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Pesticides are used to kill the pests and insects which attack on crops and harm them. Different kinds of pesticides have been used for crop protection for centuries. Pesticides benefit the crops; however, they also impose a serious negative impact on the environment. Excessive use of pesticides may lead to the destruction of biodiversity. Many birds, aquatic organisms and animals are under the threat of harmful pesticides for their survival. Pesticides are a concern for sustainability of environment and global stability. This chapter intends to discuss about pesticides, their types, usefulness and the environmental concerns related to them. Pollution as a result to overuse of pesticides and the long term impact of pesticides on the environment are also discussed in the chapter. Moving towards the end, the chapter discusses the methods to eradicate the use of pesticides and finally it looks forward towards the future impacts of the pesticide use the future of the world after eradicating pesticides.
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253
© Springer International Publishing Switzerland 2016
K.R. Hakeem et al. (eds.), Plant, Soil and Microbes,
DOI 10.1007/978-3-319-27455-3_13
Effects of Pesticides on Environment
Isra Mahmood , Sameen Ruqia Imadi , Kanwal Shazadi , Alvina Gul ,
and Khalid Rehman Hakeem
Contents
1 Introduction 254
2 Pesticide Use: From Past to Present 255
3 Pesticide Registration and Safety 256
4 Classifi cation of Pesticides 258
5 Merits of Pesticide Use 258
6 Risks Associated with Pesticide Use 260
6.1 Threats to Biodiversity 261
6.1.1 Threats to Aquatic Biodiversity 261
6.1.2 Threats to Terrestrial Biodiversity 262
7 Pesticide Impact on Human Health 264
7.1 Acute Effects of Pesticides 264
7.2 Chronic Effects of Pesticides 265
8 Conclusion and Future Prospects 265
References 266
Abstract Pesticides are used to kill the pests and insects which attack on crops and
harm them. Different kinds of pesticides have been used for crop protection for
centuries. Pesticides benefi t the crops; however, they also impose a serious negative
impact on the environment. Excessive use of pesticides may lead to the destruction
of biodiversity. Many birds, aquatic organisms and animals are under the threat of
I. Mahmood S. R. Imadi A. Gul (*)
Atta-ur-Rahman School of Applied Biosciences , National University of Sciences
and Technology , Islamabad , Pakistan
e-mail: alvina_gul@yahoo.com
K. Shazadi
Department of Plant Sciences , Quaid-I-Azam University , Islamabad , Pakistan
K. R. Hakeem
Faculty of Forestry , Universiti Putra Malaysia , Serdang 43400 , Selangor , Malaysia
254
harmful pesticides for their survival. Pesticides are a concern for sustainability of
environment and global stability. This chapter intends to discuss about pesticides,
their types, usefulness and the environmental concerns related to them. Pollution as
a result to overuse of pesticides and the long term impact of pesticides on the envi-
ronment are also discussed in the chapter. Moving towards the end, the chapter
discusses the methods to eradicate the use of pesticides and fi nally it looks forward
towards the future impacts of the pesticide use the future of the world after eradicat-
ing pesticides.
Keywords Pesticides Environment Chronic effects of pesticides Environmental
hazards Pesticide registration
1 Introduction
A pesticide is a toxic chemical substance or a mixture of substances or biological
agents that are intentionally released into the environment in order to avert, deter,
control and/or kill and destroy populations of insects, weeds, rodents, fungi or other
harmful pests. Pesticides work by attracting, seducing and then destroying or miti-
gating the pests. Pests can be broadly defi ned as “ the plants or animals that jeopar-
dize our food , health and / or comfort ”.
The use of pesticides has increased many folds over the past few decades.
According to an estimate, about 5.2 billion pounds of pesticides are used worldwide
per year. The use of pesticides for pest mitigation has become a common practice
all around the world. Their use is not only restricted to agricultural fi elds, but they
are also employed in homes in the form of sprays, poisons and powders for control-
ling cockroaches, mosquitoes, rats, fl eas, ticks and other harmful bugs. Due to this
reason, pesticides are frequently found in our food commodities in addition to their
presence in the air (Pesticides n.d. ). Pesticides can be natural compounds or they
can be synthetically produced. They may belong to any one of the several pesticide
classes. Major classes include organochlorines, carbamates, organophosphates,
pyrethroids and neonicitinoids to which most of the current and widely used pesti-
cides belong (Pesticides 101-A Primer n.d. ). Pesticide formulations contain active
ingredients along with inert substances, contaminants and occasionally impurities.
Once released into the environment, pesticides break down into substances known
as metabolites that are more toxic to active ingredients in some situations (What Is
a Pesticide n.d. ).
Pesticides promise the effective mitigation of harmful bugs, but unfortunately,
the risks associated with their use have surpassed their benefi cial effects. Non-
selective pesticides kill non-target plants and animals along with the targeted ones.
Moreover, with the passage of time, some pests also develop genetic resistance to
pesticides. This chapter focuses on the use of pesticides since the ancient times,
I. Mahmood et al.
255
merits of pesticide usage and most importantly, the harmful impact of pesticides on
human health and the environment.
2 Pesticide Use: From Past to Present
The use of pesticides dates back to the times of Ancient Romans where people used
to burn sulphur for killing pests and used salts, ashes and bitters for controlling
weeds. A Roman naturalist urged the use of arsenic as an insecticide (History of
pesticide use 1998 ).
In 1600s, a mixture of honey and arsenic was used for controlling ants. In late
1800s, farmers in the USA started using certain chemicals such as nicotine sulphate,
calcium arsenate and sulphur for fi eld related posts; however; their efforts were
unfruitful because of the primitive methods of application (Delaplane 2000 ). In
1867, an impure form of copper, arsenic was used to control the outbreak of
Colorado potato beetle in the USA (History of pesticide use 1998 ). The major
breakthrough in pesticide development occurred in the period around and after
World War-II, when several effective and inexpensive pesticides were synthesised
and produced. This period is marked by the discovery of Aldrin, dichlorodiphenyl-
trichloroethane (DDT) in 1939, Dieldrin, β-Benzene Hexachloride (BHC),
2,4-Dichlorophenoxyacetic acid (2,4-D), Chlordane and Endrin (Jabbar and Mallick
1994 ; Delaplane 2000 ). A glimpse on the historical account about pesticide use is
mentioned in Table 1 .
Fungicides, captan and glyodin and organophosphate insecticide Malathion were
introduced between 1950 and 1955 followed by the discovery of triazine herbicides
in the years 1955–1960 (Jabbar and Mallick 1994 ). An experimental wartime herbi-
cide named Agent Orange was developed by Monsanto in 1961–1971 and was used
during the Vietnam War (History of pesticide use 1998 ). Moreover, in 1961, the use
of pesticides also reached its peak. However, after 1962, there was a marked
Table 1 Historical account of pesticide use
Year Events
1867 Paris Green (form of copper arsenite) was used to control Colorado potato beetle
outbreak
1885 Introduction of a copper mixture by Professor Millardet to control mildew
1892 Potassium dinitro-2-cresylate was produced in Germany
1939 DDT discovered by Swiss chemist Paul Muller; organophosphate insecticides and
phenoxyacetic herbicides were discovered
1950s Fungicides captan and glyodin and insecticide malathion was discovered
1961–1971 Agent Orange was introduced
1972 DDT offi cially banned
2001 Stockholm Convention
Effects of Pesticides on Environment
256
decrease in the development of new pesticides as the public attention was drawn to
the environmental hazards associated with indiscriminate pesticide use. In 1962, an
American scientist Rachel Carson highlighted in her book, Silent Spring, that spray-
ing DDT in the fi eld causes sudden death of non-target organisms (Jabbar and
Mallick 1994 ; Delaplane 2000 ) either by direct or indirect toxicity.
Silent Spring resulted in silence in the fi eld of research on pesticide discovery
and development. However, in the late 1960s, it opened a new arena in which “inte-
grated pest management” (IPM) was introduced. IPM is a method in which biologi-
cal predators or parasites are used for controlling the pests. Although the pest
population can be reduced to signifi cantly low levels, especially in pest outbreak
situations, but unfortunately IPM was not a substitute for chemical pesticides
(Delaplane 2000 ). In 1970–1980s, pyrethroids, sulfonylureas, synthetic fungicides
triadimefron and metaxyl were introduced (History of pesticide use 1998 ). In 1972,
DDT was completely banned in the USA followed by the placement of restriction
on the use of Endosulfan, Dieldrin and Lindane. The list of banned pesticides has
increased ever since. In 2001, 179 nations signed an international treaty known as
Stockholm Convention that was intended to completely ban twelve Persistent
Organic Pollutants (POP’s) including DDT. Later in 2013, the European Union
(EU) supported to banning the use of neonicotinoid pesticides (Jacobs n.d. ).
It has been observed that the overuse of pesticides on aquatic ecosystems has led
to a serious threat to species of fi sh including salmon. Pesticides are also seen to
affect primary producers and macro-invertebrates (Macneale et al. 2010 ). In
Pakistan, before 1980, Plant Protection Department of Government of Pakistan was
responsible for the import and distribution of pesticides. Pesticide purchase was on
pre-payment basis and there was also subsidy on it. However, in 1980, this respon-
sibility was passed on to the private sector. Since that time, there has been a steady
increase in pesticide import and consumption in Pakistan. Registration of a pesti-
cide is renewed sporadically, which ensures the safety of used pesticides (Jabbar
and Mallick 1994 ).
Currently, preference is given to biological control of pests. This is a bioeffector-
method of controlling pests using biocontrolling agents including other living
organisms. These biocontrolling agents are also known as bio-rational pesticides.
An example of bio-rational pesticide is Insect growth regulators (IGRs) which are
the hormones that regulate insect growth without affecting non-target organisms
(Delaplane 2000 ).
3 Pesticide Registration and Safety
Registration of a pesticide is a complex, legal and administrative process that takes
a considerable amount of time and resources and requires expertise and skills of
registration authority as well as pesticide manufacturers. In this process, potential
effects associated with the use of pesticide on human health and the environment are
assessed (Monaco et al.
2002 ) in order to ensure the safety of active as well as inert
ingredients used in the manufacturing of pesticide.
I. Mahmood et al.
257
Registration is an important aspect of pesticide management that ensures that the
pesticide product released in the market is authorised and is used only for the
intended purpose. It also enables authorities to implement control over quality,
price, packaging, labelling, safety as well as advertisement of pesticides to ascertain
protection of users’ interests (WHO 2010 ). In the registration process, registrant or
the manufacture is required to conduct research and analyse different tests related to
product chemistry before submitting the application or data report. These tests
gauge the potential pesticide risks on humans, animals and non-target species as
well as the fate of the pesticide once it is released in the environment (FAO 2002 ;
WHO 2010 ). Registration process of pesticides is explained in Fig. 1 .
Data report or application of registration include several aspects related to pesti-
cide such as physical and chemical properties of active ingredient as well as formu-
lated product, analytical methods, proposed environmental toxicity and human
health hazards, recommended uses and labels, safety data, effectiveness for the
intended use, container management, and disposal of waste products. Application is
reviewed and analysed by the scientist in registration authority and after environ-
mental, human and biodiversity risks assessment, the authority approves the pesti-
cide as safe to be use or rejects it if it does not meet the standards as set by the
regulatory and registration authorities. Furthermore, the registration authority
ensures that each registered pesticide continues to meet the highest safety standards.
Hence, previously registered pesticides are being reviewed to ensure that they meet
Research by manufacturer before registration decision
Submission of data report to registration authority by
manufacturer
Review of the data report by registration authority
Final decision by the registration authority either to
accept or reject registration
Fig. 1 Pesticide
registration process
Effects of Pesticides on Environment
258
current scientifi c, safety and regulatory standards. This process is called re-
registration (Damalas and Eleftherohorinos
2011 ).
4 Classifi cation of Pesticides
Pesticides are known to be one of the extremely useful and benefi cial agents for
preventing losses of crops as well as diseases in humans. Based on the action,
pesticides can be classifi ed as destroying, repelling and mitigating agents. Insects
and pests are getting immune to the commercial pesticides due to over usage.
Recently pesticides have been developed which target multiple species (Speck-
Planche et al. 2012 ). Nowadays, chemical pesticides and insecticides are becom-
ing a dominant agent for eliminating pests. When these chemical pesticides are
used in a combination of effective natural enemy than that result in enhanced inte-
grated pest management and act as a comprehensive prophylactic and remedial
treatment (Gentz et al. 2010 ).
On the level of population, the effects of pesticides depend on exposure and
toxicity, as well as on different factors like life history, characteristics, timing of
application, population structure and landscape structure (Schmolke et al. 2010 ).
Nerve targets of insects which are known for development of neuroactive insecticides
include acetylcholinesterase for organophosphates and methylcarbamates, nicotinic
acetylcholine receptors for neonicotinoids, gamma-aminobutyric acid receptor
channel for polychlorocyclohexanes and fi proles and voltage gated sodium chan-
nels for pyrethroids and dichlorodiphenyltrichloroethane (Casida and Durkin 2013 ).
It is an observation that the use of neonicotinoid pesticides is increasing. These
pesticides are associated with different types of toxicities (Van Djik 2010 ).
Worldwide pesticides are divided into different categories depending upon their
target. Some of these categories include herbicides, insecticides, fungicides, rodenti-
cides, molluscicides, nematicides and plant growth regulators. Non-regulated use of
pesticides has led the environment into disastrous consequences. Serious concerns
about human health and biodiversity are raising due to overuse of pesticides (Agrawal
et al. 2010 ). Pesticides are considered to be more water soluble, heat stable and polar
which makes it very diffi cult to reduce their lethal nature. Pesticides are not only
toxic to people related to agriculture, but they also cause toxicity in industries and
public health work places. Depending upon the target species, pesticides can cause
toxicities in natural fl ora, natural fauna and aquatic life (Rashid et al. 2010 ).
5 Merits of Pesticide Use
Pesticides provide primary as well as secondary benefi ts. The former ones are
obvious after direct usage of pesticides such as the killing of insects that feed on
crops. Later are the result of the primary benefi ts and they are for longer periods.
I. Mahmood et al.
259
Worldwide, 40 % of the agricultural produce is lost due to plant diseases, weeds
and pests collectively. If there would have been no pesticides, crop losses would
have been many folds greater. Moreover, these crop saving substances not only
protect the crops from damage rendered by pests, but they also increase the yields
of crops considerably (Benefi ts of Pesticides and Crop Protection Chemicals n.d. ).
In their study, Webster et al. ( 1999 ) indicated that there is a signifi cant increase in
crop production due to pesticide usage and stated that economic losses without
pesticide use would be much more signifi cant. According to an estimate, yield of
bread grains has increased about 10–20 % due to herbicide usage and insect pol-
linators are responsible for the production of 70 % of the food (What are the ben-
efi ts n.d. ).
As discussed above, crop production would decline if crops are not protected by
the disastrous effects of pests. Decline in food production would create food short-
age that would ultimately result in increased prices of food commodities (Benefi ts
of Pesticides and Crop Protection Chemicals n.d. ). Therefore, pesticides indirectly
play a role in keeping the food prices under control.
Many agricultural commodities are vulnerable to attack by afl atoxins and
insect control is necessary to prevent the passage of these toxins from insect to
plant. Afl atoxin is a carcinogen that can cause liver and other type of cancer in
humans, lowers the body’s natural immune response, and can impair growth and
development in children. Crop protection chemicals are used to control insect
mediated afl atoxin contamination (Benefi ts of Pesticides and Crop Protection
Chemicals n.d. ).
Pesticides also prevent disease outbreaks through the control of rodent and insect
vectors hence they contribute to improved human health. Deaths of about seven mil-
lion people all around the world have been prevented through insecticide mediated
killing of disease vectors. The most signifi cant example is of malaria control that
was responsible for an average of 5000 deaths per day (Ross 2005 ). Many tick,
rodent and insect-borne diseases such as encephalitis, yellow fever, bubonic plague,
typhoid fever, typhus, Rocky Mountain spotted fever have been kept in control by
the effective use of pesticides (Benefi ts of Pesticides and Crop Protection Chemicals
n.d. ; Cunningham n.d. ).
Protection of farm and agricultural lands means protection of all forms of life.
Pesticides protect forests and other wildlife habitats from invasive species of
plants and non-native insects and other pests. Improved agricultural yields help
the farmers to produce more food without expanding their agricultural land which
consequently protects biodiversity (Benefi ts of Pesticides and Crop Protection
Chemicals n.d. ).
Insecticides also improve home sanitary conditions by keeping the population of
bugs in control (Delaplane 2000 ). Moreover, pesticides also preserve the beauty of
recreational spots by controlling weeds and also prevent structural damage associ-
ated with termite infestations (Benefi ts of Pesticides and Crop Protection Chemicals
n.d. ). Moreover, herbicides and insecticides are used to preserve the turf on grounds,
pitches and golf course (Aktar et al.
2009 ).
Effects of Pesticides on Environment
260
6 Risks Associated with Pesticide Use
Risks associated with pesticide use have surpassed their benefi cial effects. Pesticides
have drastic effects on non-target species and affect animal and plant biodiversity,
aquatic as well as terrestrial food webs and ecosystems. According to Majewski and
Capel ( 1995 ), about 80–90 % of the applied pesticides can volatilize within a few
days of application (Majewski and Capel 1995 ). It is quite common and likely to
take place while using sprayers. The volatilized pesticides evaporate into the air and
subsequently may cause harm to non-target organism. A very good example of this
is the use of herbicides, which volatilise off the treated plants and the vapours are
suffi cient to cause severe damage to other plants (Straathoff 1986 ). Uncontrolled
use of pesticides has resulted in reduction of several terrestrial and aquatic animal
and plant species. They have also threatened the survival of some rare species such
as the bald eagle, peregrine falcon and osprey (Helfrich et al. 2009 ). Additionally,
air, water and soil bodies have also being contaminated with these chemicals to
toxic levels.
Among all the categories of pesticides, insecticides are considered to be most
toxic whereas fungicides and herbicides are second and third on the toxicity list.
Pesticides enter the natural ecosystems by two different means depending upon
their solubility. Water soluble pesticides get dissolve in water and enter ground
water, streams, rivers and lakes hence causing harm to untargeted species. On the
other hand, fat soluble pesticides enter the bodies of animals by a process known as
“bioamplifi cation” as shown in Fig. 2 . They get absorbed in the fatty tissues of ani-
mals hence resulting in persistence of pesticide in food chains for extended periods
of time (Warsi n.d. ).
The process of bioamplifi cation can be described as follows:
Legend
P
Owl
Shrews
Grasshoppers
Pesticide Conc.
12P
4P 4P
4P
P
P
P
P
P
P
P
P
P
P
P
P
Fig. 2 Bioamplifi cation of
pesticide in the
environment
I. Mahmood et al.
261
1. Small concentration of pesticide enters the bodies of animal that are in low level
in the food chain such as grasshopper (primary consumer).
2. Shrews (secondary consumer) eat many grasshoppers and therefore the concen-
tration of pesticide will increase in their bodies.
3. When the high level predator such as owl eats shrews and other prey, the pesti-
cide concentration eventually increases many folds in its body.
Therefore, the higher the trophic level, the greater will be the pesticide concentra-
tion which is known as bioamplifi cation. This process disrupts the whole ecosystem
as more species in higher trophic levels will die due to greater toxicity in their bod-
ies. This will eventually increase the population of secondary consumers (shrews)
and decrease the population of primary consumers (grasshoppers) (Warsi n.d. ).
6.1 Threats to Biodiversity
The threats associated with the use of uncontrolled use of these toxins cannot be
overlooked. It is the need of the hour to consider the pesticide impact on populations
of aquatic and terrestrial plants, animals and birds. Accumulation of pesticides in
the food chains is of greatest concern as it directly affects the predators and raptors.
But, indirectly, pesticides can also reduce the quantity of weeds, shrubs and insects
on which higher orders feed. Spraying of insecticides, herbicides and fungicide
have also been linked to declines in the population of rare species of animals and
birds. Additionally, their long term and frequent usage lead to bioaccumulation as
discussed above (Pesticides reduce biodiversity 2010 ).
6.1.1 Threats to Aquatic Biodiversity
Pesticides enter the water via drift, by runoff, leaching through the soil or they may
be applied directly into surface water in some cases such as for mosquitoes’ control.
Pesticide-contaminated water poses a great threat to aquatic form of life. It can affect
aquatic plants, decrease dissolved oxygen in the water and can cause physiological
and behavioural changes in fi sh populations. In several studies, lawn care pesticides
have been found in surface waters and water bodies such as ponds, streams and lakes
(How Pesticides Affect the Environment n.d. ). Pesticides which are applied to land
drift to aquatic ecosystems and there they are toxic to fi shes and non-target organ-
isms. These pesticides are not only toxic themselves but also interact with stressors
which include harmful algal blooms. With the overuse of pesticides, a decline in
populations of different fi sh species is observed (Scholz et al. 2012 ).
Aquatic animals are exposed to pesticides in three ways (Helfrich et al. 2009 ).
Dermally : Direct absorption via skin
Breathing : Uptake via gills during breathing
Orally : Entry via drinking contaminated water
Effects of Pesticides on Environment
262
About 80 % of the dissolved oxygen is provided by the aquatic plants and it is
necessary for the sustenance of aquatic life. Killing of aquatic plants by the herbi-
cides results in drastically low O
2 levels and ultimately leads to suffocation of fi sh
and reduced fi sh productivity (Helfrich et al. 2009 ). Generally, levels of pesticides
are much higher in surface waters than groundwater probably because of surface
runoff from farmland and contamination by spray drift (Anon 1993 ). However, pes-
ticides reach underground through seepage of contaminated surface water, improper
disposal and accidental spills and leakages (Pesticides in Groundwater 2014 ).
Aquatic ecosystems are experiencing considerable damage due to drifting of
pesticides into the lakes, ponds and rivers. Atrazine is toxic to some fi sh species and
it also indirectly affects the immune system of some amphibians (Forson and Storfer
2006 ; Rohr et al. 2008 ). Amphibians are chiefl y affected by pesticides contaminated
surface waters, in addition to overexploitation and habitat loss (The Asian Amphibian
Crisis 2009 ). Carbaryl has been found toxic for several amphibian species, whereas,
herbicide glyphosate is known to cause high mortality of tadpoles and juvenile frogs
(Relyea 2005 ). Small concentrations of malathion have been shown to change the
abundance and composition of plankton and periphyton population that conse-
quently affected the growth of frog tadpoles (Relyea and Hoverman 2008 ).
Moreover, chlorpyrifos and endosulfan also cause serious damage to amphibians
(Sparling and Feller 2009 ). Dr. Hayes discovered that 10 % of male frogs raised in
atrazine-contaminated water developed into females. Male frogs that were geneti-
cally males phenotypically developed ovaries within their testes. They also devel-
oped the tendency to mate with other males and lay sustainable eggs (Environmental
Impacts n.d. ). The reproductive potential of aquatic life forms also reduces due to
herbicide spraying near weedy fi sh nurseries which eventually reduces the amount
of shelter that is required by young fi sh to hide from predators (Helfrich et al. 2009 ).
6.1.2 Threats to Terrestrial Biodiversity
Pesticide exposure can also cause sub-lethal effects on terrestrial plants in addition
to killing non-target plants. Drifting or volatilization of phenoxy herbicides can
injure nearby trees and shrubs (Dreistadt et al. 1994 ). Herbicide glyphosate increases
susceptibility of plants to diseases (Brammall and Higgins 1988 ) and reduces seed
quality (Locke et al. 1995 ). Even low doses of herbicides, sulfonylureas, sulphon-
amides and imidazolinones have a devastating impact on the productivity of non-
target crops, natural plant communities and wildlife (Fletcher et al. 1993 ).
Pesticides have not even spared the terrestrial animal populations. Populations of
benefi cial insects such as bees and beetles can signifi cantly decline by the use of
broad-spectrum insecticides such as carbamates, organophosphates and pyrethroids.
Insect population has also been found to be greater on organic farms compared to
non-organic ones. Synergistic effects of pyrethroids and triazole or imidazole
fungicides are harmful to honey bees (Pilling and Jepson 2006 ). Neonicotinoids
insecticides such as clothianidin and imidacloprid are toxic to bees. Imidacloprid
even at low doses negatively affects bee foraging behaviour (Yang et al.
2008 ) in
addition to reducing learning capacity (Decourtye et al. 2003 ). The greatest havoc
I. Mahmood et al.
263
wreaked by neonicotinoids was the sudden disappearing of honey bees at the very
start of the twenty-fi rst century. This was a major concern to the food industry as 1/3
of the food production depends on pollination by bees. Honey and wax obtained
from commercial hives were reported to contain a mixture of pesticides of which
neonicotinoids shared a signifi cant portion. Since 2006, each year, honey bee popu-
lations have dropped by 29–36 % (Environmental Impacts n.d. ).
Since pre-agricultural times, 20–25 % of the bird populations have declined. One
of the major causes of this massive decline is the use of pesticides which was not
known before 1962. Pesticide accumulation in the tissues of bird species leads to
their death. Bald eagle populations in the USA declined primarily because of expo-
sure to DDT and its metabolites (Liroff 2000 ). Fungicides can indirectly reduce
birds and mammal populations by killing earthworms on which they feed. Granular
forms of pesticides are disguised as food grains by birds. Organophosphate insecti-
cides are highly toxic to birds and they are known to have poisoned raptors in the
elds. Sublethal quantities of pesticides can affect the nervous system, causing
behavioural changes (Pesticides reduce biodiversity 2010 ).
Pesticides can be applied as liquid sprays on the soil or crop plant, may be incor-
porated or injected into the soil or applied as granules or as a seed treatment. Once
they have reached their target area, pesticides disappear via degradation, dispersion,
volatilisation or leaching into surface water and groundwater; they may be taken up by
plants or soil organisms or they may stay in the soil (Hayo and Werf 1996 ). The major
concern of pesticide overuse is their leaching into the soil, which affects the microbes
residing in it. Soil dwelling microbes help the plants in many different ways, such as
nutrient uptake; breakdown of organic matter and increasing soil fertility. But indi-
rectly they are also advantageous to humans as we heavily depend on plants.
Unfortunately, pesticide overuse may have drastic consequences and a time may come
when we would not have any more of these organisms and soil may degrade.
Several soil microbes are involved in the fi xation of atmospheric nitrogen to
nitrates. Chlorothalonil and dinitrophenyl fungicides have been shown to disrupt
nitrifi cation and de-nitrifi cation bacteria dependent processes (Lang and Cai 2009 ).
The herbicide, triclopyr inhibits soil bacteria involved in the transformation of
ammonia into nitrite (Pell et al. 1998 ). Glyphosate, a non-selective herbicide,
reduces the growth and activity of nitrogen-fi xing bacteria in soil (Santos and Flores
1995 ) whereas, 2,4-D inhibits the transformation of ammonia into nitrates carried
out by the soil bacteria (Frankenberger et al. 1991 ).
Herbicides also cause considerable damage to fungal species in soil as pesti-
cides trifl uralin and oryzalin both are known to inhibit the growth of symbiotic
mycorrhizal fungi (Kelley and South 1978 ) that help in nutrient uptake.
Oxadiazon has been known to reduce the number of fungal spores (Moorman
1989 ) whereas triclopyr is toxic to certain species of mycorrhizal fungi
(Chakravarty and Sidhu 1987 ).
Earthworms play a signifi cant role in the soil ecosystem by acting as bio-
indicators of soil contamination and as models for soil toxicity testing. Earthworms
also contribute to soil fertility. Pesticides have not spared earthworms from their
toxic effects and the later is exposed to the former mainly via contaminated soil pore
water. Schreck et al. (
2008 ) reported that insecticides and/or fungicides produce
Effects of Pesticides on Environment
264
neurotoxic effects in earthworms and after a long term exposure they are physiolog-
ically damaged (Schreck et al. 2008 ). Glyphosate and chlorpyrifos have deleterious
effects on earthworms at the cellular level causing DNA damage. Glyphosates affect
feeding activity and viability of earthworms (Casabé et al. 2007 ). Goulson reviewed
the harms of neonicotinoids on environment and animal life. He reported that as
neonicotinoids have a tendency to accumulate in the soil, therefore, they can kill
earthworms such as Eisenia foetida species (Goulson 2013 ).
7 Pesticide Impact on Human Health
Pesticides have improved the standard of human health by controlling vector-borne
diseases, however, their long term and indiscriminate use has resulted in serious
health effects. Human beings especially infants and children are highly vulnerable to
deleterious effects of pesticides due to the non-specifi c nature and inadequate appli-
cation of pesticides. As the pesticide use has increased over the past few decades, the
likelihood of exposure to these chemicals has also increased considerably.
According to World Health Organization, each year, about 3,000,000 cases of pes-
ticide poisoning and 220, 000 deaths are reported in developing countries (Lah 2011 ).
About 2.2 million people, mainly belonging to developing countries are at increased
risk of exposure to pesticides (Hicks 2013 ). Besides, some people are more suscepti-
ble to the toxic effects of pesticide than others, such as infants, young children, agri-
cultural farm workers and pesticide applicators (Pesticides and Human Health n.d. ).
Pesticides enter the human body through ingestion, inhalation or penetration
via skin (Spear 1991 ). But the majority of people get affected via the intake of
pesticide contaminated food. After crossing several barriers, they ultimately
reach human tissues or storage compartments (Hayo and Werf 1996 ). Although
human bodies have mechanisms for the excretion of toxins, however, in some
cases, it retains them through absorption in the circulatory system (Jabbar and
Mallick 1994 ). Toxic effects are produced when the concentration of pesticide in
the body increases far more than its initial concentration in the environment
(Hayo and Werf 1996 ).
The effects of pesticides on human health are highly variable. They may appear
in days and are immediate in nature or they may take months or years to manifest
and hence are called chronic or long-term effects. Acute and chronic effects of pes-
ticide exposure on human health are discussed below.
7.1 Acute Effects of Pesticides
Immediate effects of pesticide exposure include headache, stinging of the eyes and
skin, irritation of the nose and throat, skin itching, appearance of the rash and blisters
on the skin, dizziness, diarrhoea, abdominal pain, nausea and vomiting, blurred
I. Mahmood et al.
265
vision, blindness and very rarely death. Acute effects of pesticide exposure are not
severe enough for someone to seek medical help (Pesticides and Human Health n.d. ).
7.2 Chronic Effects of Pesticides
Chronic effects of pesticides are often lethal and may not appear even for years.
These are long term effects that cause damage to multiple body organs. Pesticide
exposure for prolonged periods of time results in following consequences:
Pesticide exposure can cause a range of neurological health effects such as loss
of coordination and memory, reduced visual ability and reduced motor signalling
(Lah 2011 ).
Long-term pesticide exposure damages the immune system (Culliney et al. 1992 )
and can cause hypersensitivity, asthma and allergies.
Pesticide residues have been found in the bloodstream of cancer patients com-
pared to normal individuals. Pesticides have been associated with leukaemia,
brain cancer, lymphoma, cancer of the breast, prostate, ovaries, and testes
(Pesticides and Human Health n.d. ).
The presence of pesticides in the body for a longer time also affects reproductive
capabilities by altering the levels of male and female reproductive hormones.
Consequently, it results in stillbirth, birth defects, spontaneous abortion and
infertility (Pesticides and Human Health n.d. ).
Lon-term exposure to pesticide also damages liver, lungs, kidneys and may cause
blood diseases.
Ingestion of organochlorines causes hypersensitivity to light, sound, and touch,
dizziness, tremors, seizures, vomiting, nausea, confusion and nervousness (Lah 2011 ).
Exposure to organophosphates and carbamates causes, symptoms similar to those of
increased neurotransmitter-acetylcholine. These pesticides interfere with the normal
nerve signal transduction and exposure to them causes headaches, dizziness, confu-
sion, nausea and vomiting, muscle and chest pain. Diffi culty breathing, convulsions,
coma and death may occur in severe cases (Pesticides and Human Health n.d. )
Pyrethroids can cause an allergic skin response, aggressiveness, hyper- excitation,
reproductive or developmental effects in addition to causing tremors and seizures
(Lah 2011 ). It is observed that there is a relationship between pesticides and
Parkinson’s disease and Alzheimer’s disease (Casida and Durkin 2013 ).
8 Conclusion and Future Prospects
Pesticides have proved to be a boon for the farmers as well as people all around the
world by increasing agricultural yield and by providing innumerable benefi ts to
society indirectly. But the issue of hazards posed by pesticides to human health and
the environment has raised concerns about the safety of pesticides. Although we
Effects of Pesticides on Environment
266
cannot completely eliminate the hazards associated with pesticide use, but we can
circumvent them in one way or the other. Exposure to pesticides and hence the
harmful consequences and undesirable effects of this exposure can be minimised by
several means such as alternative cropping methods or by using well-maintained
spraying equipments. Production of better, safe and environment friendly pesticide
formulations could reduce the harmful effects associated with the pesticide usage.
If the pesticides are used in appropriate quantities and used only when required or
necessary, then pesticide risks can be minimised. Similarly, if a less toxic formula-
tion or low dose of a toxic formulation is used, the havoc can be curbed. As
Paracelsus also once said “ The right dose differentiates a poison from a remedy ”.
There are organochlorines, which are used as pesticides. These pesticides are
least biodegradable and their use is banned in many countries. Besides this fact,
organochlorines are highly used in many places. This results in serious health haz-
ards. Water pollution is on the rise due to these pesticides, even at low concentra-
tion, these pesticides have serious threat to the environment (Agrawal et al. 2010 ).
The majority of farmers are unaware of the potential toxicities of pesticides. They
have no information about types of pesticides, their level of poisoning, hazards and
safety measures to be taken before use of those pesticides. Due to this reason, toxic
and environmentally persistent chemicals are used to kill pests which can also lead
to intentional, incidental or occupational exposure. These compounds have long
term effects on human health. Awareness should be arranged for these farmers to
reduce the uses of toxic pesticides (Sharma et al. 2012 ).
In future chemical pesticides can be used in combination with natural treatments
and remedies which result in more sustainable elimination of pests and insects. This
combination not only promises environmental sustainability, but also has diverse
applications in controlling of urban pests and invasive species (Gentz et al. 2010 ).
Pesticides have also posed a serious threat on biological integrity of marine and
aquatic ecosystems. It is the need of time to integrate the studies of different disci-
plines including toxicology, environmental chemistry, population biology, commu-
nity ecology, conservation biology and landscape ecology to understand direct and
indirect effects of pesticides on the environment (Macneale et al. 2010 ) .
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The pesticides belong to a category of chemicals used worldwide as herbicides, insecticides, fungicides, ro-denticides, molluscicides, nematicides, and plant growth regulators in order to control weeds, pests and dis-eases in crops as well as for health care of humans and animals. The positive aspect of application of pesti-cides renders enhanced crop/food productivity and drastic reduction of vector-borne diseases. However, their unregulated and indiscriminate applications have raised serious concerns about the entire environment in general and the health of humans, birds and animals in particular. Despite ban on application of some of the environmentally persistent and least biodegradable pesticides (like organochlorines) in many countries, their use is ever on rise. Pesticides cause serious health hazards to living systems because of their rapid fat solu-bility and bioaccumulation in non-target organisms. Even at low concentration, pesticides may exert several adverse effects, which could be monitored at biochemical, molecular or behavioral levels. The factors af-fecting water pollution with pesticides and their residues include drainage, rainfall, microbial activity, soil temperature, treatment surface, application rate as well as the solubility, mobility and half life of pesticides. In India organochlorine insecticides such as DDT and HCH constitute more than 70% of the pesticides used at present. Reports from Delhi, Bhopal and other cities and some rural areas have indicated presence of sig-nificant level of pesticides in fresh water systems as well as bottled drinking mineral water samples. The ef-fects of pesticides pollution in riverine systems and drinking water in India has been discussed in this review.
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Majority of the farmers are unaware of pesticide types, level of poisoning, safety precautions and potential hazards on health and environment. According to the latest estimate, the annual import of pesticides in Nepal is about 211t a.i. with 29.19% insecticides, 61.38% fungicides, 7.43% herbicides and 2% others. The gross sale value accounts US $ 3.05 million per year. Average pesticides use in Nepal is 142 g a.i./ha, which is very low as compared to other Asian counties. The focus of this paper is to analyze the use and application status of pesticides in Nepal to aware the society about adverse effects of chemical pesticides in the environment . Pesticidal misuse is being a serious concern mainly in the commercial pocket areas of agricultural production, where farmers are suffering from environmental pollution. Incidence of poisoning is also increasing because of intentional, incidental and occupational exposure. Toxic and environmentally persistent chemicals are being used as pesticides. Many studies showed that the chemical pollution of the environment has long-term effects on human life. It is therefore essential that manufacture, use, storage, transport and disposal of chemical pesticides be strictly regulated. The Journal of Agriculture and Environment Vol:13, Jun.2012, Page 67-72 DOI: http://dx.doi.org/10.3126/aej.v13i0.7590
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Colonization of root tissues in tomato seedlings genetically resistant to Fusarium oxysporum f.sp. radicis-lycopersici Jarvis & Shoemaker occurred following exposure to a sublethal concentration of the herbicide glyphosate (1.0 mM for 24 h prior to inoculation). The glyphosate-induced colonization was associated with an inefficiency in incorporation of phenolic materials into the papillae and into the modified cortical cell walls normally formed in response to this pathogen. Glyphosate-induced susceptibility decreased when the glyphosate was applied at 24 or 48 h after inoculation. Plants supplied with exogenous L-phenylalanine failed to exhibit reduced susceptibility after glyphosate exposure. In radial growth bioassays, growth of the fungus was unaffected by 4.0 mM glyphosate. α-Aminooxyacetic acid, an inhibitor of phenylalanine ammonia lyase, also increased the severity of the disease in resistant plants. Glyphosate also induced susceptibility to an isolate of F. solani f.sp. pisi, which was normally n...
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Bacteria, fungi, and algae differ in their responses to pesticides; responses are often related to the biochemical mechanisms of action of the pesticide and pesticide concentrations in the soil. Total microbial populations in soils are often unaffected or only slightly affected by pesticide applications, but populations and activities of individual species or groups (e.g. cellulose decomposers) of microorganisms may be greatly affected. Pesticide concentrations greater than those resulting from field applications can cause interruption of microbial activities and shifts in populations. Most pesticides used at field rates do not appear to cause significant lasting effects on the microbial activities most related to soil fertility. Methods for interpreting the responses of microorganisms treated with pesticides are discussed. In general, the changes in microbial populations due to pesticide applications are no more severe than changes caused by natural environmental stresses. The effects of pesticides on crop residue decomposition, nutrient cycling, and root symbi-onts are reviewed with respect to production practices. Please view the pdf by using the Full Text (PDF) link under 'View' to the left. Copyright © 1989. . Copyright © 1989 by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, 5585 Guilford Rd., Madison, WI 53711 USA
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Neonicotinoids are now the most widely used insecticides in the world. They act systemically, travelling through plant tissues and protecting all parts of the crop, and are widely applied as seed dressings. As neurotoxins with high toxicity to most arthropods, they provide effective pest control and have numerous uses in arable farming and horticulture.However, the prophylactic use of broad-spectrum pesticides goes against the long-established principles of integrated pest management (IPM), leading to environmental concerns.It has recently emerged that neonicotinoids can persist and accumulate in soils. They are water soluble and prone to leaching into waterways. Being systemic, they are found in nectar and pollen of treated crops. Reported levels in soils, waterways, field margin plants and floral resources overlap substantially with concentrations that are sufficient to control pests in crops, and commonly exceed the LC50 (the concentration which kills 50% of individuals) for beneficial organisms. Concentrations in nectar and pollen in crops are sufficient to impact substantially on colony reproduction in bumblebees.Although vertebrates are less susceptible than arthropods, consumption of small numbers of dressed seeds offers a route to direct mortality in birds and mammals.Synthesis and applications. Major knowledge gaps remain, but current use of neonicotinoids is likely to be impacting on a broad range of non-target taxa including pollinators and soil and aquatic invertebrates and hence threatens a range of ecosystem services.
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Pesticides represent extremely useful chemical and biochemical agents for the prevention of crop losses and disease in humans. They act by destroying, repelling or mitigating pests. Insects constitute one of the pests which are very difficult to control. With the pass of the time, insects have become resistant to pesticides because the current insecticides are designed to act through one mechanism of action. For this reason, there is an increasing need for the design of more potent and versatile insecticides. The present study is focused on the development of a fragment-based approach for the in silico discovery of multi-target insecticides from a heterogeneous database of compounds. The present methodology was based on a QSAR discriminant model which classified correctly more than 90% of insecticides and inactive compounds in both, training and prediction series. Also, it permitted the automatic and efficient extraction of fragments responsible of insecticidal activity against several mechanisms of action and new molecular entities were suggested as possible multi-target insecticides.