Concentrations of Organochlorine, Organophosphorus, and Pyrethroid Pesticides in Rivers Worldwide (2014–2024): A Review

Abstract

The extensive use of pesticides has led to the contamination of natural resources, sometimes causing significant and irreversible damage to the environment and human health. Even though the use of many pesticides is banned, these compounds are still being found in rivers worldwide. In this review, 205 documents have been selected to provide an overview of pesticide contamination in rivers over the last 10 years (2014–2024). After these documents were examined, information of 47 river systems was organized according to the types of pesticides most frequently detected, including organochloride, organophosphorus, and pyrethroid compounds. A total of 156 compounds were classified, showing that 46% of these rivers contain organochlorine compounds, while 40% exhibit organophosphorus pesticides. Aldrin, hexachlorocyclohexane, and endosulfan were the predominant organochlorine pesticides with concentration values between 0.4 and 37 × 10⁵ ng L⁻¹. Chlorpyrifos, malathion, and diazinon were the main organophosphorus pesticides with concentrations between 1 and 11 × 10⁵ ng L⁻¹. Comparing the pesticide concentrations with standard guidelines, we found that the Ganga River in India (90 ng L⁻¹), the Owan and Okura Rivers in Nigeria (210 and 9 × 10³ ng L⁻¹), and the Dong Nai River in Vietnam (68 ng L⁻¹) exceed the permissible levels of aldrin (30 ng L⁻¹).

1. Introduction

The exponential growth in the human population has created a pressing need to increase food production [1]. The agriculture industry has enhanced its production process through the use of pesticides, contributing to the security of nearly one third of global crop production [2]. Pesticides help raise crop yields, allowing producers to meet consumer expectations [3,4]. Furthermore, the use of pesticides reduces costly inputs such as labor and fuel, providing significant economic benefits [5]. Agriculture is responsible for around 85% of global pesticide use [6]. Additionally, pesticides are used in public health programs to control diseases (e.g., dengue and malaria) and to manage unwanted vegetation (e.g., weeds and grass) in urban green areas [7]. Consequently, a substantial increase in the global use of pesticides is noted every year [8]. According to the Food and Agriculture Organization (FAO), more than 3 million tons of pesticides are used worldwide each year [9].

A pesticide is a chemical substance or mixture of substances deliberately introduced into the environment to control, prevent, or eliminate any type of pest [10]. Pesticides can be categorized by their target into insecticides, herbicides, and fungicides [11]. Globally, 33% of applied pesticides are insecticides, 40% are herbicides, 10% are fungicides, and 17% are categorized as other types [12]. Additionally, pesticides are classified based on their chemical structures into categories such as organochlorines, organophosphorus, pyrethroids, carbamates, pyrethroids, triazines, and azoles [13]. Despite their benefits, the widespread use of pesticides has raised significant environmental concerns due to their high persistence and bioaccumulation [14]. Only around 0.1% of applied pesticides effectively eradicate the target pests, while the majority are widely dispersed into the environment [15]. Pesticides are considered some of the most important environmental pollutants due to their substantial adverse effects on various environmental media, including soil, air, and water [16,17].

Aquatic ecosystems, in particular, are severely affected by pesticide use [18,19,20,21]. Today, almost all water bodies worldwide, such as rivers, lakes, and estuaries, are contaminated with pesticides [22]. Pesticides can be transported to these water bodies through industrial and municipal discharges, agricultural runoff, farming activities, sewage, domestic wastewater, and stormwater runoff [21,23]. The level of contamination in a water body is influenced by its location and the type of beneficial uses it sustains [24]. Pollution of river water is a global concern because rivers are essential resources for agriculture irrigation, hydroelectric power, residential use, livestock watering, and drinking water [25,26]. Surface water serves as the primary source of urban water supply [27]. Different types of pesticide residues are continuously detected in rivers [28]. As a result, pesticides accumulate in animals and plants, leading to substantial instability throughout the food chain [29]. Pesticide residues can be found in vegetables, fruits, processed food, aquatic products, and drinking water, which represent a health risk for humans [11,30,31,32,33,34]. Although water can be treated to reduce these compounds, removing a wider range of pesticides from surface and drinking water remains a significant challenge due to the high costs involved [35]. The use of adsorbent materials is one of the most effective methods for removing pesticides from water [36,37].

Pesticides are usually toxic compounds, and even small amounts can cause significant harm [38]. The human body can be exposed to pesticides both directly and indirectly [39]. Direct exposure occurs through inhalation, skin contact, or ingestion during pesticide application, while indirect exposure results from consuming food or water contaminated with pesticides [40,41]. The severity of damage depends on the concentration and toxicity of each pesticide, as well as the frequency and duration of exposure [42]. Pesticide exposure has been correlated with a wide range of diseases including asthma, diabetes, leukemia, and Parkinson’s disease [6]. Approximately 3 million people suffer from pesticide poisoning annually, leading to around 200,000 deaths worldwide [43]. However, this number may be higher due to under-reporting, inadequate data, and undiagnosed cases [44]. Pesticide use can also affect non-target organisms, including the following: (1) aquatic species (e.g., fish and turtles) [23,45,46,47,48]; (2) fauna (e.g., bees, butterflies, birds, reptiles, and crocodilians) [49,50,51,52,53,54,55]; and (3) soil microflora [56,57].

Regulatory limits for pesticides in water bodies are essential to prevent negative impacts on the environment and human health [58]. In the absence of globally accepted standards for pesticide residues, many countries have developed their own regulations. However, limits established by the World Health Organization (WHO) are the most widely recognized [22].

Pesticides are necessary for meeting the global demand for food. However, their extensive use, improper application, and inadequate wastewater management have led to the contamination of river waters. Since water is vital for all living beings, its preservation is crucial for future generations. Monitoring pesticide concentration in rivers is a valuable tool for assessing the environmental impact of their use. The aim of this review article is to show some important aspects of pesticides, such as their concentrations in river waters around the world from 2014–2024.

Approximately 2000 active ingredients have been registered as pesticides, categorized into more than 60 chemical groups [59]. Comparative studies between these different groups are essential to obtain a comprehensive understanding of pesticide contamination. Organophosphorus and pyrethroid compounds are among the most commonly used pesticides globally, while organochlorines are highly persistent in the environment [60,61,62]. This research focuses on these three types of pesticides, which are presented in separate sections. In each section, information about their chemical properties, classification, presence in food, and persistence is provided. Additionally, a comparison of pesticide concentration values in rivers around the world with regulated limits is showed. Finally, the effects of pesticides on both the environment and human health are discussed.

2. Research Methodology

This study conducts a comparative analysis to identify the types and concentrations of pesticides detected in the waters of different rivers around the world. The aim is to identify the rivers with the highest pesticide levels to highlight both the environmental and health impacts of pesticide use. The selection process was performed through five steps: (1) research design, (2) data collection, (3) inclusion and exclusion criteria, (4) data evaluation, and (5) selection. Figure 1 shows the document selection process.

2.1. Research Design

This study aims to answer the following research questions:

₋

What are the main pesticides detected in river waters worldwide?

₋

What are the concentrations of these pesticides? Do they comply with the specifications regulated by institutions?

₋

What are the environmental and human health implications of pesticide exposure?

2.2. Data Collection

The databases used for this review were Google Scholar and ScienceDirect. The search was limited from 2007–2024. In each database, the research was performed using the following keywords: pesticides, river, water, pollution, concentrations, organochlorine, organophosphorus, and pyrethroids.

2.3. Inclusion and Exclusion Criteria (Shortlisting)

Inclusion criteria:

• Type of document: journal article, book, book chapter, review, report;
• Language: English;
• Year: 2007–2024;
• Peer-reviewed article;
• Methodology: quantitative analysis;
• Type of pesticide: organochlorine, organophosphorus, and pyrethroid compounds.

Exclusion criteria:

• Type of document: proceedings, thesis;
• Accessibility: the document is not accessible or cannot be downloaded;
• Language: non-English;
• Year: before 2007;
• Non-peer-reviewed;
• Methodology: qualitative analysis;
• Other types of pesticides.

2.4. Data Evaluation

Data were evaluated using two criteria to enable effective comparison:

(1)

Documents were excluded if pesticide concentrations were reported in groundwater systems;

(2)

Documents were excluded if all reported pesticide concentrations were below 1 ng L⁻¹.

After this data evaluation, a total of 205 documents were selected for this review.

2.5. Selection

For the comparison of rivers between 2014–2024, a final exclusion was performed based on the following criteria:

(1)

Only documents published within the last ten years (2014–2024) were selected;

(2)

To prevent duplication of rivers, the document reporting the highest pesticide levels was selected.

A total of 47 documents were chosen after completing these five steps.

Classification

The 47 rivers were categorized based on the type of pesticides detected: organochlorine (19), organophosphorus (17), and pyrethroid compounds (1). Each river was classified according to the predominant type of pesticide reported, as shown in Figure 2. If multiple pesticide types were equally predominant, classification was based on the pesticide with the highest concentration. From these tables, rivers were also categorized by country, and consequently, by geographical distribution. Finally, rivers were grouped by sampling year to facilitate the analysis of trends in pesticide concentrations.

2.6. Physicochemical Properties of Pesticides

Physicochemical properties such as half-life in water, solubility, and organic-carbon normalized water–solid distribution coefficients of the main pesticides found in this study are shown in

Table 1. Physicochemical properties and guideline values of the main pesticides found in this study [63,64,65,66].

Substance Group	Pesticides	DT50w * (days)	Sw ** (mg L−1)	Koc *** (mL g−1)	Guideline Value (ng L−1)
Organochlorine	Aldrin	3830	0.027	17,500	30
	Hexachlorocyclohexane	292–438	10	12,589	2000
	Endosulfan	20	0.32	11,500	NMa (HBV = 20,000)
Organophosphorus	Chlorpyrifos	29.6	1.05	8151	300,000
	Malathion	6	148	1800	NMa (HBV = 900,000)
	Diazinon	50	60	609	B
Pyrethroid	Cypermethrin	1–35	0.004	20,800	B
	Deltamethrin	17	0.002	10 × 106	B
	Permethrin	1	0.2	100,000	E

* DT_50w: half-life in water; ** S_w: solubility in water at 20 °C; *** K_oc: organic-carbon normalized water–solid distribution coefficient. NM^a: non-mentioned (HBV: health-based value recommended by WHO); B: unlikely to occur in drinking water (WHO); E: excluded by WHO (not recommended for direct addition to drinking water).

. Additionally, guideline values recommended by the World Health Organization (WHO) (REF) for drinking water are provided.

3. Results

3.1. Organochlorine Pesticides

Organochlorine pesticides (OCPs) are mainly composed of chlorine, hydrogen, and carbon. For several decades, OCPs have been employed to control pests in agriculture and for vector control in humans [67]. Despite their utility, they are one of the most toxic and hazardous persistent organic pollutants (POPs) and present a serious risk to the environment due to their long-range environmental transport ability and bioaccumulation potential [68]. However, the effects of OCPs on the environment depend on their concentration, dosage, and persistence [69]. OCPs are lipophilic compounds that can adhere to the fatty tissues of mammals and accumulate in water, sediments, soil, and plants [67]. Despite the ban imposed on their use, OCPs continue to be detected at considerable levels across different regions worldwide [70]. OCPs can be divided into three main groups [71]: (1) diphenyl aliphatics (e.g., DDT (dichlorodiphenyltrichloroethane) and DDD (dichlorodiphenyldichloroethane)), (2) cyclodienes (e.g., endosulfan, heptachlor, aldrin, dieldrin, and endrin) and (3) cyclohexanes (e.g., α-, β-, γ-, δ-HCH (hexachlorocyclohexane)). Figure 3 shows the chemical structures of some OCPs and their lethal dose (LD₅₀) values [72,73].

Table 2. Mean concentrations of organochlorine and other pesticides detected in rivers around the world.

River/Country	Substance Group	Pesticides	Concentration (ng L−1)	Season/Month/Year	Agricultural Product	Reference
1. Fraskour–Damietta, Nile River, Egypt	Organochlorine	Endrin	430	January, 2009	Cotton	[76]
		Dieldrin	1081
		p,p-DDD	1209
		p,p-DDT	2268
	Organophosphorus	Chlorpyrifos	578
		Triazophos	1488
2. Ganga River, India	Organochlorine	DDT	54	Summer, 2019	NM	[77]
		HCH	269
		Aldrin	90
		Heptachlor	519
		Endosulfan	54
3. Owan River, Nigeria	Organochlorine	α-BHC	380	June, 2013	Rubber, cocoa, plantain, maize	[78]
		Aldrin	210
		DDT	120
		Ʃ-Endosulfan	310
	Carbamate	Carbofuran	30
	Triazine	Atrazine	150
4. Somme River, France	Organochlorine	Ʃ-HCH	93	April, 2014	NM	[79]
5. Yangtze River, China	Organochlorine	Ʃ-HCH	0.4	November, 2016	NM	[80]
6. Dong Nai River, Vietnam	Organochlorine	Aldrin	68	Rainy season, 2016	Rice, maize, sorghum	[81]
		Heptachlor	40
		Dieldrin	24
		Endrin	27
7. Chenab River, Pakistan	Organochlorine	α-HCH	12	April–June, 2018	Wheat, rice	[82]
		Aldrin	0.6
		Ʃ-Endosulfan	6
8. Pampanga River, Philippines	Organochlorine	Dieldrin	30 *	Dry season, (February), 2017	Rice	[83]
		Endrin aldehyde	589 *
		δ-BHC	372 *
		Ʃ-Endosulfan	64 *
9. Nuble River, Chile	Organochlorine	Ʃ-HCH	18	Wet season, (April–August), 2014	Blueberries	[84]
		Heptachlor	1
		Aldrin	2
		α-endosulfan	0.3
10. Indus River, Pakistan	Organochlorine	Ʃ-HCH	60	December, 2013	Wheat, cotton, rice, sugarcane	[85]
		Ʃ-DDTs	105
11. Nairobi River, Kenya	Organochlorine	β-HCH	19	Dry and rainy seasons (February–July), 2009	NM	[86]
		Heptachlor	40
		Aldrin	15
		Endrin	7
12. Kibos-Nyamasaria River, Kenya	Organochlorine	Dieldrin	103	Wet season	Tomatoes, maize, cassava	[87]
		Ʃ-Endosulfan	102
		Ʃ-HCH	96
		Ʃ-DDTs	162
13. Krishna River, India	Organochlorine	Ʃ-HCH	12	September, 2019	Cotton, paddy	[88]
		Ʃ-Endosulfan	5
		Aldrin	4
14. Okura River, Nigeria	Organochlorine	Aldrin	9000	NM	Banana	[89]
		Endosulfan	6100
15. Brahmaputra River, India	Organochlorine	Ʃ-HCH	8	June, 2012	Potato	[90]
		Ʃ-Endosulfan	3
16. Periyar River, India	Organochlorine	Ʃ-HCH	15	August–September, 2019	Rice	[91]
		Ʃ-Endosulfan	2
17. Barandu River, Pakistan	Organochlorine	Ʃ-HCH	429	March, 2018	Tobacco	[92]
		Aldrin	2
		Ʃ-Endosulfan	9
18. Quequén-Grande River, Argentina	Organochlorine	Ʃ-Endosulfan	3	July 2014–July 2015	Soybean, potatoes	[93]
19. Tucututemo River, Venezuela	Organochlorine	Aldrin	21 *	Dry and rainy seasons (April–October), 2013–2016	NM	[94]
		Dieldrin	18 *

* Non-average value; NM: not mentioned.

provides the concentrations of different organochlorine pesticides detected in 19 rivers worldwide. Additionally, the presence of other types of pesticides is mentioned. In these rivers, aldrin (18%), HCH (22%), and endosulfan (22%) are the predominant organochlorine compounds. In a previous study, DaSilva 2021 et al. [61] mentioned that these pesticides are commonly detected in surface waters. Furthermore, Kida et al. [74] reported that DDT and HCH are the main organochlorines used in agriculture. According to the World Health Organization (WHO) (2019), aldrin is classified as discontinued for use as a pesticide, whereas HCH and endosulfan are categorized as moderately hazardous (Class II) [75].

The concentrations of OCPs show noticeable differences with values between 0.4 and 9000 ng L⁻¹ (Table 2). Considering all reported compounds, the Okura River in Nigeria and the Fraskour–Damietta zone (Nile River) in Egypt exhibit the highest pollution levels [76,89] (Figure 4a). The Okura River shows the highest concentration values of aldrin (9000 ng L⁻¹) and endosulfan (6100 ng L⁻¹). Therefore, the Nile River contains considerable levels of DDT, dieldrin, and endrin, with concentration values of 2268, 1081, and 430 ng L⁻¹, respectively.

Other types of organochlorine compounds with irreversible environmental impacts have been reported in rivers worldwide, as shown in Figure 4b. The Ganga and Pampanga Rivers present high concentration values of heptachlor (519 ng L⁻¹) and endrin aldehyde (589 ng L⁻¹), respectively [77,83]. Additionally, the Owan River in Nigeria and the Barandu River in Pakistan show values of 380 for α-BHC and 429 ng L⁻¹ for Ʃ-HCH, respectively [78,92].

The World Health Organization (WHO) (2017) has established that the maximum acceptable concentration for aldrin in drinking water is 30 ng L⁻¹ [95]. According to this limit, the waters of the Ganga River (90 ng L⁻¹) [77], Owan River (210 ng L⁻¹) [78], Dong Nai River (68 ng L⁻¹) [81], and Okura River (9000 ng L⁻¹) [89] exceed the permissible levels of aldrin for human consumption. In contrast, the waters of the Chenab [82], Nuble [84], Nairobi [86], Krishna [88], Barandu [92], and Tucututemo [94] Rivers exhibit pesticide concentrations within allowable limits, all being below 22 ng L⁻¹. Due to their particular chemical compositions, OCPs can persist in the environment for long periods of time (see Table 1). Aldrin has moderate persistence with a half-life of 4–10 years in the environment, while DDT has high persistence with a half-life of 2–15 years [96].

3.2. Organophosphorus Pesticides

Organophosphorus pesticides (OPPs) are derivates of phosphoric, phosphonic, thiophosphoric, or phosphinic acids [97,98,99]. They are globally recognized as the most extensively used class of pesticides due to their low cost, simple synthesis, and high efficacy [100,101]. OPPs have been used extensively after the ban on OCPs [97]. With over 100 different types, OPPs constitute one of the largest groups of pesticides and represent almost 34% of the pesticides produced and sold for agricultural purposes [102,103,104]. In developing countries, OPPs have become indispensable for supporting economies that depend on agriculture [97]. However, their widespread use has raised environmental concerns. According to Farkhondeh et al. [105], OPPs represent a serious environmental pollutant. These pesticides reduce water quality due to their high persistence, lipophilicity, environmental accumulation, and potential for long-range transference [96]. OPPs can be classified into three main groups based on their chemical structure: (1) aliphatic (e.g., dimethoate, dichlorvos, malathion, and omethoate), (2) phenyl (e.g., methyl-parathion, parathion, tetrachlorvinphos) and (3) heterocyclic (e.g., diazinon and chlorpyrifos) [106]. Figure 5 shows some chemical structures of organophosphorus pesticides and their LD₅₀ values [107,108].

Table 3. Mean concentrations of organophosphorus and other pesticides detected in rivers around the world.

River/Country	Substance Group	Pesticides	Concentration (ng L−1)	Season/Month/Year	Agricultural Product	Reference
1. Kurose River, Japan	Organophosphorus	Diazinon	348	March 2016–February 2017	Rice, beans, wheat, potatoes	[110]
2. Shangyu Region, China	Organophosphorus	Dichlorvos	1560	August, 2014	Waxberry, grape	[111]
		Malathion	360
		Parathion	290
3. Guangzhou River, China	Organophosphorus	Chlorpyrifos	19	Wet season (July), 2012	Chinese chive, banana	[112]
		Malathion	4
		Dimethoate	58
	Pyrethroid	Cypermethrin	5
4. Júcar River, Spain	Organophosphorus	Chlorfenvinphos	97 *	October, 2010	Barley, garlic, onion, oat, potato, tomato, wheat, oranges	[113]
		Chlorpyrifos	36 *
		Diazinon	9 *
		Malathion	9 *
	Triazine	Atrazine	8 *
5. Langat River, Malaysia	Organophosphorus	Quinalphos	18	September, 2015	Cane orchard, oil palm plantation	[114]
		Diazinon	9
		Chlorpyrifos	20
6. Hooghly River, India	Organophosphorus	Methyl-parathion	45	May–June, 2014–2015	Cabbage, cauliflower, chili, oilseeds, lentil	[115]
		Monocrotophos	9
	Organochlorine	Ʃ-HCH	1988
		Ʃ-endosulfan	122
7. Aliakmonas River, Greece	Organophosphorus	Chlorpyrifos ethyl	33	February, 2001	Rice, corn, sugar beets, cotton	[116]
		Parathion methyl	149
8. Tano River, Ghana	Organophosphorus	Parathion	268	Rainy season (October), 2017	Cocoa, maize	[117]
		Methamidophos	241
		Malathion	303
		Chlorpyrifos	383
		Profenofos	303
	Organochlorine	δ-HCH	59
		γ-HCH	2
	Pyrethroid	Permethrin	19
		Deltamethrin	12
9. Linggi River, Malaysia	Organophosphorus	Chlorpyrifos	28	July, 2018	Palm oil plantation	[118]
		Diazinon	33
		Quinalphos	36
10. Sarno River, Italy	Organophosphorus	Diazinon	2 *	2018	Tomato	[119]
		Dimethoate	6 *
		Malathion	5 *
		Chlorpyrifos	12 *
		Dichlorvos	2 *
11. Volturno River, Italy	Organophosphorus	Diazinon	1	2017–2018	Cereals, potatoes, vineyards, olive	[120]
		Dimethoate	2
		Malathion	1
		Chlorpyrifos	5
12. Han River, China	Organophosphorus	Methamidophos	39	June–September, 2015	NM	[121]
		Dichlorvos	20
		Omethoate	48
		Diazinon	48
		Malathion	7
		Parathion	16
13. Mahaweli River, Sri Lanka	Organophosphorus	Diazinon	390,000 *	August, 2019	Rice	[122]
14. Tamazula River, Mexico	Organophosphorus	Diazinon	30	June 2008–July 2009	Tomatoes, bell peppers, cucumber, eggplant	[63]
		Chlorpyrifos	30
		Malathion	6
	Organochlorine	Endosulfan	36
		Aldrin	23
15. Godavari River, India	Organophosphorus	Chlorpyrifos	410	September 2011–July 2012	Cotton, chili, brinjal, tur, tomato, wheat, lemon, orange, jowar	[123]
16. Amazon River, Brazil	Organophosphorus	Malathion	535 *	November–December, 2019	NM	[124]
		Chlorpyrifos	700 *
17. Lerma River, Mexico	Organophosphorus	Malathion	311,760	July–September, 2019	Maize, wheat	[125]
		Glyphosate	252,000

* Non-average value; NM: not mentioned.

presents the concentrations of organophosphorus and other types of pesticides detected in 17 rivers worldwide. Notably, chlorpyrifos (22%), malathion (20%), and diazinon (18%) are the main compounds found. Pundir et al. [109] mentioned that residues of these specific compounds are commonly found in river waters.

In this study, the Mahaweli River in Sri Lanka and the Lerma River in Mexico are identified as the most polluted with OPPs (Figure 6a). The highest concentration is found in the Mahaweli River, with a value of 3.9 × 10⁵ ng L⁻¹ of diazinon [122]. The Lerma River also shows elevated concentrations of malathion (3.1 × 10⁵ ng L⁻¹) and glyphosate (2.5 × 10⁵ ng L⁻¹) [125]. According to the World Health Organization (WHO) (2017), the health-based values in drinking water for both malathion and glyphosate are 9 × 10⁵ ng L⁻¹ [95]. Therefore, the concentrations of these OPPs in the Mahaweli and Lerma Rivers comply with these specified limits.

Intermediate concentrations of OPPs were also detected in other rivers around the world, as shown in Figure 6b. For instance, the Shangyu River shows the presence of dichlorvos (1560 ng L⁻¹), malathion (360 ng L⁻¹), and parathion (290 ng L⁻¹) [111]. The Amazon River is contaminated with chlorpyrifos (700 ng L⁻¹) and malathion (535 ng L⁻¹) [124], while the Tano River contains considerable levels of chlorpyrifos (383 ng L⁻¹), malathion (303 ng L⁻¹), profenofos (303 ng L⁻¹), parathion (268 ng L⁻¹), and methamidophos (241 ng L⁻¹) [117].

The Júcar and Tamazula Rivers exhibit lower concentrations of chlorpyrifos, with values of 36 and 30 ng L⁻¹, respectively [63,113]. Compared to organochlorine pesticides, OPPs exhibit lower persistence in river waters, with half-life values of approximately 29 days for chlorpyrifos, 50 days for diazinon, and 33 days for parathion [126]. The health-based values in drinking water for parathion, dichlorvos, and chlorpyrifos are 1 × 10⁴, 2 × 10⁴, and 3 × 10⁴ ng L⁻¹, respectively [95]. In these rivers, all organophosphorus concentrations show unsafe levels of health concern.

3.3. Pyrethroid Pesticides

Pyrethroids (PYs) are synthetic insecticides derived from pyrethrins, which are natural insecticides found in Chrysanthemum flowers [127]. PYs are some of the most extensively used insecticides around the world [128]. They have extensive applications in agricultural, veterinary, public, and residential pest control. Additionally, they are found in pet shampoos, medications, uniforms, and repellants [129]. Compared to traditional pesticides such as OCPs and OPPs, PYs have lower potential to pollute the environment [130]. However, their extensive use has led to their presence in aquatic environments worldwide [131]. Surface waters can be contaminated with PYs through surface runoff or drainage channels from agricultural or urban areas [130].

PYs are considered less harmful to humans compared to other pesticides because the human body can metabolize and eliminate them with a half-life of approximately 6 h [132]. However, PY compounds are highly toxic to aquatic species. Concentrations as low as 1 pg L⁻¹ can induce acute toxicity in fish, amphibians, aquatic insects, mollusks, and phytoplankton [131,133,134]. For instance, Corcellas et al. [135] reported PY pesticides in 100% of fish tissue samples from rivers in Spain. PYs act as neurotoxins, specifically affecting the receptor sites of voltage-gated sodium channels [136,137].

PY pesticides can be classified into two groups: (1) Type I pyrethroid pesticides, which have a basic structure of cyclopropane carboxylic ester (i.e., tetramethrin and permethrin) and (2) Type II pyrethroid pesticides, which contain a cyano group (i.e., cypermethrin, deltamethrin, and fenvalerate) [138,139,140,141] (see Figure 7). Some pyrethroids contain olefinic structures that can form either cis- or trans-isomers [142]. Usually, cis-isomers are more toxic than trans- ones [143].

Table 4. Mean concentrations of pyrethroids and other pesticides detected in rivers around the world.

River/Country	Substance Group	Pesticides	Concentration (ng L−1)	Season/Month/Year	Agricultural Product	Reference
1. Lis River, Portugal	Pyrethroid	Cypermethrin	664	February 2018–May 2019	NM	[146]
	Organochlorine	Aldrin	1153
		γ-HCH	1085
	Organophosphorus	Chlorpyrifos	159
2. Dongjiang River, China	Pyrethroid	Cypermethrin	41.4	Wet season (July), 2015; dry season (November), 2015	Orange	[147]
		Deltamethrin	12.5
	Organochlorine	Ʃ-HCHs	104.6
		Ʃ-DDTs	75
	Organophosphorus	Metamidophos	26
		Dichlorvos	4.4
		Acephate	74.9
		Chlorpyrifos	16
		Triazophos	43.1
3. Jiulong River, China	Pyrethroid	Cypermethrin	609 *	Wet season (July), 2009; dry season (December), 2009	Pomelo, banana	[148]
	Organophosphorus	Triazophos	1055 *
4. Benue River, Nigeria	Pyrethroid	Cypermethrin	930,000	NM	Cocoa, cotton, rice	[149]
		Permethrin	1,520,000
		Deltamethrin	1,140,000
	Organochlorine	Aldrin	3,750,000
		Dieldrin	5,240,000
		Dichlorvos	1,060,000
	Organophosphorus	Diazinon	1,170,000
		Chlorpyrifos	910,000
5. Sassandra River, Ivory Coast	Pyrethroid	Cypermethrin	13	Rainy season (April), 2021–October 2021	NM	[150]
		Deltamethrin	5.5
6. Elbe River, Czech Republic	Pyrethroid	Kadethrin	26,000	NM	NM	[144]
7. Paraguay-Paraná River, Argentina	Pyrethroid	Cypermethrin	740	October 2010–July 2012	Rice	[151]
	Organochlorine	Ʃ-Endosulfan	120
	Organophosphorus	Chlorpyrifos	110
8. Thamirabarani River, India	Pyrethroid	Cypermethrin	77 *	March–July	Cashew, tea, cotton, paddy, rubber	[152]
	Organochlorine	Endosulfan	1776 *
		Aldrin	98 *
		Endrin	246 *
9. Citarum River, Indonesia	Pyrethroid	Deltamethrin	4000 *	August, 2021	NM	[145]
10. Suquía River, Argentina	Pyrethroid	α-Cypermethrin	30.4 *	March–August, 2010	Soybean, corn	[153]
	Organochlorine	Endosulfan-sulfate	4.1 *
11. Ceará River, Brazil	Pyrethroid	Cypermethrin	368	July, 2014	NM	[154]
		Deltamethrin	171
		Permethrin	47
	Organophosphorus	Malathion	226

* Non-average value; NM: not mentioned.

shows the concentration of pyrethroids and other pesticides detected in 11 rivers worldwide. Among these rivers, cypermethrin (53%) and deltamethrin (29%) are the predominant pesticides found. Both compounds are classified as moderately hazardous (Class II) by the WHO [75]. Cypermethrin was found in all cases except in the Elbe River (Czech Republic) and Citarum River (Indonesia) [144,145]. Tang et al. [130] mentioned that cypermethrin was the most frequently detected pyrethroid compound in surface waters worldwide, indicating the widespread presence of this pesticide across different geographical regions.

Notably, the Benue River in Nigeria shows the highest concentrations (Figure 8a), with values of 9.3 × 10⁵, 11.4 × 10⁵, and 15.2 × 10⁵ ng L⁻¹ for cypermethrin, deltamethrin, and permethrin, respectively [149]. Interestingly, the Elbe River exhibits a high concentration of kadethrin (0.26 × 10⁵ ng L⁻¹) [144].

Figure 8b shows the concentrations of cypermethrin and deltamethrin in other contaminated rivers around the world. A significant level of pollution is observed in the Citarum River, where the concentration of deltamethrin measures 40 × 10² ng L⁻¹ [145]. The Jiulong, Lis, and Paraguay-Paraná Rivers present similar concentrations of cypermethrin, with values of 6.09 × 10², 6.64 × 10², and 7.4 × 10² ng L⁻¹, respectively [146,148,151]. Lower cypermethrin concentrations were observed in the Ceará, Thamirabarani, Dongjiang, Suquía, and Sassandra Rivers, with values of 368, 77, 41, 30, and 13 ng L⁻¹, respectively, [147,150,152,153,154] (Table 4). All rivers shown in Table 4 exhibit concentrations below the maximum residue limits in drinking water, which are 1 × 10⁸, 0.5 × 10⁸, and 1 × 10⁸ ng L⁻¹ for cypermethrin, deltamethrin, and permethrin, respectively [149]. Usually, pyrethroids exhibit lower persistence in water compared to organochlorine and organophosphorus pesticides. For example, cypermethrin has a half-life of 30 days in water, whereas deltamethrin persists for approximately 17 days [155].

In order to emphasize the impact of pesticide use, it is essential to analyze the geographical distribution of the 47 rivers mentioned in this review. Organochlorine, organophosphorus, and pyrethroid pesticides are found in nearly every region of the globe (see Figure 9). It is important to note that in some regions, the absence of detected pesticides does not mean they are not present. In many cases, pesticides are inadequately monitored, or not monitored at all. Furthermore, these compounds cannot be detected as they enter the hydrological cycle and are transported over long distances.

Based on the literature review conducted in this study, Figure 10 shows the geographical distribution of river percentages across continents. The highest proportion of rivers considered in this review is observed in Asia (49%). In this continent, 23 rivers are located in India (seven), China (six), Pakistan (three), and other Asian countries (seven). Globally, China is the nation with the highest level of pesticide application [156].

Additionally, 19% of the rivers mentioned here are located in America. Specifically, nine rivers are situated in Argentina (three), Mexico (two), Brazil (two), Venezuela (one), and Chile (one). It is important to mention that Brazil was the largest user of pesticides in America in 2021 [157]. In Brazil, the presence of malathion is detected in the Amazon and Ceará Rivers (Table 3 and Table 4). This pesticide is also detected in the Lerma and Tamazula Rivers of Mexico (Table 3).

In Africa, eight rivers are located in Nigeria (three), Kenya (two), Egypt (one), Ghana (one), and Ivory Coast (one), representing 17%. In this study, organochlorine pesticides are detected in seven of these African rivers: the Owan, Benue, Okura, Nairobi, Kibos-Nyamasaria, Nile, and Tano (Table 2, Table 3 and Table 4). Finally, the lowest percentage is observed in Europe (15%). Here, only seven rivers are located in Italy (two), France (one), Spain (one), Greece (one), Portugal (one), and the Czech Republic (one). Chlorpyrifos is detected in the Júcar, Aliakmonas, Sarno, and Volturno Rivers (Table 3).

A total of 156 compounds were identified and classified in this review (Table 2, Table 3 and Table 4). Figure 11 shows the percentage distribution of organochlorine, organophosphorus, pyrethroid, carbamate, and atrazine pesticides found in this study. Organochlorine and organophosphorus pesticides were the most frequently detected in river waters, with 46% of the rivers containing organochlorines and 40% containing organophosphorus residues. Pyrethroid compounds were detected in a lower proportion (13%). Finally, atrazine and carbamates were the least frequently detected, representing just 2 and 1% of the total pesticide compounds, respectively.

The trend of pesticide concentrations in these rivers is shown in Figure 12. Note that some rivers have been excluded due to the absence of reported data (season of sampling). Annually, only the highest concentration of each pesticide has been considered.

Globally, pesticide use continues to rise [157]. In this study, this trend is also observed. In 2014, organochlorine (dichlorvos and HCH), organophosphorus (malathion and permethrin), and pyrethroid (cypermethrin and deltamethrin) pesticides were detected at concentrations below 2000 ng L⁻¹. Zhang et al. [158] reported that organophosphorus compounds were the most widely used pesticides globally in 2014.

In this study, the lowest pesticide concentrations were detected in 2015 and 2016. Notably, organochlorine pesticides were the predominant compounds in 2016. In 2017, a slight increase in the levels of organochlorine and organophosphorus levels was observed, with values of 589 ng L⁻¹ for endrin and 383 ng L⁻¹ for chlorpyrifos. Pesticide concentrations increased significantly in 2018, with organochlorine compounds (aldrin and HCH) reaching values of 1153 and 1085 ng L⁻¹, respectively. Among all studies considered in this review, the highest concentrations of organophosphorus pesticides were observed in 2019, with notable levels for diazinon (390,000 ng L⁻¹, Mahaweli River) malathion (311,760 ng L⁻¹, Lerma River), and glyphosate (252,000 ng L⁻¹, Lerma River). Finally, a high level of deltamethrin (4000 ng L⁻¹) was detected in 2021. According to the FAO, total pesticide use in agriculture reached 3.54 million tons of active ingredients in 2021 [9].

4. Discussion

Despite the fact that some of the pesticides discussed in this study are banned, their presence in river waters remains detectable across nearly every region in the world. Furthermore, the concentrations of these pesticides have been progressively increasing. Some of the implications of the pesticide occurrence in rivers are the following: food contamination, human health risks, and impact on the ecosystems.

4.1. Food Contamination

The dispersion of pesticides in the environment has led to contamination of human food. Residues of organochlorine, organophosphorus, and pyrethroid pesticides are commonly detected in food worldwide [159].

Organochlorine pesticides (OCPs) are regularly applied during the growth of various fruits and vegetables to enhance yield. However, the concentration of OCPs in fruits and vegetables depends not only on the amount sprayed on them but also on the pesticide levels in the soil and irrigation water [160]. For instance, DDT has been found in potatoes, onions, and pineapples [161,162], while HCH has been detected in apples, oranges, pawpaw, and radishes [162,163,164,165]. Moreover, residues of endosulfan and aldrin have been identified in green chili and cabbage [166,167].

Similarly, organophosphorus pesticides have been detected in vegetables, fruits, and cereals [168]. Malathion residues have been found in onions, oranges, nectarines, soybeans, and tangerines [169,170,171,172], while diazinon has been detected in carrots, zucchini, and strawberries [171,173,174]. Chlorpyrifos has been identified in spinach, broccoli, parsley root, cauliflower, guavas, bananas, grapes, tomatoes, garlic, peach, and lemons [163,167,169,171,172,174,175,176], as well as in cereals like millet, maize, wheat, and sorghum [177].

Regarding pyrethroids, cypermethrin has been detected in cucumbers, mangoes, apricots, and peaches [171,172,173], while deltamethrin has been found in watermelon, eggplant, and grapes [170,171,172,178]. Additionally, contamination of aquatic systems with pyrethroids increases the presence of these compounds in animal-derived food products such as meat and milk [179].

4.2. Human Health Risks

Organochlorine pesticides are well-known for their toxicity and can cause serious health issues. Exposure to OCPs can affect the normal functions of the endocrine and nervous systems of living beings [180]. Endosulfan may result in renal and uterine problems while DDT can interfere with estrogen receptors, producing estrogenic effects [181,182]. Additionally, HCH causes damage to the neurological and endocrine systems, whereas aldrin can cause reproductive system issues [183].

Even at trace levels, organophosphorus pesticides (OPPs) can cause significant health damage [184]. They inhibit the acetylcholinesterase (AChE) activity in the nervous system, leading to disruptions in neuromuscular transmission [105]. The toxicity of OPPs depends on their chemical structure and the duration of exposure [185]. Parathion is classified as extremely hazardous (Class Ia) and is known to cause liver and cardiac problems [75,186]. Chlorpyrifos and diazinon are classified as moderately hazardous (Class II) [75]. Furthermore, exposure to chlorpyrifos has been associated with an increased risk of Parkinson´s disease, as well as neurotoxic and immunotoxic effects [187,188]. Finally, malathion and dichlorvos have been classified as potentially carcinogenic to humans [189], whereas glyphosate is associated with endocrine and reproductive issues [190,191].

Human exposure to pyrethroids has significantly increased over the years due to their transmission into the food chain [192,193]. When humans consume aquatic organisms contaminated with PYs, these compounds can be transferred into the human body [194]. Another pathway of exposure to PYs is through residues present in vegetables and fruits [143,195]. PYs cause damage to the endocrine, neurological, reproductive, and immunological systems [196,197,198,199]. Cypermethrin induces degenerative changes in the ovaries and increases glucose and lipid levels in the blood [199]. Permethrin affects cardiovascular, digestive, and hepatic functions, while deltamethrin is associated with hepatotoxicity and nephrotoxicity [200].

4.3. Impact on the Ecosystems

Pesticide runoff into water bodies can have negative effects on aquatic ecosystems [201]. All aquatic organisms are highly susceptible to the toxicity of pesticides [202]. These compounds can cause significant damage to fish, amphibians, and invertebrates, leading to reduced biodiversity and altered community structures.

The mobility of pesticides in the environment allows them to migrate across the different environmental media, including soil, air, and water bodies [203]. When pesticides enter the soil, they can degrade microorganisms such as bacteria, fungi, algae, earthworms, and insects [204]. These microorganisms are crucial for maintaining soil health, fertility, and ecosystem functions [205]. Additionally, the presence of pesticides can inhibit soil enzymes, which are vital catalysts for essential biochemical processes [56].

5. Future Research Directions

Based on the findings of this study, potential directions for future research include the following:

i.

Source identification: Implement studies to determine the sources of pesticide contamination in water bodies to prevent their spread. These efforts should be supported by global collaboration, incorporating scientific research, regulatory frameworks, and active community engagement;

ii.

Monitoring programs: Establish monitoring programs to assess pesticide levels in major rivers, taking their geographical distribution into account;

iii.

Technological advancements: Develop new or modified materials, technologies, and processes capable of reducing or eliminating pesticides in water bodies. These advancements should be accessible, sustainable, and cost-effective.

6. Conclusions

This review showed that the widespread use of pesticides has led to contamination of rivers across different regions worldwide. Despite the ban on their use, some of these compounds continue to be detected at higher concentrations. In this study, organochlorine and organophosphorus pesticides were the most frequently detected compounds in the period 2014–2024. River pollution represents a serious threat to the planet, mainly due to the diseases caused by pollutants such as pesticides. Understanding the transportation, toxicity, persistence, and presence of these compounds in food and drinking water is essential for proposing new and modified technologies to reduce their presence in natural resources.