International Journal of

Environmental Research
and Public Health

Review
Pesticides in Drinking Water—A Review
Muhammad Syafrudin 1 , Risky Ayu Kristanti 2 , Adhi Yuniarto 3 , Tony Hadibarata 4, * , Jongtae Rhee 1 ,
Wedad A. Al-onazi 5 , Tahani Saad Algarni 5 , Abdulhadi H. Almarri 6 and Amal M. Al-Mohaimeed 5

1 Department of Industrial and Systems Engineering, Dongguk University, Seoul 04620, Korea;
udin@dongguk.edu (M.S.); jtrhee@dgu.edu (J.R.)
2 Faculty of Military Engineering, Universitas Pertahanan, Bogor 16810, Indonesia; risky.kristanti@idu.ac.id
3 Department of Environmental Engineering, Faculty of Civil, Planning and Geo-Engineering, Institut
Teknologi Sepuluh Nopember, Surabaya 60111, Indonesia; adhy@its.ac.id
4 Department of Environmental Engineering, Faculty of Engineering and Science, Curtin University Malaysia,
CDT 250, Miri 98009, Malaysia
5 Department of Chemistry, King Saud University, Riyadh 11451, Saudi Arabia;
walonazi@ksu.edu.sa (W.A.A.-o.); tahanis@ksu.edu.sa (T.S.A.); muhemeed@ksu.edu.sa (A.M.A.-M.)
6 Department of Chemistry, College of Alwajh, Tabuk University, Tabuk 1144, Saudi Arabia; aalmarri@ut.edu.sa
* Correspondence: hadibarata@curtin.edu.my; Tel.: +60-85-630100 (ext. 2501)

Abstract: The ubiquitous problem of pesticide in aquatic environment are receiving worldwide
concern as pesticide tends to accumulate in the body of the aquatic organism and sediment soil,
posing health risks to the human. Many pesticide formulations had introduced due to the rapid
growth in the global pesticide market result from the wide use of pesticides in agricultural and
non-agricultural sectors. The occurrence of pesticides in the water body is derived by the runoff
from the agricultural field and industrial wastewater. Soluble pesticides were carried away by
water molecules especially during the precipitation event by percolating downward into the soil





 layers and eventually reach surface waters and groundwater. Consequently, it degrades water
Citation: Syafrudin, M.; Kristanti, quality and reduces the supply of clean water for potable water. Long-time exposure to the low
R.A.; Yuniarto, A.; Hadibarata, T.; concentration of pesticides had resulted in non-carcinogenic health risks. The conventional method
Rhee, J.; Al-onazi, W.A.; Algarni, T.S.; of pesticide treatment processes encompasses coagulation-flocculation, adsorption, filtration and
Almarri, A.H.; Al-Mohaimeed, A.M. sedimentation, which rely on the phase transfer of pollutants. Those methods are often incurred
Pesticides in Drinking Water—A with a relatively high operational cost and may cause secondary pollution such as sludge formation.
Review. Int. J. Environ. Res. Public Advanced oxidation processes (AOPs) are recognized as clean technologies for the treatment of
Health 2021, 18, 468. water containing recalcitrant and bio-refractory pollutants such as pesticides. It has been adopted as
https://doi.org/10.3390/
recent water purification technology because of the thermodynamic viability and broad spectrum of
ijerph18020468
applicability. This work provides a comprehensive review for occurrence of pesticide in the drinking
water and its possible treatment.
Received: 3 December 2020
Accepted: 5 January 2021
Keywords: pesticides; water; fate; occurrence; advanced oxidation processes
Published: 8 January 2021

Publisher’s Note: MDPI stays neu-

tral with regard to jurisdictional clai-
ms in published maps and institutio- 1. Introduction
nal affiliations. Pesticides are recognized as reagents for protecting crops against harmful pests and
diseases in humans. The beneficial outcome of pesticides makes it become an important
tool to maintain and improve the living standard of the global population. An average
of 2 million tons of pesticides was used each year globally to confront weeds, insects and
Copyright: © 2021 by the authors. Li-
pests [1]. The conventional classification of pesticides based on the target species includes
censee MDPI, Basel, Switzerland.
This article is an open access article
herbicides, insecticide, rodenticide, fungicide and so forth [2]. Herbicides and insecticides
distributed under the terms and con-
are the most common type of pesticide used, dominating 47.5% and the latter 29.5% of
ditions of the Creative Commons At-
the total pesticide consumption [1]. The primary pesticide consuming countries including
tribution (CC BY) license (https:// China, the USA, Argentina, India, Japan, Canada, Brazil, France, Italy and Thailand [2].
creativecommons.org/licenses/by/ The pest control revolution has begun in the 1970s with the development of pesticides
4.0/). based on toxic heavy metals such as copper, lead, mercury and arsenic. This was followed

Int. J. Environ. Res. Public Health 2021, 18, 468. https://doi.org/10.3390/ijerph18020468 https://www.mdpi.com/journal/ijerph
Int. J. Environ. Res. Public Health 2021, 18, 468 2 of 15

by the discovery of dichlorodiphenyl trichloroethane (DDT) during World War II [1]. The
use of DDT increased enormously due to its effectiveness against almost all pest species at
low dosage. Because of the great use, adverse impact on the environment and mankind
had become apparent as soon as DDT became popular. After DDT has been banned for
agricultural and domestic use, a wide variety of synthetic pesticides has been produced,
such as organophosphate and pyrethroid which are still toxic to the environment [3]. The
continuous and excessive use of a wide range of pesticide eventually harm the non-target
species and causes the pesticide residues to appear in many unexpected sites [4]. Under
constant chemical pressure, pesticides had led to the development of resistant strains in
which the pests and insects get immune to the pesticide [3].
The application of pesticides give rise to a range of benefits, including increased the
quality and quantity of food and reduced insect-borne disease but raised the issues on the
potential detrimental effects to the environment, including water resources. The associated
environmental impacts are mainly due to the persistent and ubiquitous characteristics of
various pesticides that posed havoc to the biodiversity [2]. The dissolution of pesticides
depends on the nature of the compound, pesticide application techniques and climatic
factors. The pesticides that are not readily degrading will either get accumulated in soils
or mobilized from one site to another in the form of degraded products, with unknown
toxicity to human health [2].
The occurrence of pesticides in the water body is derived by the runoff from the
agricultural field and industrial wastewater. Despite the soil matrix that serves as a storage
compartment of pesticide due to the high affinity of agrochemicals with soil, surface water
resources like streams, estuaries and lakes, as well as the groundwater are susceptible to
pesticide contamination because of the close interconnection of soil with water bodies. The
low concentration of pesticides built up in water can get magnified through the food chain
and enter aquatic organisms that are hazardous for human consumption [2]. Importantly,
chronic exposure to pesticides through water ingestion can mimic the human body’s
hormones that reduce body immunity, interrupt hormone balance, trigger reproductive-
related issues, posing carcinogenic effects and reduce intelligence particularly towards the
children under the body development stage [5].
This study reviewed the type of pesticide found in the water bodies, the sources of
pesticide contamination, the fate and occurrence of pesticides in soil and water, the toxicity
impacts on human health and the available treatment method of the pesticide-contaminated
water. A recent study of pesticide-contaminated surface water that occurred in Tanjung
Karang located at Kuala Selangor, Malaysia was also reviewed in this article.

2. Type of Pesticide Pollutants in Water

Pesticides are categorized into several distinct groups based upon their target species,
such as insecticide, herbicides and fungicides being the most used in agricultural farmland
and urban settings [1]. Table 1 reviewed the classes and chemical compounds of insecticide,
herbicide and fungicide. Herbicides are weed-killing compounds and normally included in
plant growth regulators. Insecticides are used in farmlands, food storage facilities or home
garden to control insects. Fungicides prevent fungus infection in plants or seeds, which is
usually applied before fungus present or after fungus infect the plant species [6]. Besides,
the pesticide can be classified based on the mode of action on the pests such as destroying,
mitigating and repelling reagent [3]. A more scientific way of pesticide classification is
based upon their chemical composition. Table 2 outlined the main components of some of
the common groups of pesticides.
Int. J. Environ. Res. Public Health 2021, 18, 468 3 of 15

Table 1. Classification of pesticide based on target species.

Pesticide Class: Substance

Organochlorine: Endosulfan
Organophosphate: Diazinon, Malathion, parathion, chlorpyrifos
Carbamate: Aldicarb, carbofuran, carbaryl
Insecticide [7]
Pyrethroid: Deltamethrin, Fenpropathrin
Neonicotinoid: Acetamiprid, thiamethoxam
Phenylpyrazole degradate: Aldicarb sulfoxide, Endosulfan sulfate
Triazine: Atrazine, cyanazine
Herbicide [8,9]
Chloroacetamide: alachlor, butachlor, dimethenamid, metolachlor
Benzamide: Fluopicolide, zoxamide
Carboxamide: Boscalid captofol
Fungicide [10] Chlorinated hydrocarbon: Hexachlorbenzene
Organophosphate: Edifenphos, iprobenfos
Chlorophenyl: Dichloran, quintozene

Table 2. Pesticide classification according to chemical composition and provided with some of their general characteristics [4].

Group Chemical Composition Characteristics Effects

Tend to accumulate in fatty
Non-polar and lipophilic Lipid soluble, toxic to variety
Organochlorine (DDT, aldrin, tissue of animal,
atoms including carbon, of animals and long-term
lindane, chlordane) biomagnification effect via
chlorine, hydrogen atoms. persistence.
food chain.
Soluble in organic solvent as
Aliphatic, cyclic and Tend to infiltrate into aquifer
Organophosphate (Malathion, well as water. Less persistence
heterocyclic possess central and reach groundwater.
diazinon, parathion) than chlorinated
phosphorus atom in molecule. Affect central nervous system.
hydrocarbons.
Alkaloid obtained from petals Less persistent than other
of plant species, namely, pesticides, therefore safest to
Pyrethroids (pyrethrins) Affect nervous system.
Chysanthemun be used as household
cinerariefolium. insecticides.
Chemical structure based on
Only killed limited spectrum
alkaloid of a plant species,
Carbamates (Carbaryl) Relatively low persistence. insects but highly toxic to
namely Physostigma
vertebrate species.
venenosum.
Biological (Becillus
Microorganism, viruses and Applied against forest pests
thuringiensis, Bt and its Affect other caterpillars.
their metabolic products. (butterflies) and crops.
subspecies)

The traditional pesticide before the 1940s was derived from the toxic heavy metal of
arsenic, copper, lead and mercury. These chemicals are partially soluble in water; therefore,
their residues present in foods are of far greater concern than in drinking water. Synthetic
organic pesticides such as chlorinated hydrocarbons introduced during World War II have
rarely contaminated the groundwater but tend to accumulate toxic concentrations in food
chains. Some of the examples of chlorinated hydrocarbons are DDT, aldrin, endrin and
chlordane, which are relatively insoluble in water but more likely to be chemically bound
to the soil particles. Organophosphorus compounds such as diazinon and malathion are
synthetic organic pesticides that are developed to replace the chlorinated hydrocarbon
pesticides. Organophosphorus pesticides are still highly toxic to humans but their ability
to decompose rapidly in the environment reduce their occurrence in groundwater. Carba-
mate pesticides are also being introduced to replace chlorinated hydrocarbons. The active
ingredients of carbamate pesticides are not likely to be adsorbed to soil particles, therefore
these compounds may have made their way into surface waters [11].
Int. J. Environ. Res. Public Health 2021, 18, 468 4 of 15

3. Sources and Fate of Pesticides in Water

The detectable concentration of pesticide in surface waters and groundwater found
in agricultural and urban land use areas [12]. Pesticide moves into water bodies via point
source and nonpoint source. Point source that originates from a fixed site including
chemical runoff during improper storage, loading, disposal as well as the misapplication of
pesticides to water bodies. A direct movement of pesticides into groundwater is a common
type of point source pollution, in which the pesticides enter the water wells result from
pesticide spills and improper disposal of pesticides. Urban use of insecticide is considered
as a point source pesticide in surface waters. The non-point source is the movement of
pesticides from large areas across the watersheds and eventually reached the water bodies
over the time. Non-point sources of pesticide originate from the agricultural field initiate
by the runoff and erosion events, leading to the gradual leaching of pesticides into the
ground and surface water [13].
Contamination of pesticides in water is caused by the persistent chemicals of pesticides
released from agricultural activities, urban use and pesticide production factories. Farmers
is the key users of pesticide that apply an enormous amount of pesticide to protect and
increase crop yields. Besides, the wood treatment industry uses an enormous amount of
insecticide to treat the raw material. Depending on the pesticide’s characteristics, chemical
compounds from the pesticide applied to the preserved material tend to be released
into the environment, becoming one of the sources of pesticide contamination in surface
waters. Despite the great use of pesticides in the agricultural sectors, the urban use of
pesticides mainly in-house gardening for pest control is an important source of pesticide
contamination in water. The insecticide is detected more profoundly in urban settings than
other types of pesticides such as herbicide and fungicide [10]. Since the green revolution,
increase consumption of pesticides led to the active production of pesticide formulations,
which increase the pesticide manufacturer around the world [6]. Inevitably pesticide
leaching processes throughout the pesticide manufacturing processes as well as in the
dumping site and wastewater effluents contribute to point-source pesticide contamination.
To summarize, pesticides in surface waters sourced by the run-off event, atmospheric
deposition event, wastewater discharge and spills event, while pesticide in groundwater
sourced by the pesticide-treated field, waste disposal site and pesticide manufacturing sites.
The study on the fate and transport of pesticides is important for knowing their
circulation in the biosphere. Pesticides meet a variety of fates after being applied on Earth
and Figure 1 showed the general picture of their fates in the environment. The pesticide
that is not taken up by plants will either be retained in the soil or subjected to degradation
into other chemical forms. Soluble pesticides will be carried away by water molecules
especially during precipitation events by percolating downward into the soil layers and
eventually reaching the groundwater. Otherwise, those insoluble chemicals tightly bound
to soil particles accumulate in the topsoil layer, which has a high possibility subjected to
runoff and erosion to surface waters, contaminating lakes, stream and river with pesticides.
Pesticides are most susceptible to runoff immediately after the application on the soil
surface between 0.25 to 0.85 cm from the soil surface [13]. Pesticide contamination in
water also contributed by the volatilized pesticides in the atmosphere, in which they
redeposited in the rain during the rainfall event and then enter the surface water bodies
and soil. However, this pathway is relatively insignificant. In general, pesticides enter
the hydrological system mainly via surface loss and leaching through soil layers, whereby
the degree of pesticide contamination in water is affected by the properties of pesticide,
characteristics of soil, site conditions, as well as the application and management practices
of pesticide [14].
Int. J. Environ. Res. Public Health 2021, 18, x  5 of 16 
 Int. J. Environ. Res. Public Health 2021, 18, 468 5 of 15

 
Figure 1. Fate of pesticide. 
Figure 1. Fate of pesticide.

The potential for surface loss and leaching into groundwater is determined by the 
The potential for surface loss and leaching into groundwater is determined by the
characteristics of pesticides such as the half-life, solubility and adsorption capacity of the
characteristics of pesticides such as the half‐life, solubility and adsorption capacity of the 
pesticides. Since most pesticides are organic compounds, they typically undergo degra-
pesticides. Since most pesticides are organic compounds, they typically undergo degra‐
dation through microbial, photochemical or chemical reactions. Microbial degradation
dation through microbial, photochemical or chemical reactions. Microbial degradation in‐
including the mineralization process in which pesticide breaks down into carbon dioxide
cluding the mineralization process in which pesticide breaks down into carbon dioxide 
and co-metabolization where microbial reaction transforms pesticide into other chemical
and co‐metabolization where microbial reaction transforms pesticide into other chemical 
forms. Photochemical 
forms.  Photochemical degradation
degradation ofof pesticides
pesticides isis 
called photolysis
called  photolysis in which the the 
in  which  pesticides
pesti‐
decomposed in the presence of ultraviolet (UV) light. Chemical degradation of pesticide
cides decomposed in the presence of ultraviolet (UV) light. Chemical degradation of pes‐
occurs via redox reaction and hydrolysis with air, water and other compounds exist in soil
ticide occurs via redox reaction and hydrolysis with air, water and other compounds exist 
compartments. Pesticides with a low biodegradation rate have a long half-life and tend to
in soil compartments. Pesticides with a low biodegradation rate have a long half‐life and 
persist in the environment that potentially contaminate the water sources. Besides, pesti-
tend to persist in the environment that potentially contaminate the water sources. Besides, 
cide degradation processes produce metabolites, inorganic end-product and transformants
pesticide degradation processes produce metabolites, inorganic end‐product and trans‐
which can have either lower or higher toxicity than the parent pesticide. Moreover, the mo-
formants which can have either lower or higher toxicity than the parent pesticide. More‐
bility of the pesticide is governed by the adsorption capacity and solubility of the pesticide.
over, the mobility of the pesticide is governed by the adsorption capacity and solubility 
Pesticides that are strongly adsorbed
of  the  pesticide.  Pesticides  that  to soil are
are  strongly  less likely
adsorbed  to infiltrate
to  soil  are  less downward the soil
likely  to  infiltrate 
profile but can easily be carried by eroded soil particles via surface runoff and eventually
downward the soil profile but can easily be carried by eroded soil particles via surface 
reached surface water [14]. For pesticide having low degradation rate, weak adsorption
runoff and eventually reached surface water [14]. For pesticide having low degradation 
capacity to soil particles and high solubility that is greater than 30 mg/L can potentially
rate, weak adsorption capacity to soil particles and high solubility that is greater than 30 
leach and
mg/L  can  dissolve in water.
potentially  leach  Among the pesticide
and  dissolve  used,
in  water.  atrazine
Among  the which is normally
pesticide  used as
used,  atrazine 
an herbicide is recognized as a highly potential leach compound into the groundwater due
which  is  normally  used  as  an  herbicide  is  recognized  as  a  highly  potential  leach  com‐
to its high persistency. Cyanazine has a short half-life, therefore lower leaching potential.
pound into the groundwater due to its high persistency. Cyanazine has a short half‐life, 
Methyl parathion is another low leaching potential pesticide because of its high adsorption
therefore  lower  leaching  potential.  Methyl  parathion  is  another  low  leaching  potential 
capacity to soil particles and lower persistency. The 2,4-D is a water-soluble pesticide able
pesticide because of its high adsorption capacity to soil particles and lower persistency. 
to rapidly break down by biological action and therefore is less likely to accumulate in soil
The 2,4‐D is a water‐soluble pesticide able to rapidly break down by biological action and 
and has less persistency [15].
therefore is less likely to accumulate in soil and has less persistency [15]. 
4. Occurrence of Pesticide and Health Effect
4. Occurrence of Pesticide and Health Effect 
The occurrence of pesticides in specific environmental compartments, such as in
soilsThe occurrence of pesticides in specific environmental compartments, such as in soils 
and streambed sediment, groundwater and surface water is a widespread issue [16].
and streambed sediment, groundwater and surface water is a widespread issue [16]. Dis‐
Distribution of a range of pesticides in streams and groundwater largely depends on
tribution of a range of pesticides in streams and groundwater largely depends on the land‐
the land-use settings and characteristics of the hydrologic system with consideration of
use settings and characteristics of the hydrologic system with consideration of the past 
the past and present use of pesticides. Pesticide detected most frequently in streams
and present use of pesticides. Pesticide detected most frequently in streams and ground‐
and groundwater were those in most use and with the compound characteristics of high
water were those in most use and with the compound characteristics of high mobility and 
mobility and persistence in the hydrologic system.
persistence in the hydrologic system. 
Based on the National Water-Quality   Assessment (NAWQA), pesticides are found
more often in surface waters than groundwater, being 25 pesticides detected more than

 
Int. J. Environ. Res. Public Health 2021, 18, 468 6 of 15

10% of the time in surface waters and 2% of the time in groundwater of various land-use
setting in agricultural, urban and mixed land use [12]. This proves that the occurrence of
pesticides in surface waters is prevalent because of the direct and rapid overland mobi-
lization of pesticides via surface runoff. Groundwater that is less vulnerable to pesticide
contamination can be explained by the slow water infiltration rate through the soil into
the aquifer. However, the extended travel time enables the pesticides to undergo transfor-
mation, dispersion and sorption that make contamination of groundwater more difficult
to recover once it is contaminated. Of the 25 pesticides, 11 of them are herbicides that
are widely applied in the agricultural field, 7 are herbicides used extensively in urban
settings and 6 are insecticides applied in both agricultural and urban settings [12]. In
undeveloped areas, detected pesticide in surface water and shallow groundwater is least
often. In mixed land-use settings, the frequency of pesticide occurrence detected at stream
draining watershed is similar to agricultural or urban settings because of the contribution
of pesticides from multiple sources. Similarly, the detection frequency in shallow ground-
water is prevalent over the major aquifers. According to the investigation, the pesticides
that occurred most frequently in the streams and groundwater are the five agricultural
herbicides—atrazine with its degradate, deethylatrazine, metolachlor, cyanazine, alachlor
and acetochlor, the five non-agricultural herbicides—simazine, prometon, tebuthiuron,
2,4-D and diuron, as well as the 3 most extensive use insecticide—diazinon, chlorpyrifos
and carbaryl [12]. For comparison, the insecticide was found more frequently in the urban
stream than urban groundwater and also found in a higher concentration in comparison to
agricultural settings.
Historical use of pesticides with their degradates and residues such as organochlorine
is mostly found in soil, sediment and cell tissue of biota [12]. Review of a largely agricultural
country of China, the history used of organochlorine in agricultural activities led to the
different level of pesticides contamination in the groundwater, which is mainly driven
by the extreme hydrogeological condition. The leaching of pesticides as well as their
metabolites downward from soil surface had contaminated the shallow basins in China [17].
Despite the great importance of pesticides in maintaining good quality and protecting
the crops or raw materials, they pose a high degree of concern in human health because
of the tendency of pesticide to bioaccumulate in the human cell membrane which inter-
rupts the body functioning system. Humans are exposed to pesticides in water mainly
through dermal contact and ingestion [18,19]. Pesticide exposure has been proven to result
in immunosuppression, hormone disruption, reduce intelligence, reproductive distortion
and cancer. Impacts of pesticide exposure to humans can be categorized into acute health
problems and chronic health problems. Chronic health problems encompass neurological
effects such as onset Parkinson’s disease, reduce the attention span, memory disturbances,
reproductive problems, disrupt infant development, birth defect and cancer. Acute health
effects depend on the pesticide toxicity and the most common effects are reduced vision,
headaches, salivation, diarrhea, nausea, vomiting, wheezing, coma and even death. Moder-
ate pesticide poisoning leads to mimic intrinsic asthma, bronchitis and gastroenteritis [18].
In Malaysia, there is limited data that documented the effects of pesticides on human
health. The study on utilizing biological markers to associate the effects of pesticide expo-
sure to human health would be useful to evaluate the health risk [19]. A reviewed study
by Samsuddin et al. documented that populations that are chronically exposed to low
dose mix-pesticide are more likely to have cardiovascular diseases [20]. Another article
revealed that the endosulfan led to the overexpression of stromelysins, a protein from the
metalloproteinase family, which in turn degenerated the proteins involved in atheroscle-
rosis progression [21]. Besides, few works have reviewed whether pesticide exposure
could reduce semen quality, lower the sperm count and change the sperm’s morphol-
ogy [21,22]. Literature also reported that farmers had a high chance of inducing prostate
cancer and allergic or non-allergic asthma due to the frequent exposure to the chlorinated
pesticide [23,24]. In animal studies, the genotoxicity effect of exposing organophosphate
to orang-asli children was studied, which is observed through the changes in comet tail
Int. J. Environ. Res. Public Health 2021, 18, 468 7 of 15

length [25,26]. Other animal study also found that rats exposed to organophosphate
resulted in testosterone and hormone disruption in the testis [27].
As a measure to protect public health, guideline levels for pesticides in drinking water
have been implemented by national governments. There are several guideline values,
where few of them are issued by World Health Organization (WHO), the United States,
Australia, the European Union and Japan. The guideline values may differ based on the
socio-economical, dietary, geographical condition and industrial conditions [28]. Table 3
showed the guideline value for a certain number of pesticides in drinking water issued
by WHO aimed for a water quality that is suitable for long-term consumption. These
guideline values were made available for the use of regulatory authorities.

Table 3. Guideline value of pesticide level in drinking water [28].

Guideline Value Guideline Value

Pesticide Pesticide
(Microgram/L) (Microgram/L)
Alachlor 20 Metolachlor 10
Aldicarb 10 Molinate 6
Atrazine 2 Pentachlorophenol 9
Bentazone 300 Permethrin 20
Carbofuran 7 Propanil 20
Chlordane 0.2 Pyridate 100
DDT 2 Simazine 2
Hexachlorobenzene 1 2,4,5-T 9
Isoproturon 9 Terbuthylazine 7
Lindane 2 Trifluralin 20

5. Pesticide-Contaminated Water Treatment Method—Advanced Oxidation Processes

The conventional method of pesticide treatment processes encompasses coagulation-
flocculation, adsorption, filtration and sedimentation, which rely on the phase transfer
of pollutants. Those methods are often incurred with a relatively high operational cost
and may cause secondary pollution such as sludge formation [29]. Besides, indiscriminate
use and the presence of a wide range of pesticide formulation available around the globe
make the compound of pesticide in water harder to be removed. Therefore, alternative
treatment processes are required to seek a long-term and feasible method to treat pesticide-
contaminated water.
Advanced oxidation processes (AOPs) are recognized as clean technologies for the
treatment of water containing recalcitrant and bio-refractory pollutants such as pesticides.
It has been adopted as recent water purification technology because of the thermodynamic
viability and broad spectrum of applicability [29,30]. The main concept of AOPs in the
water treatment process is based on the in-situ generation of highly reactive hydroxyl
radicals that indiscriminately oxidize a wide range of recalcitrant organic pollutant for
complete mineralization of organic contaminants to carbon dioxide, water and mineral
salts and capable of transforming the compound of pesticide into more biodegradable
species [31,32]. Hydroxyl radicals can be produced from different pathways using a combi-
nation of oxidants, catalysts and ultraviolet irradiation and this makes the classification of
AOPs based on the source of generation of hydroxyl (OH) radicals [33]. Table 4 showed
some of the combinations of AOPs.
Int. J. Environ. Res. Public Health 2021, 18, 468 8 of 15

Table 4. Combination of advanced oxidation processes (AOPs) [33].

AOPs Combination
Photocatalysis UV/TiO2 ; UV/TiO2 /H2 O2
Fenton: Fe2+ /H2 O2
Fenton based
Photo-Fenton: Fe3+ /H2 O2 /UV
Ozone based O3 /H2 O2 ; O3 /UV; O3 /UV/H2 O2
Sonolysis Ultrasound (US)/O3 ; US/H2 O2 ; US/UV/TiO2
ElectroFenton: Fe3+ /H2 O2 (e− )
Electrochemical oxidation
SonoElectroFenton: US/Fe3+ /H2 O2 (e− )

The integration of several AOPs into a sequence of complimentary water treatment

processes is a common method to yields a more biodegradable effluent which can be further
treated by the conventional biological process to reduce the reagent consumption and thus
more economical in comparison to AOPs alone [32]. Based on previous studies, AOPs
are recommended as pre-treatment steps to convert the pesticide to a more biodegradable
intermediates, then followed by a biological treatment process to convert them into biomass,
carbon dioxide, hydrochloric acid, biogas and water. This is mainly due to the inefficient
removal of bulk chemical oxygen demand (COD) by AOPs to a level below the regulation
standard for some recalcitrant pesticide compounds [29,34,35]. An article by Quiroz et al.
also documented the extensive use of AOPs to treat pesticide-contaminated water [33].
In the field of AOPs, Fenton reactions have been widely studied for the remediation
of pesticide-contaminated water because of the faster rate of pollutant removal and its
ability to completely mineralized a wide variety of organic compounds [32,36]. In the
Fenton process, Fenton’s reagent, which is prepared by adding iron salts as a catalyst in
the hydrogen peroxide solution to generate strong hydroxyl radicals at an acidic condition.
The general mechanisms of the Fenton process are shown in Table 5. It is worth noting
that the depletion rate of Fe2+ is comparatively higher than the regeneration rate of Fe2+
from Fe3+ as illustrated in Table 5 Reaction 2. Because of this, the addition of Fe2+ or
FeSO4 in the medium presence with hydrogen peroxide is necessary for continuous Fenton
reaction to take place, which is not economical. Moreover, adding more Fe2+ result in
more iron sludge produced that need to be handle in a proper way to avoid secondary
pollution [37]. The drawbacks can be overcome by including the ultraviolet irradiation in
the Fenton system, which is commonly known as the photo-Fenton process. The presence
of UV visible irradiation with Fenton reagent enhance the process efficiency because of
the capability to produce an additional source of hydroxyl radicals through photolysis of
hydrogen peroxide and the photoreduction of Fe3+ to Fe2+ as illustrated in Table 5 Reaction
3, which subsequently increase the hydroxyl radicals yields and reduce the amount of
Fe2+ required in Fenton reaction [38]. The optimum condition of the Fenton system has
been studied which focusing on the pH, Fe2+ dose and the H2 O2 dose [31]. From the
study, the pH of the system needs to be kept at 3, because this is the optimum condition
for the decomposition of hydrogen peroxide to produce hydrogen radicals and prevent
the scavenging of hydroxyl radicals via dissociation and auto-decomposition of hydrogen
peroxide as illustrated in Table 5 Reaction 5. Also, a lower pH value that is below or
equal to 3 inhibits the occurrence of iron precipitation which enhances the UV radiation
transmission into water. The hydrogen peroxide dosage depends on the COD of water,
where the optimum COD: H2 O2 ratio is 1:2.2 and 1:4.4 for photo-Fenton and Fenton
treatment, respectively. For the Fe2+ dosage, the optimum H2 O2 :Fe2+ ratio is 50:1 and 100:1
for photo-Fenton and Fenton treatment, respectively [31]. As can be seen, photo-Fenton
treatment reduced the consumption of H2 O2 and Fe2+ to half in comparison to the Fenton
process, which proved that the photo-Fenton process is more economical, more efficient
in removing pollutants and produce less sludge. Another literature study by Oller et al.
reported that the photo-Fenton reaction successfully eliminated six targeted water-soluble
Int. J. Environ. Res. Public Health 2021, 18, 468 9 of 15

pesticides that are ineffectively removed by the TiO2 catalytic process [39]. However,
the major drawbacks of the photo-Fenton process are the periodic addition of hydrogen
peroxide that increase the operational cost and the use of UV visible light sources [38].

Table 5. Chemical reactions of Fenton/photo-Fenton process [37,38].

Reaction No. Fenton/Photo-Fenton Reaction Explanation

Chain initiation. Ferrous ions (Fe2+ ) catalysed the oxidation of
1 Fe2+ + H2 O2 → Fe3+ + •OH + OH−
hydrogen peroxide, generating hydroxyl radical.
Fe3+ + H2 O2 → Fe2+ + H+ + HO2 •
2 Fe3+ + HO2 • → Fe2+ + H+ + O2 Mechanisms involve in the regeneration of Fe2+ .
Fe3+ + O2 •− → Fe2+ + O2
Hν H2 O2 → 2OH Presence of UV visible irradiation in Fenton reaction increase
3
Fe(OH)2+ + hν → Fe2+ + OH the hydroxyl radical production and regenerate Fe2+ .
R + H2 O2 → P1
4 Reactive radical attaches the pollutants.
R + •OH → P2
Fe2+ + •OH → Fe3+ + OH−
5 Reactions that scavenge the hydroxyl radical.
H2 O2 + •OH → HO2 • + H2 O
• Free radical.

Moreover, heterogeneous photocatalysis is another appealing option to restore water

contaminated with pesticide, that involves the use of solid photocatalyst to form a col-
loidal suspension under sunlight radiation to remove toxic substance in water [33]. The
heterogeneous photocatalytic degradation has been proved to be able to remove a wide
range of pesticides and the common pesticides being tested are triazine, thiocarbamide,
phosphorated and chlorinated pesticide [33]. The solid catalyst act as an active site for
adsorption of reactants and desorption of products. TiO2 is the most common semicon-
ductor used as a photocatalyst because of the cost-effectiveness, high stability, non-toxicity
and unique photocatalytic efficiency [40]. Table 6 summarized the reaction mechanism
involves in the heterogeneous photocatalysis reaction. Because TiO2 has a bandgap energy
of 3.2 V, the adsorption of UV light that is equal or greater than the bandgap energy of the
semiconductor is required to activate or induce the charge separation. After excitation,
the electron will move from valence band to conduction band, forming electron-hole pairs
that act as electron donors or acceptors for the molecules that are in contact with the
semiconductor [41]. On the surface of the semiconductor, the generated electron-hole pairs
undergo redox reactions in the aqueous solution to produce hydroxyl radicals [40]. The
reactive radicals will then attack the pollutants in the solution. This process gradually de-
composes the contaminant, avoiding the residue and sludge production, thereby reducing
the probability of secondary pollution. Besides, the catalyst remains unchanged during
operation, therefore no consumable chemicals are required. Moreover, the contaminant
is strongly adsorbed to the surface of the solid catalyst which make the photocatalytic
process capable of removing contaminants effectively even at a very low concentration
of contaminants in solution and this saves the water production cost [41]. However, this
process relies on the UV absorption for activation and only 5% of solar irradiation falls
within the UV range, resulting in lower production efficiency of reactive radicals. The
study to improve the performance of TiO2 has been studied extensively, which is through
the doping of TiO2 with foreign ions to narrow the TiO2 bandgap energy, thereby facilitates
the generation of reactive radicals under visible light [38].
Int. J. Environ. Res. Public Health 2021, 18, 468 10 of 15

Table 6. Chemical reaction of heterogeneous photocatalysis reaction [40,41].

Heterogeneous Photocatalysis Mechanisms Explanation

Photocatalyst + hν → h+ + e− Semiconductor absorb UV light producing electron-hole pairs.
h+ + H2 O → • OH + H+ [Oxidation]
Reaction of holes in valence band with water molecules on the
e− + O2 → • O2 − [Reduction]
• O − + H+ → • OOH surface of catalyst produce hydroxyl radical. Reaction of electron in
2 conduction band with oxygen generate superoxide radical, which
2 • OOH → • O2 + H2 O2
then further reaction to produce hydroxyl radical.
H2 O2 + • O2 − → • OH + OH− + O2
h+ + OH− → OH
Other mechanisms involve in the production of hydroxyl radical.
H2 O2 + hν → 2OH
h+ + pollutant → (pollutant)+
Reactive radical attack or degrade the pollutant in solution.
Pollutant + (• OH, h+ , • OOH or O2 − ) → degradation
product

6. Case Study of Pesticide Contamination in Asian Countries

6.1. Malaysia
Tanjung Karang located in Kuala Selangor is a popular rice cultivation land in
Malaysia. Pesticides are enormously applied in the rice cultivation land to increase crop
yields and reduce crop damages. The consequence of the continuous and increasing use of
pesticides has inevitably led to the contamination of the Tengi River, which is the source of
the drinking water supply for a conventional drinking water treatment plant (Sungai Sireh
Drinking Water Treatment Plant) and paddy irrigation. Based on the recent investigation by
Elfikri et al. [42], eleven pesticides were detected in the river with concentrations ranging
between 2.7 ng/L to 4493.1 ng/L and four pesticides detected in the finished water from
the treatment plant with concentrations ranging between 5.2 ng/L–56.6 ng/L. The most
frequently detected pesticides along the sampling site were imidacloprid with the highest
detection level of 57.7 ng/L at downstream, which commonly used as insecticides and
tebuconazole at a maximum detection level of 512.1 ng/L at the middle stream, which
commonly used as fungicides in the rice cultivation land. This is attributed to the frequent
application of the two pesticides, which are known to be applied every 15 days after the
rice cultivation as protective measures by farmers [42]. The concentration of pesticides
increases from the upper stream to the lower stream of the river. The Middle stream of the
sampling point was detected with the highest concentration of propiconazole (4493.1 ng/L),
followed by difenoconazole (1620.3 ng/L) and buprofezin (729.1 ng/L). Downstream of
the Tengi River was reported to be the most polluted site with the greatest number of com-
pounds pesticide being detected. Among the pesticide detected in the downstream river,
propiconazole was among the pesticide compounds detected with the highest average
concentration of 260.81 ng/L [42]. The higher detection level of pymetrozine might be
due to its characteristics such as high-water solubility, slow degradation, non-volatile and
exhibit a low adsorption capacity to soil particles. Besides, downstream rivers become the
hotspot of a wide range of pesticides because of the release of irrigation water from paddy
farms and oil palm plantations to the downstream after the sluice is opened.
The drinking water treatment plant that uptakes the water from the Tengi River in
supplying potable water resources to the population in Tanjung Karang and Sekinchan. The
conventional water treatment method, the filtration-coagulation-flocculation-sedimentation
process, is adopted in the water treatment plant. As a safety consideration, it is necessary to
investigate the pesticide contaminant removal efficiency of the water treatment process by
the treatment plant to ensure safe drinking water. Before the water treatment process, nine
pesticides with a maximum detection level of 392.8 ng/L were detected in water samples.
After the combined water treatment process, all the targeted pesticide compounds were
found to be less than 0.1 microgram/L which is below the standard level regulated by
European Health-Based Chemical Standards [42]. The finished water test had found the
four pesticides (pymetrozine, tebuconazole, propiconazole and buprofezin) were inade-
Int. J. Environ. Res. Public Health 2021, 18, 468 11 of 15

quately removed by the treatment process, with 23% of imidacloprid, 14% of buprofezin
and propiconazole, as well as 12% of tebuconazole remain in the finished water. The five
pesticides (pymetrozine, tricyclazole, chlorantraniliprole, azoxystrobin and trifloxystrobin)
not detected in the finished water were completely removed by filtration, which is a process
after the coagulation-flocculation processes [42].
The authors furthered their study to investigate the ingestion risk on the population of
510 in Tanjung Karang, who consumed the finished water supplied by the water treatment
plant through the questionnaires survey [42]. It is generally known that chemicals with
an octanol-water partition coefficient (log Kow) between 2–4 absorb well through the skin
and log Kow exceeds 5–6 tend to bioconcentrate in the lipid membrane [43]. Therefore, the
health impacts studied in this article focused on the consequences of chronic exposure to
the four pesticides detected in the finished water, which is specifically on non-carcinogenic
health risks. Hazard quotient (HQ) is a parameter to justify the level of non-carcinogenic
risk by considering the daily exposure dose to the reference dose of target pesticide com-
pound according to United States Environmental Protection Agency (USEPA). An HQ
less than one specifies no significant risk, otherwise specifies significant non-carcinogenic
health risks. The HQ results of the four target pesticides were less than 1, signifies daily
ingestion of water supply from the treatment plant will have no significant chronic health
risks. The hazard index (HI) is also determined for different age groups, classified into
kindergarten, primary school, secondary school, adult and elder. The HI for all age groups
is less than one, indicate no significant non-carcinogenic health risk upon the exposure
to the combination of 4 target pesticides in the treated water. On the other hand, the
young age groups were exposed to the highest level of targeted pesticide in comparison
to the higher age groups because of the greater water consumption by the young age
population [42]. Because the concentration of pesticides could vary according to many
factors such as paddy farming season and the selection of pesticide by farmers, advanced
water treatment processes that perform higher pesticides removal efficiency in water are
recommended in water treatment facilities to guarantee the safest water supply to the
population in Tanjung Karang and Sekichan [42].
Another study reported the concentration of selected organochlorine and organophos-
phate pesticides in the Selangor River in Malaysia. The organochlorine pesticides detected
were lindane, heptachlor, endosulfan, dieldrin, endosulfan sulfate, DDT and DDE whereas
for organophosphate pesticides, they were chlorpyrifos and diazinon. The concentration
range of detected residual pesticides in the Selangor River, Malaysia during 2002–2003 were
10.1 ng/L for lindane as the lowest pesticide concentration and 1848.7 ng/L for endosulfan
as the highest pesticide concentration. The study has revealed that agriculture, urban and
industrial activities in the state of Selangor coupled with high population growth have
caused deterioration in its river water quality. It was found that pesticides detected in raw
river water intake were not removed by conventional water treatment process [44].

6.2. Japan
In Japan, paddy fields contribute significantly to the pesticide contamination of
Japanese rivers because they account for about 50% of Japan’s agricultural lands of
4.8 million ha. This non-point source pollution of rice pesticides is of great concern because
river water accounts for about 70% of drinking water sources in Japan. The Shinano River,
known as the Chikuma River in its upper reaches, is the longest and widest river in Japan
and the third largest by basin area. It is located in northeastern Honshu. Among the total of
53 chemicals found, 22 were herbicides, 15 were insecticides, 11 were fungicides and 5 were
metabolites. The concentrations of chemicals found ranged from 3 ng/L (bromobutide)
to 8200 ng/L (isoprothiolane). The transfer of pesticide in Shinano River water to the
sea means pesticide entering rivers will also affect marine organisms, especially fish and
may subsequently affect humans consuming marine organisms [45]. The Kurose River,
a river in Hiroshima Prefecture, is approximately 43 km long. The Kurose River flows
through urban and agricultural areas on the Kamo Plateau, including Higashi-Hiroshima
Int. J. Environ. Res. Public Health 2021, 18, 468 12 of 15

city, before entering the Seto Inland Sea. The Kurose River has a surface area of approxi-
mately 250 km2 . Agricultural runoff and wastewater containing industrial and household
pollutants enter the Kurose River. The water flowing from the Kurose River into the Seto
Inland Sea will, therefore, transfer OPs that may affect aquatic organisms, especially fish, in
the Seto Inland Sea and these OPs may subsequently affect humans. The concentrations of
pesticide found ranged from 2.8 ng/L (fenarimol) to 1194 ng/L (diazinon). Cyanazine was
the most frequently detected pesticide, followed by simetryn and then diazinon. The pres-
ence of simetryn and isoprothiolane was largely attributed to rice paddy farms, whereas
diazinon was associated mostly with vegetable farms and orchards. The diazinon and
isoprothiolane patterns were consistent with their use of controlling insects and fungi in the
prefecture [46]. The high contamination of Kurose River water with pesticides compared
to other rivers may be due the runoff of pesticide residues from a big agricultural area in
Hiroshima prefecture, including Higashi-Hiroshima City, which is cultivated with rice and
vegetables crops in which high amounts of pesticides were used for controlling pests [47].

6.3. China
The huge utilization of pesticides has reduced the existence of pests and has in-
creased crop production in China. However, the application of pesticides at such high
concentrations has induced residual pesticides in soil. Huangpu River basin has been
an agriculturally developed region since ancient times due to abundant radiation and
heat, heavy rainfall, numerous rivers and lakes and fertile soil. The water quality of the
Huangpu River was severely affected by agricultural non-point source pollution as well
as industrial and urban sewage, which resulted in the water quality falling to Class III–
IV, impacting the basic ecological functions and service of the river. Among the total of
29 pesticides analyzed, 18 were present in every sample taken from the Huangpu River.
The concentration of target pesticides in water samples ranged from <LOQ (buprofezin) to
607.30 ng/L (carbendazim). The concentration of carbendazim is high because it widely
used as a broad-spectrum fungicide in the cultivation of crops, such as rice, wheat and
cotton [48]. The Dongjiang River basin is located in southern China with a total area of
35,636 km2 . It flows through one of the China’s most developed provinces, Guangdong.
The main land use types in Dongjiang River basin are mixed forest, agriculture land and
orchard, composing approximately 66%, 17% and 5% of the total area. Among the total of
3 pesticides (Chlorpyrifos, triazophos and isoprothiolane) tested, the highest concentration
of chemicals found was 279.51 ng/L (isoprothiolane). Isoprothiolane is an organosulfure-
ous fungicide used to prevent diseases of paddy rice, with a usage of 35,320 kg in the study
area [49].

6.4. India
River Yamuna, one of the major rivers of India with a total stretch of 345,843 km2 ,
passes through Haryana state along its eastern border. However, due to high-density
population growth and fast industrialization, Yamuna has become one of the most polluted
rivers in the world. The concentration of Hexachlorocyclohexane and DDT at different
sites of the river ranged between 12.76–593.49 ng/L and 66.17–722.94 ng/L, respectively.
In canals the values were found between 12.38–571.98 ng/L and 109.12–1572.22 ng/L for
Hexachlorocyclohexane and DDT [50]. The Gomti River, one of the major tributaries of
the River Ganga originates from a natural reservoir in the swampy and densely forested
area. The river serves as one of the major source of drinking water for the Lucknow
City, the State capital of Uttar Pradesh with a population of about 3.5 million. Among
the sample analyzed, 21 pesticide were present in river water and bed sediment taken
from the Huangpu River. In the water of Gomti River, pesticide residues ranged between
2.16 to 567.49 ng/L and in the bed sediments it ranged from 0.92 to 813.59 ng/L. It was
suggested that source of DDT contamination is from the aged and weathered agricultural
soils with signature of recently used DDT in the river catchments. The results revealed
that bed-sediments of the Gomti River are contaminated with lindane, endrin, heptachlor
Int. J. Environ. Res. Public Health 2021, 18, 468 13 of 15

epoxides and DDT and may contribute to sediment toxicity in the freshwater ecosystem of
the river [51]. The concentrations of pesticide detected in some rivers in Asia is summarized
in Table 7.

Table 7. Concentrations of pesticide in some Asian rivers reported in literature.

Country Location Concentration Reference

Tengi River 2.7 ng/L–4493.1 ng/L [42]
Malaysia
Selangor River 10.1 ng/L–1848.7 ng/L [44]
Shinano River 3 ng/L–8200 ng/L [45]
Japan
Kurose River 2.8 ng/L–1194 ng/L [47]
Huang Pu River ND–10,370 ng/L [48]
China
Dongjiang River ND–279.51 ng/L [49]
Yamuna River 12.38 ng/L–1572.22 ng/L [50]
India
Gomti River 0.92 ng/L–813.59 ng/L [51]

7. Conclusions
The occurrence of pesticides in the water poses a deleterious effect on human health,
where the effect magnitude depends on the solubility, half-life, adsorption capacity,
biodegradability of the pesticide compounds. In the future, chemical pesticides will
continue to perform a vital role in pest management. Despite evaluations of the efficacy,
ease of use and cost of pesticides, the potential adverse effects of pesticides should be
taken into consideration to achieve long-term sustainability pest management. Research in
the field of pesticide development and technologies should be enhanced for compatible
ecological based pest management. Assessment of pesticide residue management, the
fate of pesticides and application technology would be useful for reducing the adverse
health impacts from pesticides and its alternatives. With no justification for completely
phasing out the chemical pesticide, pesticide users are recommended to replace the use
of synthetic pesticides with bio-pesticide that exert a lesser environmental impact and
also to ensure the correct application of pesticides in the agricultural system. Besides,
Integrated Pest Management (IPM) is an ideal strategy for managing pests and insects in
urban and agricultural settings that offer long-term prevention of pests by natural means.
With the selective pesticide for backup in IPM, the usage of pesticides could be reduced
to a larger extent, reducing the occurrence of pesticide compounds in water. As for safety
measures, the water bodies in which pesticide compounds have been detected should
undergo constant monitoring and potable water should undergo advanced water treatment
processes if required.

Author Contributions: Conceptualization, J.R. and T.H.; formal analysis, R.A.K., W.A.A.-o. and A.Y.;
writing—original draft preparation, M.S. and T.H.; writing—review and editing, M.S., T.S.A., A.H.A.
and A.M.A.-M. All authors have read and agreed to the published version of the manuscript.
Funding: This research received no external funding.
Conflicts of Interest: The authors declare no conflict of interest.

References
1. De, A.; Bose, R.; Kumar, A.; Mozumdar, S. Targeted Delivery of Pesticides Using Biodegradable Polymeric Nanoparticles; Springer:
New Delhi, India, 2014; ISBN 978-81-322-1689-6.
2. Sharma, A.; Kumar, V.; Shahzad, B.; Tanveer, M.; Sidhu, G.P.S.; Handa, N.; Kohli, S.K.; Yadav, P.; Bali, A.S.; Parihar, R.D.
Worldwide pesticide usage and its impacts on ecosystem. SN Appl. Sci. 2019, 1, 1446. [CrossRef]
3. Mahmood, I.; Imadi, S.R.; Shazadi, K.; Gul, A.; Hakeem, K.R. Effects of Pesticides on Environment. In Plant, Soil and Microbes;
Hakeem, K., Akhtar, M., Abdullah, S., Eds.; Springer: Cham, Switzerland, 2016; ISBN 978-33-192-7455-3.
4. Ortiz-Hernández, M.L.; Sánchez-Salinas, E.; Dantán-González, E.; Castrejón-Godínez, M.L. Pesticide biodegradation: Mechanisms,
genetics and strategies to enhance the process. Biodegrad. Life Sci. 2013, 251–287. [CrossRef]
Int. J. Environ. Res. Public Health 2021, 18, 468 14 of 15

5. Yadav, I.C.; Devi, N.L.; Syed, J.H.; Cheng, Z.; Li, J.; Zhang, G.; Jones, K.C. Current status of persistent organic pesticides residues
in air, water, and soil, and their possible effect on neighboring countries: A comprehensive review of India. Sci. Total Environ.
2015, 511, 123–137. [CrossRef] [PubMed]
6. Young, L.; Rao, S.R.; Cort, S.G. Industry Corner: The Pesticide Market and Industry: A Global Perspective. Bus. Econ. 1996, 31,
56–60.
7. Wolfram, J.; Stehle, S.; Bub, S.; Petschick, L.L.; Schulz, R. Insecticide Risk in US Surface Waters: Drivers and Spatiotemporal
Modeling. Environ. Sci. Technol. 2019, 53, 12071–12080. [CrossRef] [PubMed]
8. Battaglin, W.A.; Hay, L.E. Effects of Sampling Strategies on Estimates of Annual Mean Herbicide Concentrations in Midwestern
Rivers. Environ. Sci. Technol. 1996, 30, 889–896. [CrossRef]
9. Leu, C.; Singer, H.; Stamm, C.; Müller, S.R.; Schwarzenbach, R.P. Simultaneous Assessment of Sources, Processes, and Factors
Influencing Herbicide Losses to Surface Waters in a Small Agricultural Catchment. Environ. Sci. Technol. 2004, 38, 3827–3834.
[CrossRef]
10. Zubrod, J.P.; Bundschuh, M.; Arts, G.; Brühl, C.A.; Imfeld, G.; Knäbel, A.; Payraudeau, S.; Rasmussen, J.J.; Rohr, J.; Scharmuller, A.;
et al. Fungicides: An Overlooked Pesticide Class? Environ. Sci. Technol. 2019, 53, 3347–3365. [CrossRef]
11. Trautmann, N.M.; Porter, K.S.; Wagenet, R.H. Pesticides: Health Effects in Drinking Water. Available online: https://ecommons.
cornell.edu/bitstream/handle/1813/3335/Pesticides+-+Health+Effects.pdf?sequence=2 (accessed on 23 October 2020).
12. Gilliom, R.J.; Barbash, J.E.; Crawford, C.G.; Hamilton, P.A.; Martin, J.D.; Nakagaki, N.; Nowell, L.H.; Scott, J.C.; Stackelberg, P.E.;
Thelin, G.P.; et al. Pesticides in the Nation’s Streams and Ground Water, 1992–2001; US Geological Survey: Reston, WC, USA, 2006;
ISBN 1411309553.
13. Aydinalp, C.; Porca, M.M. The effects of pesticides in water resources. J. Cent. Eur. Agric. 2004, 5, 5–12.
14. National Research Council; Board on Agriculture; Committee on Long-Range Soil and Water Conservation Policy. Soil and Water
Quality: An Agenda for Agriculture; National Academies Press: Cambridge, MA, USA, 1993; ISBN 9780309049337.
15. Lushchak, V.I.; Matviishyn, T.M.; Husak, V.V.; Storey, J.M.; Storey, K.B. Pesticide toxicity: A mechanistic approach. EXCLI J. 2018,
17, 1101. [CrossRef]
16. McKnight, U.S.; Rasmussen, J.J.; Kronvang, B.; Binning, P.J.; Bjerg, P.L. Sources, occurrence and predicted aquatic impact of legacy
and contemporary pesticides in streams. Environ. Pollut. 2015, 200, 64–76. [CrossRef] [PubMed]
17. Székács, A.; Mörtl, M.; Darvas, B. Monitoring pesticide residues in surface and ground water in Hungary: Surveys in 1990–2015.
J. Chem. 2015, 2015. [CrossRef]
18. Kumar, S.; Sharma, A.K.; Rawat, S.; Jain, D.; Ghosh, S. Use of pesticides in agriculture and livestock animals and its impact on
environment of India. Asian J. Environ. Sci. 2013, 8, 51–57.
19. Zaidon, S.Z.; Ho, Y.B.; Hashim, Z.; Saari, N.; Praveena, S.M. Pesticides Contamination and Analytical Methods of Determination
in Environmental Matrices in Malaysia and Their Potential Human Health Effects–A Review. Malays. J. Med. Health Sci. 2018, 14,
81–88.
20. Samsuddin, N.; Rampal, K.G.; Ismail, N.H.; Abdullah, N.Z.; Nasreen, H.E. Pesticide Exposure and Cardiovascular Hemodynamic
Parameters Among Male Workers Involved in Mosquito Control in East Coast of Malaysia. Am. J. Hypertens. 2015, 29, 226–233.
[CrossRef]
21. Dalvie, M.A.; Myers, J.E.; Thompson, M.L.; Robins, T.G.; Dyer, S.; Riebow, J.; Molekwa, J.; Jeebhay, M.; Millar, R.; Kruger, P.
The long-term effects of DDT exposure on semen, fertility, and sexual function of malaria vector-control workers in Limpopo
Province, South Africa. Environ. Res. 2004, 96, 1–8. [CrossRef]
22. Tuc, V.P.; Wangsuphachart, V.; Tasanapradit, P.; Fungladda, W.; Van Trong, P.; Nhung, N.T. Impacts of pesticide use on semen
characteristics among rice famers in Kienxuong District, Thaibinh Province, Vietnam. Southeast Asian J. Trop. Med. Public Health
2007, 38, 569.
23. Alavanja, M.C.; Samanic, C.; Dosemeci, M.; Lubin, J.; Tarone, R.; Lynch, C.F.; Knott, C.; Hoppin, J.; Barker, J. Use of agricultural
pesticides and prostate cancer risk in the Agricultural Health Study cohort. Am. J. Epidemiol. 2003, 157, 800–814. [CrossRef]
24. Hoppin, J.A.; Umbach, D.M.; London, S.J.; Henneberger, P.K.; Kullman, G.J.; Coble, J.; Alavanja, M.C.; Freeman, L.B.; Sandler, D.P.
Pesticide use and adult-onset asthma among male farmers in the Agricultural Health Study. Eur. Respir. J. 2009, 34, 1296–1303.
[CrossRef]
25. Montagner, C.C.; Vidal, C.; Acayaba, R.D.; Jardim, W.F.; Jardim, I.C.; Umbuzeiro, G.A. Trace analysis of pesticides and an
assessment of their occurrence in surface and drinking waters from the State of São Paulo (Brazil). Anal. Methods 2014, 6,
6668–6677. [CrossRef]
26. Yadav, A.S.; Sehrawat, G. Evaluation of genetic damage in farmers exposed to pesticide mixtures. Int. J. Hum. Genet. 2011, 11,
105–109. [CrossRef]
27. Narayana, K.; Prashanthi, N.; Nayanatara, A.; Bairy, L.K.; DoSOUZA, U.J. An organophosphate insecticide methyl parathion
(o-o-dimethyl o-4-nitrophenyl phosphorothioate) induces cytotoxic damage and tubular atrophy in the testis despite elevated
testosterone level in the rat. J. Toxicol. Sci. 2006, 31, 177–189. [CrossRef] [PubMed]
28. Hamilton, D.; Dieterle, R.; Felsot, A.; Harris, C.; Holland, P.; Katayama, A.; Kurihara, N.; Linders, J.; Unsworth, J.; Wong, S.S.
Regulatory limits for pesticide residues in water (IUPAC Technical Report). Pure Appl. Chem. 2003, 75, 1123–1155. [CrossRef]
Int. J. Environ. Res. Public Health 2021, 18, 468 15 of 15

29. López-Loveira, E.; Ariganello, F.; Medina, M.S.; Centrón, D.; Candal, R.; Curutchet, G. Degradation alternatives for a commercial
fungicide in water: Biological, photo-Fenton, and coupled biological photo-Fenton processes. Environ. Sci. Pollut. Res. 2017, 24,
25634–25644. [CrossRef]
30. Zapata, A.; Malato, S.; Sánchez-Pérez, J.; Oller, I.; Maldonado, M. Scale-up strategy for a combined solar photo-Fenton/biological
system for remediation of pesticide-contaminated water. Catal. Today 2010, 151, 100–106. [CrossRef]
31. Badawy, M.I.; Ghaly, M.Y.; Gad-Allah, T.A. Advanced oxidation processes for the removal of organophosphorus pesticides from
wastewater. Desalination 2006, 194, 166–175. [CrossRef]
32. Ribeiro, A.R.; Nunes, O.C.; Pereira, M.F.; Silva, A.M. An overview on the advanced oxidation processes applied for the treatment
of water pollutants defined in the recently launched Directive 2013/39/EU. Environ. Int. 2015, 75, 33–51. [CrossRef]
33. Quiroz, M.A.; Martínez-Huitle, C.A.; Bandala, E.R. Advanced Oxidation Processes (AOPs) for Removal of Pesticides from
Aqueous Media. In Pesticide-Formulations, Effects, Fate; Margarita, S., Ed.; IntechOpen: Mexico, Brazil, 2011. [CrossRef]
34. Lafi, W.K.; Al-Qodah, Z. Combined advanced oxidation and biological treatment processes for the removal of pesticides from
aqueous solutions. J. Hazard. Mater. 2006, 137, 489–497. [CrossRef]
35. Mantzavinos, D.; Kalogerakis, N. Treatment of olive mill effluents: Part I. Organic matter degradation by chemical and biological
processes—an overview. Environ. Int. 2005, 31, 289–295. [CrossRef]
36. Ghime, D.; Ghosh, P. Advanced Oxidation Processes: A Powerful Treatment Option for the Removal of Recalcitrant Organic
Compounds. In Advanced Oxidation Processes-Applications, Trends, and Prospects; Ciro, B., Ed.; IntechOpen: Chhattisgarh, India,
2020. [CrossRef]
37. Zhang, M.H.; Dong, H.; Zhao, L.; Wang, D.X.; Meng, D. A review on Fenton process for organic wastewater treatment based on
optimization perspective. Sci. Total Environ. 2019, 670, 110–121. [CrossRef]
38. Govindaraj, D.; Nambi, I.; Jaganathan, S. Nanocatalysts in Fenton Based Advanced Oxidation Process for Water and Wastewater
Treatment. J. Bionanosci. 2016, 10, 356–368. [CrossRef]
39. Oller, I.; Gernjak, W.; Maldonado, M.I.; Pérez-Estrada, L.A.; Sánchez-Pérez, J.A.; Malato, S. Solar photocatalytic degradation of
some hazardous water-soluble pesticides at pilot-plant scale. J. Hazard. Mater. 2006, 138, 507–517. [CrossRef] [PubMed]
40. Dong, S.; Feng, J.; Fan, M.; Pi, Y.; Hu, L.; Han, X.; Liu, M.; Sun, J.; Sun, J. Recent developments in heterogeneous photocatalytic
water treatment using visible light-responsive photocatalysts: A review. Rsc Adv. 2015, 5, 14610–14630. [CrossRef]
41. Ibhadon, A.O.; Fitzpatrick, P. Heterogeneous photocatalysis: Recent advances and applications. Catalysts 2013, 3, 189–218.
[CrossRef]
42. Elfikrie, N.; Ho, Y.B.; Zaidon, S.Z.; Juahir, H.; Tan, E.S.S. Occurrence of pesticides in surface water, pesticides removal efficiency in
drinking water treatment plant and potential health risk to consumers in Tengi River Basin, Malaysia. Sci. Total Environ. 2020,
712, 136540. [CrossRef]
43. Molecular Design Research Network (MDRN). Aqueous and Lipid Solubility. Available online: https://modrn.yale.edu/
education/undergraduate-curriculum/modrn-u-modules/aqueous-and-lipid-solubility (accessed on 23 October 2020).
44. Leong, K.H.; Benjamin Tan, L.L.; Mustafa, A.M. Contamination levels of selected organochlorine and organophosphate pesticides
in the Selangor River, Malaysia between 2002 and 2003. Chemosphere 2007, 66, 1153–1159. [CrossRef]
45. Tanabe, A.; Mitobe, H.; Kawata, K.; Yasuhara, A.; Shibamoto, T. Seasonal and spatial studies on pesticide residues in surface
waters of Shinano River in Japan. J. Agric. Food Chem. 2001, 49, 3847–3852. [CrossRef]
46. Chidya, C.G.R.; Abdel-dayem, S.M.; Takeda, K.; Sakugawa, H. Spatio-temporal variations of selected pesticide residues in the
Kurose River in Higashi-Hiroshima city, Japan. J. Environ. Sci. Health Part B 2018, 53, 602–614. [CrossRef]
47. Derbalah, A.S.H.; Nakatani, N.; Sakugawa, H. Distribution, seasonal pattern, flux and contamination source of pesticides and
nonylphenol residues in Kurose River water, HigashiHiroshima, Japan. Geochem. J. 2003, 37, 217–232. [CrossRef]
48. Xu, L.; Granger, C.; Dong, H.; Mao, Y.; Duan, S.; Li, J.; Qiang, Z. Occurrences of 29 pesticides in the Huangpu River, China:
Highest ecological risk identified in Shanghai metropolitan area. Chemosphere 2020, 251, 126411. [CrossRef]
49. Zhang, B.; Zhang, Q.Q.; Zhang, S.X.; Xing, C.; Ying, G.G. Emission estimation and fate modelling of three typical pesticides in
Dongjiang River basin, China. Environ. Pollut. 2020, 258, 113660. [CrossRef] [PubMed]
50. Kaushik, C.P.; Sharma, H.R.; Jain, S.; Dawra, J.; Kaushik, A. Level of pesticide residues in river Yamuna and its canals in Haryana
and Delhi, India. Environ. Monit. Assess. 2008, 144, 329–340. [CrossRef] [PubMed]
51. Malik, A.; Ojha, P.; Singh, K.P. Levels and distribution of persistent organochlorine pesticide residues in water and sediments of
Gomti River (India)—A tributary of the Ganges River. Environ. Monit. Assess. 2009, 148, 421–435. [CrossRef] [PubMed]