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Toxicity – Norwegian Researchers use Radioactivity to Trace Nanoparticles in Experimental Animals and Soil

Norwegian researchers are among the first in the world to use radioactivity to trace nanoparticles in experimental animals and soil. Their findings have made it easier to identify any negative environmental impact of nanoparticles, which are found in an increasing number of products.

"Simply put, it’s easier to find a needle in a haystack when that needle is radioactive," says Dr Deborah H. Oughton. Dr Oughton is a professor at the Norwegian University of Life Sciences (UMB), specialising in nuclear chemistry. As part of a joint research project involving UMB, the Norwegian Institute for Water Research (NIVA), Bioforsk and international research partners, she has headed the effort to develop methods for tracing nanoparticles by rendering them radioactive. The project is part of the Research Council of Norway’s programme on Norwegian Environmental Research towards 2015 (MILJO2015).

Dr Oughton and colleague Dr Erik Joner of Bioforsk, among others, came up with a method in which earthworms were fed horse dung containing radioac- tive nanoparticles of silver, cobalt and uranium. Subsequently, they were able to study the uptake and accumulation of the nanoparticles by observing how the radioactivity was distributed and then compa- ring their observations with physiological findings. In other experiments from the same project, fish were exposed to various concentrations of nanoparticles.

"One of our discoveries showed that nanoparticles can accumulate in different parts of an organism. In salmon, we witnessed that certain nanoparticles affected gill function and had a severely toxic effect. The presence of surprisingly low concentrations of certain types of nanosilvers led to gill failure and resulting death of the fish."

The study used lake water in order to optimise the relevance of the findings. The water in many lakes in Norway is relatively low in calcium. We found that this increases the amount of time nanoparticles stay in the water, says Dr Oughton.

The finding that nanoparticles may have detrimental effects on fish gives cause for concern as the presence of nanosilver has previously been detected in waste water from sewage purification plants. Nanosilver is also widely used in clothing, and studies show that washing clothes releases nanosilver into the water drainage. Nanosilver is even used in washing machines themselves in many countries, although this is not allowed in Norway.

Nanosilver was the most toxic of the group. The researchers also found out new information about the long-term behaviour of nanoparticles in soil.

“Nanoparticles break down over time through the slow release of ions. For some nanoparticles, these ions are the agents responsible for toxic effects on organisms. This gradual leakage of ions means that free nanoparticles continue to pollute the environment over a long period of time,” Dr Oughton states.

“Some types of nanosilver had a greater toxic effect than others. It is important for governments and industry to learn more about the risks involved with the various types of nanoparticles. Our research findings,