(Beyond Pesticides, August 23, 2012) Two commonly used nanoparticles have a significant impact on the growth and yield of food crops, according to a team of scientists led by University of California Santa Barbara’s Bren School of Environmental Science and Management. The study’s conclusions echo similar research findings that show human and environmental risks from nanoparticles are not fully understood, and conclude that a precautionary approach should be used until their fate and toxicity is better understood. The nanoparticles tested in the PNAS study, “Soybean susceptibility to manufactured nanomaterials with evidence for food quality and soil fertility interruption,” include zinc oxide, found in everyday products such as sunscreen, lotions, and cosmetics, and cerium oxide, used in diesel fuels to increase fuel combustion.
Zinc oxide nanoparticles enter agricultural fields through the application of biosolid (sewage sludge) fertilizers, which are composed of dried microbes previously used to process wastewater in treatment plants. Researchers discovered that soybean plants grown in soil containing zinc oxide particles bioaccumulate zinc, taking up the metal and distributing it throughout edible plant tissue. This caused a decrease in the food quality of the soybeans, and researchers indicate that it is uncertain whether the zinc that accumulates in the plant’s tissues is safe for human consumption in the form of ions and salts. “Juxtaposed against widespread land application of wastewater treatment biosolids to food crops, these findings forewarn of agriculturally associated human and environmental risks from the accelerating use of MNMs [manufactured nanomaterial],” the study notes.
Cerium oxide nanoparticles can contaminate agricultural fields through exhaust fumes from farm equipment, a likely scenario given that most all conventional soybean crops are produced with the help of industrial machinery. Soybean plants exposed to cerium oxide show a notable reduction in plant growth and yield. Though the cerium oxide particles did not bioaccumulate in plant tissues, they did have a considerable effect on the ability of soybeans to fix nitrogen, an important ecological function specific to leguminous crops. The nanomaterial concentrated at the root nodules of the plant, blocking its ability to form a relationship with the symbiotic bacteria that convert nitrogen in the air to plant-available ammonium fertilizer. The impacts of nanoparticles could lead conventional farmers to apply increasing amounts of synthetic fertilizers to make up for the loss of this natural function.
The results of this study underline the urgent need for oversight and regulation of emerging nanotechnology. While the U.S Environmental Protection Agency is required to limit industrial metal discharge into public wastewater treatment plants, there are currently no regulations curtailing the release of metal nanoparticles. Researchers explain, “MNMs — 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.” According to the scientists, “There could be hotspots, places where you have accumulation, including near manufacturing sites where the materials are being made, or if there are spills. We have very limited information about the quantity or state of these synthetic nanomaterials in the environment right now. We know they’re being used in consumer goods, and we know they’re going down the drain.”
Nanotechnology is a relatively new technology for taking apart and reconstructing nature at the atomic and molecular level. Just as the size and chemical characteristics of manufactured nanoparticles can give them unique properties, those same new properties —tiny size, vastly increased surface area to volume ratio, high reactivity— can also create unique and unpredictable human health and environmental risks. Many of the products containing nanomaterials on the market now are for skin care and cosmetics, but nanomaterials are also increasingly being used in products ranging from medical therapies to food additives to electronics. In 2009, developers generated $1 billion from the sale of nanomaterials, and the market for products that rely on these materials is expected to grow to $3 trillion by 2015.
At its fall 2010 meeting, the National Organic Standards Board (NOSB) passed a recommendation directing the USDA National Organic Program (NOP) to prohibit engineered nanomaterials from certified organic products as expeditiously as possible. While there is overwhelming agreement to prohibit nanotechnology in organics generally, there is still debate over the definition of what exactly should be prohibited and how to prohibit nanotech products in the organic industry. The recommendation deals specifically with engineered synthetic nanomaterials and purposefully omits those that are naturally occurring. Further it would block petitions seeking an exemption, and keep nanomaterials out of food packaging and contact surfaces.
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Image Source: BBC
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