They’re saying the hydraulic extraction process makes a mess and makes the drinking water stink. They also say it releases hundreds of chemicals into the water table. There is no mention of concentrations on the home page of the site.
Of course, the chemicals were already there, and natural gas has no scent (mercaptan is added to give the distinct aroma) so some of what they say is pure bs. Well, most of it.
Probably all of it. :)
These people are liars. All wells are cased all the way to the surface and pressure tested to guarantee there are no leaks.
Any thing in the water beforehand is because of natural communication between formations. There may also have been a few older wells that were drilled many decades ago that have allowed communication. But this is rare and is easily fixed.
But modern methods guarantee that will not happen. These people are patently dishonest.