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Nanopesticides are not only in an advanced state of research and development but have started to appear on the market. Industry and regulatory agencies need a consolidated and comprehensive framework and guidance for human health risk assessments. In this perspective we develop such a comprehensive framework by exploring two case studies from relevant product types: an active ingredient delivered with a nanocarrier system, and a nanoparticle as an active ingredient. For a nanocarrier system, three entities are tracked during the assessment: the nanocarrier-active ingredient complex, the empty nanocarrier remaining after the complete release of the active ingredient, and the released active ingredient. For the nanoparticle of pure active ingredient, only two entities are relevant: the nanoparticle and the released ions. We suggest important adaptations of the existing pesticide framework to determine the relevant nanopesticide entities and their concentrations for toxicity testing. Depending on the nature of the nanopesticides, additional data requirements, such as those pertaining to durability in biological media and potential for crossing biological barriers, have also been identified. Overall, our framework suggests a tiered approach for human health risk assessment, which is applicable for a range of nanopesticide products to support regulators and industry in making informed decisions on nanopesticide submissions. Brief summaries of suitable methods including references to existing standards (if available) have been included together with an analysis of current knowledge gaps. Our study is an important step towards a harmonized approach accepted by regulatory agencies for assessing nanopesticides., (© 2021. Springer Nature Limited.)

Plant protection products containing nanomaterials that alter the functionality or risk profile of active ingredients (nano-enabled pesticides) promise many benefits over conventional pesticide products. These benefits may include improved formulation characteristics, easier application, better targeting of pest species, increased efficacy, lower application rates, and enhanced environmental safety. After many years of research and development, nano-enabled pesticides are starting to make their way into the market. The introduction of this technology raises a number of issues for regulators, including how does the ecological risk assessment of nano-enabled pesticide products differ from that of conventional plant protection products? In this paper, a group drawn from regulatory agencies, academia, research, and the agrochemicals industry offers a perspective on relevant considerations pertaining to the problem formulation phase of the ecological risk assessment of nano-enabled pesticides.

For the first time, regulatory protocols defined in the OECD guidelines were applied to determine the fate properties of a nanopesticide in two agricultural soils with contrasting characteristics. The nanoformulation studied had no effect on the degradation kinetics of atrazine indicating that (1) the release of atrazine from the polymer nanocarriers occurred rapidly relative to the degradation kinetics (half-lives 36-53 days) and/or that (2) atrazine associated with the nanocarriers was subject to biotic or abiotic degradation. Sorption coefficients, derived from a batch and a centrifugation technique at a realistic soil-to-solution ratio, were higher for the nanoformulated atrazine than for the pure active ingredient. Results indicate that the nanoformulation had an effect on the fate of atrazine. However, since the protocols applied were designed to assess solutes, conclusions about the transport of atrazine loaded onto the nanocarriers should be made extremely cautiously. The centrifugation method applied over time (here over 7 days) appears to be a useful tool to indirectly assess the durability of nanopesticides under realistic soil-to-solution ratios and estimate the period of time during which an influence on the fate of the active ingredient may be expected. More detailed investigations into the bioavailability and durability of nanopesticides are necessary and will require the development of novel methods suitable to address both the "nano" and "organic" characteristics of polymer-based nanopesticides.

Nanopesticides or nano plant protection products represent an emerging technological development that, in relation to pesticide use, could offer a range of benefits including increased efficacy, durability, and a reduction in the amounts of active ingredients that need to be used. A number of formulation types have been suggested including emulsions (e.g., nanoemulsions), nanocapsules (e.g., with polymers), and products containing pristine engineered nanoparticles, such as metals, metal oxides, and nanoclays. The increasing interest in the use of nanopesticides raises questions as to how to assess the environmental risk of these materials for regulatory purposes. Here, the current approaches for environmental risk assessment of pesticides are reviewed and the question of whether these approaches are fit for purpose for use on nanopesticides is addressed. Potential adaptations to existing environmental risk assessment tests and procedures for use with nanopesticides are discussed, addressing aspects such as analysis and characterization, environmental fate and exposure assessment, uptake by biota, ecotoxicity, and risk assessment of nanopesticides in aquatic and terrestrial ecosystems. Throughout, the main focus is on assessing whether the presence of the nanoformulation introduces potential differences relative to the conventional active ingredients. The proposed changes in the test methodology, research priorities, and recommendations would facilitate the development of regulatory approaches and a regulatory framework for nanopesticides.

The rapid developments in nanopesticide research over the last two years have motivated a number of international organizations to consider potential issues relating to the use of nanotechnology for crop protection. This analysis of the latest research trends provides a useful basis for identifying research gaps and future priorities. Polymer-based formulations have received the greatest attention over the last two years, followed by formulations containing inorganic nanoparticles (e.g., silica, titanium dioxide) and nanoemulsions. Investigations have addressed the lack of information on the efficacy of nanopesticides and a number of products have been demonstrated to have greater efficacy than their commercial counterparts. However, the mechanisms involved remain largely unknown and further research is required before any generalizations can be made. There is now increased motivation to develop nanopesticides that are less harmful to the environment than conventional formulations, and future investigations will need to assess whether any promising products developed are able to compete with existing formulations, in terms of both cost and performance. Investigations into the environmental fate of nanopesticides remain scarce, and the current state of knowledge does not appear to be sufficient for a reliable assessment to be made of their associated benefits and risks. A great deal of research will therefore be required over the coming years, and will need to include (i) the development of experimental protocols to generate reliable fate properties, (ii) investigations into the bioavailability and durability of nanopesticides, and (iii) evaluation of current environmental risk assessment approaches, and their refinement where appropriate., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Degradation and sorption of six acidic pesticides (2,4-D, dicamba, fluroxypyr, fluazifop-P, metsulfuron-methyl, and flupyrsulfuron-methyl) and four basic pesticides (metribuzin, terbutryn, pirimicarb, and fenpropimorph) were determined in nine temperate soils. Results were submitted to statistical analyses against a wide range of soil and pesticide properties to (i) identify any commonalities in factors influencing rate of degradation and (ii) determine whether there was any link between sorption and degradation processes for the compounds and soils studied. There were some marked differences between the soils in their ability to degrade the different pesticides. The parameters selected to explain variations in degradation rates depended on the soil-pesticide combination. The lack of consistent behavior renders a global approach to prediction of degradation unrealistic. The soil organic carbon content generally had a positive influence on degradation. The relationship between pH and degradation rates depended on the dominant mode of degradation for each pesticide. There were positive relationships between sorption and rate of degradation for metsulfuron-methyl, pirimicarb, and all acidic pesticides considered together (all P < 0.001) and for dicamba and all bases considered together (P < 0.05). No relationship between these processes was observed for the remaining seven individual pesticides.

Adsorption of six acidic and four basic pesticides was measured in nine temperate soils. In general, sorption of acids was weak as compared to bases and followed the order dicamba

Environmental context: Nanopesticides are increasingly being developed for agricultural use, but knowledge concerning their environmental fate and effects is limited. This microcosm study brings new results about soil fate and bioaccumulation of polymeric or lipid nanoparticles carrying chlorpyrifos or tebuconazole. The nanoformulations significantly altered the fate and bioavailability of the pesticides in soil even under the real-world and complex conditions of microcosms. An increasing number of nanoformulated pesticides (nanopesticides) have been developed in recent years with the aim to improve pesticide efficiencies and reduce their impact on the environment and human health. However, knowledge about their environmental fate and effects is still very limited. This study compares the soil fate and bioaccumulation of four model nanopesticides (chlorpyrifos and tebuconazole loaded on polymeric and lipid nanocarriers) relative to the conventional formulations and pure active ingredients (all added at 0.5 mg kg−1) in microcosms containing earthworms Eisenia fetida and lettuce Lactuca sativa in two soils (LUFA 2.1 and 2.4) over a period of four months. The nanoformulations increased the soil half-life of the pesticides by up to 2 times (e.g. chlorpyrifos with lipid nanocarrier and tebuconazole with polymeric nanocarrier in LUFA 2.1), probably as a direct consequence of the slow release of the pesticide from the nanocarriers. Pesticide bioaccumulation in earthworms was often increased for the nanopesticides probably as a result of their enhanced bioavailability. The nanoformulations were also shown to affect the pesticide bioaccumulation in plants, but trends were inconsistent. Overall, the microcosm results demonstrated that nanoformulations can significantly alter the fate and bioavailability of pesticides. However, generalisations were difficult to make as the impacts depended on the type of nanocarrier, pesticide, soil used and time scale. We believe that our study contributes towards the critical mass of case studies needed to enable a judging of the benefits versus risks of nanopesticides. Environmental context. Nanopesticides are increasingly being developed for agricultural use, but knowledge concerning their environmental fate and effects is limited. This microcosm study brings new results about soil fate and bioaccumulation of polymeric or lipid nanoparticles carrying chlorpyrifos or tebuconazole. The nanoformulations significantly altered the fate and bioavailability of the pesticides in soil even under the real-world and complex conditions of microcosms. [ABSTRACT FROM AUTHOR]

Environmental context: There are great concerns around current wide usage of copper-based agrochemicals. We compare the fate of nano- and conventional forms of copper, in particular their resistance to wash-off by rain (rainfastness), following their application to citrus leaves. Results showing large differences between the formulations in the amount and forms of copper washed from the leaves provide essential information to optimise agrochemical efficacy while minimising the environmental impact. This study compares the rainfastness of nine forms of Cu, including nano and conventional Cu-based fungicide formulations, as well as their salt or bulk equivalents. Rainfastness is the ability to resist wash-off; it is a key property for improving pesticide formulations and for assessing the potential transfer of pesticides to the soil. A new protocol was developed to characterise losses of Cu from treated leaves. It consisted of dipping the leaves in rainwater and then in an acid/ethanol mixture followed by size fractionation. The proportion of Cu lost by wash-off from citrus leaves ranged from <2 % (Tribasic, nCuO or Cu(OH)2) up to 93 % (CuSO4) of the initial amount of Cu applied. Intermediate Cu losses were observed for formulations with silica (nano)particles (9–14 % of applied Cu), Kocide (22 %), ChampDP (31 %), and a formulation with graphene oxide (47 %). Smaller particles generally resulted in less wash-off, possibly due to stronger attachment to the leaf surface, but other factors such as the particle shape and solubility also played an essential role. The retention of nCuO to the leaves was particularly high, and the exact mechanisms involved (e.g. foliar uptake) deserve further work. Most of the Cu was washed off in its ionic form (>74 %). Two Cu formulations (one commercial formulation and the formulation with graphene oxide) also showed wash off in significant proportions of Cu (~17 %) in the nano-sized fraction. This study provides essential information on the amounts and forms of Cu that may reach the soil after the application of Cu-based agrochemicals. The great diversity in behaviour across the range of formulations considered highlights the need for more systematic research to fully exploit the potential improvements of current agrochemicals through (nano)formulation technologies. Environmental context. There are great concerns around current wide usage of copper-based agrochemicals. We compare the fate of nano- and conventional forms of copper, in particular their resistance to wash-off by rain (rainfastness), following their application to citrus leaves. Results showing large differences between the formulations in the amount and forms of copper washed from the leaves provide essential information to optimise agrochemical efficacy while minimising the environmental impact. [ABSTRACT FROM AUTHOR]

The octanol/water partition coefficient (Kow) for organic compounds is widely used in predictive environmental studies. A significant proportion of contaminants of surface and ground water are ionisable (e.g. many pesticides, pharmaceuticals, metabolites). Such compounds may be partially ionised dependent on the pH. Since the neutral and ionic species exhibit different polarities, the Kow value of ionisable pesticides is pH dependent. It is therefore essential to determine Kow values over the full range of pH that occurs in the environment in order to get appropriate predictors. Numerous methods are available to measure lipophilicity but only a few are appropriate for ionisable pesticides (e.g. pH metric and filter probe methods). Parameters such as pH and ionic strength need to be carefully controlled when working with ionisable compounds. Variation of these factors probably explains why literature can yield Kow values that differ by more than one order of magnitude for some compounds. In this article, Kow values obtained for six acidic pesticides with three different methods are compared as well (data from the literature, measured by pH metric method and calculated with five computer programs). The values used in predictive regression equations needs to be either measured with a suitable method or selected from the literature with great care. [Copyright &y& Elsevier]