Environmental groups are urging New Jersey lawmakers to override Gov. Chris Christie's veto of a bill that would have banned fracking waste from entering the state.

It's the latest turn in the fight over byproducts from natural gas drilling.

The environmental groups say fracking waste from other states, including Pennsylvania, would add to New Jersey's pollution problems and could threaten water supplies.

The waste produced by extracting natural gas through hydraulic fracturing may be worse than environmentalists thought, says Tracy Carluccio with the Delaware Riverkeeper Network.

"We have a thousand chemicals in play here, and many of them are carcinogenic, have very serious human health and environmental impacts," she says. "Many of them are even unregulated chemicals that don't have proper safe drinking water standards attached to them."

New Jersey Sierra Club director Jeff Tittel says the state's wastewater-treatment plants cannot safely treat all the chemicals used when drilling for natural gas.

He says fracking waste would have added to the problems caused by Hurricane Sandy.

"If fracking waste was being stored in New Jersey or processed here, we would have taken a disaster and turned it into a tragedy with billions of gallons of toxic waste going into our waterways," Tittel said.

Every previous attempt by the Legislature to override a Christie veto has been unsuccessful, but the environmentalists are hoping for a different outcome in an election year when voters may pay more attention to lawmakers' voting records.