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Pesticides risk assessments have traditionally focused on the effects on standard parameters, such as mortality, reproduction and development. However, one of the first signs of adverse effects that occur in organisms exposed to stress conditions is an alteration in their genomic expression, which is specific to the type of stress, sensitive to very low contaminant concentrations and responsive in a few hours. The aim of the present study was to evaluate the single and binary mixture toxicity of commercial products of abamectin (Kraft ® 36 EC) and difenoconazole (Score ® 250 EC) to Folsomia candida. Laboratory toxicity tests were conducted to access the effects of these pesticides on springtail survival, reproduction and gene expression. The reproduction assays gave EC 50 and EC 10 values, respectively, of 6.3 and 1.4 mg a.s./ kg dry soil for abamectin; 1.0 and 0.12 mg a.s./kg dry soil for Kraft ® 36 EC; and 54 and 23 mg a.s./kg dry soil for Score ® 250 EC. Technical difenoconazole did not have any effect at the concentrations tested. No significant differences in gene expression were found between the abamectin concentrations tested (EC 10 and EC 50) and the solvent control. Exposure to Kraft ® 36 EC, however, significantly induced Cyp6 expression at the EC 50 level, while VgR was significantly downregulated at both the EC 10 and EC 50. Exposure to the simple pesticide mixture of Kraft ® 36 EC þ Score ® 250 EC caused significant up regulation of ABC transporter, and significant down regulation of VgR relative to the controls. GABA receptor also showed significant down-regulation between the EC 10 and EC 50 mixture treatments. Results of the present study demonstrate that pesticide-induced gene expression effects precede and occur at lower concentrations than organism-level responses. Integrating "omic" endpoints in traditional bioassays may thus be a promising way forward in pesticide toxicity evaluations.

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Impact of temperature on the toxicity of Kraft 36 EC® (a.s. abamectin) and Score 250 EC® (a.s. difenoconazole) to soil organisms under realistic environmental exposure scenarios

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Heavy metals may appear in the environment as a result of different anthropogenic activities, such as agriculture practices, industry and mining. They can reach aquatic environments as complex mixtures, and single chemical toxicity as a baseline for risk assessment can underestimate the impairment of ecosystems. The aim of the present study was to evaluate combined toxicity of binary mixtures of zinc and nickel to the tropical mysid Mysidopsis juniae. Acute toxicity was assessed and mixture toxicity was modelled using the conceptual models for concentration addition and independent action to predict whether both metals act additively or whether they interact with each other inside the organism. For that, the observed mortality data were compared with the modelled data. For the single toxicity assessment, results showed that nickel induced higher toxicity than did zinc, with lethal concentrations to 50% of the organisms of 180±30μgL–1 and 260±40μg zinc L–1 respectively. In binary mixtures, both metals acted additively and no interactions were predicted by using the conceptual models. The present study has highlighted the need to fill the gaps in toxicity studies using marine species and approaches that can help improve the assessment of accurate risk in the environment.

2 Neste texto, adota-se a expressão "humano-animal", na qual a palavra "animal" é empregada com significado de "demais animais", sem excluir os humanos do reino animal. 3 Família que se autodenomina como constituída por pessoas e animais.