Pollution Status of Pesticide Residues in Food Products in Iran : A Mini-review within 2008-2018

a Student Research Committee, Department of Environmental Health Engineering, Hamadan University of Medical Sciences, Hamadan, Iran b Department of Environmental Health Engineering, Faculty of Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran c Professor, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran d Assistant Professor, Department of Environmental Health Engineering, Ahvaz Jundishapur University of Medical sciences, Ahvaz, Iran e Research Center for Environmental Pollutants, Qom University of Medical Sciences, Qom, Iran f Ph.D. Student of Environmental Health Engineering, Student Research Committee, School of Health Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran

Fruit and vegetables hold a special place in the daily diet of all people. Pesticides consist of a vast abundance of chemicals that are used to prevent, defeat, and decrease pests in different stages of fruit and vegetable cultivation (1,2). To date, at least 1,000 active pesticide components have been registered in the world. They are available in different formulations provided by manufacturers (3). Numerous varieties of pesticides, including insecticides, herbicides, disinfectants, and fungicides, are employed for pest control.
Pesticides are assigned to different groups, namely organochlorine, organophosphate, carbamate, and pyruvate (4). Despite the exceptional economic and agricultural advantages of pesticides, they give serious cause for concern due to their possible harmful effects on human health (5). Many of these pesticides and their metabolites have been associated with several diseases, such as cancer, nervous system dysfunction, brain damage, mental illness, tumor, respiratory system disorder, asthma, Parkinson's disease, reproduction birth defects, and skin disease (6).
Their lipophilicity and persistence are the features that lead to the bioaccumulation of these compounds in adipose tissues and organs of biological species. In addition, biomagnification occurs throughout the food chain and food web as a result of the high rate of contamination in top predators (7).
Although human exposure to pesticides happens via various routes, the consumption of food products containing pesticides is the main pathway. Most pesticide residues are found in food owing to the direct use of pesticides in agricultural commodities or during storage (8).
Nowadays, the use of pesticides is indispensable across the globe due to the storage of food. Therefore, many countries and international organizations have introduced several regulations for food safety and the sustainability of human health. Consequently, a monitoring system is necessary for the determination of human vulnerability to pesticides and the examination of pesticide residues in food. The present study was conducted on the pesticide contamination of food products in Iran.
For the purpose of the study, the articles published within 2008-2018 were searched in the local and international databases, including PubMed, Science Direct, Scopes, using the keywords of pesticides, food, Iran, and residual, in both Persian and English languages. The current study focused on pesticide residues in foods of vegetal and animal origin. Furthermore, the methods used to reduce residual pesticide before consumption were presented in this article. The preliminary search yielded 185 articles. After reviewing the articles, 26 studies were finally selected considering the purpose of the study. It is noteworthy that retrieved articles were classified according to the origin of food. In addition, the pesticide residues identified in studies were compared with accepted maximum residue limits (MRLs) as adopted by the FAO/WHO Codex Alimentarius Commission (9).
Based on the findings, various studies have been carried out to determine the contamination of residual pesticides in different vegetal, animal, and grain products (Table1, 2, and 3). Most pesticides have been used for pest control in plant-derived products. They are often used to attack fungal and insect-derived diseases. The pesticide residues have been evaluated in    Figure 1) Pesticides residues in various food products in Iran various food products, including rice, cucumber, tomatoes, wheat, and various types of tea and fish. The majority of studies have been conducted on products of vegetal origin. Compared to these products, the studies on pesticide contents of animal food products have been conducted on marine food products, especially fish species (Figure 1).

Pesticides residues in foods of vegetal origin
Pesticides are used to produce more and higher-quality fruit and vegetables. Despite the benefits of pesticides, pesticide residues in fruits and vegetables can adversely affect consumer health (35). The safety of food plants of the family Cucurbits, such as cucumbers and tomatoes, for pesticide residues, has been widely examined. Furthermore, in the studies reported in this review, products of vegetal origin have been more assessed for the organophosphoric pesticide group, such as Diazinon, Ethion, and Mancozeb ( Table 1).
The study of Diazinon residues in tomatoes grown in greenhouses (10) demonstrated that the mean of Diazinon residues was 5.52 times the national Maximum Residue Limit (MRL=0.05 mg/kg). Moreover, the mean of oxydemeton methyl was calculated at 1.624 mg/kg which was 1.624 times the MRL (mg/kg) (9). Values reported from pesticide residuals showed that the level of pesticides in greenhouse tomatoes was high and significant. Furthermore, it was indicated that farmers use pesticides excessively without the supervision of related organizations.
A related study examined the Ethion insecticide residues in greenhouse cucumber and the efficacy of some processes in its reduction before consumption (11). The results denoted that the maximum and minimum Ethion residues after one-hour spraying were 1.63 and 1.31 mg/kg, respectively. Furthermore, it was added that storage for 24 h and washing (2 min) reduced the initial amount of pesticide residues by 43.2% and 52.7%, respectively. It was also argued that the implementation of some simple measures, such as storage, simple washing and optimization of dosage, number of sprays, and taking time to pick up after spraying, helps to reduce the residue of  pesticides before selling. In another study, Nazemi et al. (12) studied the effect of storage and washing with various detergents on Dichlorvos residues in tomato. They found that Dichlorvos residue of the samples was below MRL during storage at room temperature and refrigerator after 8 and 10 days, respectively. Furthermore, they stated that soaking in water for 30 min, a solution of sodium chloride, acetic acid, and sodium bicarbonate decreased 35.75%, 34.62%, 14.48%, and 92.74% of Dichlorvos residue levels, respectively.

Discussion
In another study carried out by Shokrzadeh et al. (13), the levels of Diazinon and Malathion residues in all cucumber samples were lower than 0.05. Nonetheless, the residue levels of Malathion were higher in some samples. Their results demonstrated that farmers' unawareness plays a peculiar role in pesticide application, along with easy access.
Another research was performed by Ghayebzadeh et al. on the pesticide residues in tomatoes and cucumbers in the markets (14). The results of the mentioned study reported that contamination values in three sampling areas of A, B and, D were 2(22.2%), 1(11.1%), and 2(22.2%), respectively. Diazinon level in cucumber specimens was higher than MRL in one region, while it was less than MRL in another area. In their study, the presence of pesticides residues was contributed to the following reasons: a: farmers' unawareness b: incorrect use of pesticide and inappropriate spraying c: disregard for the time interval between spraying and harvesting time.

Pesticides residues in foods of animal origin
Pollutants from contaminated supplies and water, and/or from pesticide application in animal production fields can accumulate on breeding animals. Pesticide mixtures are mostly stored in the fat and tissue of animals (36). Different pesticides have been analyzed for detecting residues in food products of animal origin in Iran ( Table 2).
The amount of pesticide residues has been extensively studied in fish species. Nearly all studies have reported contamination in samples throughout the country. Though the use of organochlorine pesticides is banned in the country, researchers have traced them in environmental samples. Arzi et al. (16) investigated concentrations of hexachlorocyclohexane isomers (β,γ,δ HCH), dichlorodiphenyltrichloroethane (pp َ , pp DDD) and its metabolites (ppDDE, ppDDD), Aldrin, Dieldrin, heptachlor epoxide, endosulfan isomers (α, β), and Methoxychlor in Carp fish assemblage. They observed 14 organochlorine pesticides in all collected fish samples. The maximum and minimum concentrations of organochlorine pesticides were related to β-HCH (65.36 μg/kg) and op DDT (0.13μg/kg) observed in Mahshahr and Shadegan Carp fish, respectively.
In a similar vein, Manavi et al. examined organochlorine pesticide residues in two fish species of the southern Caspian Sea (17). The results showed that total organochlorine residues varied from 2.102 ppb-9.033 ppb in Liza aurata fish in the research area. They showed that in L. Aurata, Lindane pesticide displayed the greatest level among the evaluated components (1.642 ppb), whereas α-Lindane designated the highest mean level of the measured components (0.57 ppb). The mentioned research demonstrated that the total amount of organochlorine compounds in Rutilus frisii kutum fish was greater than that in L. aurata. Nevertheless, no significant difference was observed between these two kinds of fish regarding pesticide residues (P> 0.05). Fish feed contamination can be a potential source of direct entry and accumulation of pesticides in fish tissues (37). Based on previous studies, organophosphorus pesticides are used more frequently, compared to organochlorines (Table .2). Several studies have examined the presence of pesticide residues in biological samples. These studies indicated that pesticide residues exist in food products and can enter the body through the food chain. Behrooz et al. investigated the hair and milk of Iranian pregnant women with organochlorine pesticide contaminants (38). They examined organochlorine pesticides, such as DDT and its metabolites, Hexachlorobenzene (HCB), a-, b-, and c-hexachlorocyclohexane (HCH), and seven Polychlorinated biphenyls (PCBs). Their finding showed that c-HCH isomer concentrations mean was higher, compared to the b-HCH isomer which is generally the most prevalent HCH in biological matrices. Moreover, they denoted that the samples which were taken from the hair of women in the countryside of Nowshahr, Mazandaran, Iran had the highest concentration of p,p-DDT ( (24 ng/g) with lower p,p0-DDE/p,p0-DDT ratio (0.6 ng/g) which suggest recent exposure to fresh DDT in this region. Their results pointe to a marked difference (P<0.05) in organochlorine containing HCHs between women who consumed fish once a week and those who used fish more frequently.

Pesticides residues foods of grain origin
In grains cultivation stages, pesticides are used during the growth of the vegetative plant to protect them against the harmful effects of insects, pests, pathogens, and, weeds. Furthermore, pesticides, especially insecticides, are applied during the storage time in order to avoid product loss. Although the use of pesticides increases the quality and production of beans, the presence of residual pesticides may adversely affect consumer health in the long run. Plant protection products can be applied at the stage of primary production, as well as during crop storage (39).
In their study, Shokrzadeh et al. (31) assessed organophosphorus insecticide residues, including Diazinon and Chlorpyrifos, in Tarom and Persian rice samples ( Table 3). The experimental results showed that almost all samples contained the residual Diazinon and Chlorpyrifos insecticides. They also reported that compared to previous studies, there has been a marked increase in the mean residual Diazinon insecticide in rice samples. Furthermore, they indicate that pesticide residue quantity was correlated with the time of insecticide application and harvesting. Along the same lines, Jalalizand et al. examined the amount of Chlorpyrifos pesticide residues in sugar beet (30). In this investigation, Chlorpyrifos residues were examined in sugar beets in the towns of Isfahan province in Iran. The result of the mentioned study indicated that the pesticide residues in sugar beets were higher than the maximum permissible residues (0.01 mg/kg sugar) in all study areas. It was noted that a short time interval between harvesting and consumption could result in high levels of pesticide residues higher than acceptable levels. It has also been stated that the provision of training and awareness to farmers regarding pests control by executive agencies can reduce pesticide applications. In another study, pesticide residues, including Deltamethrin, Permethrin, and Malathion, were assessed in stored wheat samples in soil (40). The results showed that the levels of Permethrin exceeded permitted levels in 3 out of 36 wheat grain samples.
Based on the insight gained from the above-mentioned studies, residual pesticides have been observed in most cereal products. Among the pesticides, Chlorpyrifos is a commonly utilized insecticide for pest control in grains all over Iran. Moreover, as evidenced by studies, a short time interval between spraying and harvesting is an effective factor influencing the amount of pesticide residue. Moreover, training and awareness of farmers, as well as the supervision of executive organizations are the keys to the reduction of pesticide application in foods. The presence of pesticides in food products is recognized as one of the most important risk factors for non-communicable diseases. The current review article aimed to identify pesticide residues in foods of vegetal and animal origin and presented the methods used to reduce pesticide content in food before consumption.
In addition, it sought to shed light on the causes of pesticide overuse in Iran. Diazinon has been studied in many types of research and the residual has been reported in many products. Proper washing and immersion in alkaline solutions at a suitable time should be considered to decrease pesticide residues in food products before consumption. Effective factors influencing the presence of pesticide residues in food products included: farmers' unawareness, incorrect use of pesticide and inappropriate spraying, disregard for the preharvest interval (PHI). therefore, due to the excessive intake of this pesticide, it requires the special attention of responsible organizations.