Conventional wisdom tells us that berthing car exhaust is bad. It further tells us that electric cars would cut down on emissions and thus be better for the breathing population.

But, some new studies focusing on China have brought up some challenging observations on that topic. What if electric cars were worse? How could that be?

Findings from University of Tennessee, Knoxville, researchers show that electric cars 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: electric cars 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.

For electric vehicles, combustion emissions occur where electricity is generated rather than where the vehicle is used. In China, 85 percent of electricity production is from fossil fuels, about 90 percent of that is from coal. The authors discovered that the power generated in China to operate electric vehicles emit fine particles at a much higher rate than gasoline vehicles. However, because the emissions related to the electric vehicles 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.

The findings also highlight the importance of considering exposures and the proximity of emissions to people when evaluating environmental health impacts for electric vehicles. They also illuminate the distributional impact of moving pollution out of cities. For electric vehicles, about half of the urban emissions are inhaled by rural populations, who generally have lower incomes.