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Insect pollinators are routinely exposed to a complex mixture of many pesticides. However, traditional environmental risk assessment is only carried out based on ecotoxicological data of single substances. In this context, we aimed to explore the potential effects when worker honey bees (Apis mellifera L.) were simultaneously challenged by thiamethoxam (TMX) and flusilazole (FSZ). Results displayed that TMX possessed higher toxicity to A. mellifera (96-h LC 50 value of 0.11 mg a. i. L−1) than FSZ (96-h LC 50 value of 738 mg a. i. L−1). Furthermore, the mixture of TMX and FSZ exhibited an acute synergistic impact on the pollinators. Meanwhile, the activities of SOD, caspase 3, caspase 9, and PPO, as well as the expressions of six genes (abaecin , dorsal-2 , defensin-2 , vtg , caspase-1 , and CYP6AS14) associated with oxidative stress, immune response, lifespan, cell apoptosis, and detoxification metabolism were noteworthily varied in the individual and mixture challenges than at the baseline level. These data revealed that it is imminently essential to investigate the combined toxicity of pesticides since the toxicity evaluation from individual compounds toward honey bees may underestimate the toxicity in realistic conditions. Overall, the present results could help understand the potential contribution of pesticide mixtures to the decline of bee populations. [Display omitted] • Thiamethoxam showed a higher acute toxic effect on the honey bees than fluconazole. • Thiamethoxam in combination with fluconazole produced synergistic toxicity. • CYP450s had important roles in the synergism of fluconazole and thiamethoxam. • mRNA levels of 6 genes in mixtures elicited greater alterations than individuals. • Joint effects should be incorporated into ecological risk assessment of pesticide. [ABSTRACT FROM AUTHOR]

Pesticides commonly occur as mixtures in an aqueous environment, causing deleterious effects on human health and the environment. However, the mechanism underlying the combined effects on aqueous organisms remains largely unknown, especially at low concentrations. In the current study, we inspected the interactive toxicity of tebuconazole (TEB), a triazole fungicide, and bifenthrin (BIF), a pyrethroid insecticide, to zebrafish (Danio rerio) using various toxicological assays. Our data revealed that the 96 h-LC 50 (lethal concentration 50) values of BIF to fish at different life periods (embryonic, larval, juvenile, and adult periods) ranged from 0.013 (0.011–0.016) to 0.41 (0.35–0.48) mg a.i. L−1, which were lower than that of TEB ranging from 1.1 (0.88–1.3) to 4.8 (4.1–5.7) mg a.i. L−1. Combination of TEB and BIF induced synergetic acute toxicity to embryonic fish. Activities of T-SOD, POD, and GST were distinctly altered in most individual and joint administrations. Expressions of 16 genes associated with oxidative stress, cellular apoptosis, immune system, and endocrine system at the mRNA level were evaluated, and the information revealed that embryonic zebrafish were impacted by both individual compounds and their combinations. Six genes (cas9 , P53 , gr , TRα, IL-8, and cxcl-clc) exhibited greater changes when exposed to pesticide mixtures. Therefore, the joint effects induced by the pesticides at low concentrations should be considered in the risk assessment of mixtures and regulated as priorities for mixture risk management in the aqueous ecosystem. More research is needed to identify the threshold concentrations of the realistic pesticide mixtures above which synergistic interactions occur. [Display omitted] • Bifenthrin exhibited higher acute toxic effects than tebuconazole on the zebrafish. • Co-exposure of tebuconazole and bifenthrin elicited synergistic acute responses. • Synergistic oxidative stress, apoptosis and endocrine disrupting effects were observed. • Immune gene expressions (IL-8 and cxcl-clc) were significantly altered in mixtures. • Identification of single pesticides involved in synergism can benefit risk precautions. [ABSTRACT FROM AUTHOR]

The natural co-occurrence of multiple mycotoxins has been reported in cereals and cereal products worldwide. Even though the dietary exposure to mycotoxins constitutes a serious human health, most reports are limited to the toxic effect of individual mycotoxins. The purpose of the present study was to assess the combined toxic effects of zearalenone (ZEN) and fumonisin B1 (FB1) and the potential interaction of their mixture on zebrafish (Danio rerio) embryos. Our results showed that ZEN possessed the higher toxicity to embryonic zebrafish (7-day LC 50 value of 0.78 mg a.i. L−1) compared with FB1 (7-day LC 50 value of 227.7 mg a.i. L−1). The combination of ZEN and FB1 exerted an additive effect on zebrafish embryos. Meanwhile, the activities of antioxidant CAT, caspase-3, and detoxification enzyme CYP450, as well as the expressions of six genes (Mn-sod , cas9 , bax , cc-chem , ERα , and crh) associated with oxidative stress, cellular apoptosis, immune system, and endocrine system were prominently altered in the mixture exposure compared with the corresponding single treatment group of ZEN or FB1. Taken together, the regulatory standards of mycotoxins in food and feed should be updated based on the mixture effects of mycotoxins, and there is an increased need on effective detoxification methods for controlling and reducing the toxicity of multiple mycotoxins in animal feed and throughout the food supply chain. [Display omitted] • The natural co-occurrence of multiple mycotoxins is common in worldwide cereals. • Co-exposure of zearalenone and fumonisin B1 exhibited additive acute response. • Combined effects related to biochemical index changes were observed in the mixture. • Gene expression altered for oxidative stress, apoptosis, immune and endocrine system. • Regulatory standards of mycotoxins should take the mixture effects into account. [ABSTRACT FROM AUTHOR]

Pesticides scarcely exist as individual compounds in the water ecosystem, but rather as mixtures of multiple chemicals at relatively low concentrations. In this study, we aimed to explore the mixture toxic effects of fludioxonil (FLU) and triadimefon (TRI) on zebrafish (Danio rerio) by employing different toxicological endpoints. Results revealed that the 96-h LC 50 values of FLU to D. rerio at multiple developmental stages ranged from 0.055 (0.039–0.086) to 0.61 (0.33–0.83) mg L−1, which were less than those of TRI ranging from 3.08 (1.84–5.96) to 9.75 (5.99–14.78) mg L−1. Mixtures of FLU and TRI exerted synergistic effects on embryonic zebrafish. Activities of total superoxide dismutase (T-SOD) and catalase (CAT) were markedly altered in most of the individual and pesticide mixture treatments compared with the control. The expressions of 16 genes involved in oxidative stress, cellular apoptosis, immune system and endocrine system displayed that embryonic zebrafish were affected by the individual pesticides and their mixtures, and greater variations of four genes (ERɑ , Tnf , IL and bax) were found when exposed to pesticide mixtures compared with their individual compounds. Therefore, more studies on mixture toxicities among different pesticides should be taken as a priority when evaluating their ecological risk. Image 1 • Fludioxonil elicited higher toxicity than triadimefon to zebrafish. • Mixtures of fludioxonil and triadimefon displayed synergistic response on zebrafish. • Expressions of 4 genes exerted greater changes in mixtures compared with individuals. • Mixture toxic effects should be incorporated into the risk assessment of pesticides. Mixture toxicity and potential mechanism of fludioxonil and triadimefon to the zebrafish. [ABSTRACT FROM AUTHOR]

Pesticides often occur as mixtures of complex compounds in water environments, while most of studies only focus on the toxic effects of individual pesticides with little attention to the joint toxic effects. In the present study, we aimed to the mixture toxicity of beta -cypermethrin (BCY) and thiacloprid (THI) to zebrafish (Danio rerio) employing multiple toxicological endpoints. Results displayed that the 96-h LC 50 values of BCY to D. rerio at various developmental stages ranged from 2.64 × 10 (1.97 × 10–3.37 × 10) to 6.03 × 103 (4.54 × 103–1.05 × 104) nM, which were lower than those of THI ranging from 2.97 × 104 (1.96 × 104–4.25 × 104) to 2.86 × 105 (2.19 × 105–5.87 × 105) nM. Mixtures of BCY and THI exhibited synergistic response in embryonic zebrafish. Meanwhile, the enzyme activities of antioxidants (CAT and SOD) and detoxification enzyme (CarE), endogenous T-GSH and MDA contents, as well as gene expressions (tsh , crh , cxcl and bax) involved in oxidative stress, cellular apoptosis, immune system and endocrine system were obviously changed in the mixture exposure compared with the respective BCY or THI treatment. Consequently, the increased toxicity of pesticide mixture suggested that the toxicological data acquired from individual pesticide tests might underrate the toxicity risk of pesticides that actually arise in the real environment. Taken together, our present study provided evidence that mixture exposure of BCY and THI could induce additional toxic effect compared with their respective individual pesticides on D. rerio , offering valuable insights into the toxic mechanism of pesticide mixture. Image 1 • Beta -cypermethrin exerted greater toxicity than thicloprid to zebrafish. • Mixtures of beta -cypermethrin and thicloprid had synergistic effect on zebrafish. • Expressions of 4 genes exerted greater changes in pesticide mixtures. • Mixture effects should be considered in the ecological risks of pesticide. Synergistic effects and underlying mechanism of beta -cypermethrin and thiacloprid on zebrafish. [ABSTRACT FROM AUTHOR]