Worldwide pesticide usage and its impacts on ecosystem

Abstract

Pesticides are extensively used in modern agriculture and are an effective and economical way to enhance the yield quality and quantity, thus ensuring food security for the ever-growing population around the globe. Approximately, 2 million tonnes of pesticides are utilized annually worldwide, where China is the major contributing country, followed by the USA and Argentina, which is increasing rapidly. However, by the year 2020, the global pesticide usage has been estimated to increase up to 3.5 million tonnes. Although pesticides are beneficial for crop production point of view, extensive use of pesticides can possess serious consequences because of their bio-magnification and persistent nature. Diverse pesticides directly or indirectly polluted air, water, soil and overall ecosystem which cause serious health hazard for living being. In the present manuscript, an attempt has been made to critically review the global usage of different pesticides and their major adverse impacts on ecosystem, which will provide guidance for a wide range of researchers in this area.

Introduction

Pesticides are the chemicals (natural or synthetic) employed in various agricultural practices to control pests, weeds and diseases in plants. Pesticides include a wide range of herbicides, insecticides, fungicides, rodenticides, nematicides, etc. In the process of agricultural development, pesticides became a vital tool for plant protection and for enhancing crop yield. Approximately, 45% of the annual food production is lost due to pest infestation; therefore, effective pest management by using wide range of pesticides is required to confront pests and to increase the crop production [1]. However, in the last half of the nineteenth century, robust growth in the world economy including both industrial and agricultural sectors has led to the progressive mount in the generation and utilization of agriculture-based chemicals which often induce calamitous effects on the environment. Injudicious use of pesticides and other persistent organic pollutants in agricultural soils have devastated future repercussions. The persistent and ubiquitous nature of various agriculture-based pesticides and other organic pollutants has posed havoc to the mankind due to their bioaccumulation properties and high toxicity [2]. These pesticides are known to hinder the normal functioning of endocrine and reproductive systems in living organisms [3]. Certain pesticides like dichlorodiphenyltrichloroethane (DDT), chlordane, aldrin, dieldrin, endrin, mirex, heptachlor and hexachlorobenzene impart deleterious effects on human health and environment [4].

There may be other alternatives available to control crop loss due to pest attack which may include the application of various biopesticides. Developing some pest-resistant crop varieties using transgenic approaches is also one method to avoid pesticide use. But application of chemical pesticides is still preferred the most over all other alternatives to protect crops from yield loss. Presently, throughout the globe approximately 2 million tonnes of pesticides are utilized, out of which 47.5% are herbicides, 29.5% are insecticides, 17.5% are fungicides and 5.5% are other pesticides [5]. The top ten pesticide consuming countries in the world are China, the USA, Argentina, Thailand, Brazil, Italy, France, Canada, Japan and India [6]. Moreover, it has been estimated that by the year 2020, the global pesticide usage will increase up to 3.5 million tonnes [7].

Pesticides are applied to increase crop productivity; however, in due course of time, they get accumulated in plant parts, water, soil, air and biota. Extensive use of pesticides contaminates soil and water, remain in the crops and finally enter food chain, thereby posing threat to the human beings [8, 9]. The commercial use of pesticides in agriculture produces vapors of pesticides that have the ability to become air pollutant [10]. The release of pesticides into the air largely depends upon the physical and chemical properties of the active compound, application procedure and changing environment conditions [11, 12]. Further, the volatilization of water adds pesticides into the air. The pesticides get dispersed and transported from one site to other in the form of degraded products [13]. Pesticides used in agriculture are synthetic in origin and get absorbed in the soil through surface runoff from treated plants. The nature of organic compound, cropping practices, irrigation techniques and climatic factors influence the dissolution of pesticides in soil [14]. The residues of these organochlorine compounds further pollute the groundwater through leaching and in turn affect the quality of agricultural crops. Pesticides get accumulated in soils directly by its application in agriculture and domestic purposes or indirectly by deposition of airborne contaminants previously coming from different sites or areas. Soil serve as storage compartments due to high affinity of organic chemicals with soil [15]. The deposition of organic chemicals or pesticides in soil directly exposes soil organisms and also increases the risk for other higher organisms through diet and can severely affect soil ecosystem, water bodies, plants and human health [16,17,18,19]. Keeping in mind the extensive use of pesticides throughout the globe, the present review gives an overview about the application of pesticides in the world and their various impacts on the ecosystem.

Pesticides used worldwide

Pesticide usage in Africa

The economy of Africa is largely dependent on agriculture, and nearly 59% of the population makes their living from farming [20]. Despite that, the African continent has a contribution of 2–4% of global market share of pesticides which also accounts for the lowest rate of their usage in the world [20]. Due to increasing population, the food demand has been projected to enhance at a rapid rate in the next three decades and thus, demand of pesticides, herbicides and fungicides is also likely to enhance [21]. Table 1 summarizes the usage of pesticides in various African countries based on their area in the 2010 and 2014. The data show that the usage of pesticides declined in Congo and Mauritius, while in Sudan, Malawi, Togo and Rwanda, it increased in the years 2010–2014.

Table 1 Pesticide usage in African countries in the years 2010 and 2014, index on the basis of their area.

In order to maintain high yields and profits, pesticide usage becomes a necessity in agriculture [23]. Also, most of the governments encouraged the usage of pesticides since 1970 and in 1990s, amendment in several policies led to reduction in input subsidies. Such changes in policies resulted in even less monitoring by the governments. Due to this, more inflow occurred from the informal channels that caused enhanced usage of pesticides, leading to an increased import value by 261% from 2000 to 2010 [23]. Inadequate regulatory mechanisms also result in import of pesticides which are banned, and lack of awareness in the farmers causes poor pesticide practices. Pesticide registration in Western Africa is a multi-national process called as Comité Sahélien des Pesticides (CSP) [24]. It was reported that in Niger, due to limited capacity of CSP, 44% of pesticide dealers are unlicensed. Also, the registered chemicals account for only 8%, while 38% of pesticides have incomplete labels and 6% are unlabeled [25]. The same report also specified that 27% of the tested pesticides did not state the active ingredients and 30% of them belonged to poor quality. Apart from Niger, CSP was not able to implement its laws strictly in other parts also, and as a result, the pesticide importers, distributers and users could not be certified. Furthermore, among the domestically produced pesticides, the high-quality ones are exported, while the low-quality pesticides are supplied to local farmers [24]. Hence, the African market is unregulated and does not comply with the code of conduct laid out by Food and Agriculture Organization due to which most of the pesticides used are untested leading to the enhanced risks.

In Africa, lack of knowledge about the usage of pesticides has also led to the usage of those pesticides which fall under WHO risk classification system. According to Pesticide Risk Reduction Program (PRRP, [26]), in Ethiopia alone, out of 302 registered pesticides, 160 contained active ingredients which were classified as WHO class II chemicals (moderately hazardous). Case studies of other African countries also showed the usage of pesticides which were hazardous according to the WHO risk classification system. A study by Obopile et al. [27] in Botswana showed that over 50% of farmers use malathion and cypermethrin as pesticides and these are WHO class II chemicals. The same study also pointed that in Botswana, methomyl is used by 7.1% of farmers, demeton-S-methyl is used by 2.7% farmers, and dichlorvos is used by 1.8% farmers, and all these chemicals are classified under WHO class Ib pesticides (highly hazardous). A similar study conducted by Oluwole and Cheke [28] in Nigeria established that maximum farmers (78%) use monocrotophos which comes under WHO class Ib chemicals. Other pesticides that were reported included atrazine and metolachlor which fall under WHO class III chemicals (slightly hazardous), and lindane, copper sulfate and paraquat which are WHO class II chemicals. Nyirenda et al. [29] reported the usage of monocrotophos (Ib) by 41% farmers in Zambia, while in Malawi, parathion, a WHO class Ia pesticide (extremely hazardous), is used by over 25% of farmers. Other commonly used active ingredients in pesticides include glyphosate (III), malathion (III), chlorpyrifos (II), cypermethrin (II), deltamethrin (II), dimethoate (II), endosulfan (II), fenitrothion (II) and profenofos (II). These mentioned pesticides are frequently used in Benin, Ethiopia, Ghana and Senegal [30].

The common risk linked with pesticide usage is the resistance of the pests that leads to destruction of the crops despite appropriate application. It has been reported in western part of Africa that the use of pyrethroids has caused resistance in tomato bollworm (Heliothis armigera Hübner) and diamondblack moth (Plutella xylostella L.) [23, 31]. Also, resistance to pyrethroids and organophosphates was seen in an aphid (Aphis gossypii Glover), while a whitefly (Bemisia tabaci Gennadius) has been reported to develop resistance against pyrethroids, organophosphates and neonicotinoids [32, 33].

Pesticide usage in Asia

The use of pesticides in agriculture is increasing rapidly in developing countries, especially in Southeast Asia [34, 35]. WHO has reported that approximately 20% of pesticides are used in developing countries with increasing rate of usage. An annual increase in import of pesticides is reported as 61% for Cambodia, 55% for Laos and 10% for Vietnam [36].

The manufacturing of pesticides in India started in 1952, with the production of benzene hexachloride, followed by DDT. The synthesis of pesticides increased enormously. In 1958, India manufactured over 5000 metric tonnes of pesticides which increased to 85,000 metric tonnes in the mid-1990s with the registration of 145 pesticides and the major pesticides produced are insecticides [37]. India is one of the major pesticides producing countries in Asia with annual production of 90,000 tonnes, and it stands at twelfth position in the world in the manufacturing of pesticides [38]. In the past, India used and exported organochlorine pesticides on large scale including DDTs and HCHs [39]. Similarly, in Pakistan, the pesticides usage started in 1954 with the import of 250 metric tonnes [40]. The pesticides consumption in Pakistan increased to 78,132 tonnes per annum in 2003 [38, 41]. During Green Revolution period, thousands of tonnes of pesticides had been imported from Europe and the USA to control crop pest infections, locust control and suppression of malaria in Pakistan [42]. Use of pesticides in Bangladesh was low until 1970. The pesticide usage increased tremendously from 2200 million tonnes in 1980–1982 to 6500 million tonnes in 1992–1994 [43]. In Nepal, the first reported use of pesticides was DDT in 1956, which was followed by other organochlorines, organophosphates, carbamates and synthetic pyrethroids. It has been reported by plant protection division of department of agriculture, approximately 55.8 metric tonnes of pesticides is used annually in Nepal [44]. In Sri Lanka, the pesticides are mainly used in agriculture sector. DDT was the first pesticide used in Sri Lanka after World War II for malaria eradication. Pesticides were introduced in Thailand and Vietnam in mid-1950s. In Vietnam, the use of pesticides accelerated in mid-1980s during economic liberalization. The use of pesticides in agriculture increased from 20 to 30 million kg, and it further increased to 77 million kg in 2007 [45].

In China, pesticide production started in 1950 with the manufacturing of DDT. China has become the largest pesticide manufacturing country during past 50 years of development. In China, pesticides are mainly used for rice production. The consumption of pesticides in China has increased from 76 million tonnes in 1991 to 146 million tonnes in 2006. Japan is one of the largest pesticide consumers in the world and has biggest pesticide market in Asia [46]. Table 2 shows the consumption of different pesticides in the Asian countries.

Table 2 Annual pesticide consumption in different Asian countries [47]

Pesticide usage in Australia

In Australia, farmers have been prepared to incur higher chemical costs to cope with pests effectively. Primary categories of pesticides are herbicides, insecticides, fungicides and some growth regulators, overall costing a total market value of A$187 million annually [48]. Herbicides costs include use of alternate herbicide and mixtures along with higher concentration rates posing an extra cost of A$8/ha. A pictorial description of pesticide consumption in Australia is shown in Fig. 1. Several concerns affect choice for herbicide selection including possible development of herbicide resistance, price of herbicide, residual impact on non-target organisms including operators and community, market implications and overall impact on other strategies such as integrated pest management [49].

Fig. 1

Pesticide consumption in Australia [99]

Weed infestation leads to great reductions in crop productivity along with deteriorating the quality of the production. Application of herbicides for effective weed control upsurges agricultural productivity, making it desirable option for farmers. Herbicide utilization proves an effective approach for controlling weeds; however, overuse of these herbicides causes several complications such as development of herbicide-resistant biotypes due to the overuse of herbicides having common mode of action [50]. Evolution of herbicide-resistant weed biotypes is a serious problem that is now infesting crops throughout Australia [51,52,53]. Conservational agricultural systems completely rely on the use of efficient herbicides owing to their low cost and selective weed control in intensive farming systems [54]. However, development of herbicide resistance under continues use of herbicides has increased an average cost of A$55/ha for effective weed control [48].

Under continuous use of herbicides for selective weed control, development of herbicide resistance in weed biotypes has become the overwhelming threat for effective weed control in global wheat production system [54]. Application of herbicide in higher concentrations has resulted in creating more diversity in herbicide resistance. Weed populations in wheat crop are now frequently resistant and contain numerous mechanisms conferring herbicide resistance [55]. In Australia, herbicide-resistant weeds such as L. rigidum, Avena spp., R. raphanustrum, Bromus spp. and Hordeum spp. have been the most dramatic and extensive weeds [50, 51, 56,57,58,59]. Moreover, excessive application of pesticides/weedicides develop resistance in pests/weeds, thus making it difficult to control their population. In Australia, a dramatic increase in the population of herbicide-tolerant ryegrass in different regions has been reported (Fig. 2). Some weeds have also developed resistance against herbicides which work by the mechanisms like ACCase inhibition [60, 61] and ALS inhibition [62]. In Western Australia, it has been reported that common weed Avena has also developed resistance against those herbicides which work on the mechanism of inhibiting activity of acetyl-CoA carboxylase [63]. Similarly, L. rigidum, another widely spread annual weed in Western Australia, has observed to gain resistant mechanism against ACCase- and ALS-inhibiting herbicides like diclofop methyl and sulfometuron [59]. These results suggested to adopt conservation agriculture or to control weed proliferation via crop weed competition approach.

Fig. 2

(modified after Peterson et al. [64])

Abundance of herbicide-resistant ryegrass population in different regions of Australia.

Pesticide usage in Europe

The infestation of agricultural lands in the European countries has occurred rapidly due to enhanced application of insecticides, herbicides, fungicides and chemical-based fertilizers. This eventually has resulted in loss of natural habitat and heterogeneity of the farmlands and other landscapes [65, 66]. A joint survey of seven European countries including Latvia, Denmark, Germany, the Netherlands, Finland, Sweden and the UK was done on the usage of pesticides in their urban or the non-agricultural amenities [67]. In the urban areas, herbicides constitute the major pesticide contaminants. The analysis was carried in different regions and demonstrated wide variation in political interest and public discussion on “use of pesticides in urban areas”, regulation and availability of statistical data on pesticide usage. Moreover, it was reported that Denmark, the Netherlands, Germany and Sweden had a very strong political as well as public interest in lowering the application of herbicides in their urban areas to control weed. Although the UK is undergoing an episode of enhanced awareness and stringent regulations, Finland and Latvia have no specific regulation for lowering pesticide usage [67]. Although the use of pesticide has enhanced in Finland, the rate is comparatively lower when compared to other European regions [68]. It was estimated to be 5–6 metric tonnes of pesticides with active ingredients per year. A survey in 2007 was carried out in 80 Finish municipalities. One-fifth of these municipalities reported occasional of these pesticides and only about 15% of these municipalities used pesticides [67]. Determinations of pesticide in 8 different hot springs were carried out by Karasali et al. [69] in Greece. From 26 different samples, pesticides were reported in 14 of them although they did not exceed the European Union Maximum Acceptable Concentration (MAC). Lindane (γ-BHC) was the most commonly occurring pesticide. It was found in 35% samples with levels ranging from 0.005 to 0.01 µg/L. Few other pesticides detected included propachlor, phorate and chlorpyrifos ethyl, but were below the permissible limits.

Table 3 summarizes pesticide usage in European countries in the years 2010 and 2014, index on the basis of their area. Tabulated data showed that a few European countries including Denmark, France, Austria and the Netherlands reduced pesticide usage, while in others like Germany, Greece, Ireland, Czech Republic, Spain and Portugal, the usage was enhanced.

Table 3 Pesticide usage in European countries in the years 2010 and 2014, index on the basis of their area.

Pesticide and fertilizer usage in the Ukraine region was lowered from 4.2 million tonnes nutrient in 1990 to about 518 tonnes nutrient in the year 2004. Specifically, in the case of wheat, the quantity of pesticides applied in the year 1990 was 149 kg/ha which was reduced to 26 kg/ha in the year 2003. There are approximately 170 pesticides used in Ukraine of which 49 were extremely toxic, stable and super accumulative [70]. Approximately, 20% Ukraine agricultural land is polluted with DDT and 4% is contaminated with hexachlorocyclohexane [71]. In the urban areas of Ukraine, near the pesticides storehouses are still the main source of pesticide in the soil. Since long time, these stores have been used to store large quantities of hazardous pesticides [72]. The approximate pesticide product used in 2000 was about 3.1 kg/ha in the agricultural lands of Slovenia [73]. Fava et al. [74] investigated the presence of 43 hazardous pesticides and their pesticide residue on the basis of their sales, physical–chemical data and monitoring in the Italian region. Of these, 12 compounds were identified in the drinking water as determined by the European Directive 98/83/EC. It was determined that the total concentration of specific pesticides and their metabolites were more than 0.5 µg/L. Triazine levels were found to be more than 1.02 µg/L. Ferencz and Balog [75], estimated the quantity of wide arrays of pesticide in water, food stuff and soil samples from the Central Romanian region. The most significant pollutants are as follows: (1) α-hexachlorocyclohexane (6 ng/L), (2) γ-hexachlorocyclohexane (4 ng/L), (3) diazinon (20 ng/L), (4) dichlorvos (20 ng/L) in different water samples. The level of DDT was 20 µg/kg and DDE was 50 µg/kg in the contaminated soil. Table 4 elaborates pesticide usage (kg/ha) in European countries in the years 2001–2012 in the arable land and permanent crops. The countries are indexed on the basis of area (Table 4).

Table 4 Pesticide usage (kg/ha) in European countries in the years 2001–2012 in the arable land and permanent crops

In the autumn session of 2000, Environmental Protection Agency proposed that the pesticides which had glyphosate as one of their bioactive ingredients which was applied to the hard surfaces [76], are restricted or banned to be used on the hard surfaces. Therefore, the weed control in these areas is no longer carried out by applying these pesticides [77]. The statistical details of Danish Environmental Protection Agency in the years 1995–2007 revealed that the pesticide usage is reduced by 288 tonnes to 5.1 tonnes of active ingredient, and in the case of pesticide, it has been reduced by 81% of total pesticides. In 2000, A “Plant Protection Products” Trade and Usage division was setup in Latvia, Europe, and in late 2002 a “Plant Protection Products” Circulation Control Organization was established. In the Netherlands, in 2004 a National Administrative Organization Water (NAOW) was formed to control “weeds on hard surfaces.” Their goal was to develop cost-effective and permissible practice to control weeds [67]. A statistical analysis of usage of pesticides is carried out every year by the “Sewdish Chemical Inspectorate” since the year 2006 [67]. The government local authorities are making efforts in the UK to improve the efficacy of cleaner, greener and safe surrounding agenda [78].

European countries have developed certain imperative legislation in regard to pesticides usage and these include (1) Directive 2009/128/EC approved by European Parliament and Council in the year 2009: This directive is employed to attain techniques to sustainably use pesticides; (2) Regulation (EC) No. 1107/2009, proposed in the European Parliament and Council in the year 2009: This regulation maintains Plant Protection Products on the market; and (3) Regulation (EC) No. 396/2005 was proposed in the year 2005 by the European Parliament and Council: It monitors the MRLs of pesticide in the food products as well as animal and plant derived feeds [22]. Furthermore, the Russian government has formulated certain policies to enhance the availability of pesticide and their usage. These policies led to an increase in import, subsidies to farmers to procure pesticides and construction of manufacturing plants [79]. Another European Community (EC) Pesticide Legislation on the agricultural lands in Ireland determined that around 5% of agriculture area in the northern region of Ireland accounts for 69% of land treated with pesticides [80]. It was further reported in 2014 that fruit crop-growing areas of Northern Ireland had 30 types of pesticides with active constituents applied to approximately to 34,763 ha [81]. Presently in the Northern Ireland, the Pesticide Legislative Regulations are applied through Control of Pesticide Regulation, 1997, and Control of Substances Hazardous for Health and Regulation, 2003 [80].

Pesticide usage in the North/Central America

In North America, herbicides are largely used as chemical tool to manage weeds due to high labor cost in these areas [82]. Likewise, the use of certain insecticides to manage insects that cause vector-borne diseases like malaria is the only feasible option for prevention [83]. The main use of pesticides in the USA is in the agriculture industry [84]. Annually, 500 million kg of pesticides are used in the USA at a cost of $10 billion per year [85]. Atwood and Paisley-Jones [86] formulated a report and found that the USA accounts for approximately 16–18% of total world pesticide expenditure. Among the agriculture sector, herbicides (~ 59%) accounted for major pesticide expenditure, followed by insecticides (~ 14%) and fungicides (~ 10%). The magnitude of herbicide usage not only intensifies on croplands but on the wild lands as well. The researchers from University of Montana revealed that in the year 2010, approximately 200 tonnes of herbicides were sprayed on 1.2 million acres federal and tribal wild lands of USA [87]. However, in spite of its extensive implementation in the USA, pests mainly insects, weeds and pathogens ruin 37% of crops [88]. According to the report of Pimentel et al. [89], the use of insecticides (chiefly organochlorines, organophosphates and carbamates) in the USA has increased 10 times from 1945 to 2000; however, the damage caused by insects to crop also doubled from 7 to 13% during this period. Atwood and Paisley-Jones [86] listed 25 most commonly used pesticides in the agricultural fields and found that 12 are herbicides, two insecticides, four fungicides, five are fumigants and two are plant growth regulators. Among the different pesticides used in the agricultural fields, glyphosate is the most used active pesticides since 2001, followed by atrazine and metolachlor-S. Wagner et al. [90] illustrated manifold increment in the usage of herbicides in croplands of the USA. They further confirmed that glyphosate was the most active ingredients that not only harm the herbs and grasses but also pose potential threat to the native vegetation [90]. Benbrook [91] documented that since 1974, above 1.6 billion kg of active ingredients of glyphosate have been applied in the USA which contributes to 19% of the estimated global use. The researcher further documented that in the last 10 years, US farmers sprayed over two-thirds of the total volume of glyphosate from 1974 to 2014 which is approximately 1.0 kg/ha [91]. A report from Allied Market Research (AMR) demonstrated that the volume of glyphosate ingredient is expected to grow at a compound annual growth rate (CAGR) of 5.7% during 2014–2020 [92]. According to this report, the USA will hold the largest herbicide market share in North America and would produce 85% of North America market revenue in 2020 [92]. Further, in non-agriculture sectors such as home and garden, 2, 4-D is the most commonly used pesticide and is ranked first among other known pesticides. Currently, the insecticides consumption in the USA has declined due to shift toward biopesticides and other natural plant products.

Similarly, in Canada, 35 million kg of pesticides are used annually in agricultural fields [93]. Herbicides are the most prominent and widely used chemical pesticides in Canada [94]. Moreover, herbicides cover approximately 96% of total pesticides applied in Prairie Provinces of Canada [93]. In a survey made in the year 2011, 69% of the Canadian agricultural crop lands were reported to apply herbicides in order to mount the crop productivity [95]. Wilson [96] used crop insurance data from Manitoba and found that 2 million kg of herbicides are used annually in the province. According to Verrin et al. [97], the commonly used pesticides in British Columbia includes 2, 4-D, diazinon, dicamba, atrazine and simazine. These agricultural herbicides can directly cause mortality of species since they are chemically toxic [98]. Recently, statistics showed that the total amount of pesticides imports to Canada comprised of 1.32 billion U.S. dollars [99].

Mexico is the third largest market of agrochemicals in North America, and its market is growing at a CAGR of 5.2% during 2017–2022. The major agrochemicals include insecticides and herbicides that account for approximately 36% of the total market [100]. Earlier, Mexico ranked sixth in the world for the use of DDT (dichlorodiphenyltrichloroethane) [101]. Wong et al. [102] reported that between the years 1947 and 2000, approximately 250 kilotonnes of DDT was used in the country; however, the use of DDT was successfully halted by 2000 [103]. Mexico actively participates in different international agreements dealing with pesticides; however, studies have reported that Mexico still uses some pesticides such as paraquat, endosulfan, lindane, methyl bromide, parathion and malathion that are banned in other industrialized countries [104].

Pesticide usage in South America

In South America, pesticide sale increased 30% between 2003 and 2004 and was projected to increase from 5.4 billion (US $) in 2004 to 7.5 billion (US $) by 2009. The average annual growth rate for this period was 5%. Pesticides like 2, 4-D, paraquat, methamidophos, methomyl, endosulfan and chlorpyrifos had the maximum share in pesticide sale. In some countries of South America, mean usage rate of pesticides in arable lands determined by FAO is 6.5–60 kg/ha [105]. In Brazil, during the year 2013, it has been reported that half million tonnes of pesticides were marketed. Moreover, it has also been noticed that over 90% Brazilian farmers are dependent on pesticide usage [106], and the country has estimated to had used over 673 million tonnes of pesticide in 2008 [107]. The sale of pesticides increased 945.5% in Brazil between 1998 and 2008. In the year 1996, out of total sold pesticide, herbicides were sold most (56.1%) followed by insecticides (26%) and fungicides (15.4%) [108]. Soares and de-Souza Porto [109] evaluated the environmental, social and health cost due to intensive pesticide use in Brazil. They have reported that the cost of acute poisoning to around 64% using insecticides and herbicides in maize which may reach up to 85% in the next ten years.

In Argentina, agrochemical application has significantly enhanced and it has been observed that total consumption has inclined from 73 to 236 million kg/year over last decade. This accounts for turnover of 2381.16 million (US $) in the year 2012. Out of all pesticides sold during this period, maximum was herbicides (64%) followed by fungicides (20%) and insecticides (16%) [110]. In Argentina, pesticide market is mostly captured by herbicides (86.8% and mostly used herbicides are glyphosate, 2,4-D and atrazine) followed by insecticides (6.2% and mostly used insecticides are cypermethrin, chlorpyrifos, lambda-cyhalothrin) and fungicides (2.7% including epoxiconazole, tebuconazole and metconazole) [111]. During the time period from 1974 to 2003, in Colombia the registration of pesticide sharply increased to 400 from 186 active ingredients [112].

Pesticide contamination and its impacts on global ecosystem

Pesticides have become an environmental hazard as their safe storage and disposal are challenges [113]. Pesticides, when used in high quantities, pollute soil and water, causing damage to its microflora and microfauna, and also hinder the absorption of important mineral nutrients by plants [114]. To measure the ecological-toxicology of pesticides, indexes like Environmental Impact Quotient and Environmental Risk Index have been used [23]. In Benin, carbofuran, chlorpyrifos ethyl and endosulfan showed highest Environmental Risk Index [115]. The leaching of pesticides also leads to the pollution of the local water bodies. For example, the catchment area of the Lake Victoria in Kenya has six rivers that carry pollutants to the lake [113]. Winam Gulf is the most polluted part of this lake and pesticide poisoning of fishes with endosulfan was reported, and a ban on import of fishes from the lake was imposed by the European Union [113, 116]. Pesticides leach to the groundwater and pollute drinking water, which is one of the major concerns for environmentalists [117]. A study showed the presence of malathion, dieldrin and γ-HCH in the ground water and River Ganges in Kanpur [118].

Water streams contamination with pesticides is one of the serious issues in Australia. Application of triazine (a herbicide) had been extensively practiced in forestry industry in Tasmania, Australia. Reports suggested that out of 29 streams sampled, 20 contained detectable residues of triazines [119]. Median contaminations of all the samples were 2.85 and 1.05 µg/L for atrazine and cyanazine, while < 0.05 µg/L for each of metribuzin and propazine, respectively, suggesting that observed residues may cause occasional minor short-term disturbance to stream communities [119]. Residual impact of herbicide runoff from adjacent agricultural catchments is other manifestation of pesticide application. This pesticide runoff has led to the deprivation of costal and inshore ecosystems of Great Barrier Reef (GBR) [120,121,122,123]. Potential hazardous impacts of herbicide runoff have been emphasized through a range of keystone GBR marine organisms containing seagrass, corals and algae [124,125,126,127]. According to an estimate, 30,000 kg of herbicides (including atrazine, diuron, ametryn, simazine, hexazinone and tebuthiuron) have been noticed to pass into GBR World Heritage Area per year [128, 129]. However, majority of herbicides measures each year in sediments comprise of atrazine and diuron [130]. Davis et al. [131] examined seasonal dynamics in relation to movement of pesticides within agriculture captured floodplains of the lower Burdekin River. Fifteen herbicides along with one insecticide were detected in local waterways draining into the downstream of wetlands. These researchers observed that out of detected pesticides, maximum was related to sugarcane industry [131]. Atrazine and ametryn along with their degraded products (desethyl-atrazine and desisopropyl-atrazine), diuron, 2, 4-D and hexazinone were the main agrochemicals detected in higher concentrations [131]. Some other studies have documented that several herbicide residues including diuron were detected in benthic deposits tested from irrigation and drainage channels, suggesting diuron being the most abundant herbicide in terms of occurrence [132, 133]. Likewise, diuron was dominantly found in inter- and sub-tidal deposits of GBR [134, 135]. In Melbourne, Allinson et al. [136] examined water quality of five different aquatic systems and found that many pesticides were present in high concentrations which included MCPA (83%), diuron (63%) and atrazine (53%). In another study, water screening from wetlands resulted in the detection of many harmful pesticides (simazine, atrazine and terbutryn) in high concentrations (Allinson et al. [137]).

The enhanced concentration of organochlorine pesticides and polychlorinated biphenyls in the Canadian Great Lakes Basin [138] and various fungicides in surface and ground water resources in the USA [139], posed a serious problem over the health-related issues of local communities as well as the environment. The direct discharge of waste and agriculture runoffs are major sources of pesticides in water [140]. The pesticides accumulated in water get magnified through food chain and enter fishes that are toxic for human consumption [141]. In most of the studies conducted in North America, glyphosate [142] and atrazine [143] are the two commonly found pesticides in water bodies and other pesticides found in less concentration are malathion, chlorpyrifos, diazinon, lindane, dieldrin and dichlorodiphenylethane (DDE) [101]. Benbrook [91] found that the use of glyphosate in the US agricultural sector increased 300 times from 1974 to 2014 and this herbicide is in the market of the USA for the past 42 years. Murray [144] reported that the regulations which govern the production and distribution of pesticides in Central America are not enforced adequately. As a result, compounds banned in other developed countries are used continuously in Central America [145]. For example, DDT, a persistent organochlorine pesticide, is still used for control of vector in Belize [146]. The highly protected area of the coast of Mexico was also contaminated with pesticides such as DDT, lindane and endosulfan [147] which might be due to their use in agricultural fields. Overall, countries such as Canada, Mexico and the USA reported higher concentrations of DDT, chlordane, p,p′-DDE and toxaphene in air [148, 149]. According to the spatial comparison data, in spring season, the concentration of organochlorine compounds is increased compared to other seasons [150].

In most of the studies conducted in South America, chlorpyrifos, endosulfan, and cypermethrin are frequently found pesticides in water bodies [151, 152]. Albuquerque et al. [153] reported the presence of 21 herbicides, 11 fungicides, 10 insecticides and 1 plant growth regulators in surface waters of Brazil. Azinophos-methyl and chlorpyrifos were most frequently detected pesticides in surface waters and soils of Neuquén River valley of Argentina [154]. De Gerónimo et al. [155] reported that atrazine, tebuconazole and diethyltoluamide were the most detected pesticides in surface water sub-basins of Argentina. Resgalla et al. [156] conducted study to evaluate the risk due to residues of herbicide quinclorac in irrigated water against zooplankton and phytoplankton. They reported that recommended application of concentration of quinclorac has short-term indirect effects on zooplankton, but it directly affects phytoplankton.

The application of pesticides might harm the indigenous microorganisms of soil and affect the soil ecosystem, thus entering in food chain and affecting human health [157]. Pesticides interplay with soil microbes and their activities and thus change the biochemical and physiologic behavior of soil microbes [158]. Pesticides also have negative impact on soil microbial biomass and soil respiration [159]. It has been found that pesticides reduce natural symbiotic nitrogen fixation, leading to the decrease in crop yield. Pesticides like DDT, methyl parathion and pentachlorophenol interfere with signaling between leguminous plants and symbiotic soil bacteria. This results in enhanced dependence on synthetic nitrogen fertilizers along with reduced soil fertility and unsustainable crop yield [160, 161]. Daly et al. [162] reported the contamination of air and soil of Costa Rica and found that the concentration of DDT-related species was more as compared to other organochlorine pesticides used in the country. The distribution of pesticides in the soil of Canada was also determined by Daly et al. [162] by collecting soil from 22 sites. Endosulfan, dieldrin and α-hexachlorocyclohexane were the most prevalent OCPs in the soil of Canada [162]. The distribution of different pesticides in the soil mainly depends on the physical and chemical properties of soil. The amount of pesticides contamination in soils of southern Mexico was investigated by Wong et al. [102], and the results showed higher concentration of DDT in the range of 0.057–360 ng/g. Luchini et al. [163] determined high concentrations of pesticides in soils which included trifluralin and endosulfan from cotton-cropped fields in Brazil. Nakagawa et al. [164] reported the presence of high atrazine percentage in the soils of São Paulo State of Brazil. Miglioranza et al. [165] concluded that pesticides in soil environment of Argentina are present in such a concentration, which may cause threat to various tropical levels.

Pesticide contamination in the ecosystems also badly impacts other organisms like bees and wild life. In the past one decade, there is an enhancement in illegal usage of pesticides [166]. This has led to misuse and abuse of the wildlife, for example drastic effect on most raptor species like Gypaestus barbatus (bearded vulture) [167] and Aquila adalberli (imperial eagle) [168]. Other important components of ecosystems which are negatively affected by pesticide overuse are biological pest control [169], soil fertility [170] and proper crop pollination [171]. In Peru, (the Punta San Juan Marine Protected Area), Adkesson et al. [172] studied the blood of endangered species, Humboldt penguins (Spheniscus humboldti), to find out the presence of organochlorine pesticides. They reported high concentration of DDT with maximum concentration of 10 ng/g. The presence of these toxicants emphasize upon the need of temporal monitoring to protect this endangered species. In Uruguay, Pareja et al. [173] estimated the pesticide residues in 14,800 beehives and found high concentrations of coumaphos, endosulfan, ethion, chlorpyrifos and cypermethrin from active beehives. They reported that these pesticide residues cause bee disorientation and affect their global fitness which leads to weakness and productivity decrease.

The regular use of pesticides has also caused problems like human health issues and environmental problems [174]. It has been reported that for human health, food intake leads to higher toxicity exposure than by other means like drinking water and inhalation [175]. The pesticides mimic or antagonize natural hormones in human body. Long-term low-dose exposure affects human health with reducing immunity, disturbs hormonal balance, reduces intelligence and causes reproduction-related problems and cancer [176]. Farmers are generally at high risk of exposure to pesticides, herbicides, fertilizers and other chemicals. It has been found by Alavanja et al. [177] that use of chlorinated pesticides and methyl bromide is associated with prostate cancer risk in farmers. Similarly, Hoppin et al. [178] reported that pesticide exposure increases the chance of allergic and non-allergic asthma in farmers.

Kostik et al. [179] determined amount of pesticide residues in plant-based foods. Experimentation was carried out as per recommendation of European Food Authority (EFSA). In the period of 2012–2013, approximately 168 different samples of fresh vegetables like cherry, grapes, apple and manufactured jams and canned fruits had 33 different pesticides residues. The most predominant residues found were metalaxyl (0.4–0.16 mg/kg), methomyl (0.015–0.21 mg/kg) and imidacloprid (0.017–0.036 mg/kg). In another significant study conducted to estimate pesticide levels in sweet cherry in the farmland of West Mediterranean region of Turkey, it was observed that 53, 349.5 g/ha of agricultural chemicals had an active constituents in the sweet cheery plants. The percentage of copper sulfate, pesticide and mineral oils is 79.82%, 19.11% and 1.07%, respectively [180]. This pesticide contamination of fruits and vegetables is a serious issue for humans.

Conclusion and future perspectives

Synthetic pesticides are used to control the weeds and insect pests, affecting the agricultural systems. Water, soil and air serve as an important medium for transportation of pesticides from one site to another. Among different classes of pesticides, organochlorine pesticides are the most harmful one due to their slow rate of decomposition, greater stability and long half-life. These pesticides can migrate and get accumulated in the upper trophic levels of food chain. Pesticide contamination is a serious problem for each ecosystem and is harmful for all associated organisms. So, in order to control pesticide usage, new methodologies and techniques are needed in assessing the effect of widespread use of pesticides on ecosystem and efforts should be made to provide awareness among public to minimize the application of harmful pesticides. Use of biopesticides should be encouraged over chemical pesticides.