Warning over dangerous coal-based nanoparticle

Potentially dangerous nanoparticles produced through coal combustion have been discovered by scientists in the US.

These titanium suboxide nanoparticles are as small as 100 millionths of a metre. Unless captured by advanced particle traps, they can float away from power plants, travelling on air currents around the world. If inhaled they can enter the lungs and potentially the bloodstream.

Aerosol pollution

Professor Michael Hochella, from Virginia Tech, said: “The problem with these nanoparticles is there is no easy or practical way to prevent their formation during coal burning. Due to advanced technology used at U.S. based coal burning power plants most of these nanoparticles and other tiny particles are removed before the final emission of the plant's exhaust gases. But in countries where the particles from the coal burning are not nearly so efficiently removed, or removed at all, these titanium suboxide nanoparticles and many other particle types are emitted into the atmosphere.”

Almost all coal on Earth contains traces of the minerals rutile and anatase, naturally occurring and relatively inert titanium oxides. When these minerals are burned in the presence of coal, they easily and quickly converted to these unusual titanium suboxide nanoparticles. It is these which are biologically active in the dark, something which makes the particles highly suspect.

The research team found these nanoparticles not only in coal ash or coal plant waste emissions around the world, but also on city streets, in soil and wastewater treatment plants. The newly found particles – called Magnéli phases – were previously believed to be rare, and had been found only in a small area of rock formations in western Greenland, in some meteorites and moon rocks.

Although the toxicity of these particles is not fully known yet, tests have confirmed they have the potential to cause damage in the lungs. Professor Hochella said: “Future studies will need to very carefully investigate and access the toxicity of titanium suboxide nanoparticles in the human lung, and this could take years, a sobering thought considering its potential danger.”

The World Health Organisation estimates that almost 3.5m premature deaths occur worldwide because of polluted air. The research was published in Nature Communications.