Fate and impact of pesticides: new directions to explore
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The consequences of the environmental contamination by pesticides on human and ecosystem health are of major concern. A strong research effort is needed to better understand the deleterious effects of pesticides, to reduce uncertainties concerning these potential effects, and to inform public policies and citizens. This effort has to focus on different scientific fields of research such as toxicology, ecotoxicology, epidemiology, and human and social sciences. The finality is to propose solutions to reduce the risks related to the dispersion of pesticides in the environment and to decrease their harmful impacts on biodiversity, ecosystem functions, and human health.
Improving the human and ecosystem exposure measurements remains a challenge for pesticide risk assessment strategies. Standardized and integrated protocols are needed for in situ monitoring of pesticides in various ecosystems. This can allow for more realistic ecotoxicological studies as well as epidemiological surveys on the impacts of pesticides on the environment and human health. Integrating new results at different levels of organization including human activities is critical to address the difficult question of long-term effects of pesticides at low concentrations and for compound mixtures. It is therefore necessary to rely on new tools and methods, e.g., sensors, biomarkers, bio-omics, analytical platforms, dedicated to ecotoxicological approaches, predictive toxicology, and epidemiological studies.
Designing cropping systems to reduce pesticide use and/or impacts at different spatial scales and levels of organization has become a clear research orientation in Europe. In France, the Ecophyto plan called for a decrease in pesticide use. Although this objective is far to be reached, this recent policy has launched many research programs in the last 10 years. Significant progresses have been made regarding the conception and assessment of low input cropping system performances. Alternative agricultural practices such as conservation tillage, selected crop varieties, biological regulations of bioagressors at the plot, farm, and landscape scales may significantly contribute to decrease the pesticide pressure.
Improving our knowledge of pesticide transfers outside from the treated plots remains necessary before promoting measures to reduce pesticide dispersion at the watershed scale. Local processes regulating the interactions between the soil, air, vegetation, and water have to be thoroughly understood. Field observations, experimental studies, and modeling approaches addressing the dispersion of pesticides should consider both the plot and catchment scales in a variety of landscapes—from rural to peri-urban areas—and under a variety of pedoclimatic conditions. Ecological infrastructures such as buffer zones can be used in these different landscapes to reduce the dispersion. However, a quantitative assessment of their efficiency and the integration of their functioning in the pesticide transfer models are required.
Modeling pesticide fate and transport as well as their biological effects on living organisms requires a detailed knowledge of physicochemical and biological processes at microscales. These processes occur in soil porosity colonized by soil microorganisms, within plant organs and tissues, at the interface between soil, plant, air, or water. Innovative approaches for the study of these processes coupled to the development of models at these microscales can bring new insights to our understanding at macroscopical scale.
Finally, modeling the processes governing pesticide fate and effects also requires considering not only pedoclimatic parameters but also various drivers such as the cropping practices or molecular properties of pesticides. Therefore, upscaling models from local processes to the plot scale where cropping practices have a direct impact on the soil-plant-atmosphere-water compartments is required. Such an integrative approach can be achieved by combining different numerical models under modeling platforms. This allows to offer different coupling options and to cover a broader diversity of cropping systems and chemicals (in terms of behavior, mode of action, and ecotoxicological and toxicological effects).
As previously mentioned, pesticide use is at the origin of societal issues involving several factors. Studies focusing on pesticides and accounting for human and social sciences allow for a better understanding of the perception of pesticide risk by different groups, such as farmers and citizens. It can help to adapt regulatory decisions or to promote co-learning actions leading to the acceptation of protection measures to reduce pesticide exposure for different groups of citizens.
Since 1977, francophone researchers working on pesticides get together for the annual symposium of the “Groupe Français des Pesticides” association (GFP). GFP is an association aiming at gathering scientific community coming both from the private and public sectors, involved in the study of pesticides whatever the disciplines, leading to transversal views and then innovative initiatives. In 2015, the 45th symposium was held in the INRA centre in Versailles, from May 27 to 29. It was granted by INRA (EA and SPE divisions), the federation FIRE, the LabEx BASC, ONEMA, French Ministries (MAAF, MEEM), and the companies Thermo Scientific and Cluzeau Info Labo. Scientists from French (including overseas) and foreign universities and higher schools, but also from French Public Research Institutes (ANSES, BRGM, CNRS, CEA, Cirad, IFREMER, INRA, INSERM, IRD, and IRSTEA) and from the industry came for exchanging their views and respective expertise on scientific news. The event was organized by ECOSYS INRA-AgroParisTech Joint Research Unit (functional ecology and ecotoxicology of agroecosystems). The main research object of ECOSYS is the functioning of agroecosystems considered in an integrated way. To understand this functioning, the ECOSYS unit works with concepts of functional ecology and ecotoxicology, taking into account the flux of matter and energy and the functions of isolated organisms and the interaction with their environment. One research topic concerns the assessment of the environmental impacts of pesticide use in agriculture and gathers different scientists working in the domain of pesticide emission and transport in the atmosphere, soil processes including sorption, biodegradation and transport, ecotoxicological impacts on soil biota (mesofauna, macrofauna, and soil microflora), and modeling.