As the world’s population grows, the industrialization of agriculture and the expansion of livestock production to meet increasing food demand create opportunities and challenges for food safety. These challenges place more responsibility on food manufacturers and processors to ensure food safety, preventing food contamination before it reaches the consumer [1].

The continuous development of agriculture intensifies the application of pesticides globally to reduce crop yield losses and increase productivity and product quality [2]. Proximately 2 million tons of pesticides are currently applied to crops worldwide each year to increase productivity and reduce losses from pests and diseases [3]. According to the Food and Agricultural Organization (FAO) of the United Nations, the United States of America was the largest user of pesticides in 2020, while the next 10 largest pesticide users in the world are Brazil, China, Argentina, the Russian Federation, Canada, France, Australia, India, and Italy [4]. In the 2022 update, FAO reported that total pesticide use in China significantly decreased, moving China to third place in pesticide usage globally [4]. However, even though a plateau has been reached in recent years, total pesticide use has increased by approximately 50% compared to the 1990s [4]. The pesticide use by region and the top five largest pesticide users in the world are shown in Figure 1.

Pesticide regulatory systems established to protect humans and the environment vary from country to country [5]. This variability implies that each country can adopt regulations to define acceptable concentrations of particular pesticides in food and feed and restrict or prohibit the usage of particular pesticides due to their unacceptable health or environmental effects. The Joint Meeting on Pesticide Residues (JMPR) is an expert body established mutually by the FAO and the World Health Organization (WHO) that is responsible for establishing toxicological endpoints, such as acceptable daily intake (ADI) and acute reference dose (ARfD), based on experimental data. Additionally, the JMPR recommends the maximum concentrations of pesticide residues (maximum residue levels, or MRLs) in food and feed to the Codex Committee on Pesticide Residues (CCPR) for consideration [6]. The recommended MRLs in food and feed that are considered safe for consumers were finally adopted by the Codex Alimentarius Commission. The MRLs, which provide a wide margin of safety based on good agricultural practice, are the most implemented standards regarding food safety [7]. However, regardless of the prevailing framework the Codex provides, the MRLs differ considerably across countries [8].

In the EU, the European Commission regulation 396/2005 directly concerns public health, establishing a system of setting and monitoring the MRLs in food and feed [9]. In the USA, the Environmental Protection Agency (EPA) is responsible for the pesticide registration, regulations, and establishment of MRLs in food and feed following the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) and the Federal Food, Drug, and Cosmetic Act (FFDCA) [10]. The US Department of Agriculture (USDA) and the Food and Drug Administration (FDA) are responsible for measuring and collecting data on pesticide residues in fruits, vegetables, grains, meat, and dairy products nationwide and in products imported from other countries. In China, the Ministry of Agriculture and Rural Affairs (MARA) is the main pesticide regulatory body responsible for pesticide registration and management [11]. In Brazil, pesticide regulations are supervised by the Ministry of Health through the National Sanitary Surveillance Agency (ANVISA), the Brazilian Institute for the Environment and Renewable Natural Resources (Ibama), and the Ministry of Agriculture, Livestock, and Food Supplies (MAPA) [12].

Of the total amount of pesticides used worldwide, organophosphate pesticides (OPs) account for approximately 33% [13]. As effective and broad-spectrum insecticides, they are extensively used worldwide in agriculture, homes, gardens, and veterinary practices [14]. In the last decade, over 100 organophosphorus compounds have been commercially used as insecticides to control pests in agricultural food commodities [15], of which the medium- or low-toxic OPs, such as dimethoate, phoxim, chlorpyrifos, and trichlorfon, are widely used [16]. Although numerous OPs are no longer approved in most developed countries, they are still in use in many developing countries, causing long-term negative effects on human health and the environment [7]. Acute and/or chronic exposure to OPs can occur directly from occupational and non-occupational use and indirectly through the consumption of pesticide residues that can remain in food and drinking water [17]. Pesticide residues and their metabolites can contaminate soils and water, enter the food chain, and, as a final point, display toxic effects, affecting human health ^[16][18][19][16,18,19].

The increased quantity and frequency of pesticide utilization worldwide consequently increased their impact on the environment and human health. The excessive use and misuse of pesticides, especially in developing countries, can cause environmental pollution and adverse human health effects in the long run. While recognizing gaps in pesticide regulations that impact consumer safety, public health concerns related to pesticide contamination of foods and recent strategies proposed to prevent and/or reduce their adverse effects on human health and the environment are discussed. Particular attention is paid to biotic and abiotic strategies used for OPs degradation, identifying challenges and potential for future improvements.

2. Public Health Concerns Related to Pesticide Exposure

One of the major issues related to food safety is the lack of globally harmonized pesticide legislation and safety standards [20]. Pesticide MRLs in foods and feeds significantly differ, especially among developed and developing countries. The differences in regulations also cause trade issues since many developing countries use unauthorized pesticides or different MRLs [20]. Also, the EU MRLs are more stringent than the Codex MRLs, raising concern about whether the Codex MRL values sufficiently protect consumer health [20]. Most developed countries established their own MRL policies, and for developing countries, meeting the MRL requirements of developed countries can be particularly challenging [21]. Pesticide poisoning and mortality occur mostly in developing countries and are usually associated with insufficient occupational safety standards and regulations, inadequate application, and poor labeling of pesticides [22]. Inadequate regulatory systems also result in the import of pesticides banned in developed countries, while a lack of awareness among farmers and inadequate personal protective equipment cause poor pesticide practices. According to a report by the European Parliament (2021) [7] and Pesticide Atlas Kenya Edition (2022) [23], many pesticides no longer authorized in the European Union are still allowed to be manufactured and exported in developing countries. For example, until its ban in 2020, chlorpyrifos was the most commonly used pesticide in food production in the EU [24]. However, it is still being applied in China, India, and many other countries of the Global South ^[24][25][24,25]. Brazil, the largest pesticide consumer in Latin America, approved 475 new pesticides in 2019, of which about a third contain active substances that have been banned or restricted in the EU [7]. In 2019, Brazil imported 14 hazardous compounds, including chlorpyrifos, fipronil, cyanamide, and propineb [23]. Kenya, as a major importer of banned pesticides mainly from the EU and China, has registered 51 active ingredients prohibited in the EU, such as trichlorfon, atrazine, fipronil, iprodione, acetochlorines, and 1,3-dichloropropene [23]. The United States also allows the production and export of domestically banned pesticides to low- and middle-income countries where they have been linked to significant adverse health effects on the local population [26]. In addition, food containing residues of banned pesticides is frequently reimported back to the countries that allow their production and export, contributing to a global pesticide exposure risk [23]. To address the gap in the regulations of pesticides that pose risks to human health and the environment, in 2020, the European Commission drafted a legislative initiative to prohibit the production and export of hazardous chemicals banned in the EU, which is expected to come into force in 2023 [23]. There are numerous reports indicating pesticide contamination of foods. For example, an earlier study from Ghana reported that chlorpyrifos, diazinon, deltamethrin, fenvalerate, and permethrin concentrations exceeded their respective EU MRLs in some ready-to-eat vegetable samples collected from different sites along the food chain [27]. Similar results were obtained in the study of 160 samples of commonly consumed fruits and vegetables collected from all supply chain stages (distribution, storage, and handling from farm to fork) in the Kampala Metropolitan Area, Uganda. In 95.6% of the samples, multiple pesticide residues were detected, of which 91.3% were organophosphates [28]. The analysis of 1183 bovine milk samples from different locations in India demonstrated that approximately 8% contained organochlorines, organophosphates (ethion, profenofos, chlorpyrifos), synthetic pyrethroids, and phenylpyrazole residues, exceeding the MRL values. Chlorpyrifos was the most common OP detected [29]. Moreover, the residues of hexachlorocyclohexane (HCH), dichloro-diphenyl trichloroethane (DDT), and endosulfan were also found in some of the milk samples, although their usage was restricted or banned [29]. A recent study from Egypt reported that approximately 40% of the pesticide residues detected in samples of vegetables and fruits from the market exceeded the permissible MRLs. The most frequently detected pesticides were insecticides; the results obtained for lambda-cyhalothrin, fipronil, dimethoate, and omethoate in spinach, zucchini, kaki, and strawberry, respectively, indicate they may cause acute or chronic poisoning when consumed in amounts equal to 0.1 or 0.2 kg per day [30]. Another study from Egypt reported the presence of multiple pesticide residues (cypermethrin, thiamethoxam, chlorpyrifos, and lambda-cyhalothrin) in strawberry and tomato-based products available on the market. It was found that 27% of the average pesticide residues in the tested samples exceeded the maximum residue levels (MRLs) [31]. A recent study from Algeria has revealed the contamination of honey samples with OPs (methyl parathion, coumaphos, and fenitrothion), exceeding the MRL (MRL 50 ng/g) [32]. As mentioned, pesticide MRLs in food imported from outside the EU are generally higher than in foods from EU countries [33]. However, an enhanced level of pesticide residues in foods was also reported in EU countries. For example, a previous study from Poland reported an exceedingly high presence of chlorpyrifos in all of the investigated fruits and vegetable peels and also a high level of methyl parathion, especially in the peel of potatoes and pulp of zucchini [34]. Recent research from the UK has shown that out of the total 33,911 analyzed samples from imported foods (including from EU countries), 50.2% contained detectable residues, and 3.3% of the total analyzed samples were above MRLs [35]. Also, the contamination of foodstuffs, such as honey, with OP residues was reported in studies conducted in Italy, Spain, Belgium, France, Germany, Switzerland, and from outside Europe, such as South America and North America [36]. A recent study on more than 200 cereal and legume samples from Italy, Eastern Europe, and some non-European countries has reported the presence of pesticide residues in the grain samples (contamination percentage of 7%), which were below the MRLs, while no pesticide was found in the analyzed legumes. The most abundant pesticides in cereal samples were cyfluthrin, deltamethrin, phenothrin, cypermethrin, fenvalerate, chlorpyrifos, and pirimiphos-methyl [37]. The latest EFSA annual report, considering the assessment of pesticide residue levels in foods on the European market in 2021, has shown that 96.1% of the samples analyzed were below the MRL, while 3.9% exceeded this level, of which 2.5% were non-compliant [38]. The MRL exceedance and non-compliance rates were lower than those reported in 2020 (the MRL exceedance rate of 5.1% and the non-compliance rate of 3.6%). However, samples imported from third countries showed a 5-fold MRL exceedance rate (10.3%) and non-compliance rate (6.4%) compared to the EU-derived samples, which showed 2.1% MRL exceedance and 1.3% non-compliance [38]. Given the safety margins incorporated into the ADI and ARfD, the MRL exceedance does not necessarily imply a risk to human health, so case-by-case assessments are required to determine whether dietary intakes exceed the health-based limits. The EFSA report shows that no consumer intake concern was identified in the chronic health risk assessment. However, out of the total samples analyzed under the acute assessment, 1.1% exceeded the health-based guidance values (HBGVs) in 29 pesticides out of the 190 analyzed [38]. As expected, food products in developed countries are systematically monitored for pesticide residues to ensure compliance with national legislation and consumer safety. In contrast, the monitoring of food in developing countries is often restricted; nevertheless, this issue is also reported in developed countries, as shown in the case of the US, where the FDA inspects only 1–2% of import shipments [20]. Therefore, an increasing public health concern associated with pesticide contamination of food is completely justified and points out the necessity to globally harmonize and standardize MRLs to ensure consistent and effective food safety regulations worldwide. Establishing uniform MRLs is a fundamental step that must be followed to prevent and avoid any health risks. In addition, the lack of consensus regarding MRLs undermines pesticide controls, so the continuous, internationally harmonized monitoring of foods to ensure consumer safety is required. Over the past years, the main concern has been related to the potential risk of combined exposure to multiple pesticide residues in the diet and the dose addition of these compounds. According to the current regulations, the risk assessment of exposure to chemicals mainly relies on assessing individual substances and a few groups of substances that are expected to occur together [39]. The current methods used for human risk assessments assume that different components in mixtures act additively and behave as if they were dilutions of each other [39]. In this respect, the evaluation of exposure to multiple chemicals assumes that compounds with the same mechanism of toxicological action may have a cumulative effect that should be considered. In this regard, much effort has been put toward developing comprehensive frameworks dealing with human risk assessment of combined exposure to multiple chemicals ^[40][41][40,41]. As a result, methodologies developed enabled a grouping of chemicals into cumulative assessment groups (CAGs) based on their effects on target organs/systems and then with respect to their modes of action. Such methodologies have been developed only for multiple pesticide residues in food [42]. In 2021, EFSA published a report on a retrospective (2016–2018) cumulative risk assessment of dietary exposure to OPs (n = 36) and N-methyl carbamate insecticides (n = 11), which was conducted for chronic inhibition of erythrocyte acetylcholinesterase (AChE) [42]. It was concluded that cumulative exposure to pesticides, causing effects on the AChE, did not reach the threshold for regulatory consideration for any of the populations assessed [42]. However, the effects of combined exposure to multiple pesticide residues can be more complex due to their possible interactions. Scientific data about the possible synergistic effects of multiple pesticide residues as well as the effects of exposure to multiple residues that display different modes of action remains very limited ^[20][43][20,43]. Additionally, exposures to different chemicals may arise from separate sources, which should also be considered [44]. Consequently, these gaps in our knowledge may lead to an underestimation of the real health risk. Recent nutritional recommendations to increase the consumption of fruit, vegetables, and whole grains may increase dietary pesticide intakes leading to severe cumulative toxicity and increased risk of various chronic illnesses, including cancer, respiratory, metabolic, reproductive, and neurologic disorders ^[1][45][1,45]. Urinary levels of pesticides or their metabolites are commonly used as biomarkers of human pesticide exposure [46]. Recently, the European Human Biomonitoring Initiative (HBM4EU) prioritized the collection of information on human exposure to pyrethroids pesticides, organophosphate pesticides (chlorpyrifos, dimethoate, and glyphosate), polyethoxylated tallow amine (additive in glyphosate formulations), and phenyl pyrazole insecticide (fipronil) for the period 2000–2022 [47]. However, as no proper urinary biomarkers existed for dimethoate and polyethoxylated tallow amine (POEA), the European human biomonitoring data on these substances was unavailable. The study results indicate extensive exposure to pyrethroids, chlorpyrifos, and glyphosate in the general European population, with noticeable geographical differences. The highest urinary levels for all the investigated pesticides were reported in Cyprus and Valencia (Spain) [47]. As for the OPs, the high detection rate of chlorpyrifos metabolite, 3,5,6-trichloro pyridine-2-phenol (TCP), was reported in most studies. However, as chlorpyrifos and chlorpyrifos-methyl have been banned in the EU since February 2020 [48], the exposure level in the general population is expected to have decreased. Recently, POEA exposure biomarkers have been identified; the first LC-MS/MS method for rapid analysis of 11 POEA homologues in human plasma was developed and validated using the plasma samples of glyphosate-poisoned patients [49]. Several studies have shown that organic food consumption may be one way to achieve a considerable reduction in dietary exposure to pesticides, including OPs, minimizing potential health risks ^{[43][50][51][52]}[43,50,51,52]. Organic farming stipulates the non-use of synthetic fertilizers and most pesticides, leading to the absence or decrement of the concentration of pesticide residues in foods compared to conventional farming ^[45][52][45,52]. A recent study assessing the EU agricultural soils of organic and conventional farms reported that the pesticide residue levels in organic fields were 70–90% lower than in conventional ones [43]. However, although synthetic pesticides are not used in organic farming, pesticide residues can still be present in organic farming soils [53]. Furthermore, persistent compounds, such as DDT, remain at relatively high levels in organic fields, likely due to historical applications, despite being banned in many EU countries since the 1970s [54]. Therefore, to ensure minimal pesticide residue levels, transitioning to organic farming requires conversion transition periods adapted based on the initial residue mixtures and their residence time in the soil [43]. In addition, there is a severe research gap considering the effects of complex pesticide mixtures present in the soil-on-soil health and, consequently, on food quality and human health [43]. Several dietary intervention studies have shown that an organic diet significantly reduces urinary pesticide residue excretion compared to conventional food consumption [45]. However, these studies usually monitor a small number of selected pesticides and do not evaluate mineral- and plant-extract-based pesticides that are commonly used in organic farming. In addition, urinary pesticide residue excretion may result from both dietary and environmental pesticide exposure, and according to current knowledge, the relative contribution of these two sources to total chronic pesticide exposure is not possible to estimate [45]. The risk assessment of pesticide effects on human health and the environment is complex and considers the types and dosage of pesticides used, the periods and levels of exposure, and the environmental characteristics of the locality where pesticides are applied. In addition, although some toxic pesticides have been banned, they continue to be detected frequently in the environment due to their long degradation half-lives, thus contaminating the soil and water sources [55]. Therefore, although there is a requirement for pesticides to be produced, distributed, and used under regulations, due to their frequent applications, mistreatments, and heterogeneous regulatory limits, pesticides and their metabolites have been frequently detected in crops, agricultural soils, and water sources, posing a potential threat to human health ^[16][56][16,56]. Therefore, the cumulative risk assessment of the pesticide effects on human health should consider both the dietary and non-dietary routes of exposure and be regulated by an extensive legal framework harmonized globally to ensure and maintain food safety and security. Based on the above, developing and implementing improved strategies to protect human health and the environment is mandatory.

Acknowledgments: The authors acknowledge the support provided by the Ministry of Science, Technological Development and Innovations of the Republic of Serbia (No. 451-03-47/2023-01/200017).