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.
Still, the rate isn’t low enough to level the playing field between the vehicles. In terms of air pollution impacts, electric cars 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.”
On the positive side, the researchers had some good news for advocates of electric bike usage.
“Our calculations show that an increase in electric bike usage improves air quality and environmental health by displacing the use of other more polluting modes of transportation,” Cherry said. “E-bikes, which are battery-powered, continue to be an environmentally friendly and efficient mode of transportation.”
The findings were published in the journal “Environmental Science and Technology”.
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