"The health impacts are also concerning because little is known about the chemicals used in the process and there is some research showing that they have carcinogenic properties."

Source: 
The Irish News (2011) "The Fracking Debate - Potential goldmine or a ticking timebomb? - Method of gas sourcing divisive"
Person: 
Dr Carroll O'Dolan, a GP from Florencecourt, member of the Fermanagh Fracking Awareness Network