**Abstract**

The usage of carbamate pesticides in agriculture is increasing year by year. Carbamate pesticides are thioesters and esters, which are derived from aminocarboxylic acid. Carbamates are commonly utilized to improve agricultural production and protect humans and animals from disease. They were also used to control and prevent agricultural pests. However, carbamate can be highly toxic if not applied properly. Therefore, carbamate pesticides need to be monitored in fruits and vegetables. Sensitive and selective detection of carbamate pesticides using nanotechnology helps overcome the drawback of conventional methods of detecting carbamates. Nowadays, the demand for rapid, highly sensitive, and selective pesticide detection techniques is expanding to facilitate detection without complicated equipment. Due to this, this chapter focuses on nanotechnology and current detection methods for detecting residual carbamate pesticides in fruits and vegetables more precisely and faster.

**Keywords:** carbaryl, carbofuran, toxicology, recent approaches, traditional techniques, fresh produce

## **1. Introduction**

A pesticide is a hazardous chemical compound or a mixture of biological agents or chemicals that are deliberately presented into the environment to prevent, dissuade, eliminate, or control populations of insects, rodents, weeds, fungus, or other unwanted pests. Pesticides play an important role in attracting, enticing, and killing or repelling organisms. Generally, pesticides are widely applied and reported at approximately 5.2 billion pounds per year to reduce various harmful species such as microscopic fungi, weeds, rodents, and insects. Pesticide is highly applicable for pest control in agricultural areas and households to control mosquitoes, ticks, cockroaches, rats, fleas, and other dangerous creatures [1]. Using pesticides improves crop yields by controlling pathogenic microorganisms, resulting in better consumption of fresh fruits and vegetables [2]. There are four types of pesticides, namely organochlorines, carbamates, organophosphates, and pyrethroids, illustrated in **Figure 1** with their chemical structures.

Carbamate pesticides are known as esters of carbamic acid (R1 -S-CO-NR<sup>2</sup> R3 ), which are not structurally complex. They are commonly employed in farming to protect many crops, including fruits, cotton, rice, and vegetables, due to their broad biological activity, less mammalian toxicity, and minimal bioaccumulation potential [3]. Besides, it was applied as a therapeutic drug in human medicine and veterinary medicine. Carbamate has a high polarity, is water-soluble and thermodynamically unstable, which contains insecticides like carbaryl, acaricides, and fungicides [4]. Previous research found that carbamate pesticides are capable absorb in the food source's tissues such as fish, poultry, and meat, in processed foods such as vegetables, nuts, dehydrated fruits, and vegetable oils [5]. Based on FAO and WHO, in 2016, Codex Alimentarius Commission for carbamate maximum residue levels was set up to 4844 but required the presence of different combinations of pesticides. However, in European Union, carbaryl was banned in most countries [6]. This is because the carbamate residual in foods functions as acetylcholinesterase inhibitors, which can damage the brain, nervous systems, liver, muscles, and pancreas over the long term [7, 8].

It is essential to track and measure the carbamate amounts in fresh products and improve the sensitivity of the detection methods that have been developed.

**Figure 1.** *Classification of pesticides with chemical structure.*

*Extraction and Identification Techniques for Quantification of Carbamate Pesticides in Fruits… DOI: http://dx.doi.org/10.5772/intechopen.102352*

Previously, conventional methods such as chromatography, immunoassay, and surface-enhanced Raman spectroscopy (SERS), have been applied and show reliability and sensitivity to determine the presence of carbamate. However, these techniques are typically insufficient for real-time and on-site detection, which necessitates advancements in terms of preparation time and cost of machinery and highly skilled workers [9]. Hence, the development of advanced nanotechnology is one of the alternative methods that show rapid, low-cost, easy to use, and capable of detecting low concentrations of carbamate in food samples. This chapter focuses on the latest information on sample pretreatment and analytical detection strategies available from 2000 to 2021. Also, we highlight the reader with an understanding of some innovative ways to increase carbamate pesticides detection in food products.

#### **2. Types of carbamate pesticides**

Carbamate is an N-methyl produced from carbonic acid, responsible for the carbamylation of acetylcholinesterase at neuromuscular junctions in the brain and spinal cord and at neuronal synapses. Carbamate is classified as an insecticide that is physically and mechanistically comparable to organophosphate (OP) insecticides in both structure and mechanism of action. Carbamates have a reversible binding to acetylcholinesterase and do not cause the irreversible phosphorylation of the enzyme that occurs when organophosphates interact with it [10]. Consequently, carbamates are toxicologically similar to OP poisoning, with a toxic period of fewer than 24 hours [11]. Aldicarb, carbaryl, carbofuran, bendiocarb, fenobucarb, methomyl, oxamyl, propoxur, and methiocarb are the most common agents that lead to dangerous exposure. **Figure 2** below illustrates the chemical structure of carbamate pesticides available in agriculture applications.

Carbaryl is a member of the chemical family N-methyl carbamate and was discovered in 1959 for use as a carbamate pesticide in cotton in the United States. Carbaryl is a popular insecticide in agriculture, specialist turf control, ornamental production, and residential settings. Carbaryl is mildly toxic when taken orally and has low toxicity when applied topically or inhaled [12]. In outdoor conditions, carbaryl has a low persistence rate. Human exposure occurs by ingestion of residues in food, skin contact, and inhalation of airborne particles. Carbaryl blocks acetylcholinesterase in the neurological system, causing acetylcholine buildup and cholinergic hyperstimulation. In contrast to adults, immature organisms are more sensitive to the inhibition of cholinesterase (ChE). In addition to reproductive and developmental toxicity, carbaryl can also alter the immune system. It may also cause cancer in humans and be highly harmful to non-target organisms [13, 14].

Aldicarb is a carbamate insecticide active against insects, mites, and nematodes belonging to the chemical family of N-methyl carbamates. Aldicarb is water-soluble at pH 7 and a colorless crystalline substance that acts as a cholinesterase inhibitor, soil contaminant, carcinogen, and a possible endocrine disruptor. Aldicarb is acutely toxic and causes cholinergic symptoms by inhibiting acetylcholinesterase (AChE), neither genotoxic nor cancer-causing. Much information about toxicity includes developmental, long-term, short-term, reproductive, and neurotoxic studies. They are dose-dependent, rapidly reversible, and do not manifest at levels of human exposure predicted [15]. The toxicity of aldicarb is evident in even small doses with stomach cramping, dizziness, nausea, diarrhea, and convulsions [16, 17].

**Figure 2.** *Chemical structure of types of carbamate pesticides.*

Carbofuran is a wide-spectrum of N-methyl carbamate insecticide commonly used in farming to combat insects, nematodes, and mites in soil or protect forest crops, fruit, and vegetables. It is incredibly toxic to birds, mammals, fish, and wildlife due to its anticholinesterase action that inhibits acetylcholinesterase and butyrylcholinesterase. Carbofuran can disrupt the neuroendocrine system, cause reproductive disorders, and be genotoxic and cytotoxic to humans [18]. However, it did not affect a humoral immune response [15]. Besides, it is a relatively unstable chemical that degrades in weeks or months. Recently, Amatatongchai et al. [19] found carbofuran in potatoes, corn, soybean, fruits, and vegetables. Similarly, Lan et al. [20] detected carbofuran in watermelon, long bean, mango, and chives samples.

Methomyl is known as metomil or mesomile, commonly used to treat crops. It is a colorless crystalline structure soluble in organic solvents and water, which may pollute the environment. It has a wide application in biological activities and is efficient against insects [21]. Methomyl is categorized as a harmful and dangerous pesticide by the World Health Organization and the European Union [22]. Acetylcholinesterase (AChE) is inhibited by methomyl lead in a reduction of the ability of the enzyme to hydrolyze acetylcholine that buildup in the body. The most common signs of methanol include tearing of the eyes, vomiting, nausea, stomach pain, diarrhea, loss of consciousness (coma), and death due to respiratory failure [23–25]. The endocrine system is also affected by methomyl because of its capability to influence estrogen production and reproductive capabilities [26]. Presently, Guo et al. [27] identified methomyl residue in barley, millet, wheat, and rice grains. Besides, Rasolonjatovo et al. [28] found methomyl residues in tomatoes.

#### *Extraction and Identification Techniques for Quantification of Carbamate Pesticides in Fruits… DOI: http://dx.doi.org/10.5772/intechopen.102352*

Methiocarb is a carbamate pesticide that colorless, crystalline substance sparingly soluble in water and xylenes. However, it is unstable in alkaline media (pH 9). Methiocarb is a contact wide-spectrum, a residual insecticide which acts as a molluscicide, acaricide, and bird repellent since the 1960s [13]. Methiocarb is used on fruit crops and orchids to control snails and rice insects [29]. Sivaperumal et al. [30] found the methiocarb residues in mango fruits. The molecule is oxidized sequentially to sulfoxide and sulfone in the vertebrate liver. Methiocarb sulfoxide is also available in methiocarb sulfone in the form of iocarb sulfone and the combination known as methiocarb [31].

The chemical name for propoxur is 2-isopropoxyphenyl-N-methylcarbamate with a molecular weight of 209.24, which is hydrolyzed by strong alkali. Propoxur is unstable in alkaline media and has a half-life at a pH of 10 for 40 minutes. It is a non-systemic insecticide primarily used against household insect pests and domestic animal pests [32]. However, propoxur causes neurotoxicity by inhibiting acetylcholinesterase in a significant reversible manner [33]. Based on Borahan et al. [34], propoxur has been detected in raisins by gas chromatography-mass spectrometry (GC-MS). Besides, Xiao-Xue et al. [35] found propoxur in fruit samples such as plum, pear, and loquat by employing the molecularly imprinted photoelectrochemical sensor.

Through the oral pathway, oxamyl is highly toxic. Like other carbamates, exposure to oxamyl can result in cholinesterase inhibition over a short period [36]. The pure compound has a slightly sulfurous odor and is a white crystalline solid, which melts at 100–102°C and shifts to a different crystalline structure between 108 and 110°C [32]. Yaseen et al. [37] found oxamyl in peach fruit using a surface-enhanced Raman scattering. Bendiocarb is a carbamate insecticide efficient against a broad spectrum of agricultural pests. Bendiocarb is poisonous to fish, birds, and bees, and research has demonstrated that bendiocarb is unable to bioaccumulate in animals [38]. Kowalska et al. [39] stated that terbucarb residues were found in plants, and HP-LC detected it with tandem mass spectrometry (HPLC-MS/MS). Liquid fenobucarb pesticides are pale yellow or pale red. Pelle et al. [40] found fenobucarb residues in grain samples.

## **3. Physical and chemical properties of carbamate pesticide**

The straightforward technique to identify carbamate pesticides is to look at their carbamic acid N- or S-substitutions. The carbamates are classified into nine major groups: dithiocarbamates, thiocarbamates, benzimidazole carbamates, N-phenyl carbamates, ethylenebisdithiocarbamate, N,N-methyl carbamates, N-methyl carbamates, aminophenyl N-methylcarbamates, and oxime N-methylcarbamates [41]. Carbamates are typically insoluble in water molecules because it has low solubility in polar organic solvents, ethanol, or acetone. Carbamate is a polar molecule soluble in solvents with a medium polarity, including benzene, chloroform, toluene, xylene, dichloromethane, or 1,2-dichloromethanebut are insoluble in nonpolar organic solvents [42, 43]. Pure carbamate pesticides are crystalline, white, practically odorless solids with low vapor pressure and high melting point. Carbamate pesticide features include physical form, melting point, vapor pressure, and solubility [41].

#### **4. Toxicology of carbamate pesticide**

Carbamates are carbamic acid esters substituted for N-methyl carbamic acid that act as AChE inhibitors to catalyze acetylcholine (ACh). The reaction enhanced the

ACh level at a nerve synapse or neuromuscular junction, raising nerve-ending stimulation by reversible cholinesterase inhibition [44]. In contrast to organophosphates, the cholinesterase-inhibiting action of carbamates is reversible. Carbamates are toxic to rodents in doses ranging between LD50 > 200 mg/kg and LD50 > 50 mg/kg [45]. According to the classification system, the US Environmental Protection Agency and the World Health Organization (WHO) have classified carbamate as class II (moderate). Several additional factors, such as route and frequency of exposure, interactions with other impurities, and compromised physiological conditions, such as liver impairment, may all impact the level of toxicity [25, 46]. Besides, WHO includes carbamates on its endocrine-disrupting chemicals (EDCs), potentially harmful to animals and human health [47]. They discovered that EDCs might disrupt hormone production, transport, metabolism, and elimination, with developmental, behavioral, and reproductive effects resulting from these hormone-active compounds. De Coster and Van Larebeke [48] examined the endocrine-disrupting properties of chlorpropham, carbaryl, benomyl, methiocarb, pirimicarb, and propamocarb by highlighting various pathways, including nuclear receptor activation, estrogenassociated receptor activation, and membrane-bound estrogen-receptor activation, among others.

High-potential AChE-inhibitors have been utilized as toxicants, but lowpotential AChE-inhibitors have been used as prevention agents against nerve agents or as therapeutic agents in treating illnesses such as glaucoma, Alzheimer's disease, and myasthenia gravis, among other things [49]. The primary benefits of carbamate are its intense insecticidal action and poor durability since it degrades swiftly within weeks or months after being applied to crops. Carbamates are effective against a wide range of pests by blocking the enzyme cholinesterase, causing neurotoxicity, and interfering with the nervous system of the pests [50]. These chemicals also exhibit a range of neurotoxic effects not mediated by a cholinergic mechanism. Carboxylated acetylcholinesterase enzyme is a volatile version of the enzyme, and regeneration of this enzyme is comparatively quick when contrasted with the regeneration of a phosphorylated form of the enzyme [51]. Carbamates produce mild eye irritation and moderate skin irritation, depending on the specific vehicle employed, the duration of contact, and the substance applied directly to the skin that has been harmed or is in good condition, according to the manufacturer [51, 52].
