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Antimicrobial Nanoparticles in Soil Can Harm Plants

(Beyond Pesticides, August 13, 2010) A new study finds that silver nanoparticles, which are used in consumer products and in hospitals for their antimicrobial properties, can harm plant life when it enters into the natural environment. Where silver nanoparticles are present in the soil, plant species are reduced by 22 percent, with an additional 20 percent reduction of microbial biomass, as compared to those plants without the presence of nanoparticles. Researchers applied biosolids with silver nanoparticles into the soil of plants growing in intermediate sized rubber tubs, using a concentration within the range that the U.S. Environmental Protection Agency (EPA) has reported finding in biosolids from a recent survey.

“There have been a lot of lab studies looking at silver nanoparticles showing that they are highly toxic to bacteria, fungi, other microorganisms,” explained Ben Colman, PhD to Scientific American. Dr. Coleman is a postdoctoral researcher at Duke University who led the study. “Most of these studies have been conducted in very simple lab settings, [with] one species of bacteria—often the “lab rat” of the bacteria world, E [scherichia]. coli —[in] a test tube with very simple media and nanoparticles. So we wanted to move beyond this because it’s really hard to extrapolate from these single-species studies in simple environments to what will inevitably happen when these particles enter the environment.”

The particles, which are between one and 100 nanometers in size and smaller than many viruses, can enter the environment through wastewater, where it can accumulate in biosolids at wastewater treatment plants. These biosolids, also known as sewage sludge, are often sold to consumers as fertilizer, despite the fact that it can contain toxic contaminants. Sewage sludge-derived compost distributed free to gardeners by the city of San Francisco and its Utilities Commission was recently found to contain significant levels of toxins, including those with endocrine-disrupting properties such as polybrominated diphenyl ether (PBDE) flame retardants, nonylphenol detergent breakdown products, and the other heavily scrutinized antibacterial agent triclosan.

Scientists are applying nanotechnology to many industries, and much like triclosan, nanoparticles are now widely impregnated into a wide variety of consumer products to kill off bacteria, including cosmetics, sunscreens, sporting goods, clothing, electronics, baby and infant products, and food and food packaging. However, little is known about the impact of nanoparticles on human health and the environment, and mounting evidence suggests that these materials can pose significant health, safety, and environmental hazards. Nanosized particles can be released from impregnated materials via washing or sweating where they may pose numerable unknown adverse effects to humans and water systems.

Though the use of silver nanoparticles typically falls under the Federal Insecticide, Fungicide, and Rodenticide Act’s (FIFRA) definition of a pesticide as substances intended to kill pests such as microorganisms, EPA does not currently regulate it as such. In 2008, the International Center for Technology Assessment (ICTA), the Center for Food Safety, Friends of the Earth, and others including Beyond Pesticides filed a legal petition challenging EPA’s failure to regulate nanosilver as a unique pesticide. The 100-page petition addresses the serious human health concerns raised by these unique substances, as well as their potential to be highly destructive to natural environments, and calls on the EPA to fully analyze the health and environmental impacts of nanotechnology, and require labeling of all products.

You can reduce the potential environmental impacts of nanosilver by avoiding products that contain antibacterials. In addition to a slew of health and environmental effects associated with increasing chemical exposure, these antibacterial products tend to kill a wide variety of bacteria, reducing both “bad” bacteria associated with illness, as well as the “good” bacteria that perform useful functions in our environment and in our bodies. The overuse of antimicrobial chemicals has also been linked to the creation of drug-resistant bacteria, or “superbugs,” which are bacteria and viruses that have become resistant to the antimicrobial compounds and antibiotic drugs developed to control them. To download Beyond Pesticides factsheet What’s the right answer to the germ question? or for more information, including tips on how to get toxic antimicrobials out of your home, school, office or community, visit Beyond Pesticides’ Antimicrobials program page.

Additionally, this issue highlights the importance of knowing what inputs are going into our gardens, lawns, school yards and agricultural fields. The problem of contaminated compost keeps coming up because pesticide use patterns result in the contamination of treated land and EPA’s Office of Pesticide Programs allows the widespread fertilizer use of treated plant material (such as composted grass clippings).

Consumers should not be fooled by claims such as “safe” or “natural” when choosing products. Fertilizer cannot contain the U.S. Department of Agriculture (USDA) organic seal, however it can be listed on the Organic Materials Review Institute’s (OMRI) list of approved substances, and will often contain “OMRI approved” on its label. If it is not listed, then it does not meet the organic standards. For more information on labeling, visit our National Organic Standards page.

Composting is still a great way to improve the health of soil by adding much-needed organic content to soil, however, the best way to utilize organic compost, free of synthetic chemicals and avoid compost consisting of sewage sludge and other synthetic chemicals is to make it yourself. For more information, read Beyond Pesticides’ factsheet, “Compost Is the Key to Successful Plant Management.”

Source: Scientific American


2 Responses to “Antimicrobial Nanoparticles in Soil Can Harm Plants”

  1. 1
    Gladys Says:

    I have been composting for two years now and it is actually very easy especially with the new equipment. Thank you for mentioning those two words”Safe” and “naturally” because those two words are the worst marketing ploy ever!

  2. 2
    Darryl Alexander Says:

    Very disturbing story. We should press the National Institute for Occupational Safety and Health to investigate exposure of workers to the nano silver. Those in the plants that manufacture products as well as sewage treatment plant workers. We also need a long-term prospective health impact on that exposure. Workers are the inevitable canary in the mine.

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