3 February 2015

Nano-pesticides: opportunity or new risk?

The interest for nanotechnologies - the manipulation of matter on an atomic, molecular, and supramolecular scale with elements less than 100 nanometers (100×10−9 m) - has been growing, particularly since the beginning of this century. The development of nanotechnologies has attracted billions of dollars of investment in research in rich countries as they are considered by many as a major economic opportunity. Applications of nanotechnologies, so far, have been mainly in the field of medicine, electronics, fibres and smart fabrics, packaging, food additives (e.g. in milk), nanosensors (e.g. pest detectors), and cleaning of soil and water pollution.

But many believe that nano-particles can also be used for developing more efficient pesticides - nano-pesticides - and for improved veterinary medicines. In recent years, big agrochemical firms have invested large sums of money in research and elaborated new products that can protect plants through the use of much reduced quantities of pesticides (several thousand patents have already been lodged in this field). They included surface-active substances, polymers, and metal nano-particles (e.g. titanium dioxide which can both increase plant protection and stimulate photosynthesis). The advantage of these products is that they have often been designed to make active ingredients more soluble and to release their active ingredient in a slow and targeted manner. They are also able to resist longer to degradation and remain therefore present for a longer period in the soil. These qualities explain why they can be used at much reduced levels of application.

A priori, these attributes would suggest that this new generation of pesticides is more environment-friendly as it carries the potential of reducing massively the level of pesticide use in the world (approximately 3 million tons every year, still growing rapidly [read]).

So far, quantities of nano-pesticides marketed have been limited and mostly used in the US. Some experts have shown concern that there could be considerable risks in using these new pesticides on a wide scale, as they may have effects on the environment and human health that have not yet been sufficiently and fully analysed. According to experts, these products generate three main types of risks:

1. -Potential interference with biological processes, including the behaviour of cell membranes, biochemical pathways in cells and the genetic code
   

2. -The effect of surface molecules is more important than content molecules compared to traditional products, because of the small volume of nano-particles, and this effect may not be well known
   

3. -Nano-particles may move to locations in the human body or the environment not accessible to their conventional counterparts [read APVMA report, p.16 and following].
   

These characteristics imply that special measures will need to be taken when testing nano-particles in general, and nano-pesticides in particular, and that new testing protocols and techniques will need to be developed that will be able to capture all the effects of these new products. Moreover, the consequences of the designed persistence of these particles in the soil or in water have also to be assessed, as they could have important impacts on our environment.

This adds another complex chapter to the weighty issue of regulation and testing new chemical products before authorising their wide use.

While nanotechnologies definitely seem to present considerable opportunities in many domains, one can only lament that billions are being spent in developing nano-pesticides that raise serious safety issues, when experience shows that there is considerable scope for developing effective natural integrated pest control methods that do not present comparable risks.

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To know more:

1. -Australian Pesticides & Veterinary Medicines Authority (APVMA), Regulatory considerations for nanopesticides and veterinary nanomedicine, draft report, October 2014
   

2. -Kah, M. et al, Nanopesticides: State of Knowledge, Environmental Fate, and Exposure Modeling, Critical Reviews in Environmental Science and Technology Volume 43, Issue 16, 2013
   

3. -Food, environment and health, hungerexplained.org, December 2014
   

4. -On regulatory issues: New developments regarding Prof. Séralini’s article on Monsanto’s GMO maize NK 603, hungerexplained.org, December 2013

Last update:    February 2015

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