Scientists discover hazardous nanoparticles in burning coal

Scientists discover hazardous nanoparticles in burning coal

10:05 AM, 10th August 2017
The particulates known as titanium suboxide nanoparticles are unintentionally produced as coal is burned. (File photo)
The particulates known as titanium suboxide nanoparticles are unintentionally produced as coal is burned. (File photo)

VIRGINIA, US: Environmental scientists led by the Virginia Tech College of Science have discovered that the burning of coal produces incredibly small particles of a highly unusual form of titanium oxide.

When inhaled, these nanoparticles can enter the lungs and potentially the bloodstream.

The particulates known as titanium suboxide nanoparticles are unintentionally produced as coal is burned, creating these tiniest of particles, as small as 100 millionths of a meter, said the Virginia Tech-led team. When the particles are introduced into the air –unless captured by high-tech particle traps they can float away from power plant stacks and travel on air currents locally, regionally, and even globally.

As an example of this, these nanoparticles were found on city streets, sidewalks, and in standing water in Shanghai, China.

The findings are published in the latest issue of Nature Communications under team leader Michael Hochella Jr, University distinguished professor of geosciences with the College of Science, and Yi Yang, a professor at East China Normal University in Shanghai. Other study participants include Duke University, the University of Kentucky, and Laurentian University in Canada.

“The problem with these nanoparticles is that there is no easy or practical way to prevent their formation during coal burning,” Hochella said, adding that in nations with strong environmental regulations, such as the United States, most of the nanoparticles would be caught by particle traps. Not so in Africa, China, or India, where regulations are lax or non-existent, with coal ash and smoke entering the open air.

Hochella and his team found these previously unknown nanoparticles not only in coal ash from around the world and in the gaseous waste emissions of coal plants, but on city streets, in soils and storm water ponds, and at wastewater treatment plants.

“I could not believe what I have found at the beginning because they had been reported so extremely rare in the natural environment. It took me several months to confirm their occurrence in coal ash samples,” said Yang.

The newly found titanium suboxide called Magneli 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 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.

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.

More troubling, the study shows that titanium suboxide nanoparticles are biologically active in the dark, making the particles highly suspect. Exact human health effects are yet unknown.

As the titanium suboxide nanoparticle itself is produced incidentally, Hochella and his team came across the nanoparticle by accident while studying a 2014 coal ash spill in the Dan River, North Carolina. During the study of the downstream movement of toxic metals in the ash in the Dan River, the team discovered and recognized the presence of small amounts of the highly unusual titanium suboxide.

The group later produced the titanium suboxide nanoparticles when burning coal in a lab simulation.

Direct health effects on humans is only one factor. Findings of thousands of scientists have determined that the biggest driver of warming of the planet and the resulting climate change is industrial-scale coal burning. The impact of titanium suboxide nanoparticles found in the atmosphere, in addition to greenhouse gases, on animals, water, and plants is not yet known.

Funding for the research came from myriad sources, including Virginia Tech’s Institute for Critical Technology and Applied Science, National Science Foundation grants, the US Department of Energy, and several China-based research foundations, Hochella said. 

© Virginia Tech

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