One of the bigger knocks against hybrid and electric vehicles is that while they don't directly produce much in the way of harmful emissions (if they make any at all), the process of building their electric motors and batteries can be very, very bad for the environment. Take graphite, for example. It's an essential ingredient in lithium-ion battery packs, like the one shown above in the back of a Toyota Prius Plug-In. According to Bloomberg, the average hybrid car uses about 22 pounds of graphite, and pure EVs like the Tesla Model S require about 110 pounds.
Graphite mining and processing is particularly bad for the environment. In China, one of the world's leading graphite producers, the effects of the so-called "graphite rain" – a silver dust that falls from the skies in areas around the mines – along with the hydrochloric-acid-infused waste water from processing are reportedly rapidly poisoning the environments around the mines. This has led China to slash production, closing a number of mines.
Bloomberg has an excellent piece on the environmental effects of graphite, as well as the impact of China's move on the global price of the material, the latter of which is expected to impact the future pricing of electric vehicles. Hop over to the site and have a look.