**4. Pesticide residues in water bodies**

Pesticide use in both developed and developing countries has no doubt enhanced food production and ensured food security, the inappropriate and poorly regulated practices of pesticide handling and application have led to contamination of water bodies. There are several scientific reports those indicate that only 0.1% of the applied pesticides in the field reach the target organisms, and a huge amount is lost into different environmental compartments [20]. Pesticides are chemical substances with harmful chemical properties such as toxicity and persistency. They remain as such in various ecosystems for a long time and are hence called persistent organic pollutants (POPs). "Persistency may be defined as the tendency of a chemical compound to conserve its molecular integrity and chemical, physical, and functional characteristics for a certain time after being released into the soil." Pesticides are grouped into two categories—hydrophobic and hydrophilic based on which the extent of persistency of a pesticide is determined. The persistency of pesticides in the environment depends on several factors such as the type of soil, method of

pesticide application, the capacity of soil to adsorb pesticides, organic matter content of the soil, etc. Hydrophobic pesticides are persistent and hence have the properties of bioaccumulation in the environment, e.g., organochlorines (DDT, endosulfan, endrin, heptachlor, lindane). Some pesticides being persistent persist in the soil and in that course of time may experience a variety of fates. Some amount of the pesticides will be taken up by the plants, and some amount will be degraded by the native microorganisms present in that area. The remaining amount of the pesticide active ingredients or their transformed products will be carried away by water at the time of rainfall or irrigation to different sources of water. Pesticides that will percolate vertically downward in the soil horizon finally reach the groundwater table and those that will move in surface water runoff reach nearby water bodies. Some amount of insoluble chemicals that get tightly bound to soil particles on the topsoil layer are subjected to erosion and ultimately reach surface waters. Pesticide residues that remain in the soil are sometimes subjected to volatilization, in the atmosphere that get accumulated in the rain and during rainfall, finally reach different water bodies. However, water source contamination through this pathway is insignificant. Some pesticides such as herbicides, carbamates, fungicides, and some organophosphates are hydrophilic, hence transported through runoff to surface water bodies and may be leached to groundwater sources.

The occurrence of pesticide residues in the ground as well as surface water sources is a widespread issue globally [21]. Some pesticides detected in major water bodies in different countries are presented in **Table 1**. Pesticide molecules are often found more frequently in surface water sources as compared with groundwater tables [33]. The reason is that the pesticides tend to slowly filter down the soil horizon and reach the deep aquifers, whereas the precipitations and frequent irrigations enhance the chances of pesticide transfer to surface water sources. It is hard to decontaminate the water in the groundwater table and the deep aquifers once pesticide residues contaminate the sources.

Surface water source contamination by pesticides is now common case in developing countries such as India. Not only the surface and groundwater sources but also the direct drinking water sources are found to be contaminated with some pesticide residues in almost all countries around the globe. In several reports where drinking water samples were collected from hand pumps or tube wells from one state of India, about 58% of the samples were found contaminated with various pesticide residues, mainly organochlorines above United States Environmental Protection Agency standards [34]. In China, drinking water samples were found contaminated with 42 different organochlorine pesticides at a concentration ranging from 0.001 to 2.65 μg/l [35–37]. Twenty-three OC pesticide residues were detected at a concentration of 0.01–0.34 μg/l in water samples from India [23]. Water samples from Turkey had 18 different types of OCs at a concentration of 0.007–0.159 μg/l [38]. OCs at a concentration of 0.01–0.03 μg/l were found in water samples from South Africa [39]. Fourteen OCs with a concentration of 0.003–0.09 μg/l were found from Mexico water samples [40]. Twelve OCs were found in water samples of the Philippines at a concentration of 0.02–0.74 μg/l [41]. In some studies of water samples from the United States [42] and Ireland [43], two different OCs were found at a concentration of 0.0004–0.22 μg/l. The occurrence of OC pesticides in water sources of the above-said countries may be due to the previous application of pesticides as insecticides in crop fields. For an instance, in China, a pesticide, dicofol, was applied in cotton fields that later became the cause of DDT contamination of water sources [44]. In the United States also organochlorine pesticides were widely applied in cotton farms that later became


#### *Pesticides Occurrence in Water Sources and Decontamination Techniques DOI: http://dx.doi.org/10.5772/intechopen.103812*

**Table 1.**

*Pesticides detected in major water bodies in different countries.*

a major cause of water pollution [45]. Many agricultural practices sometimes enhance the distribution of pesticides in nearby water sources from crop fields. For example, rice cropping requires flooding of the fields for a long duration, which increases the chances of transfer of pesticide residues from a contaminated site to non-contaminated sites as well as to water sources. In India, the huge application of organochlorine insecticides in crop fields has become the major source of surface soil contamination [46] and water pollution [47, 48] nowadays. Organochlorine pesticides remain for a longer period in the environment and cycle through various routes such as volatilization, runoff, or leaching [49]. As a result of which organochlorine pesticide residues get transported to water sources via environmental components. Organochlorine pesticides have high Kow values and hence persist in soil for a longer duration as they get adsorbed to clay or organic matter present in soil and gradually released into water [50–52]. Sometimes organochlorine pesticides get evaporated from crop field soils into the surrounding atmosphere, get deposited in the rain, and eventually distributed in different water sources during rainfall events [53–55].

Organophosphorus pesticide residue detection in drinking water sources all around the world is noted in several published studies. This may be due to intensive OP application for crop protection. In China, OP pesticides are used at a higher amount that is about 1.5–4-fold higher as compared with other parts of the world [56]. OP pesticides were detected from water sources of Spain [57], Brazil [58], Canada [59], and United States [42] at concentration ranges of 1.01–21.95 μg/l, 0.21–0.57 μg/l, 0.01–2.56 μg/l, 0.001–0.06 μg/l and 0.06–0.22 μg/l, respectively. Compared with organochlorines, organophosphorus pesticides are less frequently detected in water sources due to their susceptibility to water hydrolysis at alkaline pH [60], photochemical degradation [61], and degradation by microbes in water bodies [62].

Carbamate pesticides such as carbofuran, carbaryl, methiocarb, fenobucarb, propoxur were found in water samples in Brazil, Spain, Vietnam, Burkina Faso. Carbofuran, carbaryl, methiocarb, fenobucarb, propoxur were detected at a concentration range of 0.06–2.95 μg/l, 0.17 μg/l, 1.35 μg/l, 0.04–0.074 μg/l, and 0.029–0.023 μg/l, respectively. The occurrence of carbamate pesticides in water bodies may be due to their use in agricultural sectors [63, 64], leaching in the soil profile [65], wash-off from plant surfaces during rainfall [66]. However, detection of a low amount of carbamate residues in water bodies may be due to its susceptibility to water hydrolysis [67], degradation by exposure to UV light [68], and degradation through the action of microbes [69].

Pyrethroids, neonicotinoids, and other pesticides were found in water samples all around the world at a concentration of 0.001–0.041 μg/l [22, 70, 71]. Drinking water samples from Burkina Faso [71], Brazil [58], Spain [57], and China [72] were found to have imidacloprid pesticide with a concentration of 0.01, 1.28, 3.99, and 8.33 μg/l, respectively. The low detected concentration of these pesticides may be due to their sensitivity to photo-degradation [73], and the concentration may be due to their usage in agricultural sectors [74].

Approximately 31 different parent herbicide residues were detected in more than 768 water samples collected from 18 countries around the world. Herbicide residues were detected in water samples from Portugal [75], Brazil [58, 76], Spain [57], Vietnam [77, 78], United States [79], Canada [59], China [80], Germany [81] at concentrations of 0.002–027 μg/l, 0.01–4.90 μg/l, 1.16–32.32 μg/l, 0.0001–0.47 μg/l, 0.03–1.8 μg/l, 0.0001–0.051 μg/l, 0.001–0.021 μg/l, 1.22–79.02 μg/l, respectively.

Herbicide glyphosate is highly water-soluble (10.5 g/l) and has a high dissociation constant and low partitioning coefficient, therefore considered as a nontoxic pesticide to humans; however, it is highly toxic to aquatic organisms. Due to widespread use,

#### *Pesticides Occurrence in Water Sources and Decontamination Techniques DOI: http://dx.doi.org/10.5772/intechopen.103812*

glyphosate residues have been found in many water sources, including drinking water, and also detected at a concentration of 1.42 μg/l in the groundwater table [82].

Different fungicides have been detected in water samples from different countries. Water samples collected from different places in Japan showed fungicide residues at concentration ranges of 0.013–0473 μg/l [22]. Fungicides are also detected at a concentration of 4.82–101.03 μg/l in Spain [57], 0.001–0.39 μg/l in Brazil [58], 0.0011–0.077 μg/l in China [83]. Fungicides are found in water samples due to their use in agricultural practices such as to control soil-borne plant diseases, seed dressings, foliar sprays, etc.

## **5. Consequences**

Though the application of pesticides provides a range of benefits such as enhancing the quality of food and increasing the quantity of food production by reducing pest-related issues of crop plants; however, the inappropriate use of pesticides has also led to potential negative effects on the environment, mainly water sources. The adverse effects of the pesticides remain in the environment for a long time as the pesticide molecules also remain persistent for a long period. Surface water bodies such as ponds, pools, ditches, streams, lakes, estuaries, and groundwater remain vulnerable to pesticide pollution. Even when the amount of pesticide residues that enter the water bodies is very less, subjected to biomagnifications, and the residues get deposited at a noticeable amount. Pesticides in water bodies have the chance to enter the body of aquatic organisms and then get transferred to others in the food chain. Man occupies the highest trophic position in a food chain, and also man has access to a number of other food chains, hence tends to acquire the highest amount of pesticide residues than other organisms by a process of biomagnification. The accumulated pesticides in the human body interfere with physiological processes, and the consequences are decreased immunity, hormonal balance disruption, reproductive system abnormalities [84], and more importantly carcinogenic effects [49], the occurrence of breast cancers [85], prostate cancers [86], abnormalities in the endocrine system [87], the occurrence of Parkinson's disease [88], and imbalance in cardiovascular system [84]. Pesticides such as organochlorines when reach non-target insects disrupt their nervous systems leading to paralysis and ultimate death. Organochlorine residues in water bodies promote endocrine system disorders in aquatic organisms such as fishes. Hence these toxic pesticides are now banned in many nations worldwide. Organophosphate pesticides inhibit the function of the enzyme-acetylcholine esterase that hydrolyzes acetyl choline [89]. Farmers and field workers sometimes when exposed to pesticides while handling or applying face pesticide poisoning, and this adds to the negative impacts of pesticides with respect to public health problems [90]. Each year about 3 million cases are registered as pesticide poisoning of which the death of 250–370,000 people is reported [91]. This may be due to handling, spraying, and storage of pesticides without improper protection measures. Not only human beings but also plants, birds, and aquatic organisms get affected when exposed to pesticide-contaminated water. Contaminated aquatic organisms such as fishes or shell fishes transfer pesticide residues in their body to humans. Hence humans may acquire pesticide residues through two major pathways—ingestion of food and water. World Health Organization (WHO) and many other health and environmental agencies established the maximum allowable quantities of about 33 pesticides for daily ingestion under the term "acceptable daily intake (ADI)."

#### **6. Decontamination techniques**

Though the use of pesticides since nineteenth century has brought revolutionary advancements in crop production sectors, the inappropriate usage has now put questions to the sustainability of the environment. The pesticide active ingredients, as well as their transformation products in different ecosystem compartments , and more importantly in drinking water sources, have now drawn the attention of environmentalists to work in the field of removal of pesticides. Pesticides are usually organic compounds, hence put through various physical, chemical, and microbial degradation processes. Microorganisms mineralize the pesticides into final small molecules such as CO2 and water. Sometimes microbes transform the pesticides into a new modified compound by changing their chemical structure, which is called co-metabolism. Photochemical degradation or photolysis is a process where the pesticide molecules are broken down in the presence of ultraviolet rays. Chemical degradation of pesticides occurs via oxidation-reduction reactions as well as by hydrolysis in air and water.

Naturally, pesticides are removed from the environment through the exposure of UV light, sedimentation, adsorption-desorption, and microbial action, but to a smaller extent. On a large scale, the removal of pesticides from the environment may involve both physical and biological processes. The typical physical methods for removal of pesticides in treatment plants include ozonation [92], fluid extraction [93], solid-phase extraction [94], photocatalytic degradation [95, 96], adsorption [97], filtration [98], and sedimentation. These methods of pesticide decontamination of water usually have high operational costs and also may create the chances of the development of secondary pollutants such as sludge. So, now there are requirements of alternative pesticide removal processes, which will be long term and feasible. One of the most promising and clean technologies for decontamination of water is Advanced Oxidation Processes (AOPs). It is now the most accepted technique for water purification as it is thermodynamically feasible and has broad-spectrum applicability. The mechanism of the process involves the production of highly reactive hydroxyl radicals within the system. Highly reactive hydroxyl radicals are formed by different processes such as by using oxidants, catalysts, or UV rays. These in situ generated hydroxyl radicals carry out the oxidation of a wide range of chemical contaminants including pesticides and their transformation products and lead to their complete mineralization to CO2, water, and inorganic elements [99, 100]. In more complex systems, AOPs are recommended as a pretreatment process that converts the pesticides into a more biodegradable form followed by a biological treatment process that converts the pesticides into CO2, water, inorganic minerals, and biomass.

Adsorption of pesticides on activated carbon materials in its different forms such as granular activated carbon [101], powdered activated carbon [102], carbon cloth [103], carbon fibers [103], black carbon [104], activated carbon composites [105], etc., has now become a cheaper and renewable method of pesticide removal from waste water. Researchers are now trying to synthesize activated carbon from cheaper sources such as agricultural wastes such as coconut fibers, sal wood, coconut shells, horseshoe crab shell, corn stillage, oil palm fronds, wood, date stones, and biochar, etc., for effective removal of pesticides.

In the last few decades, membrane technologies such as reverse osmosis and nanofiltration are found to remove pesticides from waste water efficiently. Nanofiltration is the most suitable technology for removing pesticides while reserving the inorganic nutrients in the water. The principle behind the process is the charged surface of the membrane that effectively removes pesticide molecules from treated water [106].

#### *Pesticides Occurrence in Water Sources and Decontamination Techniques DOI: http://dx.doi.org/10.5772/intechopen.103812*

Reverse osmosis (RO) is a process that eliminates impurities from drinking water including pesticides residues. Here water is passed through a membrane having a pore size of 0.0001 micron under high pressure. Only 5–10% of the ions can pass through the membrane [107], and those are included under acceptable levels as per World Health Organization (WHO). RO systems are helpful in the removal of pesticide residues; however, the cost varies depending on the capacity of the plants, level of utilization, level of salinity, presence of other contaminants, and distance from the source of water. Removal of pesticides from water by the process of reverse osmosis through the use of membranes such as aromatic polyamines, cross-linked polyethylenimine membranes, e.g., NS-100, PA300 [107], cross-linked m-phenylenediamine membrane (FT-30) [108], etc., was successfully applied later.

Biotic degradation or biodegradation is defined as the breakdown of complex pesticide molecules into smaller products. The rate at which pesticides biodegrade varies widely. Some pesticides such as DDT and dieldrin are recalcitrant. Pesticides such as organophosphates, which are biodegradable, are nowadays given more preference over recalcitrant ones such as organochlorines. The biodegradation process involves both aerobic and anaerobic methods. Also, biodegradation is divided into three categories based on the location where bioremediation is done, i.e., ex situ and in situ. In in situ treatment, bioremediation is carried out at the contaminated site itself, and it is usually the aerobic process. Some of the in situ bioremediation techniques that can be instigated to eliminate pesticides are attenuation, bioaugmentation, biostimulation, bioventing, and biosparging. In ex situ treatment, the contaminated water is removed from the polluted site, transported to other sites where the pesticides in the water are biodegraded. During biodegradation, microbes use pesticides as co-substrates in their metabolic reactions, mineralizing them and thus eliminating them from the environment. The key microbial enzymes that carried out the process are hydrolases, peroxidases, oxygenases, etc. The process of biodegradation involves three steps. In the first step, through the processes such as oxidation, reduction, and hydrolysis, the pesticides are converted into more water-soluble forms. The transformed products are converted into sugars and amino acids, which are again


#### **Table 2.**

*Microorganisms capable of degrading several pesticides.*

more water-soluble and less toxic in the second step and finally converted into CO2, salts, minerals, and water in the final step. The availability of pesticides for microbes depends on their solubility, pH of water, temperature, microbial diversity, etc. The microorganisms that can carry out the degradation of pesticides are bacteria, fungi. In some cases, it is easier when a group of microorganisms called microbial consortium is used as compared with the pure culture. Among fungi, molds, yeast, and filamentous fungi are more useful for the biodegradation of pesticides [109]. Fungi are better degraders of pesticides than bacteria due to characteristics such as specific bioactivity, growth morphology, and high resistance even at high concentrations of pesticides [110] (**Table 2**).

#### **7. Conclusion**

Clean water is an important part of human life and plays a major role in the sustainability of life on earth. Access to clean water is a fundamental human right and vital to sustaining a healthy life. However, the occurrence of pesticide residues in different water sources including drinking water has now become a universal problem. Nowadays, the increasing demand for food has resulted in intensive agricultural practices that resulted in contamination of water sources with pesticide residues; degrade the water quality in both developed and developing nations. Freshwater is a scarce and vulnerable resource that can be easily contaminated and whose original quality is hard and expensive to be restored. Water pollution through pesticides is posing deleterious effects on many types of organisms, including useful microorganisms, insects, birds, fishes, and humans.

Briefly, it can be said that agriculture has no beneficial effects on water resources. As agriculture is a primary requirement for human society, it cannot be disregarded. So only we can minimize or regulate the activities in agricultural sectors to keep down the extent of water pollution. Although pesticides are considered as easy, cheap, quick methods for eliminating pests and weeds from crop fields, pesticide users should be recommended to completely eliminate chemical pesticides and replace that with bio-pesticides that will minimize the risks of environmental hazards. Also, there are reports that showed that cheaper pesticides sustain in the environment for a long time as they are resistant to natural degradation processes. In some developed countries, the use of such pesticides is banned already but due to their low cost, these are still in use in many developing nations. Integrated pest management (IPM) is another clean way for the management of insects and pests where the growth of healthy crops is emphasized that will discourage pest attack. The areas where pesticide occurrence in water bodies became more common should undergo constant observations. The water bodies where residues have been detected should be subjected to various treatment processes for decontamination and the potable water sources should undergo advanced decontamination processes. Finally to reduce the pesticide load in water sources as well as in other ecosystem compartments is the duty for all of us to do our part through the use of non-chemical pest control methods.

#### **Acknowledgements**

Authors gratefully acknowledge Director, ICAR-National Rice Research Institute, Cuttack, India, for constant support and providing all the facilities.

*Pesticides Occurrence in Water Sources and Decontamination Techniques DOI: http://dx.doi.org/10.5772/intechopen.103812*
