Student - March 19, 2009


The number of carbon nanoparticles produced by the nano industry that end up at the bottom of lakes and rivers is negligible compared to the number that were already present and came from other sources. This conclusion was drawn from his research on several lakes by Bart Koelmans, who holds a personal chair in Aquatic ecology and water quality management.

The beds of rivers and lakes are perfect places for carbon nanoparticles (CNs) to pile up. These include particles from soot from forest fires, exhaust fumes and industry – which Koelmans calls background CNs – and those deliberately produced by the nano industry to be applied in products –anthropogenic CNs.Koelmans calculated for several lakes how many anthropogenic CNs can be expected in relation to background levels. His conclusion was that the contribution of anthropogenic CNs is very small. The number of background CNs is 10 thousand to 10 million times larger. Together with American and Swiss colleagues, he is publishing these findings in Environmental Pollution.
Nanoparticles are not new and they are released in large quantities by burning processes. Small particles are also partly made up of nanoparticles. ‘Nanoparticles are all around us’, says Koelmans. ‘They are invisible and reactive, and through various industrial processes there are more and more of them in our environment.’ He thinks it is understandable, then, that people are very worried about possible effects. Some nanoparticles penetrate deep into lungs and brains where they can cause inflammation and in some cases could be carcinogenic. For this reason some very promising industrial processes might be limited in future. Koelmans sees it as the social responsibility of producers of KNs to think about possible effects and risks of these potentially useful materials.
The results of his research seem to put the risks of newly produced CNs in perspective, however. So is nano pollution not such a problem after all? Koelmans: ‘Even if you assume a worst case scenario in which all the nanoparticles end up in the sediments, the number of anthropogenic particles is still negligible compared to the rest.’
Surprisingly enough, CNs seem to have positive effects too. In sediments, these particles mainly attach themselves to pollutants like PCBs and pesticides. This could reduce the environmental impact of these substances as they are pulled from the water into the sediments. Organisms find a complex like this much harder to absorb. However, the anthropogenic CNs contribute very little to this binding of pollutants, Koelmans concludes. ‘The nanoparticles from other sources have accumulated over millennia and they bind far more organic pollutants than any we shall produce’, he claims. ‘However, it is of interest to immobilize toxic substances by adding carbon particles to polluted river or lake beds, so reducing the biological availability and with it, the risks. We are doing this now in research together with Environmental Technology, financed by STW’.