In September, 13 families from...northeastern Pennsylvania sued Southwestern Energy Company...[alleging] that in drilling for natural gas,...Southwestern contaminated the local water supply with chemicals that caused them to suffer neurological disorders and gastrointestinal illnesses. It isn't the first lawsuit to label Marcellus drilling a health hazard. And...it's unlikely to be the last...Extraction [of the gas] involves hydraulic fracturing, or "fracking," a process in which millions of gallons of water, mixed with sand and chemicals, are pumped...into the earth to split the rock...[F]racking...is controversial because energy companies need not disclose what chemicals the drilling fluid contains...Southwestern...says...that the claims have "no factual basis"... [also refers to Chevron, Atlas Energy, Consul Energy, Dominion Resources, Shell, East Resources, ExxonMobil, XTO Energy, Cabot Oil & Gas]