When the U.S. Geological Survey released its new one-year prediction of earthquake risk on Tuesday, it said some parts of Texas and Oklahoma now face the same dangers as quake-prone areas of California—and that the rise was caused by underground disposal of wastewater produced during extraction of oil and natural gas.

Wastewater is a two-pronged problem. The increased seismic risk in areas where earthquakes are normally rare is putting some seven million people at risk, according to the USGS. Such tremors are usually small, but man-made quakes have been recorded at up to magnitude 5.6.

Then there is the water itself. Extracting oil or gas through a technique known as hydraulic fracturing, or fracking, involves pumping large quantities of water underground at high pressure to fracture rock. When the water flows back out, it is laden with chemicals used in the process, plus salts and heavy metals flushed out from the rocks. (In addition to fracking, conventional oil drilling also brings up dirty water.) Most of this water is later pumped underground. 

But it doesn’t need to be. Emerging treatment alternatives, including membrane desalination and ozone treatment, could render the water usable again. In addition, researchers are honing a large-scale distillation process that uses relatively little energy.

These processes are more expensive than shipping wastewater to a disposal well and injecting it, but the costs are not so high when the detrimental effects of pollution or earthquakes—and of diverting clean water in the first place—are considered.

In the meantime, the risks keep growing. In the Dallas-Fort Worth area in particular, the USGS says, the chances for man-made quakes have dramatically increased since 2014, and a significant earthquake there could cause up to $9.5 billion in damages.

(Read more: USGS, Washington Post, “One Way to Solve Fracking’s Dirty Problem,” “How to Clean the Gas and Oil Industries’ Most Contaminated Water”)