(Beyond Pesticides, March 4, 2010) Scientists at Purdue University have found that nanosilver that is sonicated or suspended in solution is toxic and even lethal to fathead minnows, an organism that is often used to measure toxicity on aquatic life. The study is the latest research to demonstrate the need for federal regulatory agencies to regulate emerging nanotechnologies as a unique pesticide.
The study, “The effects of silver nanoparticles on fathead minnow (Pimephales promelas) embryos,” led by Maria Sepúlveda, PhD and published in Ecotoxicology, describes the toxicity of two commercial silver nanoparticle products: NanoAmor and Sigma.
Fathead minnows at several stages of their development were exposed to varying concentrations of either suspended or stirred nanoparticle solutions for 96 hours. When the nanosilver was allowed to settle, the solution became several times less toxic, but still caused malformations in the minnows. With or without sonication, nanosilver caused irregularities, including head hemorrhages and edema, and was ultimately lethal.
“Silver nitrate is a lot more toxic than nanosilver, but when nanosilver was sonicated, or suspended, its toxicity increased tenfold,” said Dr. Sepúlveda. “There is reason to be concerned.”
Using Transmission Electron Microscopy, Dr. Sepúlveda was able to detect nanosilver particles measuring 30 nanometers or less inside the minnow embryos. Thirty nanometers is more than 3,000 times smaller than the diameter of a human hair.
“These nanosilver particles are so small they are able to cross the egg membranes and move into the fish embryos in less than a day,” said Dr. Sepulveda. “They had a potentially high dose of silver in them.”
Silver nanoparticles are now widely impregnated into a wide variety of consumer products used to kill off bacteria in odor-control clothing, bedding, vacuums, baby and infant products, food packaging and a host of others. However, very little is known about where these particles end up when such products are put to use, and little work is being done to estimate the current level of nanosilver being released into the environment.
Scientists have concluded that nanoparticles can pass easily into cells and affect cellular function, depending on their shape and size. Preliminary research with laboratory rats has found that silver nanoparticles can traverse into the brain, and can induce neuronal degeneration and necrosis (death of cells or tissue) by accumulating in the brain over a long period of time. A study conducted in 2008 and confirmed by another study in 2009 showed that washing nano-silver textiles released substantial amounts of the nanosilver into the laundry discharge water, which will ultimately reach natural waterways and potentially poison fish and other aquatic organisms.
In May, 2008, a legal petition was filed by the International Center for Technology Assessment (ICTA), the Center for Food Safety, Friends of the Earth, and others including Beyond Pesticides, 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.
So far, the U.S. federal government has invested only a small percentage of its overall nanotechnology research funding to understand the risks posed by nanomaterials, according to an analysis conducted last year by Project on Emerging Nanotechnologies, further highlighting the need for more research on the potential risks posed by nanomaterials.
Dr. Sepúlveda said she plans to develop tests to understand the effect that different nanoparticles have on fish and other organisms. She also wants to develop testing to determine nanosilver concentrations in the environment. “How are we going to know the risk unless we know the concentration of these particles?” she said.
For more information, 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.
Source: Purdue University Press Release