This brine injection well, owned by Northstar Disposal Services LLC, in Youngstown, Ohio, has halted operations after a series of small earthquakes in the Youngstown area.

COLUMBUS, Ohio — In Ohio, geographically and politically positioned to become a leading importer of wastewater from gas drilling, environmentalists and lawmakers opposed to the technique known as fracking are seizing on a series of small earthquakes as a signal to proceed with caution.

Earthquakes caused by the injection of wastewater that’s a byproduct of high-pressure hydraulic fracture drilling, aren’t new. Yet earthquakes have a special ability to grab public attention.

That’s especially true after Saturday’s quake near Youngstown, at magnitude 4.0 strong enough to be felt across hundreds of square miles. Gov. John Kasich, a drilling proponent, has shut down the wastewater well on which the quake has been blamed, along with others in the area, as the seismic activity is reviewed.

“Drilling’s very important for our economy and to help us progress as a state, but every single person in the Mahoning Valley felt this earthquake,” said state Sen. Joe Schiavoni, a Youngstown Democrat.

“I wouldn’t deem it as an emergency, but when you live in a place that you’re not used to earthquakes and you have 11 earthquakes, you’re concerned,” he said. “We need to give them some sort of confidence or security that this is going to be OK.”

Fracking involves blasting millions of gallons of water, laced with chemicals and sand, deep into the ground to unlock vast reserves of natural gas, a boon both for energy companies and a public hungry for cheap sources of fuel.

That process, though, leaves behind toxic wastewater that must be expensively treated or else pumped deep into the earth. The wastewater is extremely briny and can contain toxic chemicals from the drilling process — and sometimes radioactivity from deep underground.