"The fluids, which are mixed with sand, are predominantly water, laced with 1% ‘special sauce’. The recipes for that fraction — a mixture that includes acids, solvents and corrosion inhibitors — were until the last few years secrets guarded by the companies that seek to penetrate shale formations to release stores of fossil fuels. But in the face of widespread concern about water contamination, 21 US states have adopted mandatory disclosure rules for the mixtures, making it easier for scientists such as Ellis, of the University of Michigan at Ann Arbor, to assess their impacts." (Quoted from article)