Environmental fate of nanopesticides

The private and public sector are currently making great investments to develop organic nanoparticles as an enabling formulation technology for the delivery of bioactive substances in the pharmaceutical (i.e., nanomedecines) and agrochemical sectors (i.e., nanopesticides). Nanoformulations can offer a range of benefits including increasing efficacy, durability and a reduction of the amount of active ingredients that need to be used. Knowledge on the environmental fate of organic nanoparticles is however very limited, and it is currently not possible to assess the new environmental risks and benefits associated with the use of those new products. Taking nanopesticides as models for organic nanoparticles, the project aims at establishing the foundations for such assessment. Nanopesticides represent the priority for environmental research due to their inherent toxicity and intentional application in relatively large quantities onto crops. The overarching hypothesis of the project is that nanopesticides exhibit a behaviour that combines solute and nano features. Hence, the approach will be interdisciplinary, integrating knowledge and methodologies from the currently applied solute and nano schools. The specific objectives are to: Evaluate the suitability of existing methodologies to determine the nano and solute fate properties for nanopesticides; refine and adapt existing protocols when possible, create innovative alternative when necessary, in order to capture the dual solute-nano character of nanopesticides, Gain a fundamental understanding of the factors influencing environmental processes Elucidate possible relationships between fate processes. Laboratory experiments will be carried out on series of nanopesticides carefully selected in order to test specific hypothesis on fate processes and their interactions. The project will provide a fundamental understanding of the environmental fate of nanopesticides, which is a prerequisite to a robust assessment of environmental risks and benefits. The knowledge generated will be directly applicable to other organic nanoparticles, and will therefore provide solid scientific bases for significant improvement in the way the environmental fate of contaminants is evaluated.

Agriculture is in an urgent need of innovation to meet the growing global demands in food, feed and fuel. Large amounts of pesticides are currently used to maintain high levels of crop production, with disastrous consequences for human and environmental health. A variety of nano-enabled strategies have been proposed to improve the properties of current pesticides and increase their efficacy while decreasing their negative impact. However, what happens to those "nanopesticides" after their application is mostly unknown, and it is therefore difficult to fully assess the new risk and new benefits associated with nanopesticides relative to conventional products. This project aimed at elucidating the processes driving the environmental fate of nanopesticides. Experiments in the laboratory looked at the transport, aggregation and degradation of nanopesticides in different soils, water and plants surface. A unique set of nanopesticides was obtained from international partners with the aim to cover different types of nanocarriers (e.g. made of polymers, silica or graphene oxide), which were loaded with different pesticides. The results of the project have thus a wide domain of applicability. Overall, experimental results revealed that a great variety of behaviour is possible according to the type of nanopesticides, and as a function of the soil/water/plant properties. In some cases, there were hardly any differences in behaviour between the nano and conventional pesticides. In other cases, large differences in transport and/or degradation were observed relative to the non-nano equivalent. Consequences in terms of ground water contamination and soil accumulation were discussed considering the possible repetitive and long term use of the novel products. A new parameter (the durability criterion) and a protocol for its measurement were proposed to capture the range of situations described above, and to help developers and regulators identify the nano products that deserve further attention. In parallel to laboratory work, desk-based activities with partners from industry, academia and regulatory bodies have allowed setting up bases to harmonise the ecological risk assessment of nanopesticides at the international level.