On the political right, it's pretty popular these days to claim that the left exaggerates scientific worries about hydraulic fracturing, or "fracking."
In a recent National Review article, for instance, a Hoover Institution researcher complains that 53 percent of Democrats in California support a fracking ban "despite the existence of little if any credible scientific evidence of fracking's feared harms and overwhelming scientific evidence of its environmental benefits, including substantial reductions in both local and global pollutants."
Three or four years ago, a statement like that may have seemed defensible. The chief environmental concern about fracking at that time involved the contamination of drinking water through the fracking process—blasting water, sand, and chemicals underground in vast quantities and at extreme pressures to force open shale layers deep beneath the Earth, and release natural gas. But the science was still pretty ambiguous, and a great deal turned on how "fracking" was defined.
The entire mega-process of "unconventional" gas drilling had clearly caused instances of groundwater contamination, due to spills and leaks from improperly cased wells. But technically, "fracking" only refers to the water and chemical blast, not the drilling, the disposal of waste, or the huge industrial operations that accompany it all.