In more than a dozen states, it is legal to use the wastewater from the oil and gas industry to tamp down dust on the millions of miles of America’s dirt roads. The option is attractive to local governments, since it is cheap and effective.

A new study by scientists at Penn State contends that it is also harmful to the environment, and hazardous to Americans, because it is putting radium in the water and air.

The paper, published in the American Chemical Society journal Environmental Science and Technology, finds that many metals from the process leach into local water sources over time. Radium, in particular, leaches off the road and what remains could get kicked up in dust, and inhaled, the scientists report.

The amount of radioactivity released through the road treatment process exceeds that from spills and wastewater treatment plants combined, the scientists find.

“Spreading O&G wastewater on roads can harm aquatic life and pose health risks to humans,” according to the researchers.

The survey of wastewater involved local conditions in 14 townships in northwestern Pennsylvania.

The scientists assessed the actual wastewaters in the towns’ tanks and employed a Thermo Scientific mass spectrophotometer to look for barium, copper, iron and an assortment of other inorganic substances. Then, they separated out the organic compounds by concentrating aliquots, and conducting observations using comprehensive two-dimensional gas chromatography coupled to a time-of-flight mass spectrometer, according to the paper.

The leaching process was assessed by looking at what ran off the road, and what was left behind.

The radium was found using gamma spectroscopy, and experiments in the lab simulated spreading and runoff events.

The determination was that radium from the unpaved roads is a danger to the people and animals in Pennsylvania.

“In Pennsylvania, from 2008 to 2014, spreading O&G wastewater on roads released over four times more radium to the environment (320 millicuries) than O&G wastewater treatments facilities and 200 times more radium than spill events,” the scientists said. “Currently, state-by-state regulations do not require radium analyses prior to treating roads with O&G wastewaters.”

The states, which allow some form of O&G wastewater spreading, for various uses, include: New Mexico, Colorado, Wyoming, Nebraska, Kansas, North Dakota, South Dakota, Illinois, Indiana, West Virginia, Michigan, Tennessee, Mississippi, Virginia, and New York.

The biggest users are Ohio and Pennsylvania, especially because of the boom in the hydraulic fracturing, or fracking, natural gas industry, according to the scientists.

Some 34 percent of all the 6.6 million kilometers of roads are unpaved.

As the study indicates, there are nearly 200 substances on the market used to treat dust on dirt roads, most that are chloride salts of salt bring-based. Those salt concoctions cost about 25 cents per liter, much more costly than the readily available oil and gas wastewater, where it is can be readily used.

Each of the Pennsylvania townships studied saved about $70,000 in 2015 because they used an average of 280,000 liters on their road in that year.

“Many of the townships in Pennsylvania that spread O&G wastewaters on roads have low annual budgets for road maintenance,” the researchers said. “Based on the cost of many commercial dust suppressant, the annual township budgets would not be enough to maintain road s and suppress dust using these products.”