People who own all-electric cars where coal generates the power may think they are helping the environment.

電動汽車的用電來自燃煤發電廠，使用電動汽車的人可能認為他們保護了環境。

But a new study finds their vehicles actually make the air dirtier, worsening global warming.

但是一項新的研究表明，電動汽車實際上對空氣污染更不利，且會加劇全球變暖。

The controversial study raises major questions over the future of 'green' cars.

這項頗受爭議的研究提出了有關“環保”車未來的一些問題。

'Unfortunately, when a wire is connected to an electric vehicle at one end and a coal-fired power plant at the other end, the environmental consequences are worse than driving a normal gasoline-powered car,' said Ken Caldeira of the Carnegie Institution for Science, who wasn't part of the study but praised it.

卡耐基科學研究所（Carnegie Institution for Science）研究員肯·卡代拉（Ken Caldeira）說：“不幸的是，當一根線把電動車和一個燃煤發電廠連在一起時，造成的環境污染比普通的汽油車更嚴重。” 肯·卡代拉并未參與這項研究，但是對該研究表示贊賞。

Driving vehicles that use electricity from renewable energy instead of gasoline could reduce the resulting deaths due to air pollution by 70 percent, it concluded.

該研究指出，駕駛可再生能源發電的電動車來取代汽油車，可以使因空氣污染造成的死亡率下降70%。

Ethanol isn't so green, either, the researchers claimed.

研究員表示，乙醇也不是那么環保。

'It's kind of hard to beat gasoline' for public and environmental health, said study co-author Julian Marshall, an engineering professor at the University of Minnesota.

研究報告撰寫者之一朱利安·馬歇爾（Julian Marshall）表示，出于民眾健康和環保的考慮，“想要取代汽油很有難度”。朱利安是明尼蘇達大學（University of Minnesota）的工程學教授。

'A lot of the technologies that we think of as being clean ... are not better than gasoline.'

“很多我們認為清潔的技術……其實都比汽油好不到哪里。”

The key is the source of the electricity all-electric cars need.

關鍵取決于電動汽車用電的來源。

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 that is published Monday by the Proceedings of the National Academy of Sciences.

周一發表在《美國國家科學院院刊》的這項研究指出，如果電來自煤，那么使用電動車產生的煤煙和煙霧造成的死亡是汽油車的3.6倍，因為燃煤發電過程產生了污染。

They also are significantly worse at heat-trapping carbon dioxide that worsens global warming, it found.

同時該研究發現，由煤產電排放的溫室氣體二氧化碳更加劇了全球變暖。

The study examines environmental costs for cars' entire life cycle, including where power comes from and the environmental effects of building batteries.

調查研究了一輛車使用周期過程中付出的環境代價，包括能源從哪里來，制造電池又造成了多少環境影響。

But if the power supply comes from natural gas, the all-electric car produces half as many air pollution health problems as gas-powered cars do.

但是如果電力來自天然氣，電動車產生的空氣污染造成的健康問題將會汽油車的一半。

And if the power comes from wind, water or wave energy, it produces about one-quarter of the air pollution deaths.

如果能源來自風、水或者潮汐能，空氣污染造成的健康問題將是原來的四分之一。

Hybrids and diesel engines are cleaner than gas, causing fewer air pollution deaths and spewing less heat-trapping gas.

混合動力和柴油發電機要比汽油清潔，造成的死亡人數更少，溫室氣體的排放也更少。

But ethanol isn't, with 80 percent more air pollution mortality, according to the study.

但根據研究，乙醇不屬于此類，造成的空氣污染的致死人數要高出80%。

（翻譯：小霹靂 編輯：Julie）