In developing countries, urban areas may be at greater risk of pesticide exposure compared to semi-urban agricultural regions. To investigate this, concentrations of selected pesticides were measured in 81 human milk samples collected in urban Kolkata and semi-urban Nadia in West Bengal, India. Three classes of pesticides were investigated – legacy organochlorines and emerging pyrethroids and neonicotinoids. The average concentration of the majority of the chemicals (DDT, its metabolites, HCH isomers, bifenthrin, endosulfan), showed a clear urban > semi-urban trend. Compared with previous measurements in other Indian cities and developing nations, current HCH and DDT concentrations in urban Kolkata were high. These chemicals were detected in 100% of the samples in both the urban and the semi-urban region. Also in both regions, the Estimated Daily Intake of DDTs, HCHs, aldrin, dieldrin and the pyrethroid bifenthrin for breastfed infants exceeded the Tolerable Daily Intake in a number of samples. Three pyrethroids were detected in human milk samples in India for the first time. This indicates a shift in the usage pattern of pesticides in India from organochlorines to pyrethroids. These findings may be used to drive targeted regulation of pesticides in developing countries with similar histories of pesticide use.

Methane emitted by insects is considered to be an important source of atmospheric methane. Here we report the stimulation of methane emission in the cockroach Periplaneta americana and termite Coptotermes chaohuensis, insects with abundant methanogens, by neonicotinoids, insecticides widely used to control insect pests. Cycloxaprid (CYC) and imidacloprid (IMI) caused foregut expansion in P. americana, and increased the methane emission. Antibiotics mostly eliminated the effects. In P. americana guts, hydrogen levels increased and pH values decreased, which could be significantly explained by the gut bacterium community change. The proportion of several bacterium genera increased in guts following CYC treatment, and two genera from four could generate hydrogen. Hydrogen is a central intermediate in methanogenesis. All increased methanogens in both foregut and hindgut used hydrogen as electron donor to produce methane. Besides, the up-regulation of mcrA, encoding the enzyme for the final step of methanogenesis suggested the enhanced methane production ability in present methanogens. In the termite, hydrogen levels in gut and methane emission also significantly increased after neonicotinoid treatment, which was similar to the results in P. americana. In summary, neonicotinoids changed bacterium community in P. americana gut to generate more hydrogen, which then stimulated gut methanogens to produce and emit more methane. The finding raised a new concern over neonicotinoid applications, and might be a potential environmental risk associated with atmospheric methane.

The extensive use of neonicotinoids (NEOs) has caused the release of wide-ranging of residues to the environment and food, and their potential health risks are now receiving more attention. In this study, three surveys were conducted to obtain the overall profiles of NEO residue levels (seven NEOs and one metabolite) in Chinese tea over a period of seven years. A total of 726 tea samples were tested, and nearly 87% of the samples were found to have detectable NEO residues. The overall average detection frequency of acetamiprid was the highest, reaching 73%. Imidacloprid residues in 4.6% of the samples exceeded the Chinese maximum residue limits, whereas clothianidin and nitenpyram had been detected in Chinese tea samples since 2014. The applications of thiacloprid and thiamethoxam gradually increased, and some tea samples with high residue levels appeared in China. These findings signal the replacement of new and old varieties of NEOs in China. Both long- and short-term cumulative exposures to NEOs were calculated based on optimistic and pessimistic models recommended in the EFSA guidelines. In the three survey periods, the average total imidacloprid-equivalent concentrations were 484.63, 1713.36, and 1148.34 μg/kg, respectively. Combined with the refined point estimates and probabilistic models used in this study, the hazard quotients of NEO residues in tea for Chinese tea consumers were found to be low and within the bounds of safety.

Neonicotinoids (Neonics) have become the most widely used insecticides around the world in recent years. Due to the hydrophilic character, neonics are emerging contaminants in drinking water. In this study, we aimed to characterize and quantify the fate and transport of neonics in the drinking water treatment system and their contributions to the overall dietary risks. Seven neonics in 97 surface and drinking water samples in the city of Hangzhou, China were analyzed. The relative potency factor method was adopted in order to calculate the total neonics concentrations. We then used the Monte Carlo simulation to calculate the chronic daily intake (CDI) of total neonics from water consumption. All 16 surface water samples collected from two rivers contained at least two neonics, and more than 93% of those contained 3 or more neonics. Imidacloprid was detected in all 16 surface water samples, followed by clothianidin and acetamiprid with average concentrations of 11.9, 7.6, 17.6 ng L-1, respectively. The drinking water treatment plants removed approximately 50% of neonics from surface water. However, 68 out of 71 tap water samples that we collected from the household faucets contained at least one neonic, with the highest average concentrations of 5.8 ng L-1 for acetamiprid. The maximum of CDIs of total neonics from water consumption for adult and children were 10.2 and 12.4 ng kg-1 d-1, respectively, which are significantly lower than the acceptable daily intake (ADI). The results presented here shown drinking water consumption only represented an insignificant portion of dietary risks of total neonics, mainly due to the modern drinking water treatment technologies that are capable of removing significant amount of neonics from drinking water. However, the ubiquity of neonics in the drinking water sources to kitchen faucets, should be a concern for public health.

Little information is available about the occurrence of neonicotinoid insecticides in surface water and sediment of the metropolitan regions around the rivers in China. Here we investigate the residual level of neonicotinoids in the Guangzhou section of the Pearl River. At least one or two neonicotinoids was detected in each surface water and sediment, and the total amount of neonicotinoids (∑₅neonics) in surface water ranged from 92.6 to 321 ng/L with a geometric mean (GM) of 174 ng/L. Imidacloprid, thiamethoxam and acetamiprid were three frequently detected neonicotinoids (100%) from surface water. As for the sediment, total concentration was varied between 0.40 and 2.59 ng/g dw with a GM of 1.12 ng/g dw, and acetamiprid and thiacloprid were the common sediment neonicotinoids. Western and Front river-route of the Guangzhou section of the Pearl River suffered a higher neonicotinoids contamination than the Rear river-route, resulting from more effluents of WWTPs receiving, and intensive commercial and human activities. Level of residual neonicotinoids in surface water was significantly correlated with the water quality (p < 0.01), especially items of pH, DO and ORP, and nitrogen and phosphorus contaminants. Compared with reports about residual neonicotinoids in water and sediment previously, the metropolitan regions of the Guangzhou could be confronted with a moderate contamination and showed serious ecological threats (even heavier than the Pearl Rivers). Our results will provide valuable data for understanding of neonicotinoids contamination in the Pearl River Delta and be helpful for further assessing environmental risk of neonicotinoids.

Under laboratory conditions, the effects of thiamethoxam were investigated in larvae, pupae and emerging honey bees after exposure at larval stages with different concentrations in the food (0.00001 ng/μL, 0.001 ng/μL and 1.44 ng/μL). Thiamethoxam reduced the survival of larvae and pupae and consequently decreased the percentage of emerging honey bees. Thiamethoxam induced important physiological disturbances. It increased acetylcholinesterase (AChE) activity at all developmental stages and increased glutathione-S-transferase (GST) and carboxylesterase para (CaEp) activities at the pupal stages. For midgut alkaline phosphatase (ALP), no activity was detected in pupae stages, and no effect was observed in larvae and emerging bees. We assume that the effects of thiamethoxam on the survival, emergence and physiology of honey bees may affect the development of the colony. These results showed that attention should be paid to the exposure to pesticides during the developmental stages of the honey bee. This study represents the first investigation of the effects of thiamethoxam on the development of A. mellifera following larval exposure.

China is the largest beekeeping and honey consumption country globally. Neonicotinoids in honey can pose adverse effects on honey bees and human, but data on neonicotinoids residues in honey and its health risk remain limited in China. A total of 94 honey samples were selected from Chinese market based on production region and sale volume in 2020. Eight neonicotinoids and four metabolites were determined by liquid chromatography coupled to mass spectrometry. Health risk of neonicotinoids in honey on honey bees and human was assessed by hazard quotient (HQ) and hazard index (HI). Neonicotinoids and their metabolites were overall detected in 97.9% of honey samples. Acetamiprid, thiamethoxam, and imidacloprid were top three dominant neonicotinoids in honey with the detection frequencies of 92.6%, 90.4%, and 73.4%, respectively. For honey bees, 78.7% of honey samples had a HI larger than one based on the safety threshold value of sublethal effects. Top three neonicotinoids with the highest percent proportion of HQ larger than one for honey bees were acetamiprid (43.6%), imidacloprid (31.9%), and thiamethoxam (24.5%) and their maximum HQs were 420, 210, and 41, respectively. Based on oral median lethal doses for honey bees, both HQ and HI were lower than one in all honey samples. For human, both HQ and HI were lower than one based on acceptable daily intakes in all honey samples. Neonicotinoids concentrations and detection frequencies in honey samples and its health risk varied with production region, commercial value of nectariferous plants, number of nectariferous plants, and sale price. The results suggested extensive residues of neonicotinoids in honey in Chinese market with a variation by the characteristics of honey. The residues were likely to affect the health of honey bees, but showed no detectable effect on human health.

Neonicotinoids (NEOs) have become the most widely used insecticides in the world. However, information on the NEO concentrations in tap water based on nationwide surveys is limited in China. In this study, the levels of six NEOs were measured in tap water samples collected from 38 cities in China. Across all sampling locations, the overall frequency of detection for at least one NEO was 100%, indicating that NEOs are ubiquitous in tap water from China. Imidacloprid was the most abundant NEO (median: 7.59 ng/L), followed by (in decreasing order) clothianidin (5.46 ng/L), dinotefuran (4.55 ng/L), thiamethoxam (4.50 ng/L), acetamiprid (2.72 ng/L), and thiacloprid (0.38 ng/L). Significantly positive correlations (r = 0.655–0.902, p < 0.001) among all pairs of NEOs were observed, which showed that the sources of NEOs in tap water were common or related. Across all sampling locations, regional differences in concentrations (ΣNEOs; sum of six NEOs varied from 0.79 ng/L to 415 ng/L) were observed within China, showing an increasing trend from northern to southern China. Although the estimated daily intake of NEOs were much lower than the reference dose, the potential health risk of NEOs via tap water consumption should raise more public concern considering the high detection rates of NEOs in tap water.

Currently little is known of newer pesticide classes and their occurrence and persistence in recreational lakes. Therefore, the objectives of this study were to (1) assess average pesticide concentrations and loadings entering recreational lakes in three mixed land use watersheds throughout the growing season, (2) evaluate pesticide persistence longitudinally within the lakes, and (3) perform an ecotoxicity assessment. Six sampling campaigns were conducted at three lakes from April through October 2018 to measure the occurrence and persistence during pre, middle, and post growing season. Polar organic chemical integrative samplers (POCIS) were placed in streams near lake inlets and monthly samples were collected for analysis of twelve pesticides. Additional monthly grab water samples were taken at each POCIS location and at the midpoint and outlet of each lake. All pesticide samples were analyzed using liquid chromatography/tandem mass spectrometry (LC/MS/MS) and individual pesticide loading rates were determined. Occurrence and persistence of specific pesticides were significantly different between lakes in varying watershed land uses. Specifically, the recreational lake receiving predominately urban runoff had the highest load of pesticides, likely in the form of biocides, entering the waterbody. Concentrations of imidacloprid exceeded acute and chronic invertebrate levels for 11% and 61% of the sampling periods, respectively, with the recreational lake receiving predominately urban runoff having the most occurrences. Findings from this study are critical for preventing and mitigating potential effects of pesticides, specifically applied as biocides in urban landscapes, from entering and persisting in recreational lakes.

The ecological impacts of insecticides in aquatic areas around agricultural lands have long been ignored in the regulation scheme of pesticides in Japan. Upon the scheme, the predicted concentration of an insecticide in the main stream of a river is the only parameter considered, suggesting that the ecological impacts of insecticides on local biodiversity around agricultural fields are underestimated. To fill this knowledge gap, we measured insecticide concentrations in surface water and sediment in aquatic areas around paddy fields at 35 locations across Japan. Among the 18 insecticides considered, 15 were detected somewhere in Japan and their concentrations were generally higher in the southwestern region in Japan (e.g. Hiroshima, Saga, or Kagoshima prefectures). Most insecticides were accumulated at higher concentrations in sediment than in surface water, consistent with previous studies. We also detected insecticides applied to nursery boxes at high concentrations in surrounding aquatic areas, although such application is generally considered to have low environmental risks. In addition, derivatives of fipronil, which have similar toxicity as that of fipronil, were often detected in sediment at higher concentrations than fipronil itself. Concentrations of dinotefuran in water at two sampling points were higher than the 5% hazardous concentration (HC5), indicating a possibility of a risk of acute toxicity to aquatic organisms. Our findings indicate that ecological risk assessments of insecticides and their derivatives should be expanded to include concentrations in sediment and water around paddy fields as well.