In India pesticides are mainly used in agriculture and public health sector
(Gupta, 2004). In Asia India is the second largest manufacturer of pesticides and ranks twelfth in world. Worldwide pesticides consumption is about 2 million tonnes per year, in that about 24% is consumed in the USA, 45% in Europe and 25% in the rest of the world. India’s share is only 3.75%
(Gupta, 2004). Total pesticide consumption in India is about 62,193 MT in (2020)
(DPPQS, 2021). In India 1999-2000 out of the total consumption of pesticides 60% are in the form of insecticides, 14% are herbicides, 21% is fungicide and less than 5% are others
(Agnihotri, 2000). Pesticide exposure to the human body happens through ingestion, inhalation, skin contact and skin absorptions which results in acute and chronic health problems
(Damalas and Koutroubas, 2016). About 64% of global agricultural land (approximately 24.5 million km
2) is at risk of pesticide pollution by more than one active ingredient, in that 31% is at high risk
(Tang, 2021). In India, National Occupational Health Centre (NIOH) and Indian Council of Agricultural Research Institute (ICAR) are responsible for monitoring of health status and pesticide-residues in various samples. Roughly 5 billion kilograms of pesticides are applied worldwide per year, which has serious effects on biodiversity, nontarget organisms, and the food chain, risks to the environment and human health
(Verger and Boobis, 2013). According to WHO estimates about 3 million cases of acute poisoning occur each year due to the unsafe handling and use of pesticides with 220,000 deaths
(WHO, 1990; Blair et al., 2015) 70% of these deaths are mainly due to occupational exposure
(Yerena et al., 2005). The term
“occupational exposure” refers to a potentially harmful exposure to hazards chemicals in the occupation place
(Doxtader, 1992). Occupational exposure to pesticides occurs in agricultural workers in open fields and greenhouses, workers in the pesticide industry and eradicator of house pests. Non-occupational exposure to pesticides happens through eating food and drinking water contaminated with pesticide residue. Environment exposure is
via water, soil and air contamination from leaching, runoff and spray drift, which has harmful effects on wildlife, fish, plants and other non-target organisms
(Damalas and Eleftherohorinos, 2011).
Environmental exposure
The intensive use of pesticide leads to an enlarged risk of contamination of the environment and harmful effects on biodiversity, food security and water resources
(Malaj et al. 2014; Queyrel et al., 2016). It is estimated that less than 0.1% of pesticide applied to crops truly reaches the target, the rest of it enters into the environment
(Pimentel and Levitan, 1986). Attention to the impacts of pesticide use on the environment and ecosystems is due to the book
Silent Spring written by Rachel Carson published in 1962. Several pesticides can persist in an ecosystem for longer periods. for example, organochlorine insecticides, for instance, are still detectable in surface waters 30 years after their use and had been banned
(Larson, 2019). In the food chain, pesticide meet with nontarget organisms and accumulate in the body tissues of organisms and cause more health problems
(Lancet, 1989). Pesticide fate in the environment occur in different environmental compartments, such as air
(Bedos et al., 2002), soil
(Barriuso et al. 2008), plant
(Fantke et al., 2011) and surface and groundwater
(Baran et al., 2008). Although pesticides are directly applied in soils and plants, only 1% of pesticide sprayed is delivered to the intended target. For proper management of pesticides, it is essential to accurately assess the status of their contamination in soil, water and air
(Knapton et al., 2006).
Pesticides and the atmosphere
Outside the food chain, the atmosphere is possibly the most important medium for long-distance dispersal of pesticides. Drift and evaporation during aerial application, volatilization from crops and agricultural soils, wind erosion of contaminated soils, and emissions from manufacturing and disposal processes repetitively add of pesticides level in the atmosphere. Prevailing air currents transport these pesticides and their alteration products to a great distance
(Durham, 1976; Wolfe, 1976).
Spray application
Massive amounts of pesticides are released into the atmosphere while spraying to crops. The amount of a pesticide that grasps a target depends on a number of factors like the amount of material sprayed, the physicochemical properties of the pesticide and dispersion vehicle, the particle size distribution, the height at which the material is released, wind speed and atmospheric turbulence
(Polyrakis, 2009). Spray droplets of less than 30-mm volume mean diameter drift great distances
(Yeo, 1959; Murray and Vaughan, 1970). According to
(Woodwell et al., 1971) during aerial application of DDT to forests, less than 50% reached the target area. More than 40% of the original aqueous spray volume from an air-blast sprayer has been lost by evaporation before the droplets had fallen 11 m
(Cunningham et al., 1962). According to
(Ware et al., 1970) less than 50% of aerially applied pesticides were deposited on agricultural targets in Arizona, during summer months. During spray application spray man, helper and bystander are exposed to pesticide due to drift. so they are advised to wear protection equipment.
Volatilization from crops and soils
Pesticides mainly enter into the atmosphere is through volatilization from treated agricultural soils and plant foliage. This process competes with direct input during spray application. over 90% of the pesticide contamination of the air is only by these two routes
(Lewis and Lee, 1976). Factors determining the volatilization process include physico chemicals properties of pesticides, environmental conditions, and agricultural practices. Pesticides sprayed on to fields and used to fumigate soil can give off chemicals called volatile organic compounds, which can react with other chemicals and form a pollutant called tropospheric ozone. Pesticide use accounts for about 6 per cent of total tropospheric ozone levels (UC IPM). Volatilization may leads to the inhalation exposure of toxic chemical which lead to many health problem.
Entrainment as dust
Later reports of pesticide residues in airborne matter collected in non-agricultural areas shows long-distance transport of pesticides in the atmosphere
(Tabor, 1965). Collected airborne dust on the coast of Barbados during 1965-1966 and found airborne dust contain 1-164 ng/g of chlorinated pesticides. The dust had originated in west coast of Africa, entrained in the atmosphere, and was transported about 4,500 km by the northeast trade winds
(Costa, 2008).
Manufacturing and formulating processes
Atmospheric pollution is mainly associated with the manufacture, formulation, and packaging of pesticides. Rarely, large amounts of pesticides are released into the atmosphere from chemical manufacturing processes due to accidents or carelessness. Table 1 summarizes some incident of pesticide poisoning occur during pesticide manufacturing.
Pesticides and soil
Generally, most of the pesticide comes into contact with soil, which is a major “incubation” chamber for the decomposition. Pesticides do not remain stationary in the soil, but they move within the soil. They move by both diffusion throughout the medium and mass flow of the water in the soil
(Polyrakis, 2009). Usually, nonpersistent pesticides disappear in less than 1 month from soil, while moderately persistent chemicals take from 1 to 3 months. Persistent pesticides are present for many months after application
(Doxtader, 1992). Applied pesticide can be completely degraded by chemical degradation, photodegradation, degradation by soil microorganisms, leaching, adsorption-desorption, uptake by higher organisms and aerial movement. Common landscape herbicides disrupt this process: triclopyr inhibits soil bacteria that transform ammonia into nitrite
(Pell et al., 1998), glyphosate reduces the growth and activity of free-living nitrogen-fixing bacteria in soil
(Santos and Flores, 1995) and 2,4-D reduces nitrogen fixation by the bacteria that live on the roots of bean plants
(Arias and de Peretti, 1993), reduces the growth and activity of nitrogen-fixing blue-green algae
(Singh and Singh, 1989) and inhibits the transformation of ammonia into nitrates by soil bacteria
(Frankenberger and Tabatabai, 1991). The growth of certain species of mycorrhizal fungi were inhibited by oryzalin and trifluralin.
(Kelley and South, 1978).
Pesticides and water
The main purposes of water used by human beings is for public water supply, aesthetics and recreation, agriculture, industry and aquatic life. The applied pesticides might reach surface and groundwater through runoff, run-in and leaching
(Bicki, 1989).
Pesticides and surface water
Pesticides can reach surface water through runoff from treated plants and soil
(Kole et al., 2001). Pesticides were detected in all samples from major rivers with mixed agricultural and urban land use influences and 99% of samples of urban streams
(Bortleson and Davis, 1987) The surface water pollution by pesticides consists of two main categories,
i.
e., intentional and unintentional. Intentional includes the direct application of pesticides to water to control harmful insects or waterweeds. Unintentional pollution of water occurs in some cases,
e.
g., during the spraying of crops near streams, lakes, dishes,
etc. Also, pesticides frequently volatilize into the air. They may then return to the ground through rainfall, Organophosphorus insecticides and carbamates, and generally the new generation of compounds will not create side effects like chlorinated hydrocarbons and degraded in a period of 2-4 days in lakes and marshes. Also, the pyrethrin deltamethrin has an active life of 1 h in water
(Polyrakis, 2009). Pesticide pollution that occurred in surface water are discussed in Table 2.
Pesticides and groundwater
Pesticides applied to a site moved downward along with rain or irrigation water, reaching the water table below is known non
-point source pollution. Pesticides may enter directly into ground from spillage or back-siphoning is called point source pollution. Pesticides continue to break down slower rate after reaching groundwater because of less available light, heat, and oxygen. When groundwater becomes contaminated, the polluted water may eventually appear in the surface water of streams, rivers, and lakes. Even if the contamination is stopped, it may take years before an aquifer can purify itself through natural processes
(Polyrakis, 2009).
In India, 58% of drinking water samples drawn from various hand pumps and wells around Bhopal were contaminated with organochlorine pesticides above the EPA standards
(Kole and Bagchi, 1995). Whether a pesticide to reach groundwater determine by three major factors. They are pesticide properties (persistence and adsorption), soil properties (permeability, organic matter, soil texture, structure, and moisture), and site conditions (including rainfall, irrigation, and depth to groundwater.
Pesticides and biodiversity
Biodiversity means variety of life (plants, animals, and microorganisms) exist in the surrounding environment also consider the number of species present, the amount of genetic variation within a species, and the habitats in which the species live
(Polyrakis, 2009). About 25-50% of aerially applied pesticides and 70-90% of ground-applied pesticides truly reaches the target area
(WWF, 1999). The remaining chemicals cause potential to impact nontarget organisms (vertebrates, invertebrates, microorganisms and plants) and widely spread in the environment. by numerous ways pesticides can “drift” from the site of application which include transport of airborne particles
via air currents, runoff from fields into surface waters, leaching through soils into groundwater, transport by ocean currents carrying the pesticides between continents,
etc.). Some chemicals to persist in the environment for a number of years which the potentially affect an immense variety of wildlife, from birds feeding on infested seeds to polar bears feeding on saltwater fish, hundreds of kilo meters away mode of action is the most significant parameter for the potential impact of pesticides on nontarget organisms. The drawback is that in some cases the mode of action is completely unknown.
Birds exposure
Pesticides can harm or kill birds when they hurt their food resources contaminated with pesticide. Some pesticide cause anorexia or loss of appetite in birds causing them to starve to death. this effect is documented in several large bird that kills during migration. The U.S. Fish and Wildlife Service estimates that 67 million birds die from pesticide poisoning each year and more than 600 million birds are exposed
(Pimentel et al., 1992). Once a bird is killed by a pesticide, bird of prey or a mammalian scavenger, feed on pesticide-poisoned prey which can then in turn be poisoned. Raptors such as red-tailed hawks and great horned owls frequently feed on pesticide-poisoned prey. Many experts believe birds are amongst the most vulnerable species when it comes to pesticide exposure and serve as sentinels of the quality of the environment
(Wildlife, 1947). According to
(Costa, 2008) resident birds in India had the highest residues of HCHs compare to the migratory birds of South India. Major Impact of pesticide on birds include eggshell thinning and decrease in egg production. Various other incidence of bird’s mortality due to pesticide exposure are summarized in Table 3.
Aquatic exposure
Primary route of pesticide exposure to fish and aquatic animals are dermally while swimming in pesticide-contaminated waters, breathing through gills, orally, by drinking pesticide-contaminated water or feeding on pesticide-contaminated prey. Secondary poisoning is by feeding on dying insects poisoned by insecticides may kill themselves if the insects they consume contain large quantities of pesticides or their toxic by-products
(Helfrich et al., 2009). Pesticide exposure to fish and other aquatic animals mainly depends on its bioavailability, bioconcentration, biomagnification and persistence of pesticide in the environment. Pesticides can decrease the availability of plants and insects that serve as habitat and food for fish and other aquatic animals. Sublethal doses of some pesticides can lead to changes in behaviour, inability to avoid predators, lowered tolerance to extreme temperatures, weight loss and impaired reproduction
(Helfrich et al., 2009).
Current studies of major rivers and streams documented that 96% of all fish, 100% of all surface water samples and 33% of major aquifers contained one or more pesticides at detectable levels. The pesticide used for lawn treatments are most commonly found. pesticides at low level concentrations are highly toxic to aquatic wildlife and which decreased their populations by nearly 70 per cent. OC insecticides and pyrethroids PYs, especially synthetic ones, is the toxic group of insecticides to fish and aquatic invertebrates. PYs are highly toxic to aquatic animals because they are strongly absorbed to bottom muds
(Anderson, 1989).
OP insecticides can bioconcentrate in tadpoles, frogs, fish, and toads to levels that stance hazards to their predators. OP and CB insecticides are water soluble and metabolized quickly. They generally have short persistence and so their residues do not long-term problems for aquatic animals. The CB insecticide is extremely toxic to wildlife and fish
(Helfrich et al., 2009). Fish kills occur when pesticides are improperly applied or mix in water bodies through drift or misapplication
(Sharma et al., 2012) accidental killing due to contamination in most common
(Modra and Svobodova, 2009). Herbicide had more impact on aquatic animals. Table 4 lists various effect of pesticide on aquatic animals that occur in different part of world.
Animals exposure
Poisoning is an important cause of wildlife mortality, and is responsible for extensive population declines
(Green et al., 2004) Primary exposure to poisons happens when wildlife is intentionally poisoned for hunting
(Ogada, 2014) nor due to human-wildlife conflict
(Venkataramanan et al., 2008). Accidental poisoning may occur by secondary exposure to poisons in the environment or via contaminated food source. Amphibians are now considered the most threatened and rapidly decreasing species on Earth
(Bruhl et al., 2013) suggested that frogs are sensitive to the toxicity of pesticides that are currently used in agriculture. OCPs are among the substances restricted or banned globally under the Stockholm Convention on Persistent Organic Pollutants
(Programme, 2001). These compounds are environmentally persistent
(Dimond and Owen, 1996), toxic and apt to bioaccumulation
(Nakata et al., 2002) and have adverse effects on animals
(Doxtader, 1992). Even though these substances are stored in the fat and muscles of the animals, some of them can also be found in the brain, lungs, liver and other offal. Because milk and other dairy products contain a range of fat, these foods also contain a number of pesticides. Table 5 summarize the various effect of pesticide exposure on animals.
Humane exposure
Human are directly exposed to pesticide by missing personal protective equipment (gloves, goggles, respirator, long pant, cap) and drift while spraying. Indirect exposure is by work in pesticide treated area, drift from neighbor field, contact with residue from crop field.
(Damalas and Koutroubas, 2016). Pesticide exposure causes acute health problems like
e.
g., dizziness, headaches, nausea and skin problems. Chronic health effects like
e.
g., asthma, allergies, hypersensitivity, cancers, hormone disruption, neurological disturbance and respiratory diseases. For women reproduction, fetal development, cause early menopause and development of the child in later life
(van der Maden et al., 2014). These substances are stored in the fat and muscles of the animals, some can also find in the brain, lungs, liver and other offal. Because milk and other dairy products contain a range of fat, these foods may also contain a number of pesticides. Different incidents that occur due to pesticide exposure on human are discussed in (Table 6). Intentional or unintentional exposure of pesticide to human may cause acute and chronic health problems. Organophosphate, organochloride, and carbamate insecticide plays major role in causing such disease (Table 7).