Hydraulic fracturing, or fracking, is likely how your home gets cooled and water gets heated. But the unconventional oil and gas extraction method, currently booming across the U.S. and a cornerstone of President Trump’s energy agenda, is also behind an often-untold but growing problem: radioactive drilling waste.

Fracking is used to extract oil and natural gas from shale, but without question, water is the star resource. A Duke University study found that fracking consumed roughly 250 billion gallons of water between 2005 and 2014 to unlock the hydrocarbons but also generated about 210 billion gallons of briny, chemically laden flowback water during those same years.

This produced water contains a cocktail of industry-secret chemicals, heavy metals and naturally occurring toxic or radioactive elements like selenium and radium. To deal with the fluids, energy companies either reuse it, store it in surface ponds, send it to wastewater treatment facilities, or truck it to deep injection wells.

But these disposal methods aren’t always foolproof. A leaky pond or an ill-equipped wastewater treatment plant can inadvertently leach contaminants into groundwater or drinking water supplies, meaning public health and the environment could be at risk of exposure. And wastewater injection has been linked to a "induced" earthquakes in Arkansas, Colorado, Kansas, New Mexico, Ohio, Oklahoma and Texas.

The glaring issue with fracking’s so-called orphan waste stream, which also includes sludge, rock and soiled equipment, is how it’s “virtually unregulated” by any federal agency, according to experts cited in a Center for Public Integrity report. A patchwork of state laws and a self-policed industry thus has allowed tons of fracking waste to get “shopped around" or even illegally dumped across state lines.

Kentucky is still legally wrangling over its handling of more than 1,000 cubic yards of out-of-state radioactive fracking waste that ended up at the Blue Ridge Landfill in Estill County two years ago. According to the Richmond Register, the waste came from drilling operations in Pennsylvania, West Virginia and Ohio and was further concentrated by a wastewater treatment plant in Fairmont, West Virginia. The facility’s treatment process apparently increased the waste’s radionuclides and radioactivity, with an intensity nearly 400 times higher than EPA standards.

The Bluegrass State does not allow the transport and disposal of radioactive waste from other states, so how did it end up in this hot mess? In short, West Virginia regulators realized the toxicity of the sludge and refused to dump it in the state’s own landfills, so the Kentucky dump decided to accept it.

Kentuckian environmental regulators have since slapped Blue Ridge Landfill with a $90,000 civil penalty fine and has required the company to remediate the radioactive waste, among other punishments.

But complications remain. An Estill County group has questioned why Kentucky Attorney General Andy Beshear decided not to pursue criminal charges against the landfill, and has filed a lawsuit seeking public records to better understand the enforcement actions related to the illegal dumping.

Kentucky’s fracking waste problem is not an isolated case. The CPI report explains, “the four states in the Marcellus are taking different approaches to the problem; none has it under control. Pennsylvania has increasingly restricted disposal of drilling waste, while West Virginia allows some landfills to take unlimited amounts. Ohio has yet to formalize waste rules, despite starting the process in 2013. New York, which banned fracking, accepts drilling waste with little oversight.”

Meanwhile, the country’s love affair with oil and natural gas development—along with its significant water consumption—continues its unmitigated growth. Worryingly, we don’t actually know how much water is coming in and out of the earth during fracking production. According to the Duke study mentioned earlier, not a single, reliable source of data currently tracks water use and wastewater production from unconventional shale gas and oil operations in all 10 major U.S. basins.

"Nobody can say how much of any type of waste is being produced, what it is, and where it’s ending up,” Nadia Steinzor of the environmental group Earthworks, who co-wrote a report on shale waste, also said in the Center for Public Integrity report.

That raises the question: Who’s to say that radioactive sludge (or other hazardous fracking byproducts for that matter) won’t also end up in our own backyards one day?

Earthworks is one of many environmental organizations that filed a lawsuit against the EPA last year to update its waste disposal rules.

"Updated rules for oil and gas wastes are almost 30 years overdue, and we need them now more than ever," Adam Kron, senior attorney at the Environmental Integrity Project, said then about the reasoning behind the suit. "Each well now generates millions of gallons of wastewater and hundreds of tons of solid wastes, and yet EPA’s inaction has kept the most basic, inadequate rules in place. The public deserves better than this."