More nano knowledge needed for pesticides

Nanotechnology has begun to have an impact on many areas of our lives, having come on in leaps and bounds over the last decade or so. It is a term many of us associate with engineering and computer sciences, and perhaps with new medical treatments, but does not often conjure thoughts of environmental studies.

A paper published in the journal Critical Reviews in Environmental Science and Technology has now provided an analysis of the issues surrounding the development and use of nanopesticides, as well as the attendant risks and regulatory implications. Nanopesticides have the potential to reduce the environmental impacts of agrochemical use as well as threats to human health, but it is too early as yet to say to what extent they could or should be used.

"Nanopesticide research is emerging at high speed at the agrochemical labs, however, this topic has not reached public awareness or state authorities so far," remarked Professor Thilo Hofmann, Chair of the Environmental Geosciences Group at the University of Vienna and one of the authors of the paper.

I spoke to Dr Mélanie Kah, Assistant Professor in the Department of Environmental Sciences and co-author of the analysis, and began by asking about the environmentally beneficial applications to which nanotechnology in general has lent itself thus far.

"There are many examples, because nanoparticles have so many exciting potential properties," she explained. "Many applications have been suggested and a number are now in various stages of development. These include the use of nanoparticles for remediation purposes, to clean contaminated water and groundwater.

"Although some research is ongoing, one application that is fairly well-developed involves the injection of nanoscale zero-valent iron particles into groundwater to degrade certain contaminants. This is an example of something that is still under development but which is already being applied, as the technique is currently in use on a large scale in the United States."

A project is underway in the department which aims to help make the technique more widely applicable, and another – at the complete opposite end of the scale in terms of its development – is looking at a potential application for carbon nanotubes.

"People have suggested that carbon nanotubes could be used to replace activated carbon, the material used worldwide to decontaminate water," clarified Dr Kah. "It is suggested that carbon nanotubes have different properties which will complement activated carbon, but this is only at the laboratory scale so far."

It is important to steer clear of making broad generalisations about the risks and benefits of nanopesticides as compared to conventional pesticides, Dr Kah emphasised. They cannot be considered as a single entity; rather each case must be taken on its own merits.

"Very similarly to classical pesticide formulations, nanopesticides have many different purposes, many different fates in the environment, different levels of toxicity and various sets of advantages and disadvantages," she pointed out.

One potential advantage of nanopesticides that has often been suggested is that the rate of application could be significantly reduced because the quantity of product actually being effective could be much higher than with classical formulations. Much less would be lost. A tenth of the normal amount could be applied and hence there would be much less contamination."

Concerns have been expressed that some of the factors which make nanopesticides so effective in killing pests could also present drawbacks from an environmental perspective. There is the possibility of contamination of soil and water due to the ease of transport, enhanced toxicity and persistence of these materials. Dr Kah believes that the main threat, however, is a dearth of knowledge on the subject.

"I feel the main risk is the lack of understanding we have about the transport of these products in the environment," she said. "Even if only a tenth of the amount that would be applied if a classical formulation was being used is released, all of these particles could be going into groundwater and we would be increasing the risk of pollution."

""The potential risks are linked to a lack of understanding of the products, in terms of transport in to the environment and also in terms of toxicity," she went on. "It has been suggested that nanoparticles have a higher toxicity compared with the same material in non-nano form, but we simply do not understand these things properly yet."

To ensure that the risks to the environment and to public health are minimised while realising the full potential of nanotechnologies, filling the gaps in our knowledge will be essential. Until the effect and the fate in the ecosystem of any such product are understood, the precautionary principle suggests limiting usage to a bare minimum.

"We need a better understanding through more research, because I really believe that some could be very beneficial," Dr Kah contended. "It brings a wide array of potential applications, but as with anything we have to understand before trying it full-scale. We need more research on those products that may offer benefits to environmental or human health."

In their review of the literature on the topic, the authors also discuss how the adequacy of existing legislation and regulation may be affected in light of the development of nanopesticides in various forms.

"I think it is far too early to propose any amendments to the current regulation," Dr Kah stated. "It appears from our analysis that a lot of nanopesticides would be well covered by the European regulation on plant protection products because this regulation is very thorough; indeed it is probably the strictest in the world."

A strong starting position as far as regulation is concerned will perhaps prove a boon in terms of encouraging public confidence in those products which do reach market, having undergone rigorous study and testing. Dr Kah and her colleagues are eager to get across that a responsible and balanced view is needed.

"While we are far from claiming that nanopesticides will kill us all, our analysis is not to say that they will save the world either," she said. "More research should be done so that we can understand and judge these chemicals the same way we judge pharmaceuticals or any other compounds: on whether the advantages outweigh the risks."

For Dr Kah, the unprecedented level of control that the application of nanotechnology in the agrochemical industry may offer is the most exciting prospect. She gave pharmaceuticals as an example area where nanoscale techniques are relatively well-developed and opportunities are being taken to deliver drugs in a much more controlled manner, albeit on a smaller scale.

There is one potential method of delivery Dr Kah is particularly keen to see in action.

"The formulation describes a capsule containing a toxic pesticide where the capsule will only release its contents under very specific conditions. This could potentially dramatically reduce losses of these specified molecules towards non-target organisms or into surface water or groundwater. It may not be possible yet, but nanotechnology offers the possibility over the next decade or so to develop much better control over the chemicals we use in terms of only releasing them when they are needed."