What do we know -- and not know -- about fracking?

Fracking is in the headlines a lot these days, and everyone has an opinion about it. But how much do we really know for certain about the oil and gas extraction technique and its health effects? And how do we find out the truth among all the shouted opinions?

Fuente : http://feeds.sciencedaily.com/~r/sciencedaily/~3/a...