INTRODUCTION

Pesticides are the chemical substances which are used to kill harmful or which can

damage the living organisms (Mathews, 2019). Pesticides have been put in to different classes

based on their uses and handling e.g. bactericides, algicides, herbicides, fungicides, nematicides,

insecticides, and rodenticides, while those having carbon rings are organophosphorus,

carbamates, organochlorine, acetamides, Triazines and triazoles, pyrethroids and neonicotinoids

(Tarla et al., 2020). During the period of green revolution in Pakistan, major focus was also to

produce the harmless pesticides in order to control the widespread variety of insects and herbal

pests which can deteriorate the quality and quantity of global food stuffs (Hassaan and El-Nemr,

2020; Gunstone et al., 2021). Among the pesticides, about 85% production of pesticides is

consumed in agriculture sector while rest of pesticides are consumed for the public health

activities e.g. for controlling vector-borne diseases, unwanted or extra plants while in industries

to control insects, fungi, bacteria, pest’s algae in electrical appliances, daily used equipment and

food packaging (Gilden et al., 2010). It has been estimated that about 5.6 billion pounds of

pesticides are being utilized worldwide annually which is also increasing unexpectedly

(Alavanja, 2009). The estimated amount of pesticides being used globally is approximately 45%

in Europe, 25% in USA and 25% in rest of the world (Bourguet and Guillemaud, 2016) in which

China and USA are the top while Pakistan has been ranked at the second position in Soth Asian

(Yadav et al., 2015; Waheed et al., 2017).

practices including, herbicides, nematicides, molluscidies, rodenticides, insecticides, fungicides

and various plant growth regulators. Pesticides have a wide range of uses, sources and toxic

nature depending upon the purpose of use and synthesis (Bashir et al., 2018) and due to these

reasons; pesticides have high global concerns (Damalas and Eleftherohorinos, 2011) because

harvesters and neighborhood of the cultivated areas are exposed directly or indirectly to the

pesticides during treatment, cleaning and storage of agriculture products (Hutter et al., 2021).

Even a good pesticide is not only harmful for the plants and animals in the ecosystem but also

causes the damage to the targeted specimen organisms for which being used (Arias-Estevez et

al., 2008). Unfortunately, many new and powerful pesticides are being formulated to combat the

increasing food demand (Mostafalou and Abdollahi, 2013) because without usage of pesticides,

vegetables, fruits and cereals are attacked by pests and relevant diseases causing losses of

quantity as well as quality of food stuff. However many authors e.g. (Oliveira et al.,

2021; Riedo et al., 2021; Trudi et al., 2021) have reported several adverse impacts on plants,

animals and ecosystem due to their usage.

1.2 Types of pesticides in use

According to Gracia (2012) pesticides are categorized in to diverse groups based on ther

chemistry, modes of action, functional groups and toxicity levels. Mostly pesticides are

categorized in to fungicides, herbicides, insecticides and rodenticides based on their nature of use
(Amaral, 2014; Mnif et al., 2011). Group of pesticides based on chemical classes, are

categorized into inorganic and organic components. Inorganic pesticides contain copper sulfate,

copper, ferrous sulfate, sulfur and lime while organic pesticides are more complex having severe

chronic effects (Kim et al., 2017). Organic pesticides can be categorized further rendering to

their chemical structure, such as chlorohydrocarbon insecticides, carbamate insecticides,

organophosphorus insecticides, metabolite, synthetic pyrethroid insecticides, synthetic urea,

herbicides, benzimidazole nematocides, triazine herbicides, metal phosphide and rodenticides

(Zhang et al., 2018).

Overall the use of pesticide is expected to cross about 4 million tons/year (FAOSTAT, 2010)

because their supply all over the world is very rough and unchecked (Pimentel,2016). It has been

observed that European countries are utilizing one third of pesticide while a quarter of total

pesticide is utilized by North America. Herbicides accounts for approximately half of the total

pesticides utilized in North America including fungicides 13%, insecticides 19% and the

remaining 22% contains diversity of other materials (Gianessi and Silvers, 1992). Similarly

insecticides are also considered as predominant in emerging agricultural activities, i.e. crops and

livestock, are the chief consumers of these insecticides worldwide reaching to 74% of the yearly

utilization with 1% for forestry (Pimentel et al., 1991). Pesticides like Dichloro Diphenyl

Trichloroethane (DDT), lindane are being widely used in Scandinavian and Asian countries on

large scale for agriculture purposes. (Voldner and Li, 1995). While the maximum use of the DDT
is to resist mosquito vectors of tse-tse fly and malaria in South Africa and tropical countries. The

use of these pesticides also varies as harvests fluctuate extensively like corn, cotton crops and

soybean are the chief herbicides consumers in the world with 75% in United States of America

and 25% rest of the world, similarly insecticides are used for plantations while vegetables and

vineyards utilize maximum of the fungicides (Pimentel et al., 1991).

Pesticides are also classified on the basis of their composition named: Organophosphates,

pyrethroids, organochlorines, carbamates and chlorines. Some pesticides are soluble in water

while others are soluble in organic solvents. They perform various functions on the basis of their

composition. They usually touch the nervous system of the pests and destroy them. They are

harmless in expressions of their use for non target material (Badii and Landeros, 2007; Ortiz-

Hernandez et al., 2013).

1.2 BEHAVIOR OF PESTICIDES IN THE ECOSYSTEM

Pesticides after their utilization for target plants, are disposed of in the soil, they normally

have capacity to migrate within the soil through water by the process of transport or degradation

(Singh, 2012; Liu et al., 2015) and finally degradation of pesticide in the environment generates

many new substances or chemicals as mntioned in Figure 1 (Marie et al., 2017). Pesticides can

also move from target sites to other sites having no vegetation by the process of transfer

involving leaching, adsorption, spray drift, volatilization and runoff depending upon their

behavior (Robinson et al., 1999). Pesticides like organochlorine complexes containing DDT
which has low acute toxicity but it can produce chronic impacts because this persists in the

tissues of plants leading to long lasting destruction of growth and physiological activities,

whereas organophosphate pesticides have also slight effects, but these can produce negative

impacts if persist for a longer period in mammals (Kim et al., 2017; Damalas and

Eleftherohorinos, 2011).

Initially, pesticides are spread in the environment through air, water, soil, animals and plants but

finally these are converted to their derivatives or converted to their more complex structures. The

quantity of pesticides also contribute to a larger extent because after degradation, these chemicals

migrates towards soil, air and ground water which recirculate with their movement (Kerle et al.,

2007). Pesticide can persist for a longer period of time in environment depending upon the half

life of compounds constituting these pesticides although, a pesticide generally has a half-life of

fifteen days. It has been reported by many authors that 50% of the pesticides can exist fifteen

days after their applications to the target plants while half of that quantity (25% of the original

quantity) can exist for thirty days more. Due to posing this character of extension in the half life,

as the life time increases, the mobility of these pesticides also increase in the soil and

environment (Tiryaki and Temur, 2010).

There are various factors which effect the persistence of these pesticides which include photo-

degradation, microbial degradation and chemical degradation. The degree of degradation of these

pesticides in the environment also depends on chemistry of compounds, environmental

mobility of pesticides in the environment is exaggerated by the sorption, solubility, vapor

pressure, environmental conditions including weather, canopy, topography, ground cover and

texture, organic matter, structure of soil. By modeling the occurrence of pesticide, can be a

valuable way for evaluating the destiny and also the influence of pesticide in the surroundings,

which may be used to find out the amount, frequency of breakdown that provides the evidence

for the removal of pesticide from the environment (Sunaryani and Rosmalina, 2021; Tiryaki and

Temur, 2010).

Impacts of pesticides on plants, animals, soil ecosystem, aquatic ecosystem and atmosphere

Advantages of pesticides are converted into the disadvantages due to its harmful impacts which

are due to interference and inclusion of pesticides in the food chain especially in drinking water

sources (Tariq et al., 2003) as shown in Table 1. Health impacts are mainly associated with the

food which is contaminated with toxic pesticides. This is because pesticides sprayed mostly

effect species which are non-targeted in air, water and soil (Miller, 2004). Toxicity of pesticides

is resulted from inhalation, ingestion and absorption. If exposure to pesticides continued for a

long period, it is resulted in serious diseases including: neurological dysfunctions, hormonal

imbalance, immune system dysfunction and blood disorders etc. (Kubrak et al., 2012). Pesticides

have significant dangerous effects on plant growth, germination, and development, variations in

biochemical passageways, yield and some antioxidant enzymes as explained in Table

causing metabolic disorders (Sharples et al., 1997).

Pesticides also have adverse impacts on health of human and animals in several ways as

mentioned in Table 2. Pesticides enter into the human body by inhalation from air, dust and

vapors containing pesticides, orally by consuming contaminated water and food and by dermal

exposure through direct contact with pesticides (Sacramento, 2008). Pesticides are sprayed on

food crops from there they secrete in soil and water and pollute them for consuming and spray

drift pollute air. Exposure to these contaminated goods takes pace when these are in contact with

human body in the environment (Lorenz, 2009). People are put in trouble during management

and utilization of pesticides, as these produce toxicity during cleaning, keeping apparatus,

pollution of water, clothing and food (Hutter, 2021).

Several impacts of pesticides have also been observed on soil ecosystem as long term storage

compartment is provided by soil to pesticides having organic carbon because of its buffer,

filtering capacity and high potential of degradation as described in Table 3 (Burauel and

Bassmann, 2005). Pesticides present in soil are exposed through direct or indirect ways. Directly

these are exposed through application in the field while indirect means are accidental leakage,

spillage or run-off through plant surface (Bailey and White, 1970; Rashid et al., 2010).

Contamination of soil may occur due to uncontrolled use of pesticides which can kill non-

targeted organisms by damaging soil biomass witch effect microorganisms including bacteria,
earthworm and fungi (Azam et al., 2003) as shown in Table 4. When pesticides target non-

targeted organisms, this damage their metabolism which is required for soil fertility and pesticide

degradation (Kale and Raghu, 1989). For control of pests and plant diseases, farmers use

pesticides excessively which damage the soil adversely (Oberemok et al., 2015).

Table 1: Impacts of pesticides on plants.

S. Impact Reference

No

1 Affect plant growth, germination, and development, variations in Parveen et al., 2016

biochemical passageways, yield and some antioxidant enzymes

2 Affect the physiology of crop Giménez–Moolhuyzen

et al., 2020

3 Affect the plant growth and cause metabolic disorders Sharples et al., 1997

4 Block the photosystem II in photosynthesis pathway DelValle, et al., 1985

5 Affect the photosystem II badly in chloroplast Devine et al., 1993

6 Reduced chlorophyll a, b and total chlorophyll along with Tort and Turkyilmaz,

carotenoid contents in 2003

the leaves of pepper

7 Decrease in the supply of photosynthesis in the roots Alonge, 2000

1992

9 Reduced the growth of root and shoot Mishra et al., 2008

10 Caused nearly complete inhibition of growth in maize plants Murthy et al., 2005

11 Decrease in pods and seed yield of rice crop Mugo, 1989

12 Decrease in the growth and yield of barley plants Boonlertnirun et al.,

2005

13 Changes in vegetation growth, death of plant, decrease in Altman, 1993

reproduction capability, reduced fitness and detrimental, economic

and ecological impacts

14 Mutations in crop genes and changes in uptake of nutrients, Marrs et al., 1991

transport of nutrients and metabolism of crops

Table 2: Impacts of pesticides on human and animals.

Sr. Impacts Reference

No
1 Cause of chronic diseases which effect nervous system, reproductive Mostafalou

system, cardiovascular system, renal system and respiratory system and Abdollahi,

2012

2 Cause headaches, skin rashes, nausea, body ache, poor concentration, PAN, 2012

dizziness, cramps, panic attacks, impaired vision, birth defects, production

of benign or malignant tumors, toxicity in fetus, mutations, nerve disorders,

genetic changes, blood disorders, reproduction effects and endocrine

disruption. In animals pesticides cause potential carcinogens, reproductive

toxins, neurotoxins and immune toxins. Some studies show the development

of neurodegenerative diseases

Table 3: Impacts of pesticides on soil ecosystem.

Sr. Impact Reference

No.

1 Damages and reduction of soil biomass Azam et al., 2003

2 Damages in the local metabolism Kale and Raghu, 1989

3 Contaminate the soil nutrients and cause adverse effects on Oberemok et al., 2015
 humans and environment

4 Cause acute poisoning for microbial biomass Yadav and Devi et al.,

2015

5 Pollute surface and water bodies Yadav and Devi, 2017

6 Decline in the soil fertility Jia and Conrad, 2009

Table 4: Impacts of pesticides on aquatic ecosystem.

S. Impact Reference

No.

1 Create pollution in aquatic ecosystem and cause ecological damages Macneale et al.,

which in turn damage the natural habitat of fishes in water bodies 2010

2 Damages of aquatic life which includes fish and plants by reducing Mahmood et al.,

dissolve oxygen levels leading to changes in physiology of aquatic life 2016

3 Damage of aquatic plants, animals and marine populations Helfrich et al.,

2009
Pesticides also create pollution in aquatic ecosystem as mentioned in Table 4. by contaminating

surface and ground water. Ground water contamination cause major changes in water

quality. Even after controlled use of pesticides, traces are also found in drinking water which can

be a source of human exposure to pesticides (Macneale et al., 2010). Water, which is the

fundamental need of life, is being polluted severely because of several natural and anthropogenic

activities (Hussain and Asi, 2008). Toxicity of pesticides in aquatic ecosystem is depended on

some factors including exposure level, immune response, immunologic assay method, stress

limits and toxicity of pesticide. Toxicity of pesticides have also been found high when these are

present as composite mixture having several components (Banerjee, 1999).

Remediation technologies for pesticides removal

Due to increasing usage of pesticides, it is being a topic of great concern that how to remove

pesticides from environment. Many techniques or remedies have been discovered for the

removal of pesticides from environment including soil, water, air and food. The instant ways for

removal or reduction of pesticide from food are washing, peeling, cooking and blanching (Street,

1969). However these methods are not enough to completely remove pesticides from food due to

their stability and persistency. Biological and chemical treatments based technologies are

available for pesticide recovery from polluted soil and decommissioning of hazardous wastes

(Gavrilescu, 2009). Some suitable techniques have been given in the Table 4 which shows the

use of different technologies and plants for removal of pesticides. In this regard, Contaminant-
Immobilization Technology (CIT) is an in-situ approach used for very low effective cost for the

restoration of soil polluted by pesticides within shorter period of time. In this technique,

adsorption takes place which cause toxicity to non-targeted organisms. Minimum treatments are

required because carbonate materials are generally are taken up from biological material by

using organically active residues (Calugaru et al., 2018). Other one which is also most frequently

used is the separation technology, in which solvents and synthetic surfactants are used to remove

contaminant from sludge medium. In this remediation technique possible methods used are in the

form of are; solvents, synthetic surfactants, soil flushing, cyclodextrins and Biosurfactants. The

solvent is chosen depending on the pollutant which has to be removed (Mao and Yang, 2013).

Fenton advanced oxidation process is used to remove organochlorode pesticides (OCPs)

including DDT. DDT pesticide is highly persistent and has high bioaccumulation which is

hazardous to environment. However, this is not enough for complete removal of DDT and other

chlorinated organic toxicants. For achieving complete removal of DDT, high utilization of

ferrous salts are needed for recovery process and since the acids are used for degradation and

removal of DDT, high amounts of acids acidifies the soil and cause erosion with loss of fertility

of soil (Villa et al., 2008). Supercritical fluid extraction technique is also one of best techniques

used for extraction of polycyclic aromatic hydrocarbons from subcritical polluted water. In this

technique microorganisms are used for bioremediation and degrading the polycyclic aromatic

hydrocarbons from effluents including trinitrotoluene and poly chlorinated biphenyls (Ramos-
Contreras et al., 2019). In Electro-kinetic remediation technique, zero valance iron nano-particles

are used to prevent environment from pollutants such as polychlorinated biphenyls (PCBs) and

bio-chlorinated solvents. These are detoxified by using zero valence iron nano-particles but this

technique has limitation, as zero valence iron nano-particles have high reactivity (Tummala and

Tewari, 2018).

Photocatalysis is also good technique for degradation of pesticides which use semiconductors of

metal oxides, sulfides, metal free ions and those materials which serve as substrate for

photocatalyst in composite material. This technique may include: titanium oxide based

photocatalysis, zinc sulfide based photocatalysis, G-C 3N4 based photocatalysis and graphite

based photocatalysis (Lin and Shen et al., 2014). Phytoremediation is a biological technique for

the removal of pesticides from environment which is very cheap technique working on solar

power. Phytoremediation use efficient plant species which can remove or eliminate pesticide

pollutants from environment. This technique can remove pesticide pollutants from 0% to 70%

(Main et al., 2017). Plants remove pesticide pollutants by using Phytodegradation,

Phytoextraction and Rhizodegradation (Truua et al., 2015). These techniques are highly

ecofriendly, safe, economical or less costly and effective for the removal of pesticide pollutants

from environment (Kuppusamy et al., 2016). Algae is a potent organism for the removal of

pesticide pollutants through microalgae pesticide remediation which is a photosynthetic

organism which convert solar energy into chemical energy and has a very simple structure which
make transport of nutrients easier and faster (Chacoon-Lee and González-Mariño, 2010).

Microalgae remove pesticides from contaminated sites by bioaccumulation and considered a

potent organism for this purpose because it uses organic pollutants as their energy source

(Chojnacka, 2010). Microalgae are efficient biosorbents which not only accumulate pesticides

but also convert them into less toxic substances. The efficiency of this biodegradation is

dependent upon environmental condition, nature and concentration of pesticide which is to be

degraded (Ortiz-Hernandez et al., 2013). Microalgae can survive in any environmental condition

and are capable of efficient biodegradation of pesticides from contaminated sites

(Subashchandrabose et al., 2013).

Degradation of pesticides by using bacteria is another biological method which is very less cost

effective, ecofriendly and best technique for removal of pesticides (Gavrilescu, 2005). Bacteria

can degrade pesticides at good rate isolated from different ecosystems including bacteria from

genus Arthrobacter, Flavobacterium, Burkholderia, Peudomonas and Azobacter. This is an

effective technique which does not cause any further damage to environment. In this technique

microbes degrade pesticides for nutrients and release CO 2 and H2O in environment (Huang and

Zeng, 2008). Degradation of pesticides is also dependent on the conditions of available

environment, exposure and specie of bacteria. Efficiency of bacteria for pesticide removal is

faster in the presence of anions (Rani and Dhania, 2014) and bacteria uptake pesticide pollutants

converting them into inorganic compounds. Mycoremediation is also a biological technique for
pesticide removal which includes fungi for degradation of pesticide as fungi is a eukaryotic,

saprophytic, heterotrophic and parasitic organism which produce spore and grow in cool and

humid environment (Jobard et al., 2010). Fungi transform and detoxify pollutants by taking them

up from contaminated environment. By this procedure fungi remove pesticides from soil and

water ecosystem (Tortella et al., 2005). Fungi also cause changes in chemical structure of

pesticide and convert them into non-toxic compounds which are easily degraded by microflora

(Hai and Modin, 2012). Fungi use different processes for pesticide degradation including

Hydroxylation, Dioxylation, Dechlorination, Dehydrochlorination and Esterification. Fungi use

these processes for pesticide degradation because pesticide have various functional groups which

minimize the crop damage. Fungi attack on functional groups of pesticides and cause rapid

degradation of pesticides (Maqbool et al., 2016; Ponnuchamy et al., 2021).

Conclusions and Recommendation

Pesticides are chemical fertilizers used mostly in agriculture sector for controlling unwanted

organisms which can damage crops. Although pesticides have many benefits but also pose severe

impacts on environment. They damage our natural environment by contaminating it and cause

several health issues. Recently, removal of pesticide pollutants is a topic of major concern

worldwide. Many techniques have been developed for removal of pesticides in this regard and

many new techniques are being developed for their safe removal. Pesticides can be removed
from soil, water and environment by using plants, animals and different chemicals. Soil and

environment can be saved from pesticides toxicity by wise use of pesticide for crops.

REFERENCES

Alavanja, M.C., 2009. Introduction: Pesticides use and exposure, extensive worldwide. Rev.

Environ. Health, 24: 303-310. https://doi.org/10.1515/REVEH.2009.24.4.303

Alonge, S.O., 2000. Effect of imazaquin applications on the growth, leaf chlorophyll and yield

of soybean in the guinea savanna of Nigeria. J. Environ. Sci. Health B, 35: 321–

336. https://doi.org/10.1080/03601230009373273

Amaral, A.F.S., 2014. Pesticides and asthma: Challenges for epidemiology. Front. Publ.

Health, 2: 6. https://doi.org/10.3389/fpubh.2014.00006

Azam, F., S. Farooq and A. Lodhi. 2003. Microbial biomass in agricultural soils determination,

synthesis, dynamics and role in plant nutrition. Pak. J. Biol. Sci., 6(7): 629-

639. https://doi.org/10.3923/pjbs.2003.629.639

Badii, M.H., and J.L. Flores. 2007. Plaguicidas que afectan a la salud humana y la

sustentabilidad. Cult. Cient. Tecnol., 4(19): 21-34.

Bailey, G.W. and J.L. White. 1970. Factors influencing the adsorption, desorption, and

movement of pesticides in soil. In Single Pesticide Volume: The Triazine Herbicides, pp.

29-92. https://doi.org/10.1007/978-1-4615-8464-3_4
Banerjee, B.D., 1999. The influence of various factors on immune toxicity assessment of

pesticide chemicals. Toxicol. Lett., 107: 21–31. https://doi.org/10.1016/S0378-

4274(99)00028-4

Bashir, M.H., M. Zahid, M.A. Khan, M. Shahid, A.K. Khan, and L. Amrao. 2018. Pesticides

toxicity for Neoseiulus barkeri (Acari: Phytoseiidae) and non-target organisms. Pak. J.

Agric. Sci., 55: 63-71. https://doi.org/10.21162/PAKJAS/18.5277

Boonlertnirun, S., K. Boonlertnirun and I. Sooksathan. 2005. In: Proceedings of 43 rd Kasetsart

University Annual Conference, Thailand, 1–4 February, pp. 37–43.

Bourguet, D. and T. Guillemaud. 2016. The hidden and external costs of pesticide use. Sustain.

Agric. Rev., 19: 35-120. https://doi.org/10.1007/978-3-319-26777-7_2

Burauel, P. and F. Bassmann. 2005. Soils as filter and buffer for pesticides-experimental

concepts to understand soil functions. Environ. Pollut., 133: 11-

16. https://doi.org/10.1016/j.envpol.2004.04.011