WEST LAFAYETTE, Ind. - A nanoparticle growing in popularity as a bactericidal agent has been shown to be toxic to fish, according to a Purdue University study.
Tested on fathead minnows ╨ an organism often used to test the effects of toxicity on aquatic life -- nanosilver suspended in solution proved toxic and even lethal to the minnows. When the nanosilver was allowed to settle, the solution became several times less toxic but still caused malformations in the minnows.
"Silver nitrate is a lot more toxic than nanosilver, but when nanosilver was sonicated, or suspended, its toxicity increased tenfold," said Maria Sepulveda, an assistant professor of forestry and natural resources whose findings were published in the journal Ecotoxicology. "There is reason to be concerned."
Sepulveda 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, Sepulveda 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," Sepulveda said. "They had a potentially high dose of silver in them."
Nanosilver is growing in popularity as a component of many products. It is used to kill bacteria in goods such as odor-control clothing, countertops, cutting boards and detergents. Currently, there are few regulations for nanosilver's applications in products, but Ron Turco, professor of agronomy and the paper's co-author, said the Environmental Protection Ag
|Contact: Brian Wallheimer|