Popular nanoparticle causes toxicity in fish, study shows

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.

Maria Sepúlveda, an assistant professor of forestry and natural resources whose findings were published in the journal Ecotoxicology, 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. Thirty nanometers is more than 3,000 times smaller than the diameter of a human hair.

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 Agency is reviewing the situation.

Turco also indicated there has been little work done to estimate the current level of nanosilver being released into the environment.

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.

Sepúlveda said she 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.

Adapted from Purdue University news.

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