People who own all-electric cars in places where coal generates the power are actually making the air dirtier, according to a new study. The key is the electricity's source. If it comes from coal, the electric cars produce 3.6 times more soot and smog deaths than gas, because of the pollution made in generating the electricity, according to the study published Monday by the Proceedings of the National Academy of Sciences. They also are significantly worse at heat-trapping carbon dioxide that worsens global warming, it found.

The study examines environmental costs for cars' entire life cycle, including where power comes from and the environmental effects of building batteries. Coal produces 39 percent of the country's electricity, according to the Department of Energy, with West Virginia, Wyoming, Ohio, North Dakota and Illinois with the highest percentage of coal-fired electricity.

The study finds that overall, all-electric vehicles cause 86 percent more deaths from air pollution than do cars powered by regular gasoline. But if natural gas produces the electricity? Half as many deaths as gasoline cars. Wind, water or wave energy? One-quarter. Hybrids and diesel engines are also cleaner than gas. But ethanol isn't, with 80 percent more deaths.

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Top 12 Electric Cars in the World - YouTube http://t.co/jNqZXErhC0 ^RF — ronfeir (@ronfeir) December 11, 2014

— The Associated Press