Most of currently used active ingredients in Plant Protection Products (PPP) are organic xenobiotics. Despite in numerical terms, natural inorganic compounds represent a small minority, their usage is extremely widespread. According to FAO data, inorganics represent about half of the amount of fungicides applied in Europe in the last decade. Due to the high number of xenobiotics registered as new substances (or re-registered after the previous authorization has expired) each year, most of the EU official procedures to assess the ecological risk posed by PPP are calibrated on these chemicals. However, the regulation is common for all substances used as pesticides, disregarding their chemical nature. This work tries to assess to which extent ERA PPP EU official procedures are suitable to describe the environmental fate and related effects on non-target organisms of natural inorganic substances using copper compounds as case study. Copper is an heavy metal naturally present in most environmental compartments. It is involved in biological processes and plays an important role as micronutrient for several organisms. Beside agriculture, where its use dates back to several decades ago, copper enters many anthropogenic activities determining several kind of emissions into the environment. Predictive models usually recommended at EU level were used to estimate environmental concentrations of copper following its use as fungicide according to good agricultural practice. Estimations for soil, surface waters and groundwater were compared to monitoring data retrieved from the literature. The results will be discussed in the light of the mechanistic parameters guiding the exposure models. Also, the effects on several organisms measured in different tests was critically considered to assess the relevance of some environmental parameters in determining both the bioavailability and the overall toxicity of copper compounds, bearing in mind that copper body concentration, as for all the micronutrients involved in biological processes, is regulated by homeostatic mechanisms. The use of models such as toxicokineticstoxicodynamic models (TK/TD) or Biotic Ligand Models (BLM) can help in the evaluation of copper toxicity and bioavailability. Finally, some practical suggestions will be proposed to perform a proper ecological risk assessment of copper compounds within the framework of the EU PPP registration procedure.
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