A government list of 36 chemicals used in coal seam gas extraction in Australia includes hydrochloric and acetic acid, and napthalene- an ingredient once used in napalm as well as more mundane items such as mothballs - and many other hydrocarbons.
Fracking, or hydraulic fracturing, involves injecting a mixture of water, sand and chemicals at high pressure underground in order to fracture rock formations and release coal seam gas.
The Australian Petroleum Production and Exploration Association, which represents coal seam gas extraction applicants, said the process has been used for many years and is completely safe.
But the Queensland government introduced legislation last week to ban some chemicals that can be used during fracking, including BTEX, a mixture that contains highly toxic benzene.
Last month in the US, the Environmental Protection Agency asked nine companies that use fracking to disclose the ingredients of the chemicals they use, some of which are regarded as trade secrets.
One of the companies, BJ Services, is a supplier of fracking chemicals to coal seam gas operators in Australia.
A study by the EPA in 2004 found no ''confirmed evidence'' fracking fluids have contaminated drinking water, but new research prompted it to reopen its inquiries.
''The secrecy surrounding many of the proprietary chemicals used in fracking needs to be fully disclosed to the public,'' said the director of the Total Environment Centre, Jeff Angel. ''We continue to be extremely concerned about the lack of environmental consideration in gas drilling. The gold rush might be leading us to gas, but that should not blind us from the gold that is our pristine water catchments.''
The petroleum association said its members provide details of any chemicals used to regulators. It sent the Herald an ''indicative list'' of chemicals used in fracking in Australia, including hydrochloric acid.
Some chemicals would be expected to dissolve to safe levels, but others are more persistent.
''The large amount of salt, and chemicals like naphthalene, aren't easily biodegradable in the environment,'' said Gavin Mudd, an environmental engineer at Monash University. ''Also, the process of drilling and fracking is making the chemicals more mobile than they normally would be. Often these impacts are cumulative; some of the chemicals can slowly build up in the food chain in the long term.''