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Nanopesticides: a promising new pesticide solution?

By Virginia Tressider

August 4, 2015

Tractor spraying a field
Bulk spraying could be replaced by targeted pesticide use. Image: Tamina Miller.

Pesticides don’t have the best history when it comes to the environment and human health. Over the years we’ve learnt that, unmanaged, pesticides and other agrochemicals find their way into our ecosystems, contaminating soils, sediments and waterways and adversely impacting wildlife. But the emergence of new types of pesticides, nanopesticides, offers hope of a more environmentally-friendly approach.

An international team of researchers has been looking at the potential for using nanopesticides in agriculture within the existing regulatory landscape. The result – Nanopesticides: Guiding Principles for Regulatory Evaluation of Environmental Riskswas published in the Journal of Agricultural and Food Chemistry

The researchers investigated the benefits that could flow from this new technological development, which include the potential to increase efficacy and durability of a pesticide while at the same time reducing the amount of active ingredients present. They also explored how nanopesticides can be examined and tested to minimise or eliminate any potential hazards.

“Nanopesticides are plant protection products where nanotechnology is employed to enhance the efficacy or reduce the environmental footprint of a pesticide active ingredient,” said Rai Kookana, a scientist at CSIRO and lead author of the research.

But what exactly is the difference between nanopesticides and conventional ones? It turns out that size really matters, and small can be beautiful.

It’s the little things that count

Nanotechnology is all about the almost unfathomably small. A nanometer is one billionth of a meter. At this scale, particles have a disproportionately large surface area relative to their overall size. It’s the surface area that makes the difference, because the greater surface area ratio means more of the total volume of pesticide comes into contact with the pests. And that in turn means being able to reduce the amount of pesticide needed.

Put this way, it sounds as though nanopesticides are all up-side. And they might well be, but there are very good reasons to proceed with caution, particularly when we’re dealing with food and the environment.

Kookana and his colleagues in CSIRO Land and Water have been looking at contaminants in the environment for decades. They developed a suite of tools and knowledge for assessing and managing traditional pesticides in the environment, and are excited by the opportunities this new technology offers for minimising adverse impacts.

At the moment there are at least three different formulation types—nanoemulsions, nanocapsules and inorganic engineered nanoparticles (ENPs) — at different stages in the product development cycle. All of them can be used to improve the efficacy of the active ingredient in the pesticide itself or improve the safety of the products in the environment.

An image of many blue and red spring-shapes arranged in a ring shape
Engineered nanoparticles can be highly complex. Image: Matthew Tirrell.

A small number of nanopesticide products with either higher efficacy or a better environmental profile are already on the market. For example, a turf fungicide based on water-based (non-petroleum) nano/microemulsion technology has been developed with several attractive features. According to the product developer, the nano/micron sized particles prevent rapid settling of the emulsion, do not require frequent stirring, stop clogging of filters in spray equipment and make the formulation stable for a longer time. The “nano-formulation” allows systemic properties, which is intended to stop the product washing-off easily in the rain.

Further down the track, nanotechnology may be able to help farmers reduce the amount and spread of pesticide through the adoption of ‘smart field systems’—wireless sensors deployed in the field and linked via satellite to a laptop computer. These will be able to detect and locate crop infestations, then provide a targeted application of nanopesticide, reducing the amount and spread of the pesticide and greatly reducing the impact on the environment.

Risks and regulations

While nanopesticides are an attractive technological advancement, many of the approaches and assumptions used to assess the risks of conventional chemicals may not be appropriate for ENPs such as some used in nanopesticides.

“Currently, there is little understanding of the risk associated with this emerging technology,” Kookana says.

“It is important to establish the environmental fate and effects of nanopesticides and their inherent risks, and especially how these differ from conventional pesticides.”

The research examines the modifications that may be required to the environmental risk assessment (ERA) guidelines that are currently used to assess “conventional” pesticides. The authors propose alterations to existing ERA tests, which would mean adopting alternative testing procedures for nanopesticides.

“For some nanoformulations, such as nanoemulsions, the durability of formulations may be short-lived and the nanopesticide product may essentially be treated as a conventional formulation, requiring no additional testing,” says Kookana.

“However, where the nanoformulation is persistent, such as some slow-release nanopesticides, additional testing on the active ingredients, the nano-active complex and nano materials employed may become necessary. In such situations some of the existing conventional methods of testing are inadequate and new test methods need to be developed.”

A way forward for the regulators

A number of organisations worldwide are collaborating on an approach to addressing the hazard of ENPs, including the Australian Pesticides and Veterinary Medicines Authority (APVMA), the Food and Environmental Research Agency (FERA) of the UK, and the US Environmental Protection Agency (EPA.

Further, peak bodies including the Scientific Advisory Panel of the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) of the United States and the European Union (EU Regulations) through the REACH framework (the European framework for the assessment of chemicals), are considering how to vary the risk assessment criteria to apply to nanopesticides.

Kookana is currently leading an international project, jointly sponsored by the International Union of Pure and Applied Chemistry (IUPAC) and the APVMA, to develop guiding principles for regulatory evaluation of nanopesticides.

“Nanopesticides are an emerging technology with remarkable promise. We are excited at the prospect of partnering with universities, industry and regulatory bodies to facilitate the safe and effective application of this new technology,” he says.

Find out more about CSIRO’s biosecurity work at #CSIROprotect.


 

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