Natural gas drilling may be contributing to higher levels of salt in groundwater, which could in turn release naturally occurring radioactive radium from rocks into drinking water, according to a new study from Penn State researchers.
The findings, published in Environmental Science & Technology, suggest a possible connection between energy extraction and groundwater quality in southwestern Pennsylvania.
However, the researchers stress that drilling is not necessarily the only cause of the changes they observed.
Pennsylvania is one of the largest natural gas producers in the United States, providing about one-fifth of the country’s output in 2024. The state also has a long history of conventional oil and gas extraction, along with more recent growth in hydraulic fracturing, commonly known as fracking.
To investigate possible effects on drinking water, researchers collected samples from 91 private wells and springs in Washington and Greene counties. The homes were located at different distances from unconventional oil and gas operations, ranging from less than half a mile to more than three miles away.
The researchers collected water directly from private wells before it passed through household treatment systems or filters. Laboratory tests then measured radium, salts and other chemicals.
They found that water samples collected closer to some drilling sites tended to contain more salt. Higher salinity was also associated with increased radium levels.
Radium occurs naturally in rocks and soil in very small amounts. Normally, much of it remains attached to underground rocks. But salty water can change the chemistry surrounding those rocks and cause radium to be released into groundwater.
This matters because long-term exposure to elevated radium in drinking water can increase cancer risk. Radium behaves somewhat like calcium inside the body, meaning some of it can be deposited in bones. As the radioactive material decays, it releases energy that can damage nearby cells.
The study, however, did not find evidence of widespread radium contamination caused by fracking. Of the 91 water samples, researchers identified six that could potentially show signs of contamination involving fracking wastewater.
Samples collected within about three kilometers, or just under two miles, of drilling operations were also more likely to have elevated radium. But the association was not strong enough for researchers to conclude that proximity to drilling was responsible.
Importantly, all radium concentrations measured in the study remained within U.S. Environmental Protection Agency limits.
Another complication is that natural gas development is only one possible source of increased groundwater salinity. Road salt, septic systems, animal waste and other environmental factors can also add salt to groundwater. This makes it difficult to determine exactly where the higher salinity detected in individual wells originated.
The researchers say larger and more targeted studies will be needed to determine how much unconventional oil and gas development contributes to groundwater salinity and radium levels.
They also plan to investigate abandoned oil and gas wells. Pennsylvania’s long history of energy extraction means older wells could continue affecting underground water long after production has stopped.
The findings highlight a complex relationship between drilling, groundwater chemistry and naturally occurring contaminants. Rather than directly adding radium to drinking water, energy development may sometimes change underground conditions in ways that allow radium already present in rocks to enter the water.
