Insecticide fipronil and its transformation products in human blood and urine: Assessment of human exposure in general population of China

Insecticide-Induced Metabolic Dysregulation in Model Microbe E. coli Discovered by Comprehensive Metabolic Profiling

Fipronil, malathion, and permethrin are widely used insecticides in agriculture, public areas, and residential spaces. The globally abused application of these chemicals results in residues surpassing established maximum residue levels, giving rise to potential toxicity in unintended organisms. Long-term exposure and the persistent accumulation of these insecticides in animals and humans pose threats such as neurotoxicity, liver and kidney damage, and microbiota dysbiosis. Despite the known risks, the specific impact of these insecticides on gut microbiota and their metabolic processes, as well as the subsequent effects on host health, remain largely unknown. This study aimed to address this gap by utilizing nonpathogenic Escherichia coli as a representative of human gut bacteria and examining its growth and metabolic perturbations induced by exposure to fipronil, malathion, and permethrin. Our research showed that exposure of E. coli to fipronil, malathion, and permethrin at physiologically relevant concentrations resulted in significant growth inhibition. Furthermore, we have observed the biodegradation of fipronil and permethrin by E. coli, while no biodegradation was found for malathion. Thus, E. coli is capable of degrading fipronil and permethrin, thereby enabling the removal of those substances. Next, we studied how insecticides affect bacterial metabolism to understand their influence on the functions of the microbes. Our metabolomics analysis revealed chemical-dependent alterations in metabolic profiles and metabolite compositions following insecticide exposure. These changes encompassed shifts in carboxylic acids and derivatives, organooxygen compounds, as well as indoles and their derivatives. To gain a deeper insight into the systematic changes induced by these insecticides, we conducted a metabolic pathway analysis. Our data indicated that fipronil, compared with malathion and permethrin, exhibited opposite regulation in glycine, serine, and threonine metabolism and valine, leucine, and isoleucine biosynthesis. In summary, our study demonstrates the capability of E. coli to degrade fipronil and permethrin, leading to their removal, while malathion remains unaffected. Additionally, we reveal chemical-dependent alterations in bacterial metabolism induced by insecticide exposure, with specific impacts on metabolic pathways, particularly in pathways related to amino acid metabolism.

Forever Pesticides: A Growing Source of PFAS Contamination in the Environment

BACKGROUND

Environmental contamination by fluorinated chemicals, in particular chemicals from the per- and polyfluoroalkyl substances (PFAS) class, has raised concerns around the globe because of documented adverse impacts on human health, wildlife, and ecosystem quality. Recent studies have indicated that pesticide products may contain a variety of chemicals that meet the PFAS definition, including the active pesticide ingredients themselves. Given that pesticides are some of the most widely distributed pollutants across the world, the legacy impacts of PFAS addition into pesticide products could be widespread and have wide-ranging implications on agriculture and food and water contamination, as well as the presence of PFAS in rural environments.

OBJECTIVES

The purpose of this commentary is to explore different ways that PFAS can be introduced into pesticide products, the extent of PFAS contamination of pesticide products, and the implications this could have for human and environmental health.

METHODS

We submitted multiple public records requests to state and federal agencies in the United States and Canada and extracted relevant data from those records. We also compiled data from publicly accessible databases for our analyses.

DISCUSSION

We found that the biggest contributor to PFAS in pesticide products was active ingredients and their degradates. Nearly a quarter of all US conventional pesticide active ingredients were organofluorines and 14% were PFAS, and for active ingredients approved in the last 10 y, this had increased to 61% organofluorines and 30% PFAS. Another major contributing source was through PFAS leaching from fluorinated containers into pesticide products. Fluorination of adjuvant products and "inert" ingredients appeared to be limited, although this represents a major knowledge gap. We explored aspects of immunotoxicity, persistence, water contamination, and total fluorine load in the environment and conclude that the recent trend of using fluorinated active ingredients in pesticides may be having effects on chemical toxicity and persistence that are not given adequate oversight in the United States. We recommend a more stringent risk assessment approach for fluorinated pesticides, transparent disclosure of "inert" ingredients on pesticide labels, a complete phase-out of post-mold fluorination of plastic containers, and greater monitoring in the United States. https://doi.org/10.1289/EHP13954.

A preliminary understanding of the relationship between synthetic phenolic antioxidants and early pregnancy loss: Uncovering the potential molecular mechanisms

Mounting evidence suggests that environmental pollutants may affect reproductive health, potentially leading to adverse outcomes like pregnancy loss. However, it remains unclear whether exposure to synthetic phenolic antioxidants (SPAs) correlates with early pregnancy loss (EPL). This study explores SPA exposure's link to EPL and its potential molecular mechanisms. From 2021 to 2022, 265 early pregnant women (136 serum and 129 villus samples) with and without EPL were enrolled. We quantified 17 SPAs in serum and chorionic villus, with AO1010, AO3114, BHT, AO2246, and BHT-Q frequently being detected, suggesting their ability to cross the placental barrier. AO1135 showed a positive relationship with EPL in sera, indicating a significant monotonic dose-response relationship (p-trend <0.001). BHT-Q exhibited a similar relationship with EPL in villi. Inhibitory effects of BHT-Q on estradiol (E2) were observed. Molecular docking revealed SPA-protein interactions involved in E2 synthesis. SPA-induced EPL might occur with specific serum levels of AO1135 and certain villus levels of AO1010, BHT-Q, and AO2246. BHT-Q emerges as a potential biomarker for assessing EPL risk. This study provides insights into understanding of the exposure to SPAs and potential adverse outcomes in pregnant women.

Immunoassays and Emerging Analytical Techniques of Fipronil and its Metabolites for Food Safety: A Review

Fipronil, classified as a phenylpyrazole insecticide, is utilized to control agricultural, public health, and veterinary pests. Notably, its unique ecological fate involves degradation to toxic metabolites, which poses the risk of contamination in water and foodstuffs and potential human exposure through the food chain. In response to these concerns, there is a pressing need to develop analytical methodologies for detecting fipronil and its metabolites. This review provides a concise overview of the mode of action, metabolism, and toxicology of fipronil. Additionally, various detection strategies, encompassing antibody-based immunoassays and emerging analytical techniques, such as fluorescence assays based on aptamer/molecularly imprinted polymer/fluorescent probes, electrochemical sensors, and Raman spectroscopy, are thoroughly reviewed and discussed. The focus extends to detecting fipronil and its metabolites in crops, fruits, vegetables, animal-derived foods, water, and bodily fluids. This comprehensive exploration contributes valuable insights into the field, aiming to foster the development and innovation of more sensitive, rapid, and applicable analytical methods.

The diabetogenic effects of pesticides: Evidence based on epidemiological and toxicological studies

While the use of pesticides has improved grain productivity and controlled vector-borne diseases, the widespread use of pesticides has resulted in ubiquitous environmental residues that pose health risks to humans. A number of studies have linked pesticide exposure to diabetes and glucose dyshomeostasis. This article reviews the occurrence of pesticides in the environment and human exposure, the associations between pesticide exposures and diabetes based on epidemiological investigations, as well as the diabetogenic effects of pesticides based on the data from in vivo and in vitro studies. The potential mechanisms by which pesticides disrupt glucose homeostasis include induction of lipotoxicity, oxidative stress, inflammation, acetylcholine accumulation, and gut microbiota dysbiosis. The gaps between laboratory toxicology research and epidemiological studies lead to an urgent research need on the diabetogenic effects of herbicides and current-use insecticides, low-dose pesticide exposure research, the diabetogenic effects of pesticides in children, and assessment of toxicity and risks of combined exposure to multiple pesticides with other chemicals.

Associations between seminal plasma triclosan and low sperm quality: A case-control study

OBJECTIVE

Triclosan (TCS), a novel endocrine disrupter, has induced widespread human exposure due to its widespread use in personal care products. Environmental TCS exposure was suggested to be associated with human semen quality. However, little is known about seminal plasma TCS concentration and the risk of low sperm quality. This case-control study is established to examine the relationship between seminal plasma TCS and the risk of low sperm quality.

STUDY DESIGN

One hundred men with low sperm quality as cases and one hundred normal men as controls were recruited a fertility clinic in Shijiazhuang, China, during 2018-2019. Seminal plasma TCS concentration was determined using an ultrahigh-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS). Sperm concentration, sperm count, sperm motility and sperm progressive motility were evaluated according to World Health Organization (WHO) guidelines to assess the sperm quality. We used the Mann-Whitney rank-sum test and Kruskal-Wallis test to assess the differences of seminal plasma TCS concentration between the cases and the controls. In addition, logistic regression analysis was used to estimate the associations between seminal plasma TCS concentrations and low sperm quality risk adjusting for age, body mass index (BMI), abstinence time, smoking, and drinking RESULTS AND CONCLUSIONS: The level of seminal plasma TCS was observed slightly but not significantly higher in the case group than the control group. We also observed significant association between seminal plasma TCS concentrations and semen parameters in both control and case groups. Moreover, the seminal plasma TCS levels at the fourth quartile were found to be more likely to exhibit low sperm quality risk with increased adjusted odds ratios of 2.36 (95% confidence interval 1.03-5.39) compared to the first quartile. Our results reveal that seminal plasma TCS concentration was positively associated with low sperm quality risk.

Fipronil and its transformation products in the Yangtze River: Assessment for ecological risk and human exposure

Fipronil (FP), a phenylpyrazole insecticide, is widely used in agricultural, residential, and veterinary settings. It is toxic to ecosystems and humans; moreover, some of its transformation products are more toxic than FP. A comprehensive profile of the contamination of the Yangtze River by FP and its transformation products (FPs) is not yet available. This study aims to fill this data gap. A total of 144 water samples were collected from 72 sampling locations along the river during the wet (June 2021) and dry (December 2020) seasons. High detection rates (85.4-91.7%) of FPs were found, with ΣFPs' median concentration of 0.49 ng/L. The parent compound FP was the most abundant (median: 0.13 ng/L), followed by FP-desulfinyl (0.08), FP-sulfone (0.07), FP-detrifluoromethylsulfinyl (DTF, 0.07), FP-sulfide (0.06) and FP-amide (0.06). Their concentrations increased significantly from the upper to the lower reaches; for approximately every 100 km toward the lower reaches, the level of FPs increased by 13-15%. The urban region and wet season had the higher FPs contamination. Through water ingestion, the human exposure risk posed by FPs in the river was acceptable; however, the ecological risk assessment showed a moderate to high risk posed by FPs. Follow-up studies are warranted to establish integrated ecological risk assessment models and conduct epidemiological risk assessments among population groups with high exposure levels of FPs. Given the high ecological risk of FPs, regular monitoring of them in the Yangtze River is necessary. FP-DTF was reported in surface water for the first time.

Prenatal exposure to pesticides and domain-specific neurodevelopment at age 12 and 18 months in Nanjing, China

BACKGROUND

The extensive usage of pesticides has led to a ubiquitous exposure in the Chinese general population. Previous studies have demonstrated developmental neurotoxicity associated with prenatal exposure to pesticides.

OBJECTIVES

We aimed to delineate the landscape of internal pesticides exposure levels from pregnant women's blood serum samples, and to identify the specific pesticides associated with the domain-specific neuropsychological development.

METHODS

Participants included 710 mother-child pairs in a prospective cohort study initiated and maintained in Nanjing Maternity and Child Health Care Hospital. Maternal spot blood samples were collected at enrollment. Leveraging on an accurate, sensitive and reproducible analysis method for 88 pesticides, a total of 49 pesticides were measured simultaneously using gas chromatography-triple quadrupole tandem mass spectrometry (GC-MS/MS). After implementing a strict quality control (QC) management, 29 pesticides were reported. We assessed neuropsychological development in 12-month-old (n = 172) and 18-month-old (n = 138) children using the Ages and Stages Questionnaire (ASQ), Third Edition. Negative binomial regression models were used to investigate the associations between prenatal exposure to pesticides and ASQ domain-specific scores at age 12 and 18 months. Restricted cubic spline (RCS) analysis and generalized additive models (GAMs) were fitted to evaluate non-linear patterns. Longitudinal models with generalized estimating equations (GEE) were conducted to account for correlations among repeated observations. Weighted quantile sum (WQS) regression and Bayesian kernel machine regression (BKMR) were applied to examining the joint effect of the mixture of pesticides. Several sensitivity analyses were performed to assess the robustness of the results.

RESULTS

We observed that prenatal exposure to chlorpyrifos was significantly associated with a 4 % decrease in the ASQ communication scores both at age 12 months (RR, 0.96; 95 % CI, 0.94-0.98; P < 0.001) and 18 months (RR, 0.96; 95 % CI, 0.93-0.99; P < 0.01). In the ASQ gross motor domain, higher concentrations of mirex (RR, 0.96; 95 % CI, 0.94-0.99, P < 0.01 for 12-month-old children; RR, 0.98; 95 % CI, 0.97-1.00, P = 0.01 for 18-month-old children), and atrazine (RR, 0.97; 95 % CI, 0.95-0.99, P < 0.01 for 12-month-old children; RR, 0.99; 95 % CI, 0.97-1.00, P = 0.03 for 18-month-old children) were associated with decreased scores. In the ASQ fine motor domain, higher concentrations of mirex (RR, 0.98; 95 % CI, 0.96-1.00, P = 0.04 for 12-month-old children; RR, 0.98; 95 % CI, 0.96-0.99, P < 0.01 for 18-month-old children), atrazine (RR, 0.97; 95 % CI, 0.95-0.99, P < 0.001 for 12-month-old children; RR, 0.98; 95 % CI, 0.97-1.00, P = 0.01 for 18-month-old children), and dimethipin (RR, 0.94; 95 % CI, 0.89-1.00, P = 0.04 for 12-month-old children; RR, 0.93; 95 % CI, 0.88-0.98, P < 0.01 for 18-month-old children) were associated with decreased scores. The associations were not modified by child sex. There was no evidence of statistically significant nonlinear relationships between pesticides exposure and RRs of delayed neurodevelopment (P_nonlinearity > 0.05). Longitudinal analyses implicated the consistent findings.

CONCLUSION

This study gave an integrated picture of pesticides exposure in Chinese pregnant women. We found significant inverse associations between prenatal exposure to chlorpyrifos, mirex, atrazine, dimethipin and the domain-specific neuropsychological development (i.e., communication, gross motor and fine motor) of children at 12 and 18 months of age. These findings identified specific pesticides with high risk of neurotoxicity, and highlighted the need for priority regulation of them.

Pet dogs transfer veterinary medicines to the environment

Worldwide, the number of pet dogs increases yearly, and as a result so does the use of veterinary medicines for flea and tick control. We investigated the potential transfer of veterinary flea products from dogs to the environment in a 'proof of principle' experiment. For this purpose, samples of hair, urine, and water after swimming were investigated. Nine dogs were recruited for this study, eight of which had been recently treated with an ectoparasiticide product. Hair and urine samples were tested for afoxalaner, fluralaner, fipronil and imidacloprid. Interestingly, contamination with ectoparasiticides was frequently demonstrated in samples from dogs untreated with these particular substances, suggesting widespread secondary transfer. In addition, hair retrieved from a bird's nest contained fipronil, fluralaner and imidacloprid, indicating a potential pathway for the exposure of juvenile birds. Three of the dogs also participated in a swimming experiment. One had been treated with oral fluralaner, whilst the remaining two had received other compounds not included in our study. However, in all three dogs, both fluralaner and imidacloprid were detected in hair samples. Fluralaner concentrations in the swimming water exceeded Dutch water quality standards, indicating a potential risk to the aquatic environment. Imidacloprid levels increased after each swimming dog, but did not breach Dutch water quality standard levels. These findings all call for improvements in the current risk assessment and management for veterinary medicines, by including companion animals and their exposure pathways into ecosystems.

In vitro investigation of endocrine disrupting effects of pesticides on Ca2+-signaling in human sperm cells through actions on the sperm-specific and steroid-activated CatSper Ca2+-channel

BACKGROUND

Ca²⁺-signaling controls sperm cell functions necessary for successful fertilization. Multiple endocrine disrupting chemicals have been found to interfere with normal Ca²⁺-signaling in human sperm cells through an activation of the sperm-specific CatSper Ca²⁺-channel, which is vital for normal male fertility.

OBJECTIVES

We investigated 53 pesticides for their ability to interfere with CatSper mediated Ca²⁺-signaling and function in human sperm cells.

METHODS

Effects of the pesticides on Ca²⁺-signaling in human sperm cells were evaluated using a Ca²⁺-fluorometric assay. Effects via CatSper were assessed using the specific CatSper inhibitor RU1968. Effects on human sperm function and viability were assessed using an image cytometry-based acrosome reaction assay and the modified Kremer's sperm-mucus penetration assay.

RESULTS

28 of 53 pesticides were found to induce Ca²⁺-signals in human sperm cells at 10 µM. The majority of these 28 active pesticides induced Ca²⁺-signals through CatSper and interfered with subsequent Ca²⁺-signals induced by the two endogenous CatSper ligands progesterone and prostaglandin E₁. Multiple active pesticides were found to affect Ca²⁺-mediated sperm functions and viability at 10 µM. Low nM dose mixtures of the active pesticides alone or in combination with other environmental chemicals were found to significantly induce Ca²⁺-signals and inhibit Ca²⁺-signals induced subsequently by progesterone and prostaglandin E₁.

CONCLUSIONS

Our results show that pesticides, both alone and in low nM dose mixtures, interfere with normal Ca²⁺-signaling in human sperm cells in vitro in low nM concentrations. Biomonitoring of the active pesticides in relevant matrices such as blood and reproductive fluids is very limited and the effects of real time human pesticide exposure on human sperm cells and fertility thus remains largely unknown. To which extent human pesticide exposure affects the chances of a successful fertilization in humans in vivo needs further research.

Prenatal Exposure to Emerging Plasticizers and Synthetic Antioxidants and Their Potency to Cross Human Placenta

Gestational exposure to environmental chemicals and subsequent permeation through the placental barrier represents potential health risks to both pregnant women and their fetuses. In the present study, we explored prenatal exposure to a suite of 46 emerging plasticizers and synthetic antioxidants (including five transformation products of 2,6-di-tert-butyl-4-hydroxytoluene, BHT) and their potency to cross human placenta based on a total of 109 maternal and cord serum pairs. Most of these chemicals have rarely or never been investigated for prenatal exposure and associated health risks. Eleven of them exhibited detection frequency greater than 50% in maternal blood, including dibutyl fumarate (DBF), 2,6-di-tert-butylphenol (2,4-DtBP), 1,3-diphenylguanidine (DPG), methyl-2-(benzoyl)benzoate (MBB), triethyl citrate (TEC), BHT, and its five metabolites, with a median concentration from 0.05 to 3.1 ng/mL. The transplacental transfer efficiency (TTE) was determined for selected chemicals with valid measurements in more than 10 maternal/cord blood pairs, and the mean TTEs exhibited a large variation (i.e., 0.29-2.14) between chemicals. The determined TTEs for some of the target chemicals were comparable to the predicted values by our previously proposed models developed from molecular descriptors, indicating that their transplacental transfer potency could be largely affected by physicochemical properties and molecular structures. However, additional biological and physiological factors may influence the potency of environmental chemicals to cross human placenta. Overall, our study findings raise concern on human exposure to an increasing list of plastic additives during critical life stages (e.g., pregnancy) and potential health risks.

Exposure assessment of neonicotinoid insecticides and their metabolites in Chinese women during pregnancy: A longitudinal study

Neonicotinoid insecticides (NNIs) are the most widely used insecticides globally and ubiquitous in the environment, which has led to widespread human exposure. However, studies on internal exposure levels of NNIs and their metabolites in pregnant women are scarce. In this study, we measured nine parent NNIs and ten main metabolites in 1224 urine samples donated by 408 pregnant women at three trimesters. In the urine samples, the unadjusted vs. specific gravity (SG) adjusted median concentrations and detection frequencies (DFs) of desmethyl-acetamiprid (DM-ACE; 1.01 vs. 1.08 ng/mL; DF: 99.7%), 5-hydroxy-imidacloprid (5-hydroxy-IMI; 0.54 vs. 0.56 ng/mL; 98.5%), imidacloprid-olefin (IMI-olefin; 0.41 vs. 0.44 ng/mL; 99.3%), and desnitro-imidacloprid (DN-IMI; 0.12 vs. 0.12 ng/mL; 90.4%) were higher than their corresponding parent NNIs, acetamiprid (ACE; <0.01 vs. <0.01 ng/mL; 26.4%) and imidacloprid (IMI; 0.04 vs. 0.04 ng/mL; 69.9%). The unadjusted and SG-adjusted median concentrations of clothianidin (CLO), thiamethoxam (THM), and desmethyl-clothianidin (DM-CLO) were 0.05 vs. 0.07, 0.05 vs. 0.06, and 0.04 vs. 0.05 ng/mL, with the DFs of 61.0%, 57.5%, and 75.7%, respectively. The cumulative exposure level, imidacloprid-equivalent total NNIs (IMI_eq), was generated by the relative potency factor approach considering the toxic effects of NNIs and their metabolites. The unadjusted IMI_eq varied from 0.17 ng/mL (SG-adjusted: 0.20) to 1969 ng/mL (SG-adjusted: 1817) with a median of 14.1 ng/mL (SG-adjusted: 14.1). A decreased trend was observed in urinary NNIs and their metabolites throughout the three trimesters. Maternal age, educational level, and household income were related to the concentrations of NNIs and their metabolites. DM-ACE, 5-hydroxy-IMI, and IMI-olefin were significantly lower in winter than in autumn; DN-IMI, THM, CLO, and DM-CLO were significantly higher in both summer and autumn than in winter. The maximum estimated daily intake of IMI_eq [34.8 μg/kg-body weight (bw)/d] was lower than the chronic reference dose of IMI (57 μg/kg-bw/d) currently recommended by the United States Environmental Protection Agency. Human health risk of exposure to NNIs and their main metabolites warranted further studies.

Occurrence of Phenylpyrazole and Diamide Insecticides in Lactating Women and Their Health Risks for Infants

To investigate the exposure of infants to phenylpyrazole and diamide insecticides during lactation, we collected 3467 breast milk samples of lactating women from 100 cities of 24 provinces in China and prepared 100 pooled samples together city-by-city. Among phenylpyrazole insecticides, fipronil and its metabolites (63-100%) were widely detected in breast milk, with total detection concentrations ranging from 178 to 2947 ng/L (median: 921 ng/L). Among diamide insecticides, chlorantraniliprole and flubendiamide were detected in breast milk, but their detection frequencies (20-85%) and concentration levels (nondetected to 89.9 ng/L) were far lower than those of total fipronils. The average estimated daily intake of infants exposed to total fipronils through breast milk is 209 ng/kg-bw/day by upper-bound scenario evaluation, which is higher than the acceptable daily intake (200 ng/kg-bw/day). This study indicates that infants have far higher exposure levels to fipronil than adults, while exposure levels to other types of phenylpyrazoles and diamide insecticides are low.

Association between urinary dialkylphosphate metabolites and dyslexia among children from three cities of China: The READ program

Exposure to organophosphate (OP) insecticides has been found to be related to neurodevelopmental disorders in children. However, no study has examined the association between OP insecticide exposure and the risk of dyslexia among children. We aimed to explore the association between OP insecticide exposure, indicated by urinary dialkylphosphate metabolites (DAPs), and the risk of dyslexia among Chinese Han children from three cities. A total of 845 children (422 dyslexics and 423 non-dyslexics) from Tongji Reading Environment and Dyslexia research program were included in the current case-control study. We measured six DAPs in urine samples, collected from November 2017 to December 2020. Logistic regression models were used to estimate odds ratios (ORs) for the association between DAPs and dyslexia risk, adjusting for potential confounders. The detection frequencies of DAPs were above 97.5%, except for diethyldithiophosphate and dimethyldithiophosphate. Diethyl phosphate metabolites (DEs) were significantly associated with the risk of dyslexia. Compared with the lowest quartile, the adjusted ORs of dyslexia risk for the highest quartile of urinary diethylthiophosphate (DETP) and diethylphosphate (DEP) were 1.82 (1.04, 3.20) and 1.85 (1.08, 3.17), respectively. In addition, the adjusted ORs for dyslexia per 10-fold of urinary DEP, DETP, and ∑DEs concentration were 1.87 (1.12, 3.13), 1.55 (1.03, 2.35), and 1.91 (1.13, 3.21), respectively. Analyses stratified by gender indicated that such associations were more significant among boys. This study suggested that exposure to OP insecticides may be related to dyslexia among Chinese Han children from the three studied cities. However, our results should be interpreted with caution because of the case-control design and the fact that only one-spot urine sample was collected from the children. More studies with children living in China are necessary concerning the relatively high levels of urinary OP metabolites in our study.

Tissue-specific accumulation, transformation, and depuration of fipronil in adult crucian carp (Carassius auratus)

Accumulation and biotransformation of pesticides in fish tissues are essential to assess their toxicity and associated human exposure risk. The mechanisms on time-dependent and tissue-specific accumulation and transformation of fipronil in adult fish are limited. An experiment consisting of 25-d uptake of fipronil at two levels (10 and 50 μg/L) and 25-d depuration in adult crucian carp (Carassius auratus) was conducted. Fipronil concentration at 25-d exposure was tissue-specific with the order of liver > kidney > blood > muscle. The uptake rate constant of fipronil in the liver (low exposure group: 2.38 ± 0.27 L/kg/d; high exposure group: 1.10 ± 0.11 L/kg/d) was significantly higher than that in other tissues (p < 0.05), and the lowest in muscle (low exposure group: 0.10 ± 0.01 L/kg/d; high exposure group: 0.16 ± 0.11 L/kg/d). The bioconcentration factors of fipronil in different tissues were 1.04-12.7 L/kg wet weight and 177-4268 L/kg lipid. The tissue-blood distribution coefficients of the liver and kidney were lower than 1 based on lipid normalized concentration but higher than 1 based on wet weight concentration, suggesting fipronil was dispersed into other tissues mainly via blood in the lipid-combination pattern. Fipronil sulfone had 1.2-32 times higher concentration and longer depuration time than fipronil, implying fipronil sulfone was more retender in fish bodies. The estimated daily intake of fipronil via fish muscle consumption at 25-d exposure was 8.5-101 and 27-320 ng/kg bw/d for adults and children, respectively. Overall, the human health risk of fipronil and its metabolites with consumption of the polluted fish cannot be negligible.

Generic Enrichment of Organic Contaminants in Human Biomonitoring: Application in Monitoring Early Life Exposures to Fipronil via Breast Milk

In human biomonitoring, a high-throughput extraction and enrichment method for multiple types of organic contaminants at the part-per-trillion level is critical yet challenging, especially in the limited sample volume. When large-scale sample analysis is involved, low cost is often what we should consider. We describe a generic and straightforward cold-induced liquid-liquid extraction (CI-LLE) strategy to meet this need. Current methods for extracting and enriching organic contaminants from biological samples often require multistep sample processing, including specially tailoring the extraction solvent or adsorbents. This method uses cold-induced phase separation to achieve the extraction and enrichment of studied organic contaminants by adjusting the proportion of acetonitrile/water mixture, so as to integrate the extraction and enrichment in one step without additional reagents and adsorbents. In this study, fipronil insecticide was used as a representative compound to determine the key parameters of CI-LLE. The optimized CI-LLE procedure allowed simultaneous extraction and enrichment of studied organic contaminants, providing excellent enrichment factors (especially for lipophilic organic contaminants). CI-LLE was further applied in monitoring early life exposures of fipronil in 109 breast milk samples. This study provided baseline data on fipronil levels in breast milk samples from China. For infants, exposure to fipronil is of concern. In summary, CI-LLE provides a feasible solution for a generic, efficient, and low-cost preparation of biological samples and promotes high-throughput batch analysis of organic contaminants for large-scale human biomonitoring.

Occurrence and ecological risk assessment of neonicotinoids and related insecticides in the Bohai Sea and its surrounding rivers, China

Systemic insecticides like neonicotinoids and the phenylpyrazole insecticide fipronil are the most widely applied insecticides around the world. Multiple studies analyzed insecticide residues in freshwater systems, but data on seawater contamination levels are scarce. This study investigates the spatiotemporal distribution and ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected transformation products (TPs) in the Chinese Bohai Sea and its surrounding rivers. Well-established neonicotinoids (acetamiprid, clothianidin, imidacloprid, thiacloprid and thiamethoxam) and TPs of fipronil and imidacloprid were frequently detected (detection frequency (DF): 42-100%) in freshwater. The median total insecticide concentration in freshwater was significantly higher in summer (72.4 ng•L-1) than in fall (23.4 ng•L-1), with major contributions from neonicotinoids, suggesting that pollution originates mostly from diffuse sources. In 2018, acetamiprid, desnitro-imidacloprid, fipronil-desulfinyl and thiacloprid were abundant in seawater (DF: 47-100%), indicating a high stability of acetamiprid and thiacloprid and a rapid photodegradation of fipronil and imidacloprid in surface waters. These results indicate that the continued use of these parent compounds may lead to their accumulation and/or of their TPs in shallow coastal seas. Consequently, this may lead to their transport to open seas, increasing their potential risk to marine organisms. Similarities between contaminant fingerprints in freshwater and seawater strongly suggest riverine discharges as main pollution source of adjacent coastal areas. This is the first study to perform an ecological risk assessment of fipronil, neonicotinoids, sulfoxaflor and selected TPs on marine ecosystems. Fipronil and its TPs demonstrated to be environmentally relevant with potential high risks for aquatic species. Our study provides novel insights into the fate and ecological risk of fipronil, neonicotinoids, sulfoxaflor and their TPs to marine species in shallow coastal seas.

Fipronil and its metabolites in human seminal plasma from Shijiazhuang, north China

Fipronil (FP) is an emerging insecticide which could induce reproductive toxicity in male rats at very low dosage, but the occurrence of FP and its transformation products (FPs) in human seminal plasma and their impacts on human semen quality have not been documented. In this study, FPs including FP, fipronil desulfinyl (FP-DES), fipronil sulfone (FP-SFO), fipronil amide (FP-AM), and fipronil sulfide (FP-SFI), were measured in seminal plasma samples (n = 200), which were collected from Shijiazhuang, north China. The cumulative concentration of FPs (ΣFPs), in the seminal plasma samples ranged from 0.003 to 0.180 ng/mL (median: 0.043 ng/mL). FP-SFO was the major target analyte (median: 0.040 ng/mL), accounting for approximately 42.3-100.0% of the ΣFPs. Significantly higher exposure levels of FPs were found in the overweight or obese group (≥25 kg/m²) vs. the normal BMI group (18.5-25 kg/m²) (ΣFPs: 0.047 vs. 0.033 ng/mL), never smoking group vs. current smoking group (ΣFPs: 0.057 vs. 0.037 ng/mL), and low sexual frequency group (<1 time/week) vs. high sexual frequency group (≥3 times/week) (ΣFPs: 0.048 vs. 0.030 ng/mL). No significant association between FPs and impaired semen quality parameter was found in this study. This is the first time to report FPs' occurrence in human seminal plasma and variations in their concentrations among people with different demographic and behavioral characteristics. Further studies on adverse effects of exposure to FPs on reproductive function are needed.

Human Exposure of Fipronil Insecticide and the Associated Health Risk

Fipronil, as an emerging phenylpyrazole insecticide, is ubiquitous in the environment and food due to its broad spectrum and persistent characteristics, but the research on pathways of human exposure to fipronil and the associated health risk is relatively unclear. In this regard, we summarize potential human exposures to fipronil through ingestion and inhalation, as well as results of human biomonitoring studies. This scientific information will contribute to future assessment of fipronil exposure and subsequent characterization of human health risks. Additionally, this Perspective highlights the lack of epidemiological studies and total diet studies for the general population on fipronil.

Bentazone in water and human urine in Wuhan, central China: exposure assessment

Bentazone is a widely used post-emergence herbicide, while no data was available on its concentrations in tap water from China and in urine among the general population. It was determined in the source (Wuhan section of the Yangtze River watershed), treated, and tap water (n = 20, 20, and 170, respectively) in different seasons (2019) in Wuhan, central China. Also, urine samples (n = 38) collected from healthy adults in Wuhan (September 2020) were analyzed to characterize its urinary concentration. Bentazone was detected in all the source and treated water samples. Its concentrations in the source water in July were higher than those in February (median: 17.9 ng/L vs. 2.86 ng/L) (p < 0.05). It cannot be removed efficiently (27.8-27.9%) by conventional drinking water treatment using NaClO, but it can be efficiently removed by using chlorine dioxide or ozone combined with activated carbon. Bentazone was frequently detected (detection frequency: 96.3%) in 160 tap water samples (underwent conventional treatment) (median: 1.95 ng/L, range: <0.02-47.0 ng/L), while it was not detectable in tap water samples that underwent ozone combined with activated carbon. Seasonal variations were found, with the lowest median concentration (ng/L) in April (0.46) and the highest in July (17.6). In addition, bentazone was frequently (92.1%) detected in human urine samples (median: 0.02 ng/mL; range: < 0.01-0.11 ng/mL). The estimated daily intake of bentazone based on its median concentration in tap water (0.04 ng/kg-body weight [bw]/day) accounted for approximately 8% of that based on the median urinary concentration (0.48 ng/kg-bw/day). This is the first time to characterize its occurrence in drinking water from China and its occurrence in the urine of the general population.

Occurrence and exposure risk assessment of organic micropollutants in indoor dust from Malaysia

Indoor dust is an important source of human exposure to hazardous organic micropollutants (OMPs) because humans spend about 90 % of their time in the indoor environments. This study initially analyzed the concentrations and compositions of OMPs in the dust of different indoor environments from Kuala Lumpur, Malaysia. A total of 57 OMPs were detected and assigned to 7 chemical classes in this study. The total concentration of OMPs ranged from 5980 to 183,000 ng/g, with the median concentration of 46,400 ng/g. Personal care products, organophosphate esters, and pesticides were the dominant groups, with their median concentrations at 12,000, 10,000, and 5940 ng/g, respectively. The concentrations and compositions of influential OMPs varied in different microenvironments, suggesting different sources and usage patterns in the house. Then, the noncarcinogenic and carcinogenic risks of exposure to these substances for diverse age groups were assessed based on the median concentration. Cumulative noncarcinogenic risks of these OMPs via ingestion pathway were estimated to be negligible (1.41 × 10^-4 - 1.87 × 10^-3). The carcinogenic risks of these OMPs were higher than 10^-6 (1.63 × 10^-6 - 6.17 × 10^-6) and should be noted. Theobromine accounted for more than 89 % of the cumulative cancer risk, implying that the carcinogenic risk of theobromine needs further monitoring in the future. Toddler was the most affected group for cancer risk among all the age groups, regardless of the microenvironments. These findings from this study may provide a benchmark for future efforts to ensure the safety of indoor dust for the local residents.

Exposure to fipronil induces cell cycle arrest, DNA damage, and apoptosis in porcine trophectoderm and endometrial epithelium, leading to implantation defects during early pregnancy

Fipronil, a phenyl-pyrazole insecticide, has a wide range of uses, from agriculture to veterinary medicine. Due to its large-scale applications, the risk of environmental and occupational exposure and bioaccumulation raises concerns. Moreover, relatively little is known about the intracellular mechanisms of fipronil in trophoblasts and the endometrium involved in implantation. Here, we demonstrated that fipronil reduced the viability of porcine trophectoderm and luminal epithelial cells. Fipronil induced cell cycle arrest at the sub-G1 phase and apoptotic cell death through DNA fragmentation and inhibition of DNA replication. These reactions were accompanied by homeostatic changes, including mitochondrial depolarization and cytosolic calcium depletion. In addition, we found that exposure to fipronil compromised the migration and implantation ability of pTr and pLE cells. Moreover, alterations in PI3K-AKT and MAPK-ERK1/2 signal transduction were observed in fipronil-treated pTr and pLE cells. Finally, the antiproliferative and apoptotic effects of fipronil were also demonstrated in 3D cell culture conditions. In summary, our results suggest that fipronil impairs implantation potentials in fetal trophectoderm and maternal endometrial cells during early pregnancy.