KNOXVILLE, Tenn. - Researchers at the University of Tennessee are suggesting that electric vehicles may be more harmful to the environment than gasoline-powered vehicles in China.

According to a press release, although EVs "have been heralded as environmentally friendly," findings from the researchers show that EVs in China have an overall impact on pollution that could be more harmful to health than gasoline vehicles.

Chris Cherry, assistant professor in civil and environmental engineering, and graduate student Shuguang Ji, analyzed the emissions and environmental health impacts of five vehicle technologies in 34 major Chinese cities, focusing on dangerous fine particles. What Cherry and his team found defies conventional logic: EVs cause much more overall harmful particulate matter pollution than gasoline cars.

"An implicit assumption has been that air quality and health impacts are lower for electric vehicles than for conventional vehicles," Cherry said. "Our findings challenge that by comparing what is emitted by vehicle use to what people are actually exposed to. Prior studies have only examined environmental impacts by comparing emission factors or greenhouse gas emissions."

Particulate matter includes acids, organic chemicals, metals and soil or dust particles. It is also generated through the combustion of fossil fuels.

The press release notes that for EVs, combustion emissions occur where electricity is generated rather than where the vehicle is used. In China, 85% of electricity production is from fossil fuels, about 90% of that is from coal. The authors discovered that the power generated in China to operate EVs emit fine particles at a much higher rate than gasoline vehicles. However, because the emissions related to the EVs often come from power plants located away from population centers, people breathe in the emissions a lower rate than they do emissions from conventional vehicles.

Still, the rate isn't low enough to level the playing field between the vehicles. In terms of air pollution impacts, EVs are more harmful to public health per kilometer traveled in China than conventional vehicles.

"The study emphasizes that electric vehicles are attractive if they are powered by a clean energy source," Cherry said. "In China and elsewhere, it is important to focus on deploying electric vehicles in cities with cleaner electricity generation and focusing on improving emissions controls in higher polluting power sectors."

The findings are published in the journal Environmental Science and Technology.