Environmental impacts of nanoparticles are not known

Tuesday 18 Jan 11

The methods currently applied in assessing the risks associated with chemicals cannot be used to determine the toxicology of nanoparticles in the environment. This has been demonstrated by a PhD project from DTU Environment.

We are increasingly surrounding ourselves with products containing nanoparticles. For example, the antibacterial properties of silver nanoparticles are used in feeding bottles, sticking plaster, refrigerators and socks. Moreover, nanoparticles are found in a variety of cleaning agents, cosmetics products and sports gear. For the past couple of years, Nanna Hartmann from DTU Environment has been studying the environmental impacts of nanoparticles.

„Because nanoparticles are now being used in many different contexts, and will be used even more products in future, they will also end up in the natural environment. This poses potential environmental and health problems,“ she says.

Now, you would have thought that determining the toxicology of nanoparticles would be a piece of cake, but Nanna Hartmann’s research has, above all, shown that we are still some way from finding the final answer to how these tests should be conducted.

The reason why studies of nanoparticles are particularly important is that substances which we otherwise know and change character at nanoscale level. Gold, for example, can trigger reactions on the nanoscale even though it is, of course, known for not oxidising and for being able to resist acid baths.

The question is what the consequences will be when nanoparticles find their way into the aquatic environment. The short answer to this is still: We don’t know.

Algae growth stunted

Nanna Hartmann’s research is based on the aquatic organisms which are also used to test the toxicology of chemicals.

„We focused on algae, water fleas and sediment worms because we expect that one of the places where nanoparticles will end up is in the aquatic environment. This is also where we would expect heavy metals to deposit, which means that we will be looking at a cocktail of nanoparticles and heavy metals; therefore, it is, of course, relevant to look at their interactions and whether they result in increasing toxicity.“

Whereas there is a well-established testing system for chemicals, the problem for the researchers is that test methods have not yet been developed which can establish, once and for all, whether certain nanoparticles are harmful to the aquatic environment. However, there are clear signs in Nanna Hartmann’s research that it is important to let innovation go hand in hand with investigations of environmental impacts as nanoparticles are incorporated into more and more products in future.

Firstly, the minute size of the nanoparticles means that the surface area in relation to mass is far greater. This means that larger numbers of harmful substances will be able to attach themselves to the particles. At the same time, their size means that they will potentially be able to penetrate organisms and their organs and cells.

„It is very clear that the entire digestive systems of the water fleas contain nanoparticles. And nanoparticles can also clog up their antennae, leading to changes in their patterns of movement. This is not something which you would normally see, a chemical substance having a direct physical impact on the organisms,“ says Nanna Hartmann.

Right test methods lacking

The testing of the water fleas shows that nanoparticles behave differently in the aquatic environment than the chemicals normally tested. So even though there are clear signs that nanoparticles will impact the aquatic environment, the problem remains: We do not as yet have the testing systems which can determine, once and for all, when the individual particles start causing direct harm to the organisms.

There is thus every reason to be cautious in our dealings with nanoparticles in future for the truth is that nobody knows how harmful they may prove to be. It is therefore a cause for concern for Nanna Hartmann that there are so many consumer products in the market which contain nanoparticles.

„My personal view is that we should perhaps think twice about sending all these gadgety products on the market. Products such as refrigerators and socks containing nanosilver or sun creams based on titanium dioxide. If it is just a question of avoiding smelly feet, then I would recommend a more cautious approach until we know more about the potential harmful effects,“ she says.

Nanna Hartmann’s PhD project
Title: Environmental impacts of engineered nanoparticles
Supervisor: Associate Professor Anders Baun, DTU Environment