Silver nanoparticles prove to be toxic
Harmful effects of silver nanoparticles: Please refer to the post Reducing the toxicity of silver.
Study done by researchers at Purdue
According to a study done at Purdue University, nanosilver suspended in solution proved toxic and even lethal to fathead minnows (a species of temperate freshwater fish).
The researchers observed the effects first when the silver nanoparticles were sonicated in the solution and later when the nanoparticles were allowed to settle. (Sonication is the act of applying sound (usually ultrasound) energy to agitate particles in a sample. It is commonly used in nanotechnology for evenly dispersing nanoparticles in liquids.)
According to Maria Sepúlveda, an assistant professor of forestry and natural resources, when nanosilver was sonicated, its toxicity increased tenfold.
In their study Sepúlveda and doctoral student Geoff Laban exposed fathead minnows to nanosilver at several stages of their development, from embryo to the point where they swim up from the bottom of their habitats to eat for the first time. Even without sonication, nanosilver caused malformations that included head hemorrhages and edema, and ultimately proved lethal. Using electron microscopy, Sepúlveda was able to detect nanosilver particles measuring 30 nanometers or less inside the minnow embryos.
Sepúlveda said, “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. They had a potentially high dose of silver in them.”
Sepúlveda now plans to develop tests to understand the effect different nanoparticles have on fish and other organisms. She also wants to develop testing to determine nanosilver concentrations in the environment. Sepúlveda said, “How are we going to know the risk unless we know the concentration of these particles?”.
According to another member of the research team, Ron Turco, professor of agronomy, it’s unclear how nanosilver exposure might affect human health. He said, “The use of nanosilver could provide a number of sanitary benefits if used properly. However, the indiscriminate inclusion of nanosilver into products to simply allow them to say they are antimicrobial is creating a cautionary issue. Nanosilver is being considered by the Environmental Protection Agency (EPA) for environmental exposure profiling, much like a pesticide.” Turco also indicated there has been little work done to estimate the current level of nanosilver being released into the environment.
Source: http://www.purdue.edu/newsroom/research/2010/100301SepulvedaNanosilver.html
March 3, 2010