Effects of clothianidin exposure on sperm quality, testicular apoptosis and fatty acid composition in developing male rats

Exploratory analysis of the associations between neonicotinoids insecticides and serum lipid profiles among US adults: A cross-sectional, population-based study

Neonicotinoid insecticides (NNIs) are widely used in agriculture, horticulture, forestry, and household environment, but their potential impact on human health remains a subject of concern. This study aimed to investigate the relationship between NNIs and their metabolites in urine with serum lipid profiles in adults using data from the National Health and Nutrition Examination Survey (NHANES) 2015-2016. The study included 1192 participants aged over 20 years with urinary NNIs levels, serum lipid parameter levels and potential confounders. Urinary concentrations of NNIs, including imidacloprid, acetamiprid, clothianidin, thiacloprid, N-desmethyl-acetamiprid, and 5-hydroxy-imidacloprid, were quantified. Serum lipids profiles, such as total cholesterol (TC), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B (Apo-B), were assessed. Considering the effects of lipid-lowering medications, the censored normal regression model was used to explore the associations between urinary NNIs and TC, TG, HDL-C, LDL-C and Apo-B levels. The results revealed a significant increase of 9.0 mg/dL (95%CI: 2.0, 16.1) in TC levels among participants with detectable N-desmethyl-acetamiprid compared to those with undetectable levels. Stratified analysis indicated that the association between N-desmethyl-acetamiprid and HDL-C levels was more pronounced among participants aged ≥ 46 years compared to those aged between 20 and 45 years with undetectable N-desmethyl-acetamiprid (pinteraction=0.044). Additionally, there were marginal effect modification of BMI on the association between N-desmethyl-acetamiprid and LDL-C (pinteraction=0.097) and Apo-B (pinteraction=0.052) levels. Specifically, participants with BMI ≥ 25 kg/m² and detectable N-desmethyl-acetamiprid tended to have higher LDL-C and Apo-B levels compared to those with BMI < 25 kg/m² and undetectable N-desmethyl-acetamiprid. However, no significant associations were observed between other NNIs and lipid profiles in the present study. To validate these findings, further longitudinal studies with larger sample sizes should be conducted, particularly within populations characterized by a high detection rate of NNIs.

Selected neonicotinoids and associated risk for aquatic organisms

Neonicotinoids are one of the newest groups of systemic pesticides, effective on a wide range of invertebrate pests. The success of neonicotinoids can be assessed according to the amount used, for example, in the Czech Republic, which now accounts for 1/3 of the insecticide market. The European Union (EU) has a relatively interesting attitude towards neonicotinoids. Three neonicotinoid substances (imidacloprid, clothianidin and thiamethoxam) were severely restricted in 2013. In 2019, imidacloprid and clothianidin were banned, while thiamethoxam and thiacloprid were banned in 2020. In 2022, another substance, sulfoxaflor, was banned. Therefore, only two neonicotinoid substances (acetamiprid and flupyradifurone) are approved for outdoor use in the EU. Neonicotinoids enter aquatic ecosystems in many ways. In European rivers, neonicotinoids usually occur in nanograms per litre. Due to the low toxicity of neonicotinoids to standard test species, they were not expected to significantly impact the aquatic ecosystem until later studies showed that aquatic invertebrates, especially insects, are much more sensitive to neonicotinoids. In addition to the lethal effects, many studies point to sublethal impacts - reduced reproductive capacity, initiation of downstream drift of organisms, reduced ability to eat, or a change in feeding strategies. Neonicotinoids can affect individuals, populations, and entire ecosystems.

Single and mixed exposure to distinct groups of pesticides suggests endocrine disrupting properties of imidacloprid in zebrafish embryos

Due to their selective toxicity to insects, nicotinoid compounds have been widely used to control pests in crops and livestock around the world. However, despite the advantages presented, much has been discussed about their harmful effects on exposed organisms, either directly or indirectly, with regards to endocrine disruption. This study aimed to evaluate the lethal and sublethal effects of imidacloprid (IMD) and abamectin (ABA) formulations, separately and combined, on zebrafish (Danio rerio) embryos at different developmental stages. For this, Fish Embryo Toxicity (FET) tests were carried out, exposing two hours post-fertilization (hpf) zebrafish to 96 hours of treatments with five different concentrations of abamectin (0.5-11.7 mg L^-1), imidacloprid (0.0001-1.0 mg L^-1), and imidacloprid/abamectin mixtures (LC₅₀/2 - LC₅₀/1000). The results showed that IMD and ABA caused toxic effects in zebrafish embryos. Significant effects were observed regarding egg coagulation, pericardial edema, and lack of larvae hatching. However, unlike ABA, the IMD dose-response curve for mortality had a bell curve display, where medium doses caused more mortality than higher and lower doses. These data demonstrate the toxic influence of sublethal IMD and ABA concentrations on zebrafish, suggesting that these compounds should be listed for river and reservoir water-quality monitoring.

Effect of Neonicotinoid Pesticides on Japanese Water Systems: Review with Focus on Reproductive Toxicity

Neonicotinoid pesticides (NPs) are neurotoxic substances. They are highly effective as insecticides owing to their water solubility, permeability, and long-lasting activity. These molecules are structurally similar to nicotine and act as nicotinic acetylcholine receptor agonists. The administration of NPs to experimental animals reportedly causes neuromuscular and reproductive disorders. Moreover, recently reported problems caused by NPs include damage to land-dwelling creatures (such as mammals and birds), hydrobiology, and ecosystems. This review summarizes the recent reports on NP concentrations detected in river systems in several Japanese regions. These values were lower than the environmental standard values; however, seasonal variations were observed. Furthermore, reports on NP-induced testicular and ovarian toxicity were examined, revealing that the mechanism of injury is mainly driven by oxidative stress. The use of NPs is declining worldwide, except in Japan; therefore, continuous monitoring remains necessary.

Imidacloprid Induces Histopathological Damage in the Midgut, Ovary, and Spermathecal Stored Spermatozoa of Queens After Chronic Colony Exposure

Bee colony health is declining as a result of several factors, including exposure to pesticides. The development and strength of honey bee colonies depend on the reproductive success of queen bees. Because flowers are sources of food for bees, foragers can accidentally collect and carry contaminated pollen and nectar to their hives; and this may compromise the longevity and the life span of individuals. Thus, the present study aimed to observe the action of imidacloprid in the midgut and ovaries of Apis mellifera queens, as well as the effects on sperm stored in their spermatheca. To this end, the apiary was divided into three experimental groups: control, commercial imidacloprid, and active ingredient imidacloprid. For toxicity assays, a sucrose solution containing 1 µg/L of imidacloprid was offered to the colonies for 42 days. A control group received only food in the same period. In both treatments with imidacloprid, the midgut of queens showed modifications in the external musculature and cellular alterations. Such changes could lead to the nonrecovery of the epithelium and subsequently malabsorption of nutrients. Moreover, the digestive cells of queen bees exposed to the commercial imidacloprid presented pyknotic nuclei, suggesting a cell death process. The main alterations observed in the ovaries of these reproductive bees treated with commercial imidacloprid were degeneration and resorption of the ovariole content, which probably affected their fertilization and colony development. There were no significant changes in the spermatozoa morphology for both treatments with imidacloprid, but this insecticide may interfere with the development and reproductive success of A. mellifera colonies because it affects the morphology and function of essential organs for the survival of queens. Environ Toxicol Chem 2022;41:1637-1648. SETAC.

Neonicotinoid insecticide metabolites in seminal plasma: Associations with semen quality

Animal studies have revealed that exposure to neonicotinoid insecticides (NNIs) could compromise male reproductive function; however, related data on the occurrence of NNIs and their specific metabolites in human seminal plasma are scarce. To explore the potential effects of NNI exposure on male semen quality, we determined the concentrations of NNIs and some of their metabolites (collectively defined as mNNIs) in seminal plasma samples collected from men (n = 191) who visited a fertility clinic in Shijiazhuang, North China from 2018 to 2019. Associations between the mNNI concentrations and semen quality parameters were assessed using linear regression models, adjusting for important covariates. In the seminal plasma samples, desmethyl-acetamiprid (DM-ACE, detection frequency: 98.4%), imidacloprid-olefin (IMI-olefin, detection frequency: 86.5%), and desmethyl-clothianidin (DM-CLO, detection frequency: 70.8%) were frequently detected at median concentrations of 0.052, 0.003, and 0.007 ng/mL, respectively; meanwhile other compounds were detected at less than the method detection limits. In the single-mNNI models, the IMI-olefin concentration was associated with decreased progressive motility [IMI-olefin concentration: percent change (%Δ) = -17.0; 95% confidence interval (CI) = -30.3, -0.92; the highest tertile compared with the lowest tertile: %Δ = -21.1; 95% CI = -37.5, -0.23]. Similar results were found in the multiple-mNNIs models. No other inverse associations were found between the other mNNI concentrations and semen quality parameters. This is the first study to identify the occurrence of mNNIs in the seminal plasma and the potential associations of their concentrations with human semen quality parameters. These findings imply an inverse association between the IMI-olefin concentration and semen quality.

Characteristics of neonicotinoid and metabolite residues in Taiwanese tea leaves

BACKGROUND

Neonicotinoids are widely used insecticides, and tea is a popular non-alcoholic beverage in Taiwan. However, the levels of neonicotinoids in Taiwanese tea leaves remain unclear. Therefore, this study aims to understand the characteristics of neonicotinoid and metabolite residues in Taiwanese tea leaves.

METHODS

In this study, 12 tea leaf samples were collected in Taiwan and extracted by solid-phase extraction before analysis by liquid chromatography-tandem mass spectrometry. In addition, the levels of neonicotinoids were compared with the maximum residue level standards from other countries.

RESULTS

In Taiwanese tea leaves, five neonicotinoids and seven metabolites were detected. Different tea species influenced the levels of neonicotinoids and their metabolites in the present study. Moreover, the levels of neonicotinoids and their metabolites in partially fermented leaves were higher than in completely fermented leaves. In Jin-Xuan tea, the levels of neonicotinoids and their metabolites in most winter-harvested teas were lower than in summer-harvested teas.

CONCLUSION

The residue levels of neonicotinoids and their metabolites were detectable in Taiwanese tea leaves. Moreover, different tea species, manufacturing processes, and harvest seasons might influence the levels of these pesticides. Therefore, the government should monitor the use of neonicotinoids. © 2021 Society of Chemical Industry.

Fucoidan Modulated Oxidative Stress and Caspase-3 mRNA Expression Induced by Sulfoxaflor in the Brain of Mice

The current study aimed to investigate the role of fucoidan in the oxidative and apoptotic effects of sulfoxaflor, a neonicotinoid sulfoximine insecticide, in the brain of Swiss albino mice (Mus musculus). Sulfoxaflor and fucoidan were administered to mice at doses of 15 mg/kg/day (1/50 oral LD50) and 50 mg/kg/day, respectively, by oral gavage for 24 h or 7 days. The tGSH, TBARS and protein levels, and GPx, GR, and GST enzyme activities were determined by spectrophotometric methods. Caspase-3 gene expression level was determined by RT-PCR. Data analysis showed that brains of sulfoxaflor-treated mice exhibited higher TBARS levels; GPx, GR, and GST enzyme activities; and caspase-3 expression levels, as well as lower levels of tGSH. Co-administration of fucoidan and sulfoxaflor reduced the TBARS levels, increased tGSH levels, and increased GPx, GR, and GST enzyme activities. Fucoidan also decreased the sulfoxaflor-induced up-regulation of caspase-3 mRNA expression. Results of the present study showed that sulfoxaflor caused oxidative stress by inducing lipid peroxidation and altering GSH-dependent antioxidants in the brain of mice. In addition, sulfoxaflor may trigger apoptotic cell death shown by the up-regulation of caspase-3. Fucoidan treatment modulated all the aforementioned alterations in the brain of mice. It was concluded that fucoidan might have antioxidant effects that support the GSH-dependent antioxidant system and can play a modulator role in oxidative stress and caspase-3 expression in the brain of sulfoxaflor treated-mice.

Thiamethoxam-induced oxidative stress, lipid peroxidation, and disturbance of steroidogenic genes in male rats: Palliative role of Saussurea lappa and Silybum marianum

Thiamethoxam (TMX) belongs to the neonicotinoid insecticide family and may evoke marked endocrine disruption. In this study, the reproductive toxicity of TMX on male rats was assessed along with the ability of Saussurea lappa (costus roots) and/or Silybum marianum extract (SM) to alleviate TMX toxicity. Male rats were allocated to seven groups and orally treated daily for 4 weeks: Control (saline), Costus (200 mg/kg), SM (150 mg/kg), TMX (78.15 mg/kg), TMX-costus, TMX-SM, and TMX-costus-SM (at the aforementioned doses). Compared with control group, TMX administration induced reductions in testicular levels of glutathione and antioxidant activities of SOD and CAT. In addition, TMX-exposed rats showed lower serum testosterone hormonal levels as well as higher malondialdehyde and nitric acid levels were detected in TMX-administered rats. On a molecular basis, mRNA expressions of StAR, CYP17a, 3β-HSD, SR-B1, and P450scc genes were significantly down-regulated in TMX group, whereas the expression of LHR and aromatase genes was up-regulated. Moreover, TMX-induced testicular damage was confirmed by histopathological screening. Importantly, however, the administration of either costus roots or SM significantly alleviated all aforementioned TMX-induced changes, indicating the effective antioxidant activities of these plant products. Interestingly, simultaneous treatment with costus root and SM provided better protection against TMX reproduction toxicity than treatment with either agent alone.

The neonicotinoid thiamethoxam impairs male fertility in solitary bees, Osmia cornuta

The ongoing loss of global biodiversity is endangering ecosystem functioning and human food security. While environmental pollutants are well known to reduce fertility, the potential effects of common neonicotinoid insecticides on insect fertility remain poorly understood. Here, we show that field-realistic neonicotinoid exposure can drastically impact male insect fertility. In the laboratory, male and female solitary bees Osmia cornuta were exposed to four concentrations of the neonicotinoid thiamethoxam to measure survival, food consumption, and sperm traits. Despite males being exposed to higher dosages of thiamethoxam, females revealed an overall increased hazard rate for survival; suggesting sex-specific differences in toxicological sensitivity. All tested sublethal concentrations (i.e., 1.5, 4.5 and 10 ng g^-1) reduced sperm quantity by 57% and viability by 42% on average, with the lowest tested concentration leading to a reduction in total living sperm by 90%. As the tested sublethal concentrations match estimates of global neonicotinoid pollution, this reveals a plausible mechanism for population declines, thereby reflecting a realistic concern. An immediate reduction in environmental pollutants is required to decelerate the ongoing loss of biodiversity.

Exposure to Organophosphate and Neonicotinoid Insecticides and Its Association with Steroid Hormones among Male Reproductive-Age Farmworkers in Northern Thailand

Several studies indicated organophosphate (OP) and neonicotinoid (NEO) insecticides are endocrine disruptors; however, data are scarce. This cross-sectional study recruited 143 male farmworkers aged 18-40 years in Fang district, Chiang Mai province, northern Thailand. OP exposure was assessed by measuring urinary dialkylphosphate (DAPs) using a gas-chromatography flame photometric detector. Urinary NEOs, their metabolites (NEO/m) and serum steroid hormones were measured using liquid chromatography-tandem mass spectrometry. Characteristics of participants were determined by face-to-face interviews. DAPs and five NEO/m were detected in more than 60% of samples. The concentration of diethylphosphate was highest among DAP metabolites (geometric mean concentration (GM: 23.9 ng/mL) and the concentration of imidacloprid (IMI) was highest among NEO/m (GM: 17.4 ng/mL). Linear regression models showed that the IMI level was positively associated with testosterone, dehydrocorticosterone (DHC) and dehydroepiandrosterone (DHEA) levels. Imidacloprid-olefin and DHEA levels were positively associated. Thiamethoxam (THX) were inversely associated with DHC and deoxycorticosterone levels. Clothianidin (CLO), THX and N-desmethyl-acetamiprid levels were positively associated with the androstenedione level. CLO and THX levels were inversely associated with the cortisone level. In conclusion, the association between NEO insecticides exposure and adrenal androgens, glucocorticoids and mineralocorticoids, suggest potential steroidogenesis activities. Our findings warrant further investigation.

Association between pesticide usage during pregnancy and neonatal hyperbilirubinemia requiring treatment: the Japan Environment and Children's Study

BACKGROUND

Maternal exposure to pesticides during pregnancy may cause oxidative hemolysis leading to neonatal hyperbilirubinemia. This investigation examined for associations between maternal use of pesticides or repellents during pregnancy and neonatal hyperbilirubinemia requiring phototherapy.

METHODS

We used the dataset from the Japan Environment and Children's Study, a large national birth cohort study registered from January 31, 2011 to March 31, 2014. The fixed data of 61,751 live births were used to evaluate the presence of neonatal hyperbilirubinemia and potential confounding factors. We employed multiple logistic regression analysis to identify correlations between the frequency of maternal pesticide or repellent use during pregnancy and clinically relevant neonatal hyperbilirubinemia.

RESULTS

After controlling for confounding factors, there were significant associations between neonatal hyperbilirubinemia necessitating phototherapy and the frequent use of indoor insecticide spray (OR 1.21, 95% CI 1.05-1.38). For spray- or lotion-type insect repellents, an opposite relationship was observed (more than a few times a week: OR 0.70, 95% CI 0.61-0.81, up to a few times a month: OR 0.84, 95% CI 0.78-0.91).

CONCLUSION

The frequent use of indoor insecticide spray during pregnancy showed an increased risk of neonatal hyperbilirubinemia requiring phototherapy, which was absent for spray- or lotion-type insect repellents.

IMPACT

The frequent use of indoor insecticide spray during pregnancy showed an increased risk of neonatal hyperbilirubinemia requiring phototherapy, which was absent for spray- or lotion-type insect repellents. This is the first study examining the effects of maternal exposure to pesticides or repellents on clinically relevant neonatal hyperbilirubinemia using a dataset from a nationwide birth cohort study. This large-scale Japanese cohort study revealed that the frequent use of indoor insecticide spray during pregnancy may increase the risk of neonatal hyperbilirubinemia requiring treatment.

Lethal and sub-lethal effects of environmentally relevant levels of imidacloprid pesticide to Eastern School Prawn, Metapenaeus macleayi

Pesticides are frequently employed to enhance agricultural production. Neonicotinoid pesticides (including imidacloprid) are often used to control sucking insects but have been shown to impact aquatic crustaceans. Imidacloprid is highly water soluble and has been detected in estuaries where it has been applied in adjacent catchments. We examined the impact of environmentally relevant concentrations of imidacloprid on Eastern School Prawn (Metapenaeus macleayi), an important exploited crustacean in Australia. Prawns were held for 8 days in estuarine water containing 0-4 μg L^-1 of imidacloprid to assess potential lethal and non-lethal impacts. There was a non-linear relationship between exposure concentration and tissue concentration, with tissue concentrations peaking at exposures of 1.4 μg L^-1 (1.16 to 1.64 μg L^-1, 90% C.I.). There was no evidence for direct mortality associated with imidacloprid exposure, but exposure did influence the organism metabolome which likely reflects alterations in metabolic homeostasis, such as changes in the fatty acid composition which indicate a shift in lipid homeostasis. There was a positive correlation between exposure concentration and moulting frequency. Shedding of the exoskeleton may represent a mechanism through which prawns can expel the contaminant from their bodies. These results indicate that prawns experience several different sub-lethal effects when exposed to these pesticides, which may have implications for the health of populations.

Wildlife consumption of neonicotinoid-treated seeds at simulated seed spills

The most likely route of exposure to high concentrations of neonicotinoids capable of producing lethal or sublethal effects in birds and mammals is consumption of treated seeds. We placed trail cameras at simulated seed spills to document wildlife consuming treated seeds during the spring planting season. We simulated 4 types of spills, corn treated with 2 concentrations of clothiandin (0.50 or 0.25 mg/seed), corn treated with thiamethoxam (0.25 mg/seed), and soybean treated with imidacloprid (0.15 mg/seed). We documented 16 species of birds and 14 species of mammals eating neonicotinoid-treated seeds at spills. Of these, we quantified consumption of treated seeds by 12 species of birds and 13 species of mammals. Birds and mammals did not consume enough seeds to exceed published LD50s in related taxa, but most species did consume enough seeds to reach or exceed thresholds for sublethal effects based on currently available studies. Birds and mammals did not increase the amount of seeds consumed over time, as would be expected if responsive to the concentration of neonicotinoids on seeds, but more birds and mammals consumed seeds over time, as a proportion of the number at spills each day. More birds also consumed seeds after a soaking rain event, which likely reduced the amount of treatment on the seeds. Importantly, wildlife are consuming seeds while neonicotinoids are still concentrated on seeds. Our findings indicate that previously held assumptions about the safety of neonicotinoid seed treatments for vertebrate wildlife need to be revisited.

Exposure Level of Neonicotinoid Insecticides in the Food Chain and the Evaluation of Their Human Health Impact and Environmental Risk: An Overview

Neonicotinoid insecticides (neonics) were the most rapidly growing class of insecticides over the past few decades, and are used mainly for vegetables, fruits, and grains. Although neonics exhibit lower toxicity in mammals and humans compared to traditional insecticides, increasing numbers of studies are demonstrating that neonics may accumulate in the food chain and environmental media. Long-term exposure to neonics may raise potential risks to animals and even to humans. The present report reviews the development, application, and prohibition of neonics in the farmland ecosystem, and summarizes the exposure level and harmful effects of these insecticides in the food chain. In addition, the present review analyzes and summarizes the evaluation of the human health impact and environmental risk of the neonics, and overviews the unresolved problems and future research directions in this field. The aim of the present report was to review the exposure level, potential toxicity, human health impact, and environmental risk assessment of neonics in various media in order to provide reliable technical support for strengthening the environmental and food safety supervision and green pesticide designing.

Clothianidin induces DNA damage and oxidative stress in bronchial epithelial cells

Clothianidin (CHN) is a member of the neonicotinoid group of insecticides. Its oxidative and DNA damage potential for human lung cells are not known. Therefore, the present study was designed to examine the effects of CHN on DNA damage and oxidative stress in human bronchial epithelial cells (BEAS-2B) treated with CHN for 24, 72, and 120 hr. Our results indicate that CHN decreased cell viability in a concentration-dependent manner. CHN induced DNA single-strand breaks because alkaline comet parameters such as tail intensity, DNA in the tail, tail moment, and tail length increased. All CHN concentrations also significantly induced the formation of DNA double-strand breaks (DSBs) because it increased phosphorylated H2AX protein foci for all treatment times and p53-binding protein 1 foci for all treatments except for the lowest concentration (0.15 mM) of 120-hr treatment. DNA damage caused by DNA DSBs was not repaired in a 24-hr recovery period. CHN also induced oxidative stress by decreasing reduced glutathione and increasing lipid peroxidation. These results make it necessary to conduct studies about the detailed carcinogenic potential of CHN in humans because it can induce both oxidative and DNA damage.

A critical review on the potential impacts of neonicotinoid insecticide use: current knowledge of environmental fate, toxicity, and implications for human health

Neonicotinoid insecticides are widely used in both urban and agricultural settings around the world. Historically, neonicotinoid insecticides have been viewed as ideal replacements for more toxic compounds, like organophosphates, due in part to their perceived limited potential to affect the environment and human health. This critical review investigates the environmental fate and toxicity of neonicotinoids and their metabolites and the potential risks associated with exposure. Neonicotinoids are found to be ubiquitous in the environment, drinking water, and food, with low-level exposure commonly documented below acceptable daily intake standards. Available toxicological data from animal studies indicate possible genotoxicity, cytotoxicity, impaired immune function, and reduced growth and reproductive success at low concentrations, while limited data from ecological or cross-sectional epidemiological studies have identified acute and chronic health effects ranging from acute respiratory, cardiovascular, and neurological symptoms to oxidative genetic damage and birth defects. Due to the heavy use of neonicotinoids and potential for cumulative chronic exposure, these insecticides represent novel risks and necessitate further study to fully understand their risks to humans.

An environmentally realistic pesticide and copper mixture impacts embryonic development and DNA integrity of the Pacific oyster, Crassostrea gigas

Frequent occurrences of pesticides in the environment have raised concerns that combined exposure to these chemicals may result in enhanced toxicity through additive or synergistic interaction between compounds. Spermatozoa and embryos of the Pacific oyster, Crassostrea gigas, were exposed to different concentrations of a pesticide mixture with and without copper, mimicking the cocktail of pollutants occurring in the oyster culture area of Arcachon Bay. For the 1× exposure condition, measured concentration corresponds to a total concentration of 1.083 μg L^-1 for the mixture of 14 pesticides and to 6.330 μg L^-1 for copper (Cu). Several endpoints including larval abnormalities, DNA damage to spermatozoa and embryo and gene expression in D-larvae were investigated. Results demonstrated that pesticide mixtures in combination with or without copper induced a dose-dependent increase in embryotoxic and genotoxic effects on D-larvae from the lowest tested dose of 0.1×. Transcription of genes involved in anti-oxidative stress (cat), respiratory chain (coxI), metal detoxification (mt1 and mt2), and cell cycle arrest and apoptosis (p53) was found to be significantly downregulated while the xenobiotic biotransformation gene gst was significantly upregulated in embryos exposed to pesticide mixture with and without Cu. These findings raise the question of the possible impacts of mixtures of pesticides and metals on wild or farmed oyster populations from polluted coastal marine areas.

Sub-lethal effects of a neonicotinoid, clothianidin, on wild early life stage sockeye salmon (Oncorhynchus nerka)

One of the categories of environmental contaminants possibly contributing to declining sockeye salmon (Oncorhynchus nerka) in the Fraser River, British Columbia, Canada is pesticides. In this 4-month study, the effects of environmentally relevant concentrations of a waterborne neonicotinoid, clothianidin (0.15, 1.5, 15 and 150 μg/L), on embryonic, alevin and early swim-up fry sockeye salmon derived from four unique genetic crosses of the Pitt River, BC stock were investigated. There were no significant effects of clothianidin on survival, hatching, growth or deformities, although genetic variation significantly affected these endpoints. Clothianidin caused a significant 4.7-fold increase in whole body 17β-estradiol levels in swim-up fry after exposure to 0.15 μg/L, but no effects were observed on testosterone levels. In addition, hepatic expression of the gene encoding glucocorticoid receptor 2 was also impacted at the highest concentration of clothianidin tested, and was found to be ∼4-fold lower compared to the sockeye reared in control water. These results indicate additional examination of clothianidin and its effects on salmonid gonad development and the reproductive and stress endocrine axes in general, is warranted.

A sublethal dose of the neonicotinoid insecticide acetamiprid reduces sperm density in a songbird

Farmland bird species are particularly exposed to pesticides through various pathways. Among pesticides, neonicotinoids insecticides are commonly used in agriculture, but their influence on bird reproductive capacities is poorly understood. In this study, we experimentally tested the effects of the neonicotinoid acetamiprid on House sparrows' sperm quality and oxidative status following ingestion of a low and field-realistic dose of the compound. To do so, 56 males were captured, held and orally dosed seven times over 19 days of experiment with either a saline solution (control) or an acetamiprid-saline solution, and sperm samples were retrieved before and after the experiment. The overall dose given to the birds corresponded to 0.5% of the LD₅₀ for the Zebra finch (5.7 mg/kg BW) spread into 7 separate doses and administered every three days over the entire duration of the study (ca. 0.07% LD₅₀ per oral dose). Sperm mobility and sperm oxidative status were unaffected by the treatment, but sperm density was. Birds that received oral doses of acetamiprid suffered a significant decline in their sperm density compared to control birds. This result was confirmed by a significant decrease in the activity of the antioxidant enzyme SOD in the sperm of acetamiprid-dosed birds. These results provide the first evidence of sublethal toxicity of acetamiprid in a songbird and suggest that passerine birds' fertility may be negatively affected by very small doses of neonicotinoids in the wild.

Imidacloprid and formulated product impacts the fatty acids and enzymatic activities in tissues of Sydney rock oysters, Saccostrea glomerata

The use of imidacloprid (IMI) and its formulated products in agriculture is a risk to aquatic organisms due to deposition into waterways from runoff and aerial spraying. However, there is limited information on the potential effects of this pesticide on commercially important shellfish, such as oysters. We investigated the impacts of IMI and Spectrum 200SC (IMI formulation) on the activity of the enzymes Glutathione-S-transferase (GST), Catalase (CAT) and Acetylcholinesterase (AChE), in different oyster tissues including the gill, adductor muscle and digestive gland. We also investigated the condition index and fatty acid composition of the flesh of oysters after 2 weeks exposure. The concentrations of IMI in the different tissues was assessed using Liquid Chromatography-Mass Spectrometry (LC-MS) after QuEChERS extraction. Higher concentrations of IMI residues were detected in the adductor muscle of the oysters, followed by the gills and with the lowest amounts recovered from the digestive gland across all the concentrations tested. IMI and Spectrum 200SC significantly affected the gill AChE activity at 2 mg/L, but digestive gland CAT, and gill and digestive gland GST were impacted at environmentally relevant concentrations (0.01 and 0.05 mg/L). In the whole oyster, 2 weeks exposure to IMI (≥0.01 mg/L) resulted in a proportional increase in saturated fatty acids (SFA), altered the polyunsaturated fatty acid (PUFA) to SFA ratio and altered the omega 3 fatty acids (n-3) to omega 6 fatty acids (n-6) ratio, but there were no effects on the condition index of the oyster. Although the oysters responded differently to the formulated product, there was no consistent difference in the sublethal effects of analytical IMI and Spectrum 200SC. This study showed that exposure to IMI and Spectrum 200SC can significantly affect the biochemical processes and metabolites in oysters, with implications for food quality and safety.

Attenuating effects of Mangifera indica leaves ethanolic extract against acetamiprid induced reproductive toxicity in male guinea pigs

Acetamiprid (ACP) belonging to the neonicotinoid family used against wide array of pests in agriculture and domestic purposes. In this study, we evaluated the attenuating effects of ethanolic extract of Mangifera indica leaves (EEMI) in averting reproductive toxicity caused by ACP in male guinea pigs. Thirty male guinea pigs were randomly assigned to five treatment groups (n = 6). Group 1 (T0) received distilled water orally; group 2 (T0-) was given 80 mg kg-1 of ACP and groups 3, 4 and 5 were treated, respectively, with EEMI at doses of 50, 100 and 200 mg kg-1 plus ACP. After 90 days, the reaction time, sexual organ weights, sperm count, motility and anomalies, spermatozoa with entire plasma membrane, testicular histology, serum testosterone concentration, testicular malondialdehyde (MDA) level, reduced glutathione (GSH) concentration, testicular superoxide dismutase (SOD) and catalase (CAT) activities were assessed. Co-administration of EEMI significantly reduced the reaction time, sperm anomalies and testicular MDA, SOD and CAT levels compared to the T0- group. Co-treatment of EEMI significantly alleviated sperm count and motility, percentage of spermatozoa with the normal plasma membrane, serum testosterone concentration, accessory sex gland weights, and testicular GSH concentrations. The ACP treatment induced cell membrane degradation in the testis and this effect was prevented with the addition of EEMI. In conclusion, ACP negatively affected the animal reproductive function and induced oxidative stress. The addition of EEMI alleviated the toxic effects of ACP on the reproductive function of male guinea pigs.

Non-target toxicity of novel insecticides

Humans have used insecticides since ancient times. The spectrum and potency of available insecticidal substances has greatly expanded since the industrial revolution, resulting in widespread use and unforeseen levels of synthetic chemicals in the environment. Concerns about the toxic effects of these new chemicals on non-target species became public soon after their appearance, which eventually led to the restrictions of use. At the same time, new, more environmentally-friendly insecticides have been developed, based on naturally occurring chemicals, such as pyrethroids (derivatives of pyrethrin), neonicotinoids (derivatives of nicotine), and insecticides based on the neem tree vegetable oil (Azadirachta indica), predominantly azadirachtin. Although these new substances are more selective toward pest insects, they can still target other organisms. Neonicotinoids, for example, have been implicated in the decline of the bee population worldwide. This review summarises recent literature published on non-target toxicity of neonicotinoids, pyrethroids, and neem-based insecticidal substances, with a special emphasis on neonicotinoid toxicity in honeybees. We also touch upon the effects of pesticide combinations and documented human exposure to these substances.

Effect of acetamiprid on the immature murine testes

Neonicotinoids, such as acetamiprid (ACE), a pesticide used worldwide, are believed to be safe for human use. These molecules are structurally similar to nicotine, act as nicotinic acetylcholine receptor (nAChR) agonists, and were shown to be associated with neuromuscular and reproductive disorders, but these experiments were primarily performed in mature animals. In this study, the effects of ACE on the testes of immature mice were examined. The exposure of 3-week-old mice to ACE-containing water for 180 days led to a decrease in body weight and mildly affected spermatogenesis. Additionally, the expression of testosterone-metabolism genes, nAChR subunit genes, and proliferation-associated genes decreased in the testes of ACE-treated mice. Our results show that immature rodents may be less sensitive to ACE than mature ones, that mice may be more likely to accumulate ACE than rats, and that the development of disorders may be affected by the accumulation of ACE in the testes.

Cytotoxicity and genotoxicity of clothianidin in human lymphocytes with or without metabolic activation system

Clothianidin (CHN) is a broad-spectrum neonicotinoid insecticide. Limited studies have been carried out on the cytotoxic and genotoxic effects of both CHN using different genotoxicity tests in human cells with or without human metabolic activation system (S9 mix). Therefore, the aim of this study is to investigate the cytotoxic and genotoxic effects of CHN and its metabolites on human lymphocyte cultures with or without S9 mix using chromosomal aberration (CA) and micronucleus (MN) tests. The cultures were treated with 25, 50, and 100 µg/ml of CHN in the presence (3 h treatment) and absence (48 h treatment) of S9 mix. Dimethyl sulfoxide (DMSO) was used as a solvent control. CHN showed cytotoxic and genotoxic effects due to significant decreases in mitotic index (MI) and nuclear division index (NDI), and significant increases in the CAs, aberrant cells, and MN formation in the absence of S9 mix when compared with solvent control. However, CHN did not significantly induce cytotoxicity and genotoxicity in the presence of S9 mix. Our results indicated that CHN has cytotoxic, cytostatic, and genotoxic potential on human peripheral blood lymphocyte cultures, but not its metabolites under the experimental conditions.

Human exposure to neonicotinoid insecticides and the evaluation of their potential toxicity: An overview

Neonicotinoid insecticides have become the fastest growing class of insecticides over the past few decades. The insecticidal activity of neonicotinoids is attributed to their agonist action on nicotinic acetylcholine receptors (nAChRs). Because of the special selective action on nAChRs in central nervous system of insects, and versatility in application methods, neonicotinoids are used to protect crops and pets from insect attacks globally. Although neonicotinoids are considered low toxicity to mammals and humans in comparison with traditional insecticides, more and more studies show exposure to neonicotinoids pose potential risk to mammals and even humans. In recent years, neonicotinoids and their metabolites have been successfully detected in various human biological samples. Meanwhile, many studies have focused on the health effects of neonicotinoids on humans. Our aims here are to review studies on human neonicotinoid exposure levels, health effect, evaluation of potential toxicity and to suggest possible directions for future research.

Exposure to neonicotinoid insecticides induces embryotoxicity in mice and rabbits

The potential toxicity of neonicotinoids (thiacloprid, acetamiprid, thiamethoxam and clothianidin) as well as related commercial products Calypso 480SC (thiacloprid mixture), Mospilan 20SP (acetamiprid mixture) and Agita 10WG (thiamethoxam mixture) on developmental capacities and quality of preimplantation embryos was evaluated. During in vitro tests, isolated 2-cell stage mice embryos were cultured in media with various concentrations of active compounds or commercial products until blastocyst formation. As found using stereomicroscopic examination, all neonicotinoids at highest (100μM) concentration negatively affected embryonic development (P<0.001). Fluorescence staining revealed that the blastocysts obtained displayed lower numbers of blastomeres and elevated incidence of cell death. Thiacloprid and acetamiprid decreased quality of blastocysts also at 10μM concentration. From the tested products only Calypso 480SC containing 10μM of thiacloprid showed harmful impact on embryo quality. In an experiment using rabbit embryos, similar negative effect of thiacloprid in vitro was recorded. In vivo testing confirmed that blastocysts collected from thiacloprid-treated mice displayed lower total cell counts than blastocysts from controls. The sensitivity of embryonic cells to neonicotinoids is in the order of thiacloprid>acetamiprid, thiomethoxam>clothianidin. Thiacloprid impairs development and quality of both mouse and rabbit preimplantation embryos, and shows embryotoxicity even at acute reference dose.

Neonatal, placental, and umbilical cord blood parameters in pregnant women residing in areas with intensive pesticide application

In rural populations, the proximity to areas with intensive pesticide application represents a risk factor of xenobiotic exposure. Here, we investigated whether newborns born to mothers residing in an area with intensive pesticide application show alterations in placental and neonatal morphometric standards, umbilical cord blood (UCB) biochemical parameters, and/or biomarkers related to oxidative stress and oxidative damage. Samples were collected from 151 healthy pregnant women residing in a rural area (rural group; RG) during the pesticide spraying (SS) and nonspraying (NSS) seasons, as well as from women from an urban population (control group; CG), and grouped according to the delivery type (vaginal or cesarean). In the vaginal delivery group, the placental weight and placental index were higher in the RG groups than in the CG (p = 0.01), whereas in the cesarean delivery group, newborn weight was lower in the RG-SS group than in the CG. In the RG-SS group, UCB erythrocyte osmotic fragility and the DNA damage index (DI) were higher, and superoxide dismutase (SOD) activity was lower than in the RG-NSS group. Acetylcholinesterase and SOD activities were found to be inversely correlated with the DI.

Prenatal and early postnatal NOAEL-dose clothianidin exposure leads to a reduction of germ cells in juvenile male mice

Neonicotinoids are pesticides used worldwide. They bind to insect nicotinic acetylcholine receptors (nAChRs) with high affinity. We previously reported that clothianidin (CTD), one of the latest neonicotinoids, reduced antioxidant expression and induced germ cell death in the adult testis of vertebrates. Here, we investigated the male reproductive toxicity of prenatal and early postnatal exposure to CTD, because it is likely that developmental exposure more severely affects the testis compared to adults due to the absence of the blood-testis barrier. Pregnant C57BL/6 mice were given water gel blended with CTD (0, 10 or 50 mg/kg/day; no-observed-adverse-effect-level [NOAEL for mice]: 47.2 mg/kg/day) between gestational day 1 and 14 days post-partum. We then examined the testes of male offspring at postnatal day 14. The testis weights and the numbers of germ cells per seminiferous tubule were decreased in the CTD-50 group, and abnormal tubules containing no germ cells appeared. Nevertheless, the apoptotic cell number and proliferative activity were not significantly different between the control and CTD-exposed groups. There were no significant differences in the androgen-related parameters, such as the Leydig cell volume per testis, the Sertoli cell number and the tubule diameter. The present study is the first demonstration that in utero and lactational exposures to CTD at around the NOAEL for mice reduce the germ cell number, but our findings suggest that these exposures do not affect steroidogenesis in Leydig cells during prenatal or early postnatal life.

Allethrin toxicity causes reproductive dysfunction in male rats

Pyrethroids are widely used for domestic and agricultural purposes and their use is increasing, especially in developing countries. Uncontrolled use of these insecticides resulted in their entry into the food chain thereby causing toxicity to different organ systems. Allethrin is one of the widely used pyrethroids, but its toxicological effects are underreported when compared to other pyrethroids. Further, its effects on the male reproductive tract remain uncharacterized. In this study, its toxicity on the male reproductive tract was evaluated by administering 25-150 mg/kg body weight allethrin to adult rats for 60 days. The mRNA expression of factors that are important in spermatogenesis (Scf, c-Kit, Hsf2, Ovol1, Brdt, Kdm3A, Ybx-2, and Grth) and steroidogenesis (StAR, 3β-HSD, 17β-HSD) was significantly downregulated. Decreased levels of testosterone, reduced sperm count and daily sperm production was also observed due to allethrin toxicity. However, sperm quality parameters assessed by computer-assisted sperm analyzer were not affected. Spermatozoa obtained from allethrin-treated rats failed to undergo acrosome reaction. Results of this study indicate that allethrin affects spermatogenesis and sperm function, thus lending further support to the growing evidence of its toxicity.

The combined effect of clothianidin and environmental stress on the behavioral and reproductive function in male mice

Neonicotinoids, some of the most widely used pesticides in the world, act as agonists to the nicotinic acetylcholine receptors (nAChRs) of insects, resulting in death from abnormal excitability. Neonicotinoids unexpectedly became a major topic as a compelling cause of honeybee colony collapse disorder, which is damaging crop production that requires pollination worldwide. Mammal nAChRs appear to have a certain affinity for neonicotinoids with lower levels than those of insects; there is thus rising concern about unpredictable adverse effects of neonicotinoids on vertebrates. We hypothesized that the effects of neonicotinoids would be enhanced under a chronic stressed condition, which is known to alter the expression of targets of neonicotinoids, i.e., neuronal nAChRs. We performed immunohistochemical and behavioral analyses in male mice actively administered a neonicotinoid, clothianidin (CTD; 0, 10, 50 and 250 mg/kg/day), for 4 weeks under an unpredictable chronic stress procedure. Vacuolated seminiferous epithelia and a decrease in the immunoreactivity of the antioxidant enzyme glutathione peroxidase 4 were observed in the testes of the CTD+stress mice. In an open field test, although the locomotor activities were not affected, the anxiety-like behaviors of the mice were elevated by both CTD and stress. The present study demonstrates that the behavioral and reproductive effects of CTD become more serious in combination with environmental stress, which may reflect our actual situation of multiple exposure.

A review of the direct and indirect effects of neonicotinoids and fipronil on vertebrate wildlife

Concerns over the role of pesticides affecting vertebrate wildlife populations have recently focussed on systemic products which exert broad-spectrum toxicity. Given that the neonicotinoids have become the fastest-growing class of insecticides globally, we review here 150 studies of their direct (toxic) and indirect (e.g. food chain) effects on vertebrate wildlife--mammals, birds, fish, amphibians and reptiles. We focus on two neonicotinoids, imidacloprid and clothianidin, and a third insecticide, fipronil, which also acts in the same systemic manner. Imidacloprid and fipronil were found to be toxic to many birds and most fish, respectively. All three insecticides exert sub-lethal effects, ranging from genotoxic and cytotoxic effects, and impaired immune function, to reduced growth and reproductive success, often at concentrations well below those associated with mortality. Use of imidacloprid and clothianidin as seed treatments on some crops poses risks to small birds, and ingestion of even a few treated seeds could cause mortality or reproductive impairment to sensitive bird species. In contrast, environmental concentrations of imidacloprid and clothianidin appear to be at levels below those which will cause mortality to freshwater vertebrates, although sub-lethal effects may occur. Some recorded environmental concentrations of fipronil, however, may be sufficiently high to harm fish. Indirect effects are rarely considered in risk assessment processes and there is a paucity of data, despite the potential to exert population-level effects. Our research revealed two field case studies of indirect effects. In one, reductions in invertebrate prey from both imidacloprid and fipronil uses led to impaired growth in a fish species, and in another, reductions in populations in two lizard species were linked to effects of fipronil on termite prey. Evidence presented here suggests that the systemic insecticides, neonicotinoids and fipronil, are capable of exerting direct and indirect effects on terrestrial and aquatic vertebrate wildlife, thus warranting further review of their environmental safety.

Allethrin induced toxicity in the male reproductive tract of rats contributes to disruption in the transcription of genes involved in germ cell production

Pyrethroids are known to be neurotoxic. However, their toxic effects including that of allethrin on the male reproductive tract are not elucidated. Adult male rats were treated orally with 25, 50, 100, and 150 mg/kg body weight allethrin every day for 60 days. Lipid peroxidation was increased (p < 0.001) in the caput, cauda, and testes. Nitric oxide production was increased (p < 0.001) in the caput, but unaltered in the cauda and testes. The activities of catalase, glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase were decreased in the caput and cauda where as a decrease was observed in the testis obtained from allethrin treated rats. In the epididymides and testes, damage to tubular architecture, congestion, degeneration of epithelial cell lining, intestinal edema, and presence of dead or degenerating spermatids were observed in a dose dependent manner. The expression profile of genes involved in spermatogenesis (Tgf-beta1), sperm maturation (Spag11e), and sperm function (Defb22) were reduced (p < 0.001) in allethrin rats. The expression of p53 gene was decreased and increased phosphorylation of MAPK (p42/p44) expression was observed the male reproductive tract tissues of allethrin treated rats. Although earlier studies have reported the effects of allethrin inhalation because of the use of mosquito coils and vaporizers, our results for the first time prove that oral exposure to allethrin could affect fertility and may contribute to deregulation of cell cycle in the male reproductive tract.

Reproductive effects of two neonicotinoid insecticides on mouse sperm function and early embryonic development in vitro

Acetamiprid (ACE) and imidacloprid (IMI) are two major members in the family of neonicotinoid pesticides, which are synthesized with a higher selectivity to insects. The present study determined and compared in vitro effects of ACE, IMI and nicotine on mammalian reproduction by using an integrated testing strategy for reproductive toxicology, which covered sperm quality, sperm penetration into oocytes and preimplantation embryonic development. Direct chemical exposure (500 µM or 5 mM) on spermatozoa during capacitation was performed, and in vitro fertilization (IVF) process, zygotes and 2-cell embryos were respectively incubated with chemical-supplemented medium until blastocyst formation to evaluate the reproductive toxicity of these chemicals and monitor the stages mainly affected. Generally, treatment of 500 µM or 5 mM chemicals for 30 min did not change sperm motility and DNA integrity significantly but the fertilization ability in in vitro fertilization (IVF) process, indicating that IVF process could detect and distinguish subtle effect of spermatozoa exposed to different chemicals. Culture experiment in the presence of chemicals in medium showed that fertilization process and zygotes are adversely affected by direct exposure of chemicals (P<0.05), in an order of nicotine>IMI>ACE, whereas developmental progression of 2-cell stage embryos was similar to controls (P>0.05). These findings unveiled the hazardous effects of neonicotinoid pesticides exposure on mammalian sperm fertilization ability as well as embryonic development, raising the concerns that neonicotinoid pesticides may pose reproductive risks on human reproductive health, especially in professional populations.