivity in the environment, as well as their unexpectedly negative effects upon the ecosystem, PPCPs have caused tremendous worry as new pollutants. Due to their constant exposure to PPCPs and increased exposure hazards, aquatic creatures are the main focus of concern. The primary area of attention should be the metabolic effects of PPCPs on species that are edible.
Due to their pervasiveness in the environment, the resulting induction of antibiotic-resistance genes, and potential effects on people, antibiotics merit special attention (Ravera et al., 2003). Significant changes in the amino acid metabolism of fish and crustaceans have been observed in metabolomics studies. It has been established that the marine medaka Oryzias melastigma's amino acid profiles are disturbed by the antibiotic sulfamethazine, which is often used to treat bacterial infections. Under the stress of sulfamethoxazole, alterations in amino acid levels were shown to be connected with hepatic damages, immunological function malfunction, oxidative stress and subsequent defences, energy shift, osmoregulation, and nucleotide metabolism in marine mussel Mytilus galloprovincialis. Antibiotics would have a negative impact on the nutritional content of fish and mussels for human consumption as a result of disrupted amino acid metabolism, which might be seen in the variable quality of dietary proteins. Antibiotics may also cause oxidative stress, which speeds up protein deterioration in the blue mussel Mytilus edulis. From the standpoint of human health, it is very important to further assess how PPCP exposure through food intake affects the production of vitamins, lipids, and other important metabolites.
Diclofenac
A non-steroidal anti-inflammatory medication (NSAID), Diclofenac has been discovered and reported in several water bodies around Europe (L. Wang et al., 2010). 972 mg/L amounts were discovered in rivers and WWTPs in Portugal (Paíga et al., 2016). Diclofenac levels in Spain varied from 1 to 54 mg/L. More particular, concentrations of diclofenac ranging from 6.72 to 940 mg/L were discovered in the Turia River Basin (Valencia, Spain). Between 258 and 1398 mg/L of concentrations have been found in Latin America (Cuernavaca, Mexico) (Rivera-Jaimes et al., 2018). A maximum of 717 mg/L of diclofenac was discovered in Chinese rivers (L. Wang et al., 2010). The concentrations in Pakistan ranged between 10 and 1800 mg/L (Scheurell et al., 2009). Diclofenac removal efficiency ranged from 26 to 60% in a WWTP in Turkey when the influent contained 295–1376 mg/L and the effluent had 119–1012 mg/L (Sari et al., 2014). Fish and mollusc samples from a river estuary in Malaysia contained diclofenac (1.42 mg/g to 10.76 mg/g) that was found in live creatures.
According to research on the toxicological effects of diclofenac on fauna, exposure to the drug at concentrations of 200, 2000, and 20,000 mg/L influences the function of the liver, lowers lipid peroxidation, and lowers the quantity of dopamine released by the fish Rhamdia quelen. At concentrations more than 25 mg/L, a decrease in the reproductive rate was seen in the freshwater crustaceans Daphnia magna and Moina macrocopa. At doses of 8 mg/L and 1000 mg/L, diclofenac has an impact on the cellular level in the fish Oryzias latipes and produces cellular toxicity, apoptosis, genotoxicity, and estrogenic effects. Animals can bio-accumulate and metabolise diclofenac. For instance, Mytilus trossulus mussels have the ability to convert diclofenac into its hydroxy-derivative molecules (4- OH and 5-OH diclofenac). Moreover, diclofenac has an impact on amphibians by causing morphological deformities, changes to heart function, and impairments to swimming ability.
Ibuprofen
Ibuprofen is a medication that acts as both an NSAIDs and an analgesic (Moro et al., 2014) and is present in water bodies either in its entirety or in fragments as metabolites like hydroxy-ibuprofen and carboxy-ibuprofen. Ibuprofen was discovered in Spain's WWTPs at a concentration of 13.74 g/L and its metabolites at 130 g/L. Ibuprofen was found in South African water samples from seawater and the estuary at concentrations of 278 mg/L, 261 mg/L, and 170 mg/L, respectively (Ngubane et al., 2019). Surface and groundwater samples from Cameroon contained ibuprofen at quantities of 516 and 276 mg/L, respectively. In the UK, ibuprofen was found in surface water at a concentration of 6297 mg/L. Exposure to ibuprofen (at a dosage of 1 mg/L) can inhibit the growth of germs. Additionally, it can cause morphological and structural changes, such as a decrease in chlorophyll synthesis and an increase in carotenoids (Moro et al., 2014). Ibuprofen at concentrations between 10 and 100 mg/L over a lengthy period of time (10 days) reduces the rate of photosynthesis in Navicula sp. Ibuprofen (250 mg/L) raises oxyradicals and causes instability of the lysosomal membrane in the frog Pelophylax ridibundus. Ibuprofen (5 to 500 g/L) exposure in zebrafish (Danio rerio) lowers the pace of development, decreases the capacity to respond to outside stimuli and swim, and is neurotoxic to the embryos. Ibuprofen (100 g/L) promotes lipid oxidation in zebra mussels (Dreissena polymorpha), while decreasing triglyceride levels and antioxidant capacity (André & Gagné, 2017).
Naproxen
Naproxen is widely used to treat mild to moderately severe pain, fever, headache, and inflammation (Neal & Moore, 2017). For some species, including those susceptible to chronic exposure, such as Pseudokirchneriella subcapitata, Brachionus calyciflorus, and Ceriodaphnia dubia, it is regarded as a hazardous substance. In the aforementioned species, doses up to 31.81 mg/L, 0.56 mg/L, and 0.33 mg/L, as well as its photo-derivatives, are thought to be even more dangerous than the original molecule. Naproxen has been detected in wastewater at Algiers, on the western shore of the Mediterranean Sea Bay, in quantities between 1220 and 9585 mg/L, and in surface water at 228.3 mg/L. Naproxen was found in Taihu Lake and WWTP in Kinmen, Taiwan, with concentrations of 0.3 µg/L and 104.3 µg/L, respectively. Additionally, it was discovered in surface water in Italy between 52.4 and 124.2 µg/L (F. Riva et al., 2019). In Pakistan, wastewater effluents from the pharmaceutical sector contained levels of this pollutant ranging from 215 to 464 µg/L. Analyzing the impacts of naproxen on marine animals has been done using the crayfish Orconectes virilis. The behaviour and motility of marine species were negatively affected by concentrations of 0.027 µg/L, 2.30 µg/L, and 14.0 µg/L (Neal & Moore, 2017). During the early stages of development, carps exposed to varied concentrations of naproxen (10, 50, 100, and 200 g/L) shown changes in their pace of development, morphology, histopathology, and in certain cases, increased mortality of organisms.
It has been demonstrated that this substance alters the levels of chlorophyll, carotenoids, and enzymatic activity in various microorganisms, including the microalgae Cymbella sp. and Scenedesmus quadricauda. Naproxen (1 and 100 mg/L) changes the mRNA expression in the gut and the expression of antioxidant genes in adult zebrafish (Danio rerio).
c. Pollutants from agricultural products
Fipronil
An insecticide, fipronil is used to control pests in agriculture and veterinary care (Stark & Vargas, 2005). Since the water used after these procedures is discharged untreated into the environmental matrix, fipronil is leached into the environment through human activities like agricultural spraying or treating pets for flea control. Fipronil and two of its derivatives were discovered in the river Elbe in Germany at concentrations ranging from 0.5 to 1.6 mg/L. Fipronil was found in eel muscle (4.05 3.73 mg/g) and liver tissue (19.91 9.96 mg/g) in the same investigation, proving that animals may bioaccumulate it. Fipronil has been discovered in Florida surface water at amounts ranging from 0.5 to 207.3 mg/L. Fipronil affects the expression of some genes in the blue crab Callinectes sapidus, such as the reduction of Vtg (vitellogenin) and EcR. (Ecdysone receptor). Salinity was discovered to be a factor in these effects. The survival in the first, second, third, and fourth phases of juvenile development can be decreased in the water flea Daphnia pulex when exposed to increasing doses of fipronil (0–80 g/L). Fipronil (35–180 g/kg in water and sediment) increases oxidative stress and lipid peroxidation in frogs, including Eupemphix nattereri tadpoles (Gripp et al., 2017). Fipronil can change the cytochrome P450 enzyme activity and cause liver damage in rats when exposed up to 15 mg/kg/day. Fipronil (0.1 to 910 g/L) induced sub-lethal changes in embryos, including as tail abnormalities and decreased hatching, in the Japanese rice fish (medaka), Oryzias latipes. Fipronil (750 mg/kg bw administered intraperitoneally) inflicted acute toxicity and histological changes on certain organs in Caspian white fish (Rutilus frisii) (Stefani Margarido et al., 2013).
Carbendazim
A broad-spectrum fungicide called carbendazim is used in agriculture to suppress pests (Andrade et al., 2016). The highest documented dietary exposure to carbendazim (0.26 mg/person/day) in China was from ingestion of residues found in tomato crops. Carbendazim at concentrations of 5 to 50 g/L demonstrated significant ecotoxic effects on the water flea Daphnia magna. It slows down reproduction and damages DNA through genotoxicity (Silva et al., 2011). By up-regulating the genes p53, Mdm2, Bbc3, and Cas8, carbendazim at 20 and 100 g/L promotes apoptosis in zebrafish (Danio rerio). Additionally, it damages the immune system and endocrine system in embryonic cells. At larval stages, exposure to carbendazim in the 4-500 g/L range causes a variety of gene expression patterns, as well as locomotor abnormalities and other behavioural changes in the species (Andrade et al., 2016).
In several species, the combined effects of competition between intra- and interspecific species for food and exposure to carbendazim (400, 800, and 1200 g/L) were studied (Del Arco et al., 2015). The tolerance of aquatic invertebrates to carbendazim is poor. For instance, after 96 hours of exposure to 25 g/L of carbendazim, 50% of the population of the flatworm Dugesia lugubris perished. The populations of the creatures belonging to the genera Cladocera, Copepod, and Rotatoria decreased at high concentrations (N33 g/L).
Atrazine
Herbicide atrazine is employed to eradicate weeds in a variety of crops, including sugar cane, corn, pineapple, and sorghum (Wirbisky & Freeman, 2017). It can enter surface and groundwater bodies through surface runoff, subterranean runoff, infiltration, and/or unintentional spilling during incorrect handling since it is soluble in water. This substance has been discovered in drinking water reserves at values of 0.42 ppb due to its ability to contaminate through the soil. The zebrafish had detrimental consequences after being exposed to 30 g/L of atrazine (Danio rerio, wild-type AB strain). It may result in the DNA losing its methylation, which would compromise the genome's protection (Wirbisky-Hershberger et al., 2017). Atrazine exposure of 10 mg/L can modify gene expression and change the number of copies of certain genes (Wirbisky & Freeman, 2017). Additionally, it has been demonstrated that atrazine exposure (300 mg/L) raises the risk of cancer, angiogenesis, and neurological changes. In the juvenile stage of the crayfish Cherax quadricarinatus, exposure to 2.5 mg/L of atrazine results in an imbalance in the sexual ratios by increasing the number of females, which has an impact on the species' reproductive rates.
Contaminants from narcotics and other drugs
Narcotics are utilised to cause human responses such central nervous system stimulation, analgesia, and narcosis (Fig. 4). Due to their detrimental impact on human health, governments often regulate the use of certain chemicals (Argoff & Silvershein, 2009).
Benzoylecgonine
The primary cocaine metabolite and an analgesic produced by the pharmaceutical industry is benzoylecgonine (López-Pacheco et al., 2019). Numerous investigations have documented the presence of benzoylecgonine in various water sources all over the world. For instance, there were between 10 and 1019 mg/L in the surface waters of Brazil, between 37 and 2130 mg/L in 30 WWTPs in Belgium, and 14.7 mg/L of benzoylecgonine in 3 rivers in London. Benzoylecgonine (500 mg/L and 1000 mg/L) exposure causes oxidative stress and inhibits acetylcholine transferase in the species Daphnia magna. This has to do with how the species reproduces and its swimming habits. This pollutant changes the mitochondrial activity in riparian plants and irrigated crops at a concentration of 1 mg/L while also reducing germination (García-Cambero et al., 2015). Through the blood of the mother, benzoylecgonine may be passed from pregnant rats to their foetuses. Animals were given an intravenous bolus dosage of 1 mg/kg bw of benzoylecgonine, followed by an infusion at a rate of 0.2 mg/kg bw/min to demonstrate how exposure can induce an organism to pass the substance on to their progeny (Morishima et al., 2001). The integrity of the lysosomal membrane and the balance of the defence enzyme activity in Dreissena polymorpha were shown to be affected by exposure to benzoylecgonine (500 and 1000 mg/L), which suggests an increase in oxidative stress.
Amphetamines
The central nervous system is stimulated by amphetamines. They are sympathomimetic amines, and dopamine, serotonin, and adrenaline are only a few of the neurotransmitters whose physiological pathways they affect. The effects of these compounds on the human body include an increase in blood pressure, heart rate, a sense of alertness, high stimulation, an improvement in cognitive function, and sensations of vast quantities of energy, along with a decrease in tiredness, sleepiness, and appetite. Amphetamine dependency is a possibility. A prescribed number of amphetamines is used medically to treat narcolepsy and attention deficit in children (Robledo Andrés, 2008). Amphetamines have an anthropogenic origin, as evidenced by their presence in several environmental matrices, including WWTPs. Aquatic animals, notably freshwater mussels (Lasmigona costata) from the Great River in Ontario, Canada, may have accumulated 4.7 mg/g of amphetamine. Organisms from two different species, the Chinook salmon (Oncorhynchus tshawytscha) and the Pacific staghorn sculpin (Leptocottus armatus), were gathered in the Puget Estuary in Washington in order to identify the bioaccumulated materials. These species bioaccumulate 245 and 25 mg/g of amphetamine, according to the study. In the bay of San Francisco, California, about 9.7 mg/L of amphetamine was discovered in the water, 3.3 mg/g in the soil, and 60 mg/g in mussels taken from 5 separate locations (Klosterhaus et al., 2013). This suggests that it can be biomagnified after undergoing bioaccumulation and moving up the food chain. Amphetamine (5 and 10 mg/L) has an impact on the zebrafish (Danio rerio) that causes hypermobility, an increase in unpredictable movements such a shift in movement direction, as well as an increase in freezing episodes.
Cocaine
In Belgium, surface water and wastewater treatment facilities included cocaine, a prohibited material that exposes animals and plants directly (García-Cambero et al., 2015). Cocaine contamination has been discovered in 37 WWTPs, 28 rivers, and amounts as high as 753 mg/L. These concentrations were used to calculate the population's consumption of cocaine. These were equated to N1.8 g of cocaine per day for per 1000 individuals. Zebrafish embryos exposed to cocaine (0.3 g/L) and its metabolites had altered protein profiles, altered lipid transport, and altered stress responses. Cocaine (40 mg/L) damages DNA, decreases the integrity of the lysosomal membrane, boosts the amount of micronucleated cells, and induces cellular death in Dreissena polymorpha (Binelli et al., 2012). Cocaine (20 mg/kg bw) can alter the lipid profile of the mouse brain, which is one of the primary regulators of the shape and function of neuronal cells.
Contaminants from the food industry
Caffeine
Caffeine is the primary ingredient in coffee, energy drinks, and several treatments for chronic disorders (Gracia-Lor et al., 2017b). The presence of caffeine in the environment is a result of human activity. Caffeine was found to be present in seawater off the coast of Spain in amounts of 857 mg/L (Dafouz et al., 2018). According to a study of 10 WWTPs in Europe, between 37 and 320 mg of caffeine per person per day are released owing to human use (Gracia-Lor et al., 2017b). Caffeine exposure has an impact on the health of living things. The behaviour and development of Galleria mellonella larvae are impacted by caffeine exposure (19.41 mg/L), and the quantity of peptides linked to brain injury is increased. It was shown that caffeine administration in mice at a dose of 2 mg/100 g bw alters embryonic development by resulting in a small deformity of the developing limbs' phalanges. In the early phases of development, 48.54 g/L exposure in zebrafish results in cellular damage, increased apoptosis, mitochondrial damage, and morphological defects (Rah et al., 2017).
Bisphenol A
Chemicals called bisphenol A (BPA) are employed in the production of epoxy resin and plastics (Staniszewska et al., 2015). BPA is a chemical that is utilised in the production of medical equipment, baby toys, plastic goods, and food packaging. Humans are exposed to this pollutant when they consume food that has been kept in a BPA-containing container. Surface water BPA and eight analogue concentrations in Taihu Lake, China, varied from 49.7 to 3480 mg/L. It has been shown that BPA may build up in the food chain. BPA was discovered in surface water in India at quantities ranging from 54 to 1950 mg/L (Yamazaki et al., 2015), whereas in the Baltic region, it was discovered in rivers and the coastal zone at amounts ranging from b5.0 to 277 mg/L (Staniszewska et al., 2015). Rats exposed to BPA (5, 25 and 125 g/kg bw) showed substantial reductions in daily weight gain, an increase in gamma globulin, produced liver damage, and promoted liver cell death (Kazemi et al., 2017). When BPA is present in Asellus aquaticus at levels of 8.6 mg/L in the water and 13.5 mg/L in the sediment, it disrupts the endocrine system. Female rats exposed to BPA (10 mg/kg bw) experienced earlier puberty, which may have had an impact on their reproductive systems.
Personal care products
Triclosan
Triclosan is an antibiotic used in the formulas of several personal care items, including toothpaste and antibacterial gels. The FDA in the USA regulates the use of triclosan in personal care products (Timeline of Ozone National Ambient Air Quality Standards (NAAQS) | US EPA, n.d.). In China, triclosan has been discovered in various river sediments (0.10–64.9 mg/g). It was discovered in surface water (0.005–0.31 µg/L), WWTPs (0.13–2.90 µg/L), and surface sediments (0.9–672 µg/L) in Minnesota, USA (Lyndall et al., 2017). An increase in oxidative stress in the species Dreissena polymorpha is one of the outcomes in organisms subjected to 580 mg/L of triclosan (C. Riva et al., 2012). At a concentration of 6.25 µg/L, triclosan also shortens the life duration, survival rate, and fertility of Brachionus havanaensis and Plationus patulus. At a concentration of 0.868 µg/L, it can interfere with gonadal differentiation and development in the frog Pelophylax nigromaculatus, changing the species' sex ratios. In a research, mice were given triclosan at doses of 10, 100, and 200 mg/kg diet/day. This caused tumours in the animals by activating the CAR and PPAR receptors, which control the mechanism that boosts DNA synthesis in the liver.
Surfactants
There are other types of surfactants used in personal care products, and triclosan is also subject to FDA regulation (Timeline of Ozone National Ambient Air Quality Standards (NAAQS) | US EPA, n.d.). Alkyl sulphates are among the most popular ones. A combination of linear primary alkyl ether sulphates (AES) is utilised as an emulsifier in home cleaning solutions, such as sodium lauryl ether sulphate (SLS), an anionic surfactant. SLS concentrations in cleaning goods typically range from 1–30% and in cosmetic products from 0.01–50%. SLS concentrations in home wastewater can range from 0.4 to 12 mg/L, however. SLS has a number of drawbacks, one of which is that it reduces the floccus size of activated sludge in WWTPs. Additionally, it makes microorganisms poisonous by attaching to enzymes, structural proteins, phospholipids, or by altering the bacterial cell's hydrophobicity (Paulo et al., 2017). Diverse SLS concentrations have been shown to have an impact on aquatic organisms, including the marine microalga Dunaliella salina, which is inhibited by a concentration of 4.68 mg/L, and the fresh water microalga Pseudokirchneriella subcapitata, which is inhibited by a concentration of 2.10 mg/L (Pavlić et al., 2005).
Human consumption of anthropogenic contaminants and their presence in drinking water reservoirs
In drinking water reservoirs, WWTPs, DWTPs, and other locations where people come into touch with these polluted water resources, ACs have been discovered (Fawell & Nieuwenhuijsen, 2003). For instance, water from some rivers, like the Yangtze River in China, is utilised for drinking purposes. Triclosan was discovered in this river at values of 1.85 mg/L, and it was calculated that children and adults consume 0.02 mg/kg bw and 0.03 mg/kg bw of triclosan daily, respectively. Additionally, certain pesticides including butachlor (0.47 g/L) and fipronil (0.04 g/L) are present in the drinking water in Vietnam. Pesticide contamination can come via infiltration or direct contact with the substance. The same ACs have been found in groundwater from the River Ganges Basin (India), including acetaminophen (1.92 mg/L), caffeine (208 mg/L), carbamazepine (27.2 mg/L), sulfamethoxazole (3.49 mg/L), diclofenac (1.56 mg/L), naproxen (2.37 mg/L), ibuprofen (49.4 mg/L), and triclos After drinking water treatment in Milan, groundwater samples were examined. The analytical profile showed that the groundwater included 10.3 mg/L of carbamazepine, 0.61 mg/L of benzoylecgonine, 4.44 mg/L of cocaine, 683 mg/L of BPA, and 5.2 mg/L of caffeine. There have been reports of 335 mg/L of carbamazepine, 276 mg/L of ibuprofen, 518 mg/L of diclofenac, 111 mg/L of acetaminophen, and 1285 mg/L of sulfamethoxazole in groundwater in Sub-Saharan Africa. A Brazilian lake called Guarapiranga had 12 mg/L of cocaine and 179 mg/L of benzoylecgonine. In addition, drinking water in five places in Brazil has 22 mg/L of cocaine and 652 mg/L of benzoylecgonine (Campestrini & Jardim, 2017). Two recent studies conducted in China discovered the following ACs (expressed as AC maximum concentration in raw water to AC concentration in effluent) before and after the water treatment procedure in a DWTP: Acetaminophen in the range of 37.1 to 6.4 mg/L, carbamazepine in the range of 1.01 to 0.65 mg/L, caffeine in the range of 14.2 to 3.8 mg/L, indomethacin in the range of 12.0 to 5 mg/L, lincomycin in the range of 4.3 to 2.5 mg/L, sulfamethoxazole in the range of 35.4 to 5.4 mg/L. After water treatment, BPA was discovered in a DWTP in Taiwan at a concentration of 38 mg/L. Based on these findings, it was calculated that an individual's daily BPA consumption ranges from 4.3 to 76 ng/day when taking into account that they drink 2 L of water each day. Analyses of water samples from Madrid's DWTP revealed AC contamination, including BPA (5123 mg/L), ethyl paraben (11.97 mg/L), and methylparaben (9.87–85.89 mg/L) (Alda et al., 2018). DWTP that purifies water from the Mediterranean El Llobregat River conducted yet another investigation (Spain). Even after the course of therapy, acetaminophen, carbamazepine, hydrochlorothiazide, thiabendazole, diltiazem, nor-verapamil, BPA, and propyl-paraben were found. The amount of ACs removed from treated water from a WTP in the Gdask (Poland) area was calculated, and the following results are expressed as concentration range and percentage of compound removal from untreated water): 4.9–5.6 mg/L (0.0%) of ranitidine, 9.3–44.0 mg/L (44.5%) of acetaminophen, 12.7-158.7 mg/L (61.3%) of caffeine, 2.1-6.0 mg/L (88.9%) of carbamazepine (Kot-Wasik et al., 2016).
Brazilian drinking water samples that were taken from a neighbourhood water delivery system were examined (Sodré et al., 2018). Atrazine and caffeine levels in the samples were determined to be 3.3 mg/L and 16 mg/L, respectively (Sodré et al., 2018). Atrazine levels ranged from 5–68 mg/L in Croatian drinking water samples taken from public water sources. The atrazine concentration in drinking water was monitored in Ohio, USA, from 2006 to 2008, and it was found to range from 0 to 15.7 g/L.
Microplastics
MPs are brought on by improper plastic trash disposal (Chen et al., 2020). MPs are microscopic particles (less than 5 mm) made of raw plastic components, such as the tiny spheres found in toothpaste, soap, and other items (Dodson et al., 2020). When MPs are present just in the environment or when they mix with other pollutants (such as heavy metals, industrial dyes, etc.) to produce extremely toxic chemicals, MPs pose severe dangers to human health and aquatic creatures (Li et al., 2020). As a result, a lot of research has been done and published on the basic processes of interaction between MPs and other environmental pollutants.
Identification of microplastics in environmental matrices
MPs are increasingly causing environmental problems. These pollutants have been found in a number of environmental areas. The scientific community is now pursuing research to understand the basic and application elements of MPs as a new hot issue. Even though other CECs have made progress, more work has to be done to detect and characterise MPs in environmental matrices in order to offer solid and trustworthy information regarding their occurrence and environmental destiny. To accurately assess the toxicological and health concerns associated with these pollutants, information about the shape, colour, identity, size, and other properties of MPs is crucial.
MPs in environmental matrices have been studied using a variety of approaches. There are numerous types of spectroscopies, including Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, gas chromatography-mass spectrometry (GC-MS), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), field flow fractionation, scanning electron microscopy (SEM), fluorescence microscopy, flow cytometry, dynamic light scattering.
MPs are mostly present in the environment in conjunction with other inorganic and organic substances, notwithstanding the excellent advances made in this field of study. As a result, procedures for detection and characterisation still need to be modified to allow for the production of trustworthy data. Recently, a thorough review paper examined all methods used for MP separation, characterisation, identification, and detection. For this use, AFM was regarded as a developing method. It should be noted, nonetheless, that a variety of methodologies must be taken into account in order to collect precise information regarding the identification, characterisation, and identification of MPs in environmental matrices (Fu et al., 2020).
Since MPs were recently found for the first time in human placenta, there has been a lot of discussion about the dangers these pollutants pose to human health. Endocrine disruptors, which long-term cause significant human limitations, were discovered on the surface of MPs (Ragusa et al., 2021). In the same vein, human peripheral blood cells (in vitro) were cytotoxic and genotoxic to PE-MPs. Even at low doses, PE-MPs produced genetic instability, as demonstrated by the cytokinesis-block micronucleus Cytomel test. Additionally, after exposure to PE-MPs, micronucleation, nucleoplasm bridge development, and nuclear bud formation increased (Çobanoğlu et al., 2021).
It is acknowledged that MP consumption can have a variety of toxicological consequences, even if little is known about the ecotoxicological effects of MPs in various species. MPs have a detrimental effect on a number of essential processes, including reproduction, growth, eating, and development (Trestrail et al., 2020). It is well acknowledged that humans consume MPs mostly through the consumption of aquatic species, namely fish and shellfish (Senathirajah et al., 2021).
Sources And Pathways Of Emerging Contaminants
Emergent contaminants have the same sources as conventional pollutants since they are released into the environment through industrial activities, emissions, wastewater discharges, and effluent disposal Fig. 9. The two main categories of contamination sources are point sources and non-point sources. Point sources are defined as toxins that are emitted from a single place and whose inputs into environmental systems may be distinguished geographically; these sources frequently have concentrated loadings. Typical examples include discharges from industrial activities and sewage treatment plants and mineral(s) extraction. Pollution coming from diffuse, hazy sources that typically cover wide regions is referred to as a non-point source or diffuse source. Typical examples are rain overflow in urban or industrial regions and runoff caused by the application of bio-solids or manure to soils. Diffuse sources are often found in lower concentrations than point sources and are thought to be more sensitive to the process of natural attenuation. It is challenging to trace diffuse sources all the way back to the polluter, the original source.
Therefore, it is challenging to manage and gauge the impact of dispersed sources on the ecosystem. Figure 10 below illustrates common routes and receptors for developing pollutants. It is exemplary but not all conceivable pathways and receptors are shown here. It is commonly acknowledged that ECs in water sources are greatly influenced by wastewater sources and their artificial recharge/infiltration to the subsurface. They are a significant source of worldwide pollution. This is more likely to happen in areas with inadequate regulation, extremely basic regulation, or no regulation at all for wastewater treatment. Furthermore, even in cases where treatment systems are cutting edge, removal may not be thorough, and as a result, these sources can significantly contribute to environmental pollution. Similar to other point sources, landfills are significant ones because ECs may seep from them and into groundwater or surface waters. Regarding diffuse sources, the usage of manure and biosolids derived from sewage treatment facilities is the major source of ECs in the soil. Despite the fact that this is a widely acknowledged waste management approach, residual pollutants may still be present in biosolids or manure that is put to the soil.
This has been proven by Boczkowski, J. et. al., who linked the application of manure to soil with the existence of numerous antibacterial chemicals (Hu et al., 2010). (Lapworth et al., 2012) In their article said that auxiliary channels, such as surface water-groundwater exchange from runoff, are more probable than direct paths for ECs originating from manure and bio-solids to enter groundwater (Lapworth et al., 2012). It is fair to infer that these sources will continue to significantly contribute to ECs pollution given that applying bio-solids and manure to soil is a common practise that will continue in the future.
Table:1 The toxic effects of typical ECs in the environment
| Emerging contaminant | Ecology effect | Human health effect | References |
| Engineered nanoparticles | Toxic to bacteria, plants, fish, earthworm (growth, mortality, reproduction, gene expression) | Cytotoxicity, oxidative stress, inflammatory effects, in lungs, genotoxicity, carcinogenic effects, granulomas, thickening of alveolar wall, and augmented interstitial collagen staining | (Boczkowski & Hoet, 2010) |
| Endocrine disruptors | Toxic to wildlife, human | Alter reproductively relevant, sexually-dimorphic neuroendocrine system, alter endogenous steroid levels, etc., diabetes, problems in the cardiovascular system, abnormal neural behaviors and linked to obesity. | (Frye et al., 2012), (Vandenberg et al., 2013) |
| Ionic liquids | Inhibitory effects on a variety of bacteria and fungi, influencing the growth rate of algae, toxic to invertebrates, fish and frogs | Adverse effects on neuronal process, cytotoxicity, | (Vandenberg et al., 2013), (S. H. Wang et al., 2010) |
| Perfluorinated compounds | Bioaccumulation in fish and fishery products | Accumulate primarily in the serum, kidney and liver, potentially adverse effects on developmental, reproductive systems and other damaging outcomes | (Contaminants of Emerging Concern Including Pharmaceuticals and Personal Care Products | US EPA, n.d.) |
To determine the hazards that the receptors may be exposed to, a precise relationship between the source and the receptors must be established. Who are the receptors, though? For example, in the UK, where groundwater supplies the great majority of the country's public water (about 80% in the south and southeast) and around one-third of the nation overall, receptors may include the groundwater body itself. Groundwater abstraction boreholes, groundwater discharge sites, points of compliance, and more significantly, people, other living things, or the ecosystem as a whole, are additional possible receptors.
Future Prospects
To detect substances that could pose a concern to receptors from an analytical standpoint, new techniques must be developed. Additionally, it is necessary to construct a more thorough environmental risk assessment. To this objective, chemical and biological analyses have to be coupled to get a better evaluation of the harm that ECs does to the environment. In the assessment of various corrective measures, a risk-based strategy for controlling ECs that makes a trade-off between risk reduction and cost-effectiveness is advised. The management of ECs must also be supplemented by other measures, such as better water treatment systems, waste minimization, proper waste disposal, improved chemical management and utilisation, and reduced chemical emission.
Analyzing possible interactions between anthropogenic air pollution and other climate-driven risk factors, such as severe temperatures, infrastructure damage from flooding, wildfires, etc., is an important new path for future study. For instance, the danger of wildfires can rise in exceptionally hot weather. To manage this risk, we need both empirical studies to pinpoint and measure the cause factors and projection studies that take into account a variety of climate-related measures and outcomes.