A report from as Democrat-led US government Committee has made damning reading for onshore drilling companies regarding fracking fluids.
The report, from the Energy and Commerce Committee, is the latest in a series of US administration investigations into the chemicals used in hydraulic fracturing, or fracking, during the process of drilling for oil and gas.
Despite the recent launch of a website by the drilling industry to offer greater transparency regarding fracking and the chemicals used, the report states that between 2005 and 2009 14 leading oil and gas service companies used more than 780m gallons of fracking fluids containing 750 different chemicals and additives.
Although many of the additives where harmless - bizarrely including instant coffee and nut shells - some were extremely toxic, including 29 indicated as having carcinogenic properties and regulated under the water or air polution legislation.
Compounds known as BTEX - deriving from benzene, toluene, xylene or ethylbenzene - were found to have been in some 11.4m gallons of fracking fluids used in the period investigated. The highest volume of fracking fluids containing carcinogenic additives were used in the states of Colorado, Oklahoma and Texas.
The report also criticised the use of "trade secret" or "proprietary" chemicals, which do not need to be named publically, stating that investigators believe the drilling companies are unwilling or unable to identify the chemicals used.
Members of the US House of Representatives who produced the report urged the Department of the Environment and the Environment Protection Agency to put strong protection in place to prevent the chemicals from entering water supplies.