Interest in development of nanopesticides is growing due to their potential for greater activity or more gradual release of active substances than conventional pesticides. They are often seen as a promising sustainable alternative, requiring smaller amounts of active substances per hectare. However, it is crucial to acknowledge that their nano-enabled properties can also pose additional environmental risks. For example, higher or prolonged exposure of non-target organisms. Current risk assessment frameworks do not sufficiently address these aspects.

Nanopesticides may reduce pesticide use

There are roughly two types of nanopesticides: 1) nanosized active substances that have different properties than the non-nanoform of the same active substance, and 2) conventional active substances encapsulated in a nanocarrier. Such nanocarriers can, for example, enable controlled or slow release of the active substance. These properties can lead to a reduced use of pesticides per hectare, contributing to sustainability goals.

Nanopesticides may pose different risks to the environment

However, scientists from Leiden University have warned about the potential additional risks of nanopesticides. In particular, the risks for non-target organisms, such as insects, worms, and other soil organisms. Nanopesticides can have a higher bioavailability, leading to higher concentrations of active substances in non-target organisms. Also, the controlled or slow release of nanopesticides can expose non-target organisms to active substances for extended periods. This can cause harmful effects over time. In an opinion paper, the Leiden scientists argue that the differences in effects compared to those of conventional active substances are not currently considered when assessing the safety of these nanosized substances for the environment.

Nanospecific properties need to be included in safety assessment

For this reason, the scientists stress the need to consider nanospecific properties when assessing the safety of nanopesticides. This applies to both the nanosized active substances and the nano-encapsulated active substances. In practice, this means that environmental fate and ecotoxicity studies must be carried out with individual (nano)substances and the formulated products. Alternatively, other or additional (nanospecific) parameters should be included in predictive models.

Reflections by RIVM

In Europe, the safety of pesticides is evaluated by various authorities. In the European Union, the European Food Authority (EFSA) assesses the safety of active substances used as pesticides. Individual EU European Union (European Union) member states evaluate the safety of plant protection products. This evaluation assesses the active substances as they are contained in a product, including constituents such as those enabling nano-encapsulation. However, the European Plant Protection Products Regulation lacks clarity on when assessing the risks of nanospecific effects is necessary.

In 2021, EFSA published nanospecific guidance documents, including a Guidance on risk assessment of nanomaterials to be applied in the food and feed chain: human and animal health. This guidance document can assist in assessing the safety of nanopesticides, not only of nanosized particles but also of nano-encapsulated substances. However, it is essential to note that this guidance does not address the assessment of environmental aspects. EFSA’s guidance on risk assessment of nanomaterials focusing on environmental health is expected to be covered in a separate (Part 2) document. However, the release date for this document is currently uncertain.

A supporting EFSA document, written by RIVM and published in 2020, provides an overview of existing guidance documents and other published sources related to the environmental risk assessment of nanomaterials. The document highlights areas where (additional) nanospecific attention is needed. This document will be used as the basis for future EFSA guidance on environmental risk assessment for the application of nanoscience and nanotechnology in food and feed. Some of the issues highlighted in this supporting document are also brought forward by the Leiden scientists.

It is essential to ensure the safe use of nanopesticides, as well as safety for the environment and non-target organisms. Therefore, the risk assessment of such products must adequately and sufficiently prevent possible undesirable environmental effects from applying nanosized pesticides.