Backgrounder: Shale gas and fracking

Backgrounder: Shale gas and fracking by Roberto Aguilera, Maurice B. Dusseault, John Molson, David Layzell, John Clague and additional anonymous scientist, February 16, 2012, Science Media Centre of Canada
Depending on the geology of the area, methane can naturally occur in groundwater. Methane is a colourless, odourless gas that is considered non-toxic when ingested, however it can cause suffocation at high concentrations in enclosed spaces and is highly combustible at certain concentrations. One way to determine whether increased levels of groundwater methane is due to fracking activity is through isotopic signatures. … Gas mixture composition also provides clues as to the origin of the dissolved methane. Naturally occurring methane in groundwater typically doesn’t contain other gases like ethane and propane that are found in shale gas, so the presence of these gases is another clue that fracking may be the cause. [Emphasis added]