High TDS can cause buildup of scale, which can be problematic in natural gas drilling because it damages well casings and clogs fractures. Scale buildup can also concentrate the naturally occurring chemicals found in formation water,
like NORM. (To learn more about the role of scale build up in human hazards, see Marcellus Shale Issue 4 – Understanding Naturally Occurring Radioactive Material in the Marcellus Shale.)