Tiny particles may have big environmental impact

Nanotechnology studied | Nano particles, structures and sensors may improve agriculture, but effects on people, animals and soil unknown

There is a lot of anticipation about the application and potential benefits of nanoagriculture but little said about the risks.

The goal of nanotechnology in agriculture is to boost the productivity of plants for food, fuel and other uses, but the American Chemical Society reported its reservations in a podcast.

“Scientists are describing huge gaps in knowledge about the effects of nanoparticles on corn, tomatoes, rice and other food crops,” it said.

There are titanium dioxide nano-particles in powdered sugar on doughnuts and skimmed milk, clay nanoparticles in plastic beer bottles, iron nanoparticles in toddlers’ health drinks, silver nanoparticles in cooking and cleaning items, gold nanoparticles in face creams and nanomaterials in food packaging and storage items, electronics and paints.

There is also the whole emerging science of nanotechnology in medical research, notably the potential use of nanoparticles in cancer detection and therapy.

Nanoparticles and nanotechnology refer to small substances. A nanometre is one billionth of a metre.

Nanotechnology uses structures smaller than 100 nanometres, said Jennifer Kuzma and Peter VerHage of the University of Minnesota in a 2006 report, Nanotechnology in Agriculture and Food Production. A human hair, by comparison, is 100,000 nanometres thick and a nanoparticle is 1/50,000th the width of a single strand.

Nanoparticles and nanostructures are not only invisible to the human eye and conventional microscopes but they require powerful cutting-edge technology such as transmission-electron or scanning-tunnelling microscopes to be seen. While recognizing the potential for nanotechnology, Kuzma’s report posed questions about impacts on human health.

In agriculture, researchers are looking at pesticides contained in nano-particles so that they release in an insect’s stomach to lessen risks to the environment.

Other projects being researched involve the use of nanosensors that can release water and nutrients to meet a plant’s needs long before a farmer recognizes a deficiency.

Jorge Gardea-Torresday, chair of the department of chemistry at the University of Texas at El Paso, said nanoparticles are already in use in about 1,370 consumer products.

“The particles could end up in the environment, settling in the soil, especially as fertilizers, growth enhancers and other nanoagricultural products that hit the market,” he said in an article in the Journal of Agricultural and Food Chemistry.

“Some plants can take up and accumulate nanoparticles. But it is unclear whether this poses a problem for plants or for animals (and humans) that eat them.”

Gardea-Torresday and his research team examined scientific literature to review the safety issue. They analyzed nearly 100 articles on the effects of different types of nanoparticles on edible plants and found that the uptake and buildup of nanoparticles depend on the type of plant and the size and chemical composition of the nanoparticles.

The literature review confirmed that knowledge on plant toxicity of nanomaterials is still at the foundation stage.

“In terms of food/agriculture products that use nanoparticles or nanotechnology, there are some examples where lipid nanoparticles (micelles) are used to carry vitamins, etc.,” said Maria DeRosa, associate professor at Carleton University in Ottawa.

DeRosa said nanosensors and nutrient dispensers in food crops are loosely based on the idea of targeted drug delivery in medicine where the chosen drug will treat the disease but leave healthy cells or tissue alone. Applying that concept to crop nutrients is currently inefficient.

“The side-effects of wasted crop nutrients are environmental issues such as the release of greenhouse gases, runoff into waterways, etc.,” she said. “So, the idea is to find innovative ways to deliver nutrients to crops when they are best able to use them and less likely to be wasted. If we can develop sensors that give an indication of the crops’ nutrient needs and these are linked to the delivery of those nutrients, then that would make the ideal smart fertilizer.”

One way to make use of nanoparticles in fertilizers is by taking urea and delivering it as a nanoparticle. In its nano size, it could interact with nanoscale pores on plant roots. The downside is that the spread of these nano-fertilizer particle beads could result in them being washed away.

Another way would be to have the nanoparticle act as the delivery agent with fertilizer stuffed inside a nanotube.

“I think the key thing to think about here is that metallic nanoparticles, like silver for example, will behave differently than nanoparticles made from other materials such as lipid nanoparticles or polymer nanoparticles, so we would have to look at the different cases.”

DeRosa said there are many questions about how nanoparticles in soils will affect crops and the mic-robes in the soils.

She and her co-researchers are starting a project with Environment Canada to answer those questions.

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