**Abstract**

The present review addresses the impacts of pesticides used in crops on non-target organisms in aquatic ecosystems. In recent decades, these ecosystems have received large amounts of these compounds, which are released by urban communities, rural and industrial properties. Pesticides reach the aquatic environment through different routes (leaching, irrigation, drainage, and surface runoff) and can easily reach non-target organisms, such as fish, mollusks, as well as other benthic organisms. Usually, these animals tend to undergo bioaccumulation. Exposure to these pesticides can cause numerous physiological changes by direct influence on certain cellular structures, such as on the lysosomal membrane, which can be degraded. Also, they can even react with nucleic acids resulting in several genetic injuries, thus causing adverse reactions to the body. There is a need for more incentives for the adoption of sustainable agroecological practices, as well as a ban on active ingredients harmful to the environment, in addition to strict inspection by competent environmental agencies.

**Keywords:** environmental impact, pesticides, aquatic organisms, non-target organisms, aquatic ecosystems

#### **1. Introduction**

In the last decades, with the machinery modernization and the consolidation of the sector of modern inputs, agriculture has been growing at a fast pace, with pesticides being one of the main instruments that drive the agricultural sector in productivity gains [1]. However, the indiscriminate use of these substances has easily reached non-target organisms and their effects on the environment are

varied, ranging from the reduction in the availability and quality of water to the compromise of air and food quality, harming human health. Also, it can directly affect cellular structures of aquatic or terrestrial organisms resulting in damage to biodiversity [2].

In the early 1960s, society began to worry about the adverse effects and potential risk that these pesticides posed to human health and the environment. In several countries, production, marketing, and use of many of these compounds, in particular those considered persistent organic pollutants (POPs), such as organochlorines, were banned [3]. With the ban on most organochlorine compounds (less toxic, but with greater bioaccumulation in the environment), after the Second World War, carbamate and organophosphate pesticides had their use intensified. Also, it became the most used pesticides worldwide, being widely used in developing countries with a predominantly agricultural economy [4].

These toxic substances have the potential to cause various biochemical and genetic injuries to non-target organisms. Carbamates and organophosphates, for example, are potent inhibitors of the acetylcholinesterase enzyme, which damages the nervous system of an exposed organism [5, 6]. This enzyme acts in the hydrolysis of the acetylcholine neurotransmitter in cholinergic synapses. Its inhibition can lead the individual to death due to cholinergic hyperstimulation. Pesticides are also known for their mutagenic and carcinogenic effects. They react with nucleic acids causing adverse reactions in the body. Thus, monitoring and controlling the presence of these substances in the environment are necessary, since these compounds have become a human health and environmental problems [7].

#### **2. Pesticides in aquatic environments**

Pesticides or agrochemicals are defined as:

*"Products and agents of physical, chemical or biological processes, intended for use in the sectors of production, in the storage and processing of agricultural products, in pastures, in the protection of forests, native or implanted, and of other ecosystems and also of urban environments, whose purpose is to change the composition of flora or fauna, in order to preserve them from the adverse action of living beings considered harmful" [8].*

According to the harmful species that intend to eliminate, these compounds are classified as insecticides, fungicides, herbicides, acaricides, rodenticides, molluscicides, among others. Herbicides represent 48% of the total pesticides, which is followed by insecticides (25%) and fungicides (22%) [9]. Depending on the chemical class, they can be grouped into pyrethroids, organochlorines, organophosphates, carbamates, benzoylureas, neonicotinoids, among others [10].

Pesticides arrive in the environment carried by runoff and leaching of rainwater, irrigation, and drainage or by spraying, as shown in **Figure 1**. Among these processes, runoff and leaching can contaminate reservoirs, lakes, and rivers. Also, they expose aquatic organisms at levels of pesticides that can be toxic to many species. Once present in the aquatic environment, these compounds can penetrate the organisms orally - through the ingestion of contaminated food, respiratory - through the gills, and dermal - through the surface of the body. In most cases, these organisms tend to suffer bioaccumulation [1, 13]. Pesticide exposure can cause numerous physiological changes by direct influence on

**81**

**Figure 2.**

*(esters derived from carbamic acid).*

**Figure 1.**

*Pesticide paths to the aquatic environments. Source: [11, 12].*

*Impacts of Agricultural Toxicity on Non-Target Organisms in Aquatic Ecosystem*

certain cellular structures, for example, on the lysosomal membrane, which can be degraded or can react with nucleic acids, resulting in several genetic injuries

Currently, there is a growing concern about the exacerbated use of pesticides

Organophosphate pesticides (OPs) comprise a large number of substances classified chemically as esters, amides, or derivatives of pentavalent phosphoric acids. Carbamates (CBs) are esters, or N-substituted derivatives of carbamic acid (carbamic acid monoamide) (**Figure 2**). Both have low water solubility and are, in general, easily hydrolyzable in alkaline environments [10, 15, 16]. In general, OPs need biotransformation to become toxicologically active, unlike CBs that are

*Organophosphate pesticides: (a) methyl-paration (triesters of phosphoric acid), (b) carbamate carbofuran* 

since, in recent decades, aquatic ecosystems have received alarmingly large amounts of these compounds, which are released by urban communities, rural properties, and industries. Thus, society started to worry about the adverse effects of these substances and their potential risk [14]. According to Silva et al. [4], carbamates and organophosphates are the most used pesticides worldwide. They

*DOI: http://dx.doi.org/10.5772/intechopen.93941*

that cause adverse reactions in the body [2].

already bioactive.

together account for more than 50% of what is marketed.

#### *Impacts of Agricultural Toxicity on Non-Target Organisms in Aquatic Ecosystem DOI: http://dx.doi.org/10.5772/intechopen.93941*

certain cellular structures, for example, on the lysosomal membrane, which can be degraded or can react with nucleic acids, resulting in several genetic injuries that cause adverse reactions in the body [2].

Currently, there is a growing concern about the exacerbated use of pesticides since, in recent decades, aquatic ecosystems have received alarmingly large amounts of these compounds, which are released by urban communities, rural properties, and industries. Thus, society started to worry about the adverse effects of these substances and their potential risk [14]. According to Silva et al. [4], carbamates and organophosphates are the most used pesticides worldwide. They together account for more than 50% of what is marketed.

Organophosphate pesticides (OPs) comprise a large number of substances classified chemically as esters, amides, or derivatives of pentavalent phosphoric acids. Carbamates (CBs) are esters, or N-substituted derivatives of carbamic acid (carbamic acid monoamide) (**Figure 2**). Both have low water solubility and are, in general, easily hydrolyzable in alkaline environments [10, 15, 16]. In general, OPs need biotransformation to become toxicologically active, unlike CBs that are already bioactive.

**Figure 1.**

*Emerging Contaminants*

biodiversity [2].

economy [4].

varied, ranging from the reduction in the availability and quality of water to the compromise of air and food quality, harming human health. Also, it can directly affect cellular structures of aquatic or terrestrial organisms resulting in damage to

In the early 1960s, society began to worry about the adverse effects and potential risk that these pesticides posed to human health and the environment. In several countries, production, marketing, and use of many of these compounds, in particular those considered persistent organic pollutants (POPs), such as organochlorines, were banned [3]. With the ban on most organochlorine compounds (less toxic, but with greater bioaccumulation in the environment), after the Second World War, carbamate and organophosphate pesticides had their use intensified. Also, it became the most used pesticides worldwide, being widely used in developing countries with a predominantly agricultural

These toxic substances have the potential to cause various biochemical and genetic injuries to non-target organisms. Carbamates and organophosphates, for example, are potent inhibitors of the acetylcholinesterase enzyme, which damages the nervous system of an exposed organism [5, 6]. This enzyme acts in the hydrolysis of the acetylcholine neurotransmitter in cholinergic synapses. Its inhibition can lead the individual to death due to cholinergic hyperstimulation. Pesticides are also known for their mutagenic and carcinogenic effects. They react with nucleic acids causing adverse reactions in the body. Thus, monitoring and controlling the presence of these substances in the environment are necessary, since these compounds have

*"Products and agents of physical, chemical or biological processes, intended for use in the sectors of production, in the storage and processing of agricultural products, in pastures, in the protection of forests, native or implanted, and of other ecosystems and also of urban environments, whose purpose is to change the composition of flora or fauna, in order to preserve them from the adverse action of living beings* 

According to the harmful species that intend to eliminate, these compounds are classified as insecticides, fungicides, herbicides, acaricides, rodenticides, molluscicides, among others. Herbicides represent 48% of the total pesticides, which is followed by insecticides (25%) and fungicides (22%) [9]. Depending on the chemical class, they can be grouped into pyrethroids, organochlorines, organophosphates, carbamates, benzoylureas, neonicotinoids, among others [10]. Pesticides arrive in the environment carried by runoff and leaching of rainwater, irrigation, and drainage or by spraying, as shown in **Figure 1**. Among these processes, runoff and leaching can contaminate reservoirs, lakes, and rivers. Also, they expose aquatic organisms at levels of pesticides that can be toxic to many species. Once present in the aquatic environment, these compounds can penetrate the organisms orally - through the ingestion of contaminated food, respiratory - through the gills, and dermal - through the surface of the body. In most cases, these organisms tend to suffer bioaccumulation [1, 13]. Pesticide exposure can cause numerous physiological changes by direct influence on

become a human health and environmental problems [7].

**2. Pesticides in aquatic environments**

*considered harmful" [8].*

Pesticides or agrochemicals are defined as:

**80**

*Pesticide paths to the aquatic environments. Source: [11, 12].*

#### **Figure 2.**

*Organophosphate pesticides: (a) methyl-paration (triesters of phosphoric acid), (b) carbamate carbofuran (esters derived from carbamic acid).*

Carbamates and organophosphates affect the nervous system of organisms. They inhibit the activity of the enzyme acetylcholinesterase (AChE), as demonstrated by Wang et al. [17]. In their study, AChE inhibition in carp (*Cyprinus carpio*) exposed to various concentrations of organophosphates, malathion, and triazophos, as well as carbamates fenobucarb and carbosulfan, was evaluated. In equitoxic mixtures, the authors noted that AChE activity was inhibited by the combination of triazophos and malathion, as well as triazophos and carbosulfan, with synergism occurring. The effects of organophosphates on the behavior and activity of the AChE of zebrafish larvae have also been studied, through exposure to chlorpyrifos and malathion, and changes in swimming speed (hypoactivity and hyperactivity), rest and tigmotatism have been found [18].

Recently, benzoylurea, a class of pesticide that in the past was not considered an acetylcholinesterase inhibitor, since its main mode of action is the inhibition of chitin biosynthesis in insects (which interrupts the incorporation of N-acetylglycosamine monomers), demonstrated anticholinesterase potential [19]. In 2011, this class of pesticides represented 3.6% of the world's pesticide market. Since then, its commercial importance has grown over the years [20].
