Popular nanoparticle can cause toxicity in fish

Washington, March 3 (ANI): A study by researchers at Purdue University has shown that a nanoparticle growing in popularity as a bactericidal agent is toxic to fish.

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 orestry and natural resources. "There is reason to be concerned," she added.

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.

"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," she added.

According to Ron Turco, professor of agronomy and the research paper's co-author, there has been little work done to estimate the current level of nanosilver being released into the environment.

"Silver has been used in the past as an antimicrobial agent. It's a known toxicant to microorganisms," he said.

"Nanosilver is being considered by the EPA for environmental exposure profiling, much like a pesticide," he added.

Turco said it's unclear how nanosilver exposure might affect human health; however, he said that silver solutions have been considered by some to be a probiotic, and low dosages are sometimes consumed for intestinal health.

"The use of nanosilver could provide a number of sanitary benefits if used properly," Turco said.

"However, the indiscriminate inclusion of nanosilver into products to simply allow them to say they are antimicrobial is creating a cautionary issue," he added. (ANI)