Fullerenes (C60) would pose a risk to ecosystems, according to the latest work by a team from Rice University (Texas) and the Georgia Institute of Technology published in the journal Environmental Science & technology.
These quasi-spherical carbon nanoparticles are more and more used in industry (Frontier Carbon Corporation estimates that their production should be around 10 tonnes per year by 2007) and the question of their impact on the environment makes debate. With a solubility of less than a few picograms per liter, fullerenes are generally considered to be poorly soluble in polar solvents such as water, and therefore not very dangerous. However, John Fortner and his colleagues were able to show that, under certain conditions depending for example on the pH, the C60s can form colloidal aggregates called nano-C60.
These new structures, with a diameter of 25 to 500 nm, are therefore much more soluble with rates of up to 100 milligrams per liter. Who more
is, they are perfectly stable for at least 15 weeks in an medium with an ionic strength of less than 0,05, which is the case for most natural waters. By studying their effects in solution on two types of prokaryotes (E. Coli and B. Subtilis), the researchers observed a slow growth of bacterial cultures, both aerobically and anaerobically, for a concentration of nano-C60 more than 0,5 parts per million. If these results were confirmed, it would undoubtedly be necessary, as the team recommends, to revise the C60 pollution standards (currently modeled on those of graphite) taking into account their possible interaction with the environment.
However, it should be noted that other teams dispute these conclusions.
WP 16 / 05 / 05 (Bacteria and Buckyball Clumps)