An alternative to conventional plant protection products (PPPs) may be seen in the development of engineered nanoparticles as “nanopesticides”. Those can include the encapsulation of active ingredients as a nanocarrier, a nano-formulation of the active ingredient (AI), or the development of nano-engineered structures that render pesticidal properties (Kookana et al., 2019). The ultimate effect of using nanopesticides is to reduce the environmental footprint of PPP residues while achieving similar or even enhanced pesticidal efficacy as compared to conventional PPPs. Additionally, nanopesticides can also promote targeted delivery of PPP to the crops thus increasing durability of the soils and decreasing accidental run-offs from farms to nearby water sources. As with any engineered nanoparticle, nanopesticides also exhibit one size dimension within the nano-range (by EU definition: 1-100 nm).

The increasing interest in the use of nanopesticides raises questions over how the environmental risk of these materials can be assessed for regulatory purposes. In the EU, nanopesticides may be affected by regulations that are particular to “nanoforms”, “biocides” or “plant protection products regulation” and more recently, to “regulations on residues in food and feed products”. The definitions of “nanoforms” according to REACh and other sector specific (biocides, for instance) definitions can be found in our previous blog post.

Several bottlenecks currently exist with respect to the regulation of nanopesticides. First and foremost, there is no existing regulatory definition for the term “nanopesticide”. The lack of a good definition leads to issues in judgement during risk assessment and can often lead to confusion among policy makers and manufacturers (Kah, 2015). For instance, nanopesticides may contain an extremely low concentration of AI encapsulated within a nano-carrier. The nanocarriers, by definition, are governed by the REACH regulation of nanoforms. However, some nanopesticide carriers may be slightly above the 100 nm size (distribution) limit, making them impermeable to nanoform based regulations. On the other hand, the AI itself is regulated by the plant protection products regulations. However, this regulation does not consider the effect of “nanoencapsulation” of the AI and considers only its absolute concentration, which is extremely low and well within the permissible limits, exempting it from regulatory constraints. However, research indicate that, like any other nanoparticle, nanopesticide systems can also cause different toxic effects in non-target organisms and exhibit varied physico-chemical properties from their bulk forms (Science for Environmental policy, 2021). Therefore, a risk assessment protocol and regulatory framework is required to adequately consider the nanopesticide holistically. The first step towards this would be to propose a definition for the term “nanopesticide”.

The study of fate and effects of nanopesticides also require a paramount attention during risk assessment. Fate of nanopesticides encompass several environmental processes and factors, most of which are now prescribed by various OECD guidelines and guidance documents. For instance, several aspects of fate of nanopesticides, such as sorption on to soil particles, degradation (biotic and abiotic) and leaching can be sufficiently addressed using OECD guidelines 106, 307 and 312, respectively. Nanoform specific fate studies including dissolution rate and dispersion stability in aquatic environments are also provided in OECD 318. In addition, fate of nanoforms also require comprehensive evaluation of particle size distribution, shape, surface charge, solubility and in some cases, the dustiness properties. A comprehensive utility of these OECD guidelines and guidance documents in conjunction with the physico-chemical properties mentioned above may be required for the appropriate evaluation of the fate of nanopesticides.

In this regard, while only marginally important in case of nanopesticides, the EFSA guidance on technical requirements for regulated food and feed product applications to establish the presence of small particles including nanoparticles also provide definitive decision tree layouts for the risk assessment of nanoforms in food and feed products. Certain aspects of this document may also be of value in assessing nanoparticles in applications in areas not covered directly by the food and feed sector specific definition of nanoforms. These pertain to food contact materials and AI in PPP. The technical requirements suggested in the EFSA document urge a combined evaluation of solubility and dissolution rate, particle size distribution and quantification and assessment of information from other safety studies (ecotoxicology on non-target organisms). A remarkably interesting feature in this document is that it does not strictly adhere to a strict size range of nanoforms. Rather, it considers the fraction of particles that are smaller than 500 nm. A two-tier approach to adequately measure and evaluate the effects of fraction of particles below 500 nm and then further 250 nm is proposed. This ensures the inclusion of nanopesticides also to some extent.

We, at nEcoTox GmbH are experts in nanotechnology and analytics. We can help you in designing studies according to OECD guidelines pertaining to specific nanopesticides and nano-formulations. As mentioned in the above post, determination of nanopesticide fate and toxicity in the environment includes multiple facets of studies! Contact us by email (menon@necotox.de) or by phone (+496346 9661490)!

References:
– Kah, M. (2015). Nanopesticides and nanofertilizers: emerging contaminants or opportunities for risk mitigation?. Frontiers in chemistry, 3, 64.
– “Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by SCU, The University of the West of England, Bristol. (2021)

Web:
– https://ec.europa.eu/food/plant/pesticides/approval_active_substances/eu_rules_en (accessed: April 2021)
– https://ec.europa.eu/food/plant/pesticides/max_residue_levels_en (accessed: April 2021)
– https://www.efsa.europa.eu/sites/default/files/consultation/consultation/Draft-Nano-Technical-Guidance-For-Public-Consultation.pdf (accessed: April 2021)



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