Stunted Growth

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Among countless other applications, the emerging field of nanotechnology could revolutionize pesticide use. For instance, nano-encapsulated pesticides will have the ability to kill targeted insects only—reducing the effective dose when compared to traditional pesticides. Additionally, encapsulation can be absorbed by the surface of a plant to facilitate prolonged release—a step up from conventional pesticides which are often washed away in the rain.

But questions remain about the environmental and health impacts of these nano-pesticides. Melanie Kah and Thilo Hofmann from the Department of Environmental Geosciences at the University of Vienna published an extensive analysis of this developing field of research in June 2012, and found that what’s needed is a better understanding of the fate of both the food chain and the environment following nano-pesticide application

“Nano-pesticide research is emerging at high speed at the agrochemical labs; however, this topic has not reached public awareness or state authorities so far, nor are any products available at the market,” Hofmann said in a related release. “Since those nano-pesticides have new or enhanced properties, this will…inevitably result in both new risks and new benefits to human and environmental health.”

That following August, the University of California (UC) released a study that found soybeans grown in soil that contained the common nanoparticle cerium oxide (used to increase fuel combustion) had stunted growth. The researchers concluded that a greater use of synthetic fertilizers would likely be required to ensure adequate crop growth. Patricia Holden, a professor with the UC Santa Barbara Bren School of Environmental Science & Management and the study’s lead author, said that cerium oxide could accumulate in soil “near manufacturing sites where the materials are being made, or if there are spills.”

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Holden and colleagues noted that the U.S. Environmental Protection Agency (EPA) requires pretreatment programs to limit direct industrial discharge into publicly owned wastewater treatment plants; however, “manufactured nanomaterials—while measurable in the wastewater treatment plant systems—are neither monitored nor regulated, have a high affinity for activated sludge bacteria, and thus concentrate in biosolids.”

Additionally, a recent Duke University study investigated whether anti-microbal nanosilver applications could have impacts at the ecosystem level, particularly with plants that depend on soil bacteria and fungi for nutrient absorption. For their experiment, Duke researchers created of a series of outdoor “mesocosms,” or fields of plants growing in rubber tubs. They applied 0.2 kilograms of biosolid to each tub, amending the fertilizer with 11 milligrams of silver nanoparticles per tub (this concentration is within the range that the EPA reported finding in a recent survey of biosolids from water treatment plants). The nanoparticles had a marked impact on plants’ growing ability—reducing the growth of one plant species by 22% as compared with silver-free biosolid treatment. Similarly, microbial biomass (the amount of microorganisms in the soil) was reduced by 20%.

“What we found was actually a little bit surprising,” said Ben Colman, a postdoctoral researcher at Duke University and the study’s lead author. “We added lower concentrations [of silver] to a more complex system, but rather than find no measurable effect, we found that the silver nanoparticles significantly altered the plant growth, microbial biomass and microbial activity.”

LINDSEY BLOMBERG is a senior writer at E.