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Highlights PBK models have helped to facilitate quantitative in vitro to in vivo extrapolation. PBK modelling has the potential to play a significant role in reducing animal testing. It is critical to assess the validity of PBK models built using non-animal data. A framework is needed for communicating characteristics and results of PBK modelling.

Background: Sewage sludge, the inevitable byproduct of municipal wastewater-treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. According to the report of European Commission published in 2010, 39% of sewage sludge produced in the European Union is recycled into agriculture. Management options require extensive waste characterization, since many of them may contain compounds, which could be harmful to the ecosystem, such as heavy metals, organic pollutants, etc. The present study aims to show the results of 2 years' sampling of sewage sludge-based on 130 samples collected from 35 wastewater-treatment plants situated in the North of Italy-and to assess its suitability as soil fertilizer regarding contents of nonylphenol (NP), nonylphenolethoxylates (NPnEOs), and phthalates (DEHP). Results: An effective analytic method for organic pollutants detection in the sewage sludge has been developed, showing an excellent repeatability and recoveries. Ecotoxicological risk assessment was evaluated using risk quotients (RQs) for sludge-amended soil. Most of the analyzed samples do not contain NP, NPnEOs, and DEHP at levels higher than the limit established by the draft-working document of the European Commission on Sludge. The assessment using RQs reports that NP and NPnEOs never give values higher than 1, and for DEHP the obtained RQs exceed the value of 1 just three times. Data obtained were compared to the data from other European and Asiatic countries, showing a huge variability for all the compounds considered. Conclusions: Based on the obtained results, it appears that the proposed EU limits for the selected substances on sewage sludge intended to be used as soil fertilizer in agriculture are sufficiently conservative to avoid negative effects on soil fauna.

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Pesticides are key stressors of soil microorganisms with reciprocal effects on ecosystem functioning. These effects have been mainly attributed to the parent compounds, while the impact of their transformation products (TPs) has been largely overlooked. We assessed, in a meadow soil (A),the transformation of iprodione and its toxicity on the (i) abundance of functional microbial groups, (ii) activity of key microbial enzymes and (iii) diversity of bacteria, fungi and ammonia-oxidizing microorganisms (AOM) using amplicon sequencing. 3,5-Dichloroaniline (3,5-DCA), the main iprodione TP, was identified as key explanatory factor for the persistent reduction in enzymatic activities and potential nitrification (PN), and for the observed structural changes in the bacterial and fungal community. The abundance of certain bacterial (, , and ) and fungal () groups were negatively correlated with 3,5-DCA. A subsequent study in a fallow agricultural soil (B) showed a limited formation of 3,5-DCA which concurred with the lack of effects on nitrification. Direct 3,5-DCA application in soil B induced a dose-dependent reduction of PN and NO-N, which recovered with time. assays with terrestrial AOM verified the greater toxicity of 3,5-DCA over iprodione. Nitrosotalea sinensis Nd2 was the most sensitive AOM to both compounds. Our findings build on previous evidence on the sensitivity of AOM to pesticides reinforcing their potential utilization as indicators of the soil microbial toxicity of pesticides in pesticide environmental risk analysis and stressing the need to consider the contribution of TPs in the toxicity of pesticides on the soil microbial community. Pesticide toxicity on soil microorganisms is an emerging issue in pesticide risk assessment, dictated by the pivotal role of soil microorganisms on ecosystem services. However, the focus has traditionally been on parent compounds, while transformation products (TPs) are largely overlooked. We tested the hypothesis that TPs can be major contributors on the soil microbial toxicity of pesticides, using, iprodione, and its main TP, 3,5-dichloroaniline, as model compounds. We demonstrated, by measuring functional and structural endpoints, that 3,5-dichloraniline and not iprodione was associated with adverse effects on soil microorganisms, with nitrification being mostly affected. Pioneering assays with relevant ammonia-oxidizing bacteria and archaea verified the greater toxicity of 3,5-dichloraniline. Our findings are expected to advance environmental risk assessment highlighting the potential of ammonia-oxidizing microorganisms as indicators of the soil microbial toxicity of pesticides and stressing the need to consider the contribution of TPs on pesticides soil microbial toxicity.

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