**1. Introduction**

Legumes are plants that belong to the family, *Fabaceae* or *Leguminosae*, and they include chickpeas, cowpea, lentils, soy, etc. [1]. They are highly nutritious and can be consumed as food by human beings and animals [2].

Pesticides are chemical substances that are manufactured for the control of pests in domestic, agricultural and industrial settings, among others [3]. They are classified as herbicides, fungicides, bactericides and insecticides mainly for agricultural applications [4]. Insecticides comprise carbamates, organochlorines, organophosphates, neonicotinoids, pyrethroids; herbicides include benzothiazolyl urea, carbamic and sulfanilic acids, isoxazolyl urea, phenylpyrazole and pyridinium; while fungicides contain carboxamides, carbamates, dithiocarbamates, etc. [5, 6].

Heavy metals (HMs) are a group of metals that possess high atomic weights and densities beyond 5 g/cm3 [7]. They are usually derived from agricultural, mining and industrial activities, as well as effluents [8]. It has been observed that HMs for instance, lead (Pb), cadmium (Cd), zinc (Zn), nickel (Ni) and copper (Cu), build up in the soil and in plant uptake structures and evoke injurious effects on the environment and the health status of human beings [7, 9, 10]. Besides, HMs have the propensity to be toxic when the populace are exposed to them or when they are consumed in proportions beyond the acceptable daily limits [11].

Different food stuffs such as legumes, cereals, fruits, vegetables, etc. have been contaminated with pesticides and HMs in various parts of the world. It is noteworthy that the common environmental pollutants, pesticides and HMs, increasingly cause numerous health hazards to the populace because of their permeation and upsurge in the food chain, as well as their persistence in the bionetwork [12].

In 2020, [13] identified the organophosphate pesticides (malathion, parathion, ethion and carbophenothion) in cowpea (an African legume) from Gwagwalada market in Abuja, Nigeria, through the use of Gas Chromatography–Mass Spectrometry. The levels of the pesticides found in the cowpea samples exceeded the maximum residue limits set by the European Union and the Agency for Toxic Substances and Disease Registry. Additionally, [14] confirmed the contamination of cowpea by residues of organochlorine (endosulfan and lindane), and organophosphorus (malathion) pesticides in high levels in Northern Cameroun.

Furthermore, heavy metals including nickel, cadmium, manganese and cobalt were detected in cowpea by [15]. In the research, the concentrations of nickel, cobalt and manganese discovered in the legumes were below the acceptable limits by FAO/WHO, while the cadmium concentration was beyond the FAO/WHO limit permitted. However, in a study conducted in Saudi Arabian markets, it was discovered that kidney beans and haricots contained high levels of Mn, while peas had elevated levels of zinc beyond the standard permissible levels [16]. Hence, regular monitoring of food stuffs for HM content was advocated.

It has been observed that fertilizers and pesticides are responsible for the increased level of soil pollution by non-essential micronutrients such as arsenic, cadmium, mercury, nickel and lead [17]. These non-essential micronutrients in the soil are conveyed through various plants as they accumulate in the edible portions [18]. Subsequently, the general population and animals may be exposed to the residues of these environmental contaminants (pesticides and HMs) when they consume plants that have been polluted with them.

The aim of this review chapter is to underscore the acute and chronic health risks that human beings may be exposed to during their life time as a result of the consumption of legumes contaminated with pesticides and HMs. In addition, the mechanisms through which pesticides and HMs engender different undesirable health outcomes in biological systems were highlighted.

It is envisaged that the information in this review chapter will stimulate and enhance concerted efforts towards the regular monitoring of legumes and other foodstuffs for pollutants in order to attain food safety.

#### **2. Mechanisms through which pesticides induce adverse health effects**

When human beings consume pesticides in legumes and other food sources through the dietary route, the pesticides may cause acute and chronic health risks through diverse mechanisms. For instance, organophosphate pesticides (chlorpyrifos, diazinon, dichlorvos, fenitrothion, malathion, parathion, etc.) bring about deleterious health effects by inhibiting the function of acetylcholinesterase, *Health Risks Associated with the Consumption of Legumes Contaminated with Pesticides… DOI: http://dx.doi.org/10.5772/intechopen.99673*

reducing the secretion of insulin, and perturbation of the metabolism of nutrients in living systems [19–21].

Moreover, organophosphate pesticides stimulate the release of reactive oxygen species and this phenomenon might cause oxidative stress [22, 23]. Oxidative stress refers to a disparity between the levels of prooxidants and antioxidants thereby culminating in damage to vital molecules including DNA, RNA, lipids and proteins in biological systems [24]. Oxidative stress has been identified as an important mechanism through which different kinds of pesticides cause biological injuries to human beings and animals.

The organochlorine pesticides are chlorinated hydrocarbons that persist in the environment and they include methoxychlor, dieldrin, chlordane, mirex and lindane, among others [25]. They cause the stimulation of the nervous system through the perturbation of action potentials, thereby leading to paralysis and death [26]. Dietary exposure brings about the bioaccumulation of organochlorine pesticides in the body, and this may terminate in derangements in human health [27].

Carbamates such as methiocarb, carbaryl, aldicarb, propoxur and carbofuran reversibly inhibit acetylcholinesterase in mammals and humans [19]. This group of pesticides are capable of causing apoptosis and necrotic changes in the cells of the immune system [28]. Consequently, the immune system becomes compromised and affected individuals become susceptible to various diseases when they are exposed to these pollutants in food and other sources.

Pyrethroids (e.g. allethrin, permethrin, cypermethrin and deltamethrin) are neurotoxicants and they disrupt the muscular structures and modify voltagedependent sodium channels in the body [29]. They exhibit low acute toxicity to mammals and avian species. Conversely, at low levels, pyrethroids elicit acute toxicity to diverse aquatic species and arthropods [30].

## **3. Acute health risks associated with dietary exposure to pesticides**

Acute health risks may become visible instantaneously or within 24 hours sequel to exposure to a pesticide [31]. Pesticides can have access to human bodies through the dermal [32], ocular [33], oral and respiratory [34] routes. According to [35], the exposure of the populace to pesticide residues through the oral route is about five orders of enormity compared to the other routes. It has been affirmed that pesticides can produce acute health disorders such as hypersensitivity, asthma and mortality in people [8, 36–38].

#### **4. Chronic health risks related to dietary exposure to pesticides**

It has been reported that chronic detrimental health risks do not manifest in human beings even within a day subsequent to pesticide exposure [31]. Chronic health risks evoked by exposure to pesticides in food such as legumes include congenital disabilities and decreased birth weight [36, 37]. Additionally, many organophosphate insecticides bring about declines in sperm counts, viability, density and motility; inhibition of spermatogenesis, reductions in testes weights, and sperm DNA damage in males [38]. Other chronic adverse effects of pesticides entail hindering the activities of hormones, their time of release, or mimicking these hormones, thereby culminating in reduced fertility and deformities in the male and female reproductive tracts [39]. These harmful effects may result in declines in the population of human beings affected. Also, pesticides perturb the immune system function and elicit carcinogenicity [40, 41].

#### *Legumes Research - Volume 2*

Some investigators have asserted that organochlorine pesticides and their active metabolites are linked to neurological aberrations, cancers, hypertension, cardiovascular and dermatological disorders in humans [42–44]. Besides, the exposure of the populace to organophosphate, organochlorine and carbamate pesticides may evoke chronic neurological disorders such as Alzheimer's and Parkinson's disease [45]. According to [46], pesticides affect neuronal function negatively by hyperphosphorylation and the disruption of microtubules thereby ultimately causing Alzheimer's disease.
