Coal Combustion Produces Form Of Titanium Oxide Potentially Toxic For Humans

August 28th, 2017 by James Ayre

New research from the Virginia Tech College of Science has found that coal combustion produces an unusual form of small titanium oxide particles that are potentially toxic to humans.

These titanium suboxide nanoparticles are small enough (as small as 100 millionths of a meter) that, when inhaled, they enter the lungs and can make it into a person’s bloodstream.

Image via University of Pittsburgh

Importantly, these particles float away from coal-fired power plant stacks freely on air currents, when not captured by expensive particle traps. As a result, it’s apparently the case that these nanoparticles can be found accumulated on the streets and buildings of some cities.

“The problem with these nanoparticles is that there is no easy or practical way to prevent their formation during coal burning,” commented lead researcher Michael Hochella, a Professor of Geosciences with the College of Science.

Photo via Virginia Tech

Hochella then added that, while many countries with strong environmental regulations aren’t likely to be affected too much by these nanoparticles because of the use of particle traps, countries with lax emissions standards in Asia and Africa (and elsewhere) are likely to be a different story.

“Due to advanced technology used at US-based coal burning power plants, mandated by the Clean Air Act and the Environmental Protection Agency, most of these nanoparticles and other tiny particles are removed before the final emission of the plant’s exhaust gases,” Hochella stated. “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, in part resulting in hazy skies that plague many countries, especially in China and India.”

The researchers involved in the work were able to find these unusual titanium suboxide nanoparticles in various regions and locations all around the world — including in stormwater ponds, soils, at wastewater treatment plants, on city streets, etc., as well as in coal ash and coal-fired power plant emissions themselves.

“I could not believe what I have found at the beginning, because they had been reported so extremely rarely in the natural environment,” stated researcher Yi Yang, a professor at East China Normal University in Shanghai. “It took me several months to confirm their occurrence in coal ash samples.”

The press release provides more: “The newly found titanium suboxide — called Magnéli phases — was once thought rare, found only sparingly on Earth in some meteorites, from a small area of rock formations in western Greenland, and occasionally in moon rocks. The findings by Hochella and his team indicate that these nanoparticles are in fact widespread globally. They are only now being studied for the first time in natural environments using powerful electron microscopes.

“Why did the discovery occur now? According to the report, nearly all coal contains traces of the minerals rutile and/or anatase, both ‘normal,’ naturally occurring, and relatively inert titanium oxides, especially in the absence of light. When those minerals are burned in the presence of coal, research found they easily and quickly converted to these unusual titanium suboxide nanoparticles. The nanoparticles then become entrained in the gases that leave the power plant.

“When inhaled, the nanoparticles enter deep into the lungs, potentially all the way into the air sacs that move oxygen into our bloodstream during the normal breathing process. While human lung toxicity of these particles is not yet known, a preliminary biotoxicity test by Hochella and Richard Di Giulio, professor of environmental toxicology, and Jessica Brandt, a doctoral candidate, both at Duke University, indicates that the particles do indeed have toxicity potential.”

The need is there, according to the researchers, to investigate the effects of these now ubiquitous nanoparticles on human health.

“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,” Hochella commented.

Well, perhaps, but given that these particles are produced by coal combustion, and that there are a raft of other issues accompanying reliance upon coal-fired power plants as well, perhaps more research isn’t what’s needed — but, rather, stronger actions.

The air pollution crisis in China, for instance, appears to be worsening despite efforts to date — so, regardless of further information about the dangers of coal combustion and associated air pollution, the impetus should already be there. Action will have an impact on economic output, though — no doubt the main reason that stronger actions haven’t been taken to date. That being the case, will more research on the matter really matter all that much?











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