The Occurrence and Distribution of Neonicotinoids in Sediments, Soil, and Other Environmental Media in China: A Review

Abstract

Neonicotinoids (NEOs) have emerged as viable alternatives to conventional organophosphate pesticides and are widely used in agriculture, horticulture, and household applications. However, the increasing frequency and concentration of NEOs detected in water, sediments, soil, and other environmental media have raised significant concerns about their threats to ecosystems and public health globally. This review paper compiles and integrates key findings from previous studies to analyze the overall occurrence and distribution trends of NEOs in sediments, soil, and other environmental media in China from 2019 to 2024, which has updated and analyzed new data and advanced the knowledge that the previous literature disclosed. The main findings of this work were that over the past decades, NEOs have been consistently detected in sediments, soils, and other environmental media at concentrations ranging from 1 to 10 ng g⁻¹ dw. Acetamiprid (ACE), imidacloprid (IMI), clothianidin (CLO), and thiamethoxam (THM) are the most frequently detected NEOs in sediments and soil. It was found from this work that the threshold concentration of NEOs in soil is very limited, and there are no official acceptable toxic levels of NEOs in soil/water/sediments. Only few countries have conducted the work, at the initial phase, on regulating NEOs and have established their regulatory threshold levels. The associated ecological risks and levels of human exposure in soil have been evaluated, revealing that imidacloprid and thiamethoxam present higher risks for long-term environmental contamination due to their relatively higher concentrations. In contrast, acetamiprid, clothianidin, dinotefuran, and thiacloprid exhibited lower environmental persistence, potentially posing lower ecological risks. These trends imply the need for more focused monitoring and regulatory efforts for compounds like imidacloprid, which exhibit higher concentrations in environmental media. Despite these findings, the contamination of NEOs in sediments and soils is still considered to receive insufficient attention, particularly in northern and western China. Furthermore, the presence of NEOs in other environmental media, including indoor dust, wheat grains, vegetables, and teas, warrants further investigation and concern.

1. Introduction

As conventional organochlorine pesticides were phased out under the Stockholm Convention due to their persistence in the food chain and the high eco-toxicity of both organochlorine and organophosphate pesticides, a range of alternatives has emerged in the market and is now being utilized [1,2]. Neonicotinoids (NEOs) were introduced as alternatives to organochlorine and organophosphate pesticides because of their effectiveness in pest control and their lower toxicity compared to traditional organosulfur, organochlorine, and organophosphate pesticides [3,4]. Table 1 lists the basic chemical and physical properties of common applied neonicotinoids. The NEOs move throughout plant tissues, protecting the entire crop. They are particularly effective in suppressing sucking insects and certain chewing insects, such as termites and grubs, and are widely used in seed treatments in agricultural and garden settings [5,6,7,8]. Due to these properties, neonicotinoids have been introduced and widely applied in agriculture, horticulture, and household use, including on vegetables, fruits, cotton, rice, and various economic crops, making them the fourth generation of pesticides [9,10]. Neonicotinoid pesticides account for 25% of global insecticide market sales, and such a trend is expected to continue over the next decade [11,12]. Approximately 15,000 neonicotinoid products are currently registered and applied in over 120 countries, covering more than 450 crops [13]. However, it has been reported that only about 5% of the applied neonicotinoids effectively target pests, while over 90% of the active ingredients are absorbed into the soil and eventually flow into water environments and sediments [14].

The first type of neonicotinoid, imidacloprid, was developed in the 1980s and has been available on the market since the early 1990s. It gained popularity due to its effectiveness in controlling agricultural and garden pests, as well as its lower toxicity compared to traditional pesticides containing organic sulfur, organochlorine, and organophosphorus compounds [3]. The demand for imidacloprid expanded significantly after its introduction. By 2014, it was registered in over 120 countries and accounted for more than a quarter of the global pesticide market. Neonicotinoid consumption is prevalent in developing countries and regions, though less information has been updated for the areas of China, South America, and South Asia. China, as the world’s leading supplier of imidacloprid, produced more than 23,000 tons of insecticide in 2016 [15]. However, data on the consumption and presence of neonicotinoids (NEOs) in various environmental media remain limited [16]. Previous studies have shown that emerging neonicotinoid insecticides are consistently detected in soil and water bodies across different countries and regions throughout the year [17,18]. Neonicotinoid concentrations ranging from 10 to 1000 ng L⁻¹ have been reported in countries such as the Netherlands, Spain, Canada, and the United States [3]. In some areas, particularly in urban suburbs and remote rural regions of the eastern United States and Canada, concentrations were as high as 10 µg L⁻¹ to 100 µg L⁻¹, posing a serious threat to local ecosystems [19].

Although pollution from emerging neonicotinoid insecticides has become a global concern, systematic monitoring and data on NEOs emissions and concentrations remain limited, particularly in developing countries. In many regions, there is a notable lack of established concentration standards, regulatory management, and administrative restrictions. The threshold concentration of neonicotinoids in soil is very limited, and there are no official acceptable toxic levels of neonicotinoids in soil/water/sediments. Only few countries have conducted the work, at the initial phase, on regulating neonicotinoids and have established their regulatory threshold levels (see Table 2). In China, there are studies that have focused on lakes and river tributaries near agricultural areas in the northeast and southern regions [20,21,22]. These studies assessed the occurrence and distribution of NEOs, providing insights into the ecological and human exposure risks in these areas. Despite these efforts, public awareness and concern remain low, highlighting the urgent need to bridge knowledge gaps and implement effective environmental management strategies in China and other regions worldwide.

This review builds on previous work that focused on the occurrence and distribution of neonicotinoids in Chinese rivers and streams. It aims to explore the distribution of neonicotinoids in soil, sediments, and other environmental media in China, consolidating and analyzing pioneering research on neonicotinoid occurrence while raising public awareness about potential health and ecological risks. Additionally, it seeks to provide a reference for future monitoring and regulatory efforts in China.

Table 1. Basic chemical and physical properties of neonicotinoids.

NEOs	Chemical Structure	Generation	CAS No.	Molecular Mass (g moL−1)	PKa	LogKow	Water Solubility (mg L−1)	Water–Sediment Photolysis (DT50 in Days)	Water Photolysis (DT50 in Days)	Water Hydrolysis (DT50 in Days)	Reference
Acetamiprid		First	135410-20-7	222.678	0.7	0.8	2950	4.7 (moderately fast)	34 (stable)	420 (stable)	[21,23]
Clothianidin		Second	210880-82-5	249.67	11.1	0.905	327	41–56 (stable)	<1; 0.1 (fast)	14.4 (moderately fast)	[21,23]
Dinotefuran		First	165252-70-0	202.214	12.6	−0.549	39,830	n.a.	0.2 (fast)	n.a. (stable)	[21,23]
Imidacloprid		First	80-09-1	255.661	8.00	0.57	0.58–0.61	30–129 (slow to stable)	<1, 0.2 (fast)	>365 (stable)	[21,23]
Imidaclothiz		Third	105843-36-5	261.69	n.a.	−0.23	500	n.a.	n.a.	n.a.	[13,24]
Nitenpyram		First	150824-47-8	270.72	3.1	−0.66	570,000	n.a.	n.a.	Stable at pH 3–7 Fast at pH 9	[21,23]
Thiacloprid		First	111988-49-9	252.72	n.a.	1.26	184	8–28 (stable)	10–63 (stable)	n.a. (stable)	[21,23]
Thiamethoxam		Second	153719-23-4	291.71	n.a.	0.8	4.1	31–40 (stable)	2.7–39.5 (moderately fast)	11.5 (stable)	[21,23]
Cycloxaprid		Fourth	1203791-41-6	322.75	3.42	n.a.	1616.19	n.a.	n.a.	n.a.	[25]

Table 1. Basic chemical and physical properties of neonicotinoids.

NEOs	Chemical Structure	Generation	CAS No.	Molecular Mass (g moL−1)	PKa	LogKow	Water Solubility (mg L−1)	Water–Sediment Photolysis (DT50 in Days)	Water Photolysis (DT50 in Days)	Water Hydrolysis (DT50 in Days)	Reference
Acetamiprid		First	135410-20-7	222.678	0.7	0.8	2950	4.7 (moderately fast)	34 (stable)	420 (stable)	[21,23]
Clothianidin		Second	210880-82-5	249.67	11.1	0.905	327	41–56 (stable)	<1; 0.1 (fast)	14.4 (moderately fast)	[21,23]
Dinotefuran		First	165252-70-0	202.214	12.6	−0.549	39,830	n.a.	0.2 (fast)	n.a. (stable)	[21,23]
Imidacloprid		First	80-09-1	255.661	8.00	0.57	0.58–0.61	30–129 (slow to stable)	<1, 0.2 (fast)	>365 (stable)	[21,23]
Imidaclothiz		Third	105843-36-5	261.69	n.a.	−0.23	500	n.a.	n.a.	n.a.	[13,24]
Nitenpyram		First	150824-47-8	270.72	3.1	−0.66	570,000	n.a.	n.a.	Stable at pH 3–7 Fast at pH 9	[21,23]
Thiacloprid		First	111988-49-9	252.72	n.a.	1.26	184	8–28 (stable)	10–63 (stable)	n.a. (stable)	[21,23]
Thiamethoxam		Second	153719-23-4	291.71	n.a.	0.8	4.1	31–40 (stable)	2.7–39.5 (moderately fast)	11.5 (stable)	[21,23]
Cycloxaprid		Fourth	1203791-41-6	322.75	3.42	n.a.	1616.19	n.a.	n.a.	n.a.	[25]

Table 2. Regulatory threshold levels of NEOs in soils of different countries.

Countries	RTL	Acetamiprid	Clothianidin	Dinotefuran	Imidacloprid	Thiacloprid	Thiamethoxam	References
		(μg L−1)
EU	Short-term	0.3667	3.1	n.a. 1	0.098	0.0912	0.14	[26]
	Long-term	0.3667	3.1	n.a.	0.009	0.45	1
USA	Short-term	1.6555	1.77	4.915	0.0385	18.9	3.535	[26]
	Long-term	0.36	0.05	3.1	0.01	0.97	0.74
Canada	Short-term	12	1.3	n.a.	0.54	20.35	9	[26]
	Long-term	5000	0.12	n.a.	0.16	0.68	3
Netherland	Short-term	n.a.	n.a.	n.a.	0.067	n.a.	n.a.	[27]
	Long-term	n.a.	n.a.	n.a.	0.2	n.a.	n.a.
Germany	Short-term	n.a.	n.a.	n.a.	0.0024	n.a.	n.a.	[28]
	Long-term	n.a.	n.a.	n.a.	0.1	n.a.	n.a.
Other countries	Long term short term	n.a	2.056	n.a.	0.341 0.06	13.114 0.7	4.225 0.68	[26]
Sediments	RTLSED 1	n.a.	16	n.a.	0.95	0.063	10	[26]

¹ RTL_SED denotes the regulatory threshold levels in sediment; RTL_SED was obtained from a calculation based on the average values of the regulatory threshold levels in fresh water from Canda, the EU, and the USA; RTL_SED is for countries more than Canada, the EU, and the USA; RTL_SED was not determined by default for neonicotinoid compounds within the official Canadian, US, or EU regulatory risk-assessment procedures.

Table 2. Regulatory threshold levels of NEOs in soils of different countries.

Countries	RTL	Acetamiprid	Clothianidin	Dinotefuran	Imidacloprid	Thiacloprid	Thiamethoxam	References
		(μg L−1)
EU	Short-term	0.3667	3.1	n.a. 1	0.098	0.0912	0.14	[26]
	Long-term	0.3667	3.1	n.a.	0.009	0.45	1
USA	Short-term	1.6555	1.77	4.915	0.0385	18.9	3.535	[26]
	Long-term	0.36	0.05	3.1	0.01	0.97	0.74
Canada	Short-term	12	1.3	n.a.	0.54	20.35	9	[26]
	Long-term	5000	0.12	n.a.	0.16	0.68	3
Netherland	Short-term	n.a.	n.a.	n.a.	0.067	n.a.	n.a.	[27]
	Long-term	n.a.	n.a.	n.a.	0.2	n.a.	n.a.
Germany	Short-term	n.a.	n.a.	n.a.	0.0024	n.a.	n.a.	[28]
	Long-term	n.a.	n.a.	n.a.	0.1	n.a.	n.a.
Other countries	Long term short term	n.a	2.056	n.a.	0.341 0.06	13.114 0.7	4.225 0.68	[26]
Sediments	RTLSED 1	n.a.	16	n.a.	0.95	0.063	10	[26]

¹ RTL_SED denotes the regulatory threshold levels in sediment; RTL_SED was obtained from a calculation based on the average values of the regulatory threshold levels in fresh water from Canda, the EU, and the USA; RTL_SED is for countries more than Canada, the EU, and the USA; RTL_SED was not determined by default for neonicotinoid compounds within the official Canadian, US, or EU regulatory risk-assessment procedures.

2. Occurrence and Distribution of Neonicotinoids (NEOs) in the Sediments

The following subsections discuss the nationwide occurrence of NEOs in sediments across China. The properties of those NEOs are presented in China and the major studying sites are visualized and marked in Figure 1.

2.1. Sediments in Pearl River

Neonicotinoids (NEOs) in sediments have been studied far less than in water and soil. There have been few recent studies in China that investigated the occurrence of NEOs in sediments. Based on sediment samples collected from 85 sites in the Pearl River (

Table 3. Nationwide occurrence of NEOs in sediments of China.

Site/Location in China	NEOs	Detection Frequency (%)	Conc Range (ng g−1 dw)	Median (ng g−1 dw)	References
Pearl River Guangdong (n = 85)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	92 73 98 47 82	0.01–5.33 0.01–1.91 0.02–7.16 0.01–1.48 0.01–4.34	0.16 0.28 0.55 0.08 0.09	[29]
Pearl River Guangdong (n = 9)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	100 89 0 10 78	n.d. 0.08–0.02 0.02–0.23 0.16–2.07 0.03–0.38	n.d. 0.09 0.05 0.85 0.09	[21]
Receiving rivers of WWTP 1 (Ronggui waterway), Guangdong (n = 10)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	100 80 n.d. 60 100	0.05–0.28 0.08–0.21 n.a. 0.02–0.05 0.05–0.32	0.07 0.2 n.a. 0.03 0.11	[31]
Receiving rivers upstream of WWTP 2 (Modemen waterways), Guangdong (n = 12)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	83.3 83.3 n.d. n.d. n.d.	0.02–0.84 0.04–0.10 n.a. n.a. n.a.	0.16 0.06 n.a. 0.06 n.a.	[31]
Receiving river of WWTP (Huangpu waterway), Guangdong (n = 12)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	100 100 83.3 66.7 100	0.05–0.20 0.18–0.41 0.28–0.81 0.02–0.06 0.12–0.38	0.24 0.295 0.38 0.055 0.03	[31]
Songhua River, Harbin (n = 11)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Thiacloprid Thiamethoxam	9 100 0 100 0 0 100	n.d.–0.75 0.07–0.22 n.d 0.34–12.6 n.d. n.d. 0.12–1.58	n.d. 0.11 n.d. 0.94 n.d. n.d. 0.51	[32]
Urban runoff, Guangdong and Fujian (n = 58)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	64 98 64 86 74 64	0.25–9.23 0.64–6.17 0–3.25 0.25–19.1 0–1.83 0–0.78	<0.5 <0.5 <0.5 0.91 <0.5 <0.5	[33]
Drainage ditch near a rice paddy field and receiving rivers in the Poyang Lake basin, Jiangxi (n = 16)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam Sulfoxaflor	100 88 0 31 75 0 0	0.008–0.087 n.d–0.041 n.d. n.d.–0.701 n.d.–0.038 n.d. n.d.	0.034 0.028 n.d. n.d. 0.010 n.d. n.d.	[34]
Crop field of Changmai County, Hainan (n = 112)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	99.1 99.1 93.8 99.1 92.5 8.9 63.4 99.1	0.07–106.7 0.05–12.7 0.04–32.6 0.08–116.5 0.03–3.3 0.02–0.03 0.02–1.2 0.18–56.8	0.69 0.44 0.2 4.0 0.25 0.02 0.04 0.61	[13]
Farmland river marsh, Qixing River, Heilong Jiang (n = 20)	Acetamiprid Clothianidin Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	15 100 100 n.d. n.d. 100	n.d.–0.19 0.08–0.73 0.57–6.36 0 0 0.49–2.85	0.06 0.145 1.68 n.a. n.a. 1.33	[35]

), it was reported that total concentrations of NEOs in sediments ranged from 0.11 to 11.6 ng g⁻¹ dw, with a mean ∑NEO concentration of 2.16 ng g⁻¹ dw. Imidacloprid was detected most frequently (97%) and had the highest median concentration (0.55 ng g⁻¹ dw) among the NEOs in the 85 sediment samples from the Pearl River [29]. The detection levels of NEOs in the three tributaries followed this order: Beijiang River (4.08 ± 9.01 ng g⁻¹ dw) > Dongjiang River (2.83 ± 2.82 ng g⁻¹ dw) > Xijiang River (1.30 ± 1.55 ng g⁻¹ dw) [29]. Compared to previous studies, residual NEO levels in these sediments are lower than those reported in Canada’s Wetland Prairie Pothole region but higher than in Washington’s Willapa Bay, USA [29]. Nonetheless, in another study, Imidacloprid was not detected in the sediments [30]. A potential explanation may involve the physicochemical properties of the soils or sediments, which affect the sorption/desorption mechanisms of neonicotinoids and then the detection frequencies of the given NEOs in various sediments. The sorption/desorption of NEOs at the sediment/water interface was found to depend on the pH, temperature, concentration of NEOs in water, contact time, soil characteristics, and associated water characteristics, such as the concentrations of suspended solids and dissolved organic carbon. Variations in NEO contents in different soils/sediments remain complex and require further investigation.

2.2. Sediments in Songhua River

Table 3 shows the results of Liu and co-workers’ study [32], where imidacloprid, thiamethoxam, clothianidin, and acetamiprid were detected in sediment samples, with concentrations ranging from 0.61 to 14.7 ng g⁻¹ dw and a mean of 3.63 ng g⁻¹ dw. Imidacloprid and thiamethoxam were the dominant NEO species in the sediment samples, and the detection frequency for imidacloprid, thiamethoxam, and clothianidin reached 100%. The high detection frequency of clothianidin may be attributed to the spontaneous conversion of thiamethoxam to clothianidin in the natural environment.

The total NEO levels were higher than those in the Guangzhou section of the Pearl River and Belize but lower than in samples from South China and Canada. Based on fugacity fraction results, it was proposed that the target NEOs (imidacloprid, thiamethoxam, and clothianidin) tend to diffuse from the sediments into the water [32]. This was further supported by the ratios of imidacloprid, thiamethoxam, and clothianidin in water relative to the sediment concentrations, which were 4.68–84.1, 28.3–254, and 19.2–118, respectively, indicating that the sediment may act as a secondary source affecting water quality.

2.3. Sediments in Urban Runoff, Guangdong

The study conducted by Huang’s team investigated the main factors influencing the spatial distribution of NEOs and the ecological risks posed by neonicotinoid residues in sediments [33] (Table 3). In their study, the total NEO concentrations ranged from below the reporting limit (<0.5 ng g⁻¹ dw) to 23.8 ng g⁻¹ dw, with mean and median values of 4.21 ± 5.00 and 2.73 ng g⁻¹ dw, respectively. At least one of the six neonicotinoids was detected above the reporting limit (0.5 ng g⁻¹ dw) in each sediment sample. Clothianidin was detected most frequently, while imidacloprid and thiamethoxam were also found in 86% and 74% of samples, with mean concentrations of 1.79 ± 3.17 and 0.34 ± 0.36 ng g⁻¹ dw, respectively [33].

Additionally, acetamiprid, dinotefuran, and thiacloprid were detected in 64% of the sediments, with mean concentrations of 1.30 ± 2.39, 0.26 ± 0.51, and 0.18 ± 0.15 ng g⁻¹ dw, respectively. The concentration of imidacloprid observed in their study was similar to levels found in Canada and higher than those in the U.S. and Belize. Meanwhile, acetamiprid, clothianidin, and thiacloprid concentrations were higher than those reported in Canada [33].

When comparing NEO levels across vegetation-planting areas, urban areas, and rice-planting areas, it was found that NEO residues in vegetation-planting and urban areas were similar but higher than those in rice-planting areas [33]. The detection frequency of NEOs was also similar between the vegetation-planting and urban areas, both of which were higher than that in rice-planting areas. This similarity in NEO levels and detection frequencies in vegetation-planting and urban areas is likely due to their proximity, suggesting a shared contamination source. The difference in NEO levels between vegetation-planting and rice-planting areas is attributed primarily to crop vulnerability and harvesting patterns. Due to the higher vulnerability of vegetation crops and their shorter harvesting periods, the pesticide spraying frequency is higher in these areas than in rice-cropping areas. Additionally, the composition of NEOs varied by planting type: imidacloprid, acetamiprid, and thiamethoxam were prevalent in vegetation-planting areas, while imidacloprid and clothianidin dominated in rice-planting areas.

The aquatic risk of NEOs was evaluated through a probabilistic ecological risk assessment (ERA) by constructing environmental exposure distributions (EEDs). The EEDs of NEOs in sediments were converted to concentrations in sediment pore water and then compared to the NEOs’ threshold values, which were proposed by Morrissey (2015) [36]. The probability of exceeding acute exposure thresholds was highest for dinotefuran (70%), followed by imidacloprid (64%), thiamethoxam (59%), clothianidin (39%), and acetamiprid (39%). The concentrations of dinotefuran, imidacloprid, thiamethoxam, and clothianidin exceeded the chronic exposure thresholds in all samples. Spatially, the ecological risk ranked as follows: vegetable crop areas > urban streams > rice paddies [33]. The determined concentrations of NEOs in sediments in this area were very low (Table 3); concentrations of the five main NEOs (acetamiprid, clothianidin, imidacloprid, imidaclothiz, thiacloprid, and thiamethoxam) ranged from 0.38 to 1.05 ng g⁻¹ dw. In the receiving river (Ronggui waterway) of wastewater treatment plant 1 (WWTP 1), acetamiprid, clothianidin, thiacloprid, and thiamethoxam were the dominant NEOs in the collected sediments, with detection frequencies of 100%, 80%, 60%, and 100%, respectively. In the receiving river (Modemen waterway) of WWTP 2, acetamiprid and clothianidin were the dominant NEOs, each with a detection frequency of 83.3%. In the receiving river (Huangpu River) of WWTP 3, all five NEOs were detected with high frequencies in the sediments [31].

2.4. Sediments in Drainage Ditch of Poyang Lake, Jiangxi Province

In terms of the spatial distribution, NEO concentrations detected in sediments were significantly lower than those in riverine water samples. Acetamiprid, clothianidin, imidacloprid, and thiacloprid were the four most frequently detected NEOs in sediment samples [34]. This study found that the average residual concentration of NEOs in drainage ditch sediments (0.077 ng g⁻¹ dw) was lower than in receiving rivers (0.168 ng g⁻¹ dw) [34]. However, the concentration of NEO-transformation products was notably higher in drainage ditch sediments. This suggests that NEOs are more prevalent in river systems, while drainage ditches mainly accumulate their transformation products. These products tend to build up in sediments closer to agricultural fields around Poyang Lake [34].

2.5. Sediments in the Northern Part of Hainan Province

The detection frequency of seven NEOs in soil samples ranged from 35.4% to 100%, with imidacloprid (IMI), acetamiprid (ACE), clothianidin (CLO), thiamethoxam (THM), and dinotefuran (DNT) being the most frequently detected neonicotinoids [13]. The mean concentration of the seven NEOs followed the following sequence: IMI > CLO > ACE > THM > DNT > ACE > NTP. The high detection frequency but low residual concentration of dinotefuran suggests frequent applications in crop fields, though in relatively low amounts compared to other NEOs, likely due to the crop types planted in this area. In this study, 85% of sampling sites exhibited high ecological risk (Risk Quotient, RQ > 1) based on assessments of plant, soil, sediment, and water samples. Among these media, sediments posed the highest risk, with 57.1% of sediment samples showing an RQ value greater than 1 [13].

2.6. Sediments in Qixing River, Heilong Jiang Province

The total storage of NEOs in sediments was estimated to range from 45.9 to 252 ng cm⁻² (Table 3) [35]. Four NEOs (imidacloprid [IMI], clothianidin [CLO], acetamiprid [ACE], thiamethoxam [THM], and nitenpyram [NTP]) were detected in all 20 sediment samples, with 85% of the samples containing three or more NEOs. IMI, CLO, and THM were the three dominant NEOs in the collected sediment samples, all of which were detected in every sample, while ACE was detected in only 15% of the samples. THM was found to be particularly correlated with the total organic carbon (TOC) content in the sediments, suggesting that TOC levels could significantly influence residual THM concentrations. As explained by previous studies [37,38], the cation exchange capacity of sedimentary organic matter plays a key role in driving the adsorption and stability of THM in sediments.

2.7. Sediments in Eastern China Sea

Few studies have reported NEO residues in marine sediments, including the factors influencing their occurrence and distribution in the East China Sea. Chen and colleagues pioneered the monitoring of NEOs in marine sediments, although data are not yet available in Table 3. The average concentration of total neonicotinoids in marine sediments from the East China Sea was 11.9 ± 6.22 ng g⁻¹ dw [39]. The detection frequency of individual neonicotinoids was 100%, except for imidacloprid (84%) and flonicamid (52%). Nitenpyram and dinotefuran dominated the NEO residues, with average relative contributions of 45% and 34%, respectively [39]. The high detection frequency of nitenpyram and dinotefuran is attributed to their lower adsorption to soil, causing them to be discharged into the sea and settle in the marine sediments. The residual levels of NEOs in this study were higher than those found in Jiao-zhou Bay and Willapa Bay [39]. Furthermore, the sum of the residual NEO concentrations (mean: 11.9 ng g⁻¹ dw) in marine sediments was higher than those detected in river sediments from other regions of China.

The highest NEO concentrations were detected in Hangzhou Bay (20.5 ± 4.21 ng g⁻¹ dw), while lower concentrations were found near the coast of Zhejiang Province [39]. The composition of sedimentary NEOs in Hangzhou Bay and the Zhejiang Province coastal area was consistent with the NEO composition in water and sediments from the Yangtze River estuary. Nitenpyram and dinotefuran were the two dominant species in marine sediments, estuary sediments, and water, indicating that the NEO contamination in marine sediments likely originated from the Yangtze River discharge.

In line with previous studies, the residual concentration of NEOs was statistically negatively correlated with pH levels (p < 0.05) and positively correlated with microbial diversity (p < 0.05) [39]. It was suggested that the low levels of NEOs contribute nutrients to the microbial community, promoting microbial biodiversity, which aligns with conclusions from an earlier research [40].

2.8. Overall Discussion on Section 2

The information outlined in Table 3 provides a basis for discussion. It can be suggested that clothianidin, acetamiprid, imidacloprid, and thiamethoxam will likely continue to dominate environmental residues of NEOs due to their high detection rates. This underscores the need for more stringent environmental monitoring and risk-management strategies for these pesticides. Meanwhile, the lower detection rates of dinotefuran and thiacloprid may indicate either a reduced usage trend or that they are less persistent in environmental media. Further investigation is needed to clarify these compounds’ future impact and usage trends.

In addition, it was noted that imidacloprid and thiamethoxam present higher risks for long-term environmental contamination due to their relatively higher concentrations, as Table 3 shows. In contrast, acetamiprid, clothianidin, dinotefuran, and thiacloprid exhibited lower environmental persistence, potentially posing lower ecological risks. These trends imply the need for more focused monitoring and regulatory efforts for compounds like imidacloprid, which exhibit higher concentrations in environmental media.

The determination of various neonicotinoids (NEOs) in sediment, soil matrices, and other environmental media are summarized in the supplemental materials (Tables S1–S3). These methods primarily involve dispersive liquid–liquid extraction (DLLE) and ultrasonic extraction, often combined with solid-phase extraction (SPE) for purification. For the analytical determination of NEOs in sediments, high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) are the most commonly used methods, ensuring the precise quantification of neonicotinoids even at low concentrations.

In contrast to monitoring residual neonicotinoids in water, few measurements were focused on the neonicotinoid residues in sediments. Selected case studies from limited countries are shown in

Table 4. The neonicotinoids’ occurrence in sediments of other countries and regions.

Site	NEOs	Detection Frequency (%)	Conc Range (ng g−1 dw)	Median (ng g−1 dw)	Reference
Corozal district, Belize (n = 34)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	3 1 15 0 1	n.d.–0.014 n.d.–0.053 n.d.–0.175 n.d. 1 n.d.	0.007 0.053 0.047 n.d. 0.116	[42]
Missouri Wetlands, USA (n = 157)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	n.a. 1 43 n.a. 40 n.a. 4	0–0.079 0–11.932 0–0.106 0–10.19 0–0.06 0–1.089	0 0 0 0 0 0	[43]
Prairie Pothole Regions, Canada (n = 134)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	n.d. n.d. n.d. n.d.	n.a. n.d.–4.4 n.d.–17.5 n.d.–20.0	n.d. n.d. n.d. n.d.	[44]
Ebro River Delta, Spain	Acetamiprid Imidacloprid Thiamethoxam	21 14 7.1	n.d.–2.35 n.d.–3.76 n.d.–0.46	0.81 2.51 0.46	[45]
Italy (n = 26)	Acetamiprid Clothianidin Imidacloprid Thiacloprid Thiamethoxam	15.4 7.7 0 11.5 26.9	n.d.–51.8 n.d.–60.3 n.d. n.d.–54.3 n.d.–12.7	4.35 31.37 n.d. 27.1 8.14	[46]

¹ Denotes not available.

, where the studied NEO pesticides have been restricted for use. It was observed from Table 3 and Table 4 that there are notable differences between China and other countries in terms of the occurrence of neonicotinoid residues in sediments. NEOs were detected at high concentrations in agriculturally intensive regions, such as in the Chinese Provinces of Guangdong, Jiangxi, Jiangsu, Hainan, and Heilong Jiang. It is noted that over 50% of NEOs have been detected. In Hainan Province, the detection frequency was greater than 90% for six out of eight commonly utilized neonicotinoids, with their concentrations reaching up to 116.5 ng g⁻¹ dw [13]. Neonicotinoids have also been applied in other developing countries like Belize, but the detection frequency and residual concentrations of NEOs in Belize are not comparative to China’s, which could be attributed to the larger scale of agricultural land and intensity of agricultural practice in China [41].

In contrast, the detection frequencies of neonicotinoids are very low in the countries where the use of NEOs have been restricted, such as USA, Canada, and EU countries (e.g., Italy and Spain). These discrepancies suggest that pesticide regulations, agricultural practices, and environmental-monitoring schemes are the major factors influencing NEO occurrences in sediments and water [41,47,48,49]. In comparison to the less developed countries, industrialized countries like Canada, USA, and EU appreciated the environmental impact of neonicotinoids and then implemented measures on monitoring and regulating NEOs in the relatively earlier stages. These industrialized countries have established the NEOs’ threshold concentration levels when China just started NEO monitoring and regulation in recent decades. It is an urgent need to enhance the regulation and risk assessment in regions with high agricultural activities, such as China, which is the largest producer and one of largest users of NEOs because of its agricultural and economic interests [26,50].

3. Occurrence and Distribution of NEOs in the Soil

The regional soil quality and potential environmental issues are of primary concern due to the soil’s crucial role as both a pathway and a reservoir for agricultural contaminants, such as pesticides. The increasing occurrence of NEOs in water systems contributes to soil contamination, posing potential threats to human health and ecosystems from residual NEOs. This section presents the distribution of NEOs in soil across various regions and provinces, and followed by overall discussions of the data.

3.1. In Provinces of Southern China

Southern China, particularly including the provinces of Jiangsu, Zhejiang, Jiangxi, and Guangdong, is a major cropping region in China. Gu and colleagues recently investigated the occurrence of NEOs in the soil of these four regions (Table 5) [51]. The detection frequency of imidacloprid was the highest in the soil of all four provinces, ranging from approximately 96% to 100%, followed by thiamethoxam (44%) and clothianidin (64%). Spatially, imidacloprid was the dominant NEO species in Jiangsu, with the maximum content reaching 29.88 µg kg⁻¹ dw. Thiamethoxam and clothianidin were highest in Zhejiang, at approximately 22.68 µg kg⁻¹ dw and 16.77 µg kg⁻¹, respectively. In Jiangxi, thiamethoxam (16.97 µg kg⁻¹ dw) and imidacloprid (16.40 µg kg⁻¹ dw) were the two dominant NEO species. The highest concentrations of imidacloprid, thiamethoxam, and clothianidin were 21 µg kg⁻¹ dw, 18.02 µg kg⁻¹ dw, and 14.29 µg kg⁻¹ dw, respectively. The Reference Dose (RfD) approach, integrated with the USEPA’s reference dose for human exposure risk assessment, was applied in this study. The Average Daily Doses (ADDs) model was used to evaluate the cumulative exposure risk. Based on the risk assessment results, the mean IMIRFP (46.05 μg kg⁻¹ dw) in Zhejiang province was the highest, followed by Guangdong (39.70 μg kg⁻¹ dw), Jiangxi (28.95 μg kg⁻¹ dw), and Jiangsu (19.49 μg kg⁻¹ dw). Overall, the estimated ADDs of IMIRFP for both children and adults were below the RfD for imidacloprid set by the USEPA. Therefore, NEO exposure posed a low risk to residents in the study area [51].

Yu and colleagues investigated the occurrence and human exposure risk assessment of NEOs in different cultivated soils [40]. In this study, six neonicotinoid insecticides were considered as target NEO species: imidacloprid, clothianidin, acetamiprid, imidaclothiz, dinotefuran, and flonicamid. The results showed that at least one NEO species was detected in 95% of all soil samples. The detection frequency of imidacloprid, clothianidin, and acetamiprid was highest, particularly imidacloprid, which had a detection frequency of 94% and a median concentration of 10 ng g⁻¹ dw in soil. The detection frequency and median concentrations of other NEOs were relatively low compared to imidacloprid. The Hazard Quotient method was used to assess the non-cancer human health risks of NEO exposure [52,53]. The results indicated that NEO exposure posed no risk to children and adults in the study areas, although public attention is still needed.

The occurrence of NEOs in agricultural soil and croplands, along with cultivation-derived driving factors at a regional scale, has been seldom studied in China. The study conducted by Chen and his co-workers [54] focuses predominantly on the spatial variation in NEOs in Zhejiang Province (Table 5). Among the nine target NEOs, imidacloprid showed the highest detection frequency (99.5%), while flonicamid had the lowest (32.2%). The average NEO concentration in the study region was 75.8 ng g⁻¹ dw (geometric mean: 33.7 ng g⁻¹ dw) [54].

Among the nine sampled cities in Jiangsu Province, Lishui exhibited the highest residual concentrations, followed by Jiaxing and Quzhou. In contrast, lower levels were observed in Hangzhou, Shaoxing, and Ningbo, which have less agricultural land and activity. Overall, the sum of NEOs was relatively higher in the southwest and northwest regions of Zhejiang, while lower levels were observed in the central and southeastern areas. The concentrations of individual NEOs and the total NEOs were most positively correlated with cropland coverage at a spatial resolution of 1 × 1 km². In lands cultivated with fruit, vegetables, and rice-wheat crops, imidacloprid was the dominant neonicotinoid, contributing 60%, 69%, and 53% of the total NEOs, respectively. For tea cultivation, clothianidin was the major NEO, accounting for 37% of the total NEOs. Based on results from automatic linear regression modeling, their study [54] concluded that NEO levels were associated with high cropland coverage and the cultivation type, contributing 78% and 18% to the spatial variation in NEOs, respectively. The soil temperature and pH were also positively correlated with NEO contamination levels, although their contributions were relatively minor compared to the two primary factors.

3.2. In Arable Land of Tianjin

Zhou and colleagues recently studied the occurrence trends of NEOs in lands cultivated with specific fruits and vegetables (Table 5) [55]. Among the six target NEOs, imidacloprid was the most frequently detected species, followed by acetamiprid, thiacloprid, clothianidin, thiamethoxam, and dinotefuran. The concentration of imidacloprid was also the highest among the detected NEOs, with an arithmetic mean value of 1.01 × 102 ng g⁻¹ dw in spring and 45.1 ng g⁻¹ dw in fall.

The residual NEO distribution significantly differed among farmlands, residential areas, and parks in both fall and spring. The levels of NEOs in the park and residential areas were slightly higher than those detected in the farmlands, indicating that children in urban areas may also be susceptible to NEO exposure. Soils planted with tomato, cucumber, eggplant, and pumpkin showed higher concentrations of NEOs, as did soils planted with apples, peaches, papayas, and watermelons. Imidacloprid was the most frequently detected NEO in soil, followed by acetamiprid, thiacloprid, and clothianidin. This is likely due to imidacloprid’s higher usage compared to other NEOs.

A correlation analysis revealed that the residual NEO content in the soil was positively correlated with the soil’s total organic carbon (TOC) and negatively correlated with the soil pH [55]. These findings align with previous research [56], suggesting that soil organic matter increases the affinity of NEOs for soil particles, making them less mobile at lower pH levels. Additionally, plant uptake of NEOs was influenced by the molecular structure of individual NEOs, and further research is needed to explore this mechanism in greater detail.

Table 5. Nationwide occurrence of NEOs in soil sites.

Location (China)	NEOs	Detection Frequency (%)	Conc Range (ng g−1 dw)	Median (ng g−1 dw)	ECo-Risk Assess Method	References
Pearl River Delta, South China (n = 351)	Acetamiprid Clothianidin Dinotefuran Flonicamid Imidacloprid Imidaclothiz	49 46 5 9 94 3	0.25–20 0.25–70 0.26–0.48 0.26–0.27 0.26–370 0.26–7	1.1 2.9 0.38 0.26 10 0.45	Hazard Quotient (average scenario): Detrimental risk to 7% of non-target invertebrates Sub-lethal risk to 50% of the non-target invertebrates	[40]
Zhejiang (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	25 40 10 100 0 10 10 40	n.d. 1 n.d.–16.77 n.d.–0.53 n.d.–7.27 n.d.–0.24 n.d.–0.58 n.d. n.d.–22.68	n.d. 0.74 n.d. 1.59 n.d. n.d. n.d. n.d.	Mean IMIRPF of ∑NEO of four regions (RPF method) Zhejiang: 46.05 ng g−1 dw Guangdong: 39.70 ng g−1 dw Jiangxi: 28.95 ng g−1 dw Jiangsu: 19.49 ng g−1 dw	[51]
Jiangsu (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	0 50 15 90 10 10 0 40	n.d.–1.49 n.d.–14.29 n.d.–9.33 0.49–29.88 n.d. n.d.–0.27 n.d.–0.22 n.d.–6.37	n.d. n.d. n.d. 4.34 n.d. n.d. n.d. n.d.
Jiangxi (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	25 60 5 90 0 15 0 60	n.d.–3.01 n.d.–4.43 n.d.–1.34 n.d.–16.40 n.d. n.d.–0.36 n.d. n.d.–16.97	n.d. 0.73 n.d. 1.12 n.d. n.d. n.d. 0.4
Guangdong (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	60 60 <10 90 0 <5 0 60	n.d.–1.49 n.d.–14.29 n.d.–9.33 n.d.–21. n.d. n.d.–1.20 n.d.–14.29 n.d.–18.02	0.19 0.41 n.d. 3.67 n.d. n.d. n.d. 0.54
Tianjin (spring, n = 61)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	100 52.5 1.64 100 14.8 96.7	0.19–440 n.d.–74.6 n.d.–3.28 0.74–1060 n.d.–18.2 n.d.–1560	1.64 0.17 n.d. 37.5 n.d. 1.08	n.a. 1	[55]
Tianjin (fall, n = 158)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	66.5 32.3 1.27 93 0.63 58.9	n.d.–31.9 n.d.–132 n.d.–1.35 n.d.–2610 n.d.–0.14 n.d.–31.9	0.27 n.d. n.d. 11.6 n.d. 0.2
Shouguang, Shandong (tomato soil, n = 9)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	100 100 66 85 100 22 96	0.10–7.13 0.08–1.36 n.d.–1.22 n.d.–6.017 0.067–0.27 n.d.–0.58 n.d.–4.865	0.46 0.18 0.27 1.90 0.11 0.27 0.67	SSD modelling method: Acetamiprid poses a high eco-risk in both tomato- and cucumber-cultivated soil	[56]
Shouguang, Shandong (cucumber soil, n = 9)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	100 96 11 100 100 0 55	0.035–2.134 n.d.–1.28 n.d.–0.31 0.15–8.51 0.04–0.05 n.d. n.d.–7.472	0.08 0.71 0.3 0.46 0.08 n.d. 0.124
Zhejiang (n = 195)	Acetamiprid Clothianidin Dinotefuran Flonicamid Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	64.1 86.2 94.4 32.3 99.5 47.7 80.5 65.1 81	0.16–2.55 0.4–8.91 0.64–9.28 0.21–0.96 3.9–82 0.11–0.46 0.28–4.49 0.1–0.75 0.27–8.97	0.76 2 0.96 0.47 25 0.22 0.43 0.21 1.01	n.a.	[54]
Shanbei Shanxi (n = 18)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	11 94 11 39	n.d.–8.69 n.d.–14.9 n.d.–16.9 n.d.–14.32	n.d. 4.45 n.d. n.d.	Risk Quotient: 33% samples of imidacloprid-medium–high 94% samples of clothianidin-high 38% samples of thiamethoxam-low	[37]
Guanzhong Shanxi (n = 20)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	15 30 85 20	n.d.–11.54 n.d.–26.69 n.d.–113.71 n.d.–145.04	0.15 0.3 0.85 0.2	Risk Quotient: 89% samples of imidacloprid-medium–high 67% samples of clothianidin-medium–high 22% samples of thiamethoxam-low–medium
Shannan Shanxi (n = 32)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	0 31 38 6	n.d.–184.32 n.d. n.d.–27.1 n.d.–60.33	n.d. n.d. n.d. n.d.	Risk Quotient: 57% samples of imidacloprid-medium–high 48% samples of clothianidin-medium–high 10% samples of thiamethoxam-low
Beijing, suburban wheatfield (n = 206)	Acetamiprid Imidacloprid	10.4 98.5	n.d.–121,500 n.d.–98,500	n.d. 12,700	n.a.	[57]
Hainan, Crop field of Changmai County (n = 112)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	100 98.2 100 100 73.2 35.4 76.8 98.2	0.28–1196.5 0.08–7502.9 0.09–154.2 0.63–3173.9 0.05–190.3 0.01–0.28 0.05–11.9 0.05–716.3	2.69 5.52 1.61 95.72 1.35 0.08 0.29 4.1	Risk Quotient: 45–71% of the risk was dominated by IMI, THM, and CLO 32.5% samples of imidacloprid-high-risk 35.7% samples of thiamethoxam-high-risk 14.5% samples of clothianidin-high-risk	[13]
Heilong Jiang, Farmland-rivermarsh, Qixing River (n = 22)	Acetamiprid Clothianidin Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	4.55 100 100 4.55 0 100	n.d.–0.08 0.08–14.8 1.28–133 n.d.–0.01 n.d. 0.52–29.3	0.08 0.55 7.035 0.01 n.a. 1.295	Risk Quotients of each individual NEOs in the water and soils were lower than 0.1, which indicates the low ecological risk.	[35]

¹ indicates not available.

Table 5. Nationwide occurrence of NEOs in soil sites.

Location (China)	NEOs	Detection Frequency (%)	Conc Range (ng g−1 dw)	Median (ng g−1 dw)	ECo-Risk Assess Method	References
Pearl River Delta, South China (n = 351)	Acetamiprid Clothianidin Dinotefuran Flonicamid Imidacloprid Imidaclothiz	49 46 5 9 94 3	0.25–20 0.25–70 0.26–0.48 0.26–0.27 0.26–370 0.26–7	1.1 2.9 0.38 0.26 10 0.45	Hazard Quotient (average scenario): Detrimental risk to 7% of non-target invertebrates Sub-lethal risk to 50% of the non-target invertebrates	[40]
Zhejiang (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	25 40 10 100 0 10 10 40	n.d. 1 n.d.–16.77 n.d.–0.53 n.d.–7.27 n.d.–0.24 n.d.–0.58 n.d. n.d.–22.68	n.d. 0.74 n.d. 1.59 n.d. n.d. n.d. n.d.	Mean IMIRPF of ∑NEO of four regions (RPF method) Zhejiang: 46.05 ng g−1 dw Guangdong: 39.70 ng g−1 dw Jiangxi: 28.95 ng g−1 dw Jiangsu: 19.49 ng g−1 dw	[51]
Jiangsu (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	0 50 15 90 10 10 0 40	n.d.–1.49 n.d.–14.29 n.d.–9.33 0.49–29.88 n.d. n.d.–0.27 n.d.–0.22 n.d.–6.37	n.d. n.d. n.d. 4.34 n.d. n.d. n.d. n.d.
Jiangxi (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	25 60 5 90 0 15 0 60	n.d.–3.01 n.d.–4.43 n.d.–1.34 n.d.–16.40 n.d. n.d.–0.36 n.d. n.d.–16.97	n.d. 0.73 n.d. 1.12 n.d. n.d. n.d. 0.4
Guangdong (n = 25)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	60 60 <10 90 0 <5 0 60	n.d.–1.49 n.d.–14.29 n.d.–9.33 n.d.–21. n.d. n.d.–1.20 n.d.–14.29 n.d.–18.02	0.19 0.41 n.d. 3.67 n.d. n.d. n.d. 0.54
Tianjin (spring, n = 61)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	100 52.5 1.64 100 14.8 96.7	0.19–440 n.d.–74.6 n.d.–3.28 0.74–1060 n.d.–18.2 n.d.–1560	1.64 0.17 n.d. 37.5 n.d. 1.08	n.a. 1	[55]
Tianjin (fall, n = 158)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	66.5 32.3 1.27 93 0.63 58.9	n.d.–31.9 n.d.–132 n.d.–1.35 n.d.–2610 n.d.–0.14 n.d.–31.9	0.27 n.d. n.d. 11.6 n.d. 0.2
Shouguang, Shandong (tomato soil, n = 9)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	100 100 66 85 100 22 96	0.10–7.13 0.08–1.36 n.d.–1.22 n.d.–6.017 0.067–0.27 n.d.–0.58 n.d.–4.865	0.46 0.18 0.27 1.90 0.11 0.27 0.67	SSD modelling method: Acetamiprid poses a high eco-risk in both tomato- and cucumber-cultivated soil	[56]
Shouguang, Shandong (cucumber soil, n = 9)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	100 96 11 100 100 0 55	0.035–2.134 n.d.–1.28 n.d.–0.31 0.15–8.51 0.04–0.05 n.d. n.d.–7.472	0.08 0.71 0.3 0.46 0.08 n.d. 0.124
Zhejiang (n = 195)	Acetamiprid Clothianidin Dinotefuran Flonicamid Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	64.1 86.2 94.4 32.3 99.5 47.7 80.5 65.1 81	0.16–2.55 0.4–8.91 0.64–9.28 0.21–0.96 3.9–82 0.11–0.46 0.28–4.49 0.1–0.75 0.27–8.97	0.76 2 0.96 0.47 25 0.22 0.43 0.21 1.01	n.a.	[54]
Shanbei Shanxi (n = 18)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	11 94 11 39	n.d.–8.69 n.d.–14.9 n.d.–16.9 n.d.–14.32	n.d. 4.45 n.d. n.d.	Risk Quotient: 33% samples of imidacloprid-medium–high 94% samples of clothianidin-high 38% samples of thiamethoxam-low	[37]
Guanzhong Shanxi (n = 20)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	15 30 85 20	n.d.–11.54 n.d.–26.69 n.d.–113.71 n.d.–145.04	0.15 0.3 0.85 0.2	Risk Quotient: 89% samples of imidacloprid-medium–high 67% samples of clothianidin-medium–high 22% samples of thiamethoxam-low–medium
Shannan Shanxi (n = 32)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	0 31 38 6	n.d.–184.32 n.d. n.d.–27.1 n.d.–60.33	n.d. n.d. n.d. n.d.	Risk Quotient: 57% samples of imidacloprid-medium–high 48% samples of clothianidin-medium–high 10% samples of thiamethoxam-low
Beijing, suburban wheatfield (n = 206)	Acetamiprid Imidacloprid	10.4 98.5	n.d.–121,500 n.d.–98,500	n.d. 12,700	n.a.	[57]
Hainan, Crop field of Changmai County (n = 112)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Imidaclothiz Nitenpyram Thiacloprid Thiamethoxam	100 98.2 100 100 73.2 35.4 76.8 98.2	0.28–1196.5 0.08–7502.9 0.09–154.2 0.63–3173.9 0.05–190.3 0.01–0.28 0.05–11.9 0.05–716.3	2.69 5.52 1.61 95.72 1.35 0.08 0.29 4.1	Risk Quotient: 45–71% of the risk was dominated by IMI, THM, and CLO 32.5% samples of imidacloprid-high-risk 35.7% samples of thiamethoxam-high-risk 14.5% samples of clothianidin-high-risk	[13]
Heilong Jiang, Farmland-rivermarsh, Qixing River (n = 22)	Acetamiprid Clothianidin Imidacloprid Imidaclothiz Nitenpyram Thiamethoxam	4.55 100 100 4.55 0 100	n.d.–0.08 0.08–14.8 1.28–133 n.d.–0.01 n.d. 0.52–29.3	0.08 0.55 7.035 0.01 n.a. 1.295	Risk Quotients of each individual NEOs in the water and soils were lower than 0.1, which indicates the low ecological risk.	[35]

¹ indicates not available.

3.3. In Shouguang of Shandong Province

Many domestic studies of China reported a significant annual increase in agricultural and horticulture cultivation in many sites of China. Monitoring the occurrence of NEOs in the greenhouse soil cultivated vegetable cultivation (PGVC) is urgent, so Wu and workers recently implemented monitoring efforts in Shouguang of Shandong Province (Table 5) [56]. Seven NEOs were detected in the tomato soil samples; acetamiprid, clothianidin, and imidaclothiz were the three dominant species in all tomato soil samples, and the concentration of acetamiprid was highest, with a median of 0.463 μg kg⁻¹. Six NEOs were detected in the cucumber soil samples; acetamiprid, imidacloprid, and imidaclothiz were the three dominant species in all samples of cucumber soil, and the level of imidacloprid was highest in the cucumber soil samples, which reached 0.46 μg kg⁻¹.

The occurrence of NEOs was mainly affected by the abundance of soil microorganisms, which is indirectly driven by many perspectives, including the cultivation time, temperature, and type (tomatoes and cucumber). The level of NEOs in the upper layers of the soil cultivated for 8–9 years was lower than in the upper layers of the soil cultivated for a shorter time. This could be attributed to the differing soil microorganism establishment based on different time-lengths of soil cultivation. The relatively high residual level of NEOs was tested in soil cultivating cucumber with a higher operating temperature while being compared to NEOs tested in soil cultivating tomato with a lower operating temperature. NEOs’ ecological risk assessment was conducted using the species sensitivity distribution (SSD) modeling. Acetamiprid’s toxicity was high in the tomato and cucumber greenhouse soils. In general, the ecological risk values were higher in cucumber soil cultivated for a short period and in tomato greenhouse soil cultivated for a longer period.

3.4. In Three Districts of Shanxi Province

As a major crop-producing region of China, Shanxi faces severe soil contamination issues due to the rapid development of agricultural activities. Neonicotinoid pesticides (NEOs) have been widely applied across the province, yet data on residual NEO levels in soil remain limited. A study investigated the residual levels of four widely used NEOs in Shanxi’s agricultural soils [37] (Table 5), and the study area was divided into North Shanxi, Central Shanxi, and South Shanxi.

In North Shanxi farmland, acetamiprid and imidacloprid had detection frequencies of 44.4% and 33.3%, with concentrations ranges of 5.67–14.32 µg kg⁻¹ and 1.57–5.35 µg kg⁻¹, respectively. All four NEOs were detected in greenhouses, with detection frequencies ranging from 22.2% to 100%. Acetamiprid showed the highest detection frequency (100%) in greenhouses, with concentrations between 1.21 and 14.85 µg kg⁻¹.

In Central Shanxi greenhouses, imidacloprid, clothianidin, and thiamethoxam were all detected at a 100% frequency, with concentrations of 10.46–113.71 µg kg⁻¹, 12.02–25.90 µg kg⁻¹, and 58.43–145.04 µg kg⁻¹, respectively. In Central Shanxi farmland, imidacloprid had the highest detection frequency (71.4%), with concentrations ranging from 5.74 to 18.15 µg kg⁻¹.

In South Shanxi farmland, imidacloprid and clothianidin exhibited the highest detection frequencies, at 45.5% and 36.4%, with concentrations of 3.34–25.15 µg kg⁻¹ and 12.77–184.32 µg kg⁻¹, respectively.

The ecological risk assessment, conducted using the Risk Quotient method, revealed significant potential risks associated with imidacloprid and clothianidin across North, Central, and South Shanxi. In North Shanxi farmland, clothianidin posed a medium ecological risk, while imidacloprid in Central Shanxi exhibited a high risk. Both imidacloprid and clothianidin in South Shanxi soils were categorized as having high ecological risks. A correlation analysis explored the factors influencing NEO occurrence and distribution in soils. The results indicated that clothianidin levels increased with a lower soil pH and higher organic matter content, as the polar groups of clothianidin interact with the active moieties of organic matter, enhancing adsorption onto soil particles [38]. Additionally, thiamethoxam levels were positively correlated with the cation exchange capacity (CEC), which is indirectly influenced by the organic matter content.

3.5. In the Northern Part of Hainan Province

In the northern part of Hainan Province, seven neonicotinoids (NEOs) were detected in soil samples, with detection frequencies ranging from 35.4% to 100% (Table 5). The most frequently detected NEOs were imidacloprid (IMI), acetamiprid (ACE), clothianidin (CLO), thiamethoxam (THM), and dinotefuran (DNT). The mean concentrations of the seven NEOs followed the following sequence: IMI > CLO > ACE > THM > DNT > ACE > NTP [35].

Ecological risk assessments of plants, soil, sediment, and water samples indicated that 85% of the sampling sites presented high ecological risks (Risk Quotient, RQ > 1). Among these, 45–71% of the risk was dominated by IMI, THM, and CLO. Further analysis showed that approximately 90% of the samples with RQs > 1 exhibited a 70% reduction in acute toxicity when IMI, THM, and CLO were excluded from the dataset. Compared to water and sediment, the ecological risk associated with soil was relatively lower, with 45.8% of soil samples classified as having a high risk (RQ > 1) [13].

The total concentration of five NEOs—IMI, THM, CLO, ACE, and IMIT—in the collected soil samples ranged from 2.23 to 136 ng g⁻¹dw⁻¹ with a mean concentration of 34.8 ng g⁻¹ dw⁻¹. The concentration of individual NEOs followed the following sequence: IMI > THM > CLO > ACE > IMIT. Notably, the concentration of IMI was eight times higher than that of THM, consistent with their commercial usage ratio [35]. IMI, CLO, and THM were the dominant NEOs detected in the soils, with all three showing a 100% detection frequency. This result aligns with findings from water and sediment samples, where these NEOs also exhibited full detection [35].

Unlike the strong correlation observed between dissolved organic carbon (DOC) and THM in sediments, DOC appeared to have minimal influence on the residual concentrations of NEOs in soils. This discrepancy may be attributed to the differing compositions of soil organic matter compared to those in sediments.

3.6. Overall Discussion on Section 3

A discussion can be drawn from the data presented in Table 5. It was suggested that imidacloprid exhibits the highest detection frequency in collected soils, exceeding 90%. Clothianidin and thiamethoxam are also frequently detected, with detection rates of approximately 60–80%, although they are less dominant compared to imidacloprid. In contrast, imidaclothiz, nitenpyram, and thiacloprid show low detection frequencies, which may suggest limited persistence or localized use in specific agricultural contexts. However, it was found that the determined concentrations of imidacloprid, clothianidin, and thiamethoxam in the soils were significantly lower than the concentrations observed in the sediments, by comparing the outlined information of Table 3 with that of Table 5. This suggests that sediments may act as an important reservoir and receiver for neonicotinoids from adjacent water and soil environments [29,34,48,58]. In addition, it was suggested that not only did NEOs degraded with water hydrolysis and photolysis in the soil (Table 1) but also micro-biologically degraded in the soil as Text S3 and Table S4 showed [59,60,61,62].

4. Occurrence and Distribution of Neonicotinoids in Various Environmental Media

This section presents the distribution of NEOs in various environmental media (e.g., indoor dust, wheat grains, and tea leaves) and examines the effect of neonicotinoids in the environment on entire ecosystems, such as bee colony collapse disorder (CCD), while supporting the discussion with relevant data.

4.1. Neonicotinoids in the Indoor Dust

Indoor dust has also been identified as a potential source of neonicotinoid (NEO) contamination exposure, particularly for susceptible populations, such as infants and toddlers. However, significant knowledge gaps remain regarding NEO levels in indoor dust and their associated health risks. Recently, Wang and colleagues [63] investigated NEO contamination in indoor dust from various regions in China, including Taiyuan (North China), Wuhan (Central China), and Shenzhen (South China) (

Table 6. Nationwide occurrence of NEOs in other environmental media of China.

Sample	Site/Location in China	NEOs	Detection Frequency (%)	Conc Range (ng g−1 dw)	Median (ng g−1 dw)	Human Exposure Risk Assessment	References
Dust	Taiyuan Shanxi (2016, n = 86)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	98.8 0 53.6 98.8 0 2.40	n.d. 1–177 n.d. n.d.–6.51 n.d.–169 n.d. n.d.–10.1	0.58 n.d. 10.4 1.46 n.d. n.d.	EDIdust (median, pg kg−1bw day−1): of IMIeq (estimated daily taken method) Infants: 66.6 Toddlers: 55.5 Children: 26.6 Teenagers: 12.6 Adults: 5.29	[63]
	Wuhan Hubei (2018, n = 110)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	97.3 309 30 100 74.5 30	n.d.–4227 n.d.–363 n.d.–141 0.10–2823 n.d.–367 n.d.–92.1	4.66 n.d. n.d. 5.26 0.76 n.d.	EDIdust (median, pg kg−1bw day−1) of IMIeq (estimated daily taken method) Infants: 421 Toddlers: 351 Children: 168 Teenagers: 79.4 Adults: 33.4
	Shenzhen Guangdong (2019, n = 86)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	100 57.0 29.1 100 10.1 46.8	3.82 0.61 n.d. 7.29 n.d. n.d.	3.82 0.61 n.d. 7.29 n.d. n.d.	EDIdust (median, pg kg−1bw day−1) of IMIeq (estimated daily taken method) Infants: 214 Toddlers: 178 Children: 85.4 Teenagers: 40.3 Adults: 17.0
	Guangdong (n = 40)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam N-desmethyl acetamiprid UF 5-OH-IMI	93 90 92 80 80 88 85 95 75	n.d.–6.97 n.d.–4.60 n.d.–9.65 n.d.–4.96 n.d.–0.23 n.d.–0.81 n.d.–10.7 n.d.–4.56 n.d.–12.5	0.53 0.52 0.77 0.59 0.05 0.15 2.74 1.02 0.99	Total EDIdust (pg kg −1 bw day−1) of parent NEOs, metabolite NEOs, and the sum of all NEOs (parent + metabolite) and IMIeq (estimated daily taken method) EDI of ∑NEOs (parent): 3.24 EDI of ∑NEOs (metabolite): 4.10 EDI of ∑NEOs (parent + metabolite): 7.54 EDI of IMIeq: 15.0	[64]
	Quzhou County Hebei (n = 35)	Acetamiprid Clothianidin Imidacloprid Thiamethoxam	93 87 95 93	0.06–2.13 0.01–0.1 0.1–2.18 0.09–1.33	0.41 0.07 0.07 0.2	HI-children based on ingestion (Hazard Quotient method) Acetamiprid: 0.23 Clothianidin: 5.36 × 104 Imidacloprid: 0.02 Thiamethoxam: 0.64 HI-adults based on ingestion (Hazard Quotient) Acetamiprid: 0.11 Clothianidin: 2.69 × 104 Imidacloprid: 0.01 Thiamethoxam: 0.323	[65]
Wheat	Beijing (2019)	Acetamiprid Imidacloprid	9 3	n.d.–40.5 n.d.–35.5	n.d. n.d.	Risk Quotient Almost all samples of acetamiprid-none Almost all samples of imidacloprid-none	[57]
	Beijing (2018)	Acetamiprid Imidacloprid	4.3 4.3	n.d.–11.9 n.d.–15.5	n.d. n.d.
Tea	Fujian, Yunnan, Anhui, Zhejiang (2011–2013, n = 251)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Nitenpyram Thiacloprid Thiamethoxam	86.1 0 3.2 82.9 0 26.3 6.8	n.d.–4,288 n.d. n.d.–38.66 n.d.–4,456.51 n.d. n.d.–157.37 n.d.–14,319	97.43 n.d. n.d. n.d. n.d. 27.11 n.d.	HQ%: (probabilistic risk assessment-optimistic model run):Long-term risk assessment: Acetamiprid: 0.07 Clothianidin:0.00 Dinotefuran:0.00 Imidacloprid: 0.03 Nitenpyram:0.00 Thiacloprid:0.00 Thiamethoxam:0.00 Short-term risk assessment: Acetamiprid: 3.04 Clothianidin: 0.00 Dinotefuran:0.00 Imidacloprid: 3.87 Nitenpyram: n.a. Thiacloprid: 0.02 Thiamethoxam: 0.30	[66]
	Fujian, Yunnan, Anhui, Zhejiang (2015–2016, n = 189)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Nitenpyram Thiacloprid Thiamethoxam	87.3 2.1 5.8 65.6 1.1 50.3 9.0	n.d.–4435 n.d.–31.58 n.d.–27.95 n.d.–49.36 n.d.–1.54 n.d.–518.99 n.d.–31.58	62.94 n.d. n.d. 10.34 n.d. 0.27 n.d.	HQ%: (probabilistic risk assessment-optimistic model run): Long-term risk assessment: Acetamiprid: 0.04 Clothianidin: 0.00 Dinotefuran: 0.00 Imidacloprid: 0.01 Nitenpyram: 0.00 Thiacloprid: 0.00 Thiamethoxam: 0.012 Short-term risk assessment: Acetamiprid: 3.15 Clothianidin: 0.02 Dinotefuran: 0.00 Imidacloprid: 0.45 Nitenpyram: n.a. Thiacloprid: 0.07 Thiamethoxam: 21.16
	Fujian, Yunnan, Anhui, Zhejiang (2017–2018, n = 286)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Nitenpyram Thiacloprid Thiamethoxam	51.0 5.6 7.3 57.3 5.9 30.1 8.4	n.d.–6835.95 n.d.–540.27 n.d.–112.19 n.d.–1217.32 n.d.–6.53 n.d.–279.71 n.d.–5032.27	0.53 n.d. n.d. 4.19 n.d. n.d. n.d.	HQ%: (probabilistic risk assessment-optimistic model run):Long-term risk assessment: Acetamiprid: 0.05 Clothianidin: 0.00 Dinotefuran: 0.00 Imidacloprid: 0.02 Nitenpyram: 0.00 Thiacloprid: 0.00 Thiamethoxam: 0.06 Short-term risk assessment: Acetamiprid: 4.87 Clothianidin: 0.35 Dinotefuran: 0.01 Imidacloprid: 1.06 Nitenpyram: n.a. Thiacloprid: 0.04 Thiamethoxam: 10.52
Pollen	Zhejiang (n = 69)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	41.7 33.3 22.2 50.0 19.4 19.4	n.d.–1.74 n.d.–3 n.d.–1.65 n.d.–1.6 n.d.–0.78 n.d.–1.7	n.d. n.d. n.d. n.d. n.d. n.d.	Mean ∑IMIRPF (ng g−1 dw) of 12 sites (RPF assessment) April: 5.24 May: 2.36 June: 2.95	[67]
Honey	Zhejiang (n = 10)	Acetamiprid Clothianidin Dinotefuran Imidacloprid Thiacloprid Thiamethoxam	0 10 10 20 0 10	n.d. n.d.– 0.14 n.d.– 1.71 n.d.– 2.59 n.d.– 0.63 n.d.	n.d. n.d. n.d. n.d. n.d. n.d.	Mean ∑IMIRPF (ng g−1 dw) of 12 sites (RPF assessment) April: 2.86 May:0.18 June:1.52

¹ Indicates not detected.

). Acetamiprid and imidacloprid were the most frequently detected NEOs, found in over 90% of all indoor dust samples. Additionally, NEOs such as dinotefuran, thiacloprid, DM-acetamiprid, and 5-OH-imidacloprid were reported in indoor dust for the first time.

The indoor concentrations of NEOs showed significant variation between urban and rural areas. In Wuhan and Shenzhen, urban dust samples generally had higher NEO concentrations than rural dust samples [63] The sources of NEOs in indoor dust were primarily attributed to ornamental flowers, domestic pets, insecticides used for controlling mosquitoes, fleas, flies, and cockroaches, and residues from fruits and vegetables in daily life. From 2016 to 2018, NEO consumption in Wuhan increased, aligning with the rising registration and use of NEOs in China. A cumulative exposure risk assessment using the relative potency factor (RPF) method revealed that samples collected from Wuhan in 2018 had the highest median concentration of IMIeq, at 70.1 ng g⁻¹. In Taiyuan, acetamiprid and imidacloprid were the most prevalent NEOs, detected in over 98% of the samples. For samples collected in Wuhan in 2016, acetamiprid and imidacloprid were detected in 100% of the samples, with the highest concentrations among all NEOs. Similarly, in Shenzhen, imidacloprid and acetamiprid were detected in 100% of the samples [63].

A previous study investigated neonicotinoids (NEOs) in students’ urine and dormitory dust) [64]. The detection rates of NEOs and their degradation intermediates in indoor dust ranged from 75% to 95%. Among parent NEOs detected in 93% of the indoor dust samples, the detection frequency followed the following sequence: acetamiprid (93%) > dinotefuran (92%) > clothianidin (90%) > thiamethoxam (88%) > imidacloprid (80%) ≈ thiacloprid (80%). These findings align closely with those of a previous study, which also identified acetamiprid as the most frequently detected NEO [68]. However, the median concentrations of acetamiprid and imidacloprid in this study were significantly lower than those reported previously [68] A significant correlation was observed between urinary concentrations of several NEOs and their corresponding concentrations in indoor dust, including imidacloprid, dinotefuran, clothianidin, acetamiprid-dm, and 5-OH-imidacloprid. This indicates that indoor dust is a major daily source of NEO exposure. The relative potency factor (RPF) method was used to assess human exposure risks. The analysis suggested that females were more exposed to NEOs than males, potentially due to differences in their surroundings and daily activities [64].

Mu and co-workers [65] investigated the occurrence of neonicotinoids (NEOs) in Quzhou, Hebei (as shown in Table 6). For all dust samples, the detection frequencies of clothianidin, thiamethoxam, imidacloprid, and acetamiprid were 87%, 93%, 95%, and 93%, respectively, with geometric mean concentrations of 0.18 mg kg⁻¹, 0.27 mg kg⁻¹, 0.49 mg kg⁻¹, and 0.46 mg kg⁻¹. The concentrations of NEO residues in indoor dust samples were significantly higher than those in outdoor samples. For example, the geometric mean concentration of imidacloprid in indoor samples reached 2 mg kg⁻¹, over 20 times higher than the levels detected in outdoor samples.

The Hazard Quotient (HQ) method was used for the health risk assessment. Results indicated that the current levels of accumulated pesticides in residential dust are unlikely to pose chronic health risks for children or adults [65]. However, the health risk for children under indoor exposure is nearing the risk threshold. The study suggests that long-term applications of NEOs could increase both health risks and residual NEO levels. Therefore, future monitoring studies are necessary, particularly those considering inhalation and oral ingestion as exposure pathways.

4.2. Neonicotinoids in Wheat Grains Collected from Suburban Wheat Field

Neonicotinoids (NEOs) are widely used insecticides but are rarely detected in wheat flour samples. A possible explanation is that pesticides are typically applied during the growth stage to protect against wheat pests, allowing NEOs to degrade gradually within the plants. Tao and co-workers conducted a pioneering study on the occurrence of NEOs in wheat grains [57]. Wheat grain and soil samples were collected from four districts surrounding Beijing in different directions. While neonicotinoid residues were frequently detected in the soil samples, imidacloprid exhibited particularly high detection frequencies, persisting in soil samples for three consecutive years. This indicates the continuous application of NEOs in the wheat fields studied.

Most previous research focused on NEO occurrence in commercially available wheat samples from the market. However, monitoring in situ wheat samples and their dependent soils has been limited [57]. The annually increasing use of NEOs is likely contributing to residue accumulation in wheat fields. This highlights the need for the long-term monitoring of neonicotinoid effects and the associated dietary risks in fields under continuous wheat cultivation.

4.3. Neonicotinoids Levels in Tea Leaves

Tea is a popular beverage all over the world; China is one of the largest tea-production and consumption countries, which consumes a large number of neonicotinoids for pest control of the tea-tree. However, studies on the NEOs in the tea leaves of China and human exposure risk are limited. One study investigated the NEO in tea leaves of four provinces of China from 2011 to 2018, including Zhejiang, Anhui, Fujian, and Yunnan Provinces. Samples were collected from three periods, including the years of 2011–2013, the years of 2015–2016, and the years of 2017–2018, and eight target NEOs were monitored in this study, including acetamiprid, clothianidin, dinotefuran, imidacloprid, nitenpyram, thiacloprid, and thiamethoxam. The result shows that the NEO occurrence in tea is ubiquitous (Table 6). In samples of 2011–2013, only clothianidin and nitenpyram were not detected, and the other target NEOs were all detected. In samples of 2015–2016 and 2017–2018, all eight target NEOs were detected in the collected tea samples. Among the 726 samples, at least one NEO was detected in 86.5% of total samples and two or more NEOs were detected in 67.1% of samples. However, the overall detection frequency of NEOs decreased from 2011 (92%) to 2018 (79%), which could be attributed to the control of NEOs over this period. Thiamethoxam seems to pose the highest acute risk to tea-consumers compared to the risk of other NEOs to humans. Overall, consuming tea with residual NEOs posed no health risk to consumers under the food NEOs application and agricultural practice [66].

4.4. Bee Colony Collapse Disorder Due to Neonicotinoids

Bee colony collapse disorder (CCD) is a phenomenon where worker bees from a honeybee colony abruptly disappear. This sudden loss of worker bees disrupts the hive’s functioning, leading to the eventual collapse of the colony. CCD has been a serious concern for beekeepers and scientists, since the phenomena was first identified in 2006 [67]. Its implications are substantial, as honeybees are critical pollinators for many crops, playing a vital role in agriculture and ecosystems. Many factors contribute to CCD; among them, neonicotinoids have been linked to CCD. NEOs are toxic to bees, impairing their memory, navigation, and immunity. These cases were reported in Zhejiang Province of China.

A study conducted by Tang and co-workersreported that the highest residual level of imidacloprid, at 2.59 ng g⁻¹ dw, in Zhejiang was observed in honey samples collected from Wenzhou [67]. Among the seven target neonicotinoids (NEOs) in pollen samples, imidacloprid had the highest detection frequency (50%), followed by acetamiprid (41.7%), clothianidin (33.3%), dinotefuran (22.2%), thiacloprid (19.4%), thiamethoxam (19.4%), and imidaclothiz (2.8%). The average imidacloprid concentration was highest in Wenzhou (NEOs in pollen from April to June) and Wuyi (NEOs in honey from April to May). The temporal and spatial occurrences of NEOs were investigated, and a PEX model was developed based on the Risk Quotients (RQ) method for an ecological risk assessment. Pollen samples were collected from 12 sites in Zhejiang. The highest IMI_RPF values in honey and pollen samples were 8.51 ng g⁻¹ dw and 34.93 ng g⁻¹ dw, respectively. According to data from the REX model, the integrated mean exposure value (EV) to adult bees from pollen consumption ranged from 0.13 to 5.44 ng d⁻¹ org⁻¹ across 12 study sites in Zhejiang Province. The highest EV of 10.2 ng d⁻¹ org⁻¹ was observed in Wuyi in April. Notably, risks may increase with the rising production and use of NEOs in China, underscoring the importance of monitoring NEOs across various environmental media to enhance ecological security.

5. Conclusions and Further Work

Over the past decades, due to their extensive use in agriculture and horticulture, neonicotinoids (NEOs) have been consistently detected in sediments, soils, and other environmental media at concentrations ranging from 1 to 10 ng g⁻¹ dw. The most commonly detected compounds include acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam. Contamination primarily arises from surface water runoff from adjacent agricultural areas, as well as from sewage and wastewater effluents. The presence of NEOs is more pronounced in arable lands compared to other land uses.

Most monitoring studies of NEOs have been concentrated in southern China and its developed regions, particularly the Taihu Lake area, the Yangtze River Delta, and the Pearl River Delta. This geographic focus has resulted in significant gaps in knowledge about the occurrence of NEOs in northern and northwestern regions of China. This review emphasizes the need for further investigations in these less-studied regions, especially in remote and developing areas. Additionally, relatively high residual levels of NEOs in soils and sediments in southern China suggest that future research should focus on specific sites surrounding these problematic areas.

The overall long-term ecological risks associated with NEOs are generally assessed as moderate to high, though the acute ecological risks are rarely reported. While many studies suggest that NEOs occurrence poses low to moderate risks, human health risks have shown an upward trend in recent years due to increased NEO usage, necessitating heightened public awareness and improved management practices. Furthermore, the metabolites of both traditional and novel NEOs warrant further scrutiny and monitoring across various environmental media.

Finally, there is an urgent need for nationwide, comprehensive research to address the limited studies on the contamination scope and characteristics of NEOs in China. The increasing production and consumption of NEOs could exacerbate associated risks, highlighting the critical need for robust monitoring across diverse environmental media to enhance ecological security.