A 2026 study of 91 private wells and springs in southwestern Pennsylvania found that radium concentrations increased with salinity, but every sample remained below the federal drinking-water limit. The results support additional groundwater monitoring, not a broad claim that unconventional oil and gas development caused radium contamination.

What the study examined

Researchers investigated whether unconventional oil and gas development, including horizontal drilling and hydraulic fracturing, was associated with radium in nearby private drinking-water sources. Earlier research had identified localized salinity hotspots near oil and gas operations in the Northern Appalachian Basin, but radium was not always included in those analyses.

The study was published as Allison Fenske and colleagues, “Matrix-Derived Radium Mobilization in Shallow Aquifers Near Unconventional Oil and Gas Operations,” in Environmental Science & Technology, volume 60, issue 34, pages 24342–24351 (2026). Read the paper at https://doi.org/10.1021/acs.est.6c05003.

How the research was conducted

The researchers sampled 91 private wells and springs in Washington and Greene Counties in southwestern Pennsylvania. The sites were grouped by their distance from unconventional oil and gas operations: approximately one-half mile, just under two miles, and slightly more than three miles.

Water was collected before household treatment and analyzed for radium, salinity, and major ions. Because this was an observational field study, the results can identify relationships among location and water chemistry, but they cannot establish drilling as the sole cause of any individual result.

What the study found

Salinity and radium were related

Radium concentrations increased as salinity increased. This relationship is scientifically plausible because dissolved salts can displace naturally occurring radium from mineral surfaces in the aquifer. The term matrix-derived refers to radium released from the shallow aquifer’s rock matrix rather than radium introduced directly by injected hydraulic-fracturing fluid.

Distance alone did not establish causation

Some water sources nearer oil and gas operations had higher salinity or radium, and wells within roughly two miles were somewhat more likely to have elevated radium. However, the distance relationship was not strong enough to demonstrate widespread contamination or prove that unconventional oil and gas operations caused the measured radium.

Six samples had a possible produced-water signature

Six of the 91 samples had chemistry described as consistent with mixing between produced water and shallow groundwater. This finding deserves investigation, but it does not identify the route or source of the saline water by itself. Produced water originates in subsurface formations, and naturally migrating saline or brine water can also affect shallow groundwater. A chemical resemblance therefore is not, on its own, proof of a release from an active drilling site.

Every sample was below the federal radium limit

All 91 samples were below the U.S. Environmental Protection Agency maximum contaminant level of 5 picocuries per liter for combined radium-226 and radium-228. This is the study’s clearest public-health result. The federal standard applies to public water systems, while private-well owners are generally responsible for testing and maintaining their own water supplies.

Other possible sources of salinity

Salinity in shallow groundwater is not unique to oil and gas development. Potential sources include naturally occurring brines, road salt, septic systems, animal waste, spills, and other human activities. Because higher salinity can increase radium mobility, identifying the source of the salt is essential before assigning a cause.

What the results mean

The study shows that salinity can mobilize naturally occurring radium in shallow aquifers. It also identifies a small group of samples that warrant closer investigation. It does not show widespread radium contamination from unconventional oil and gas operations, and none of the sampled water sources exceeded the federal limit.

The original hypothesis that proximity to unconventional oil and gas operations would explain radium occurrence was not clearly supported by the results. Larger studies, baseline sampling before development, repeated sampling over time, and chemical or isotopic source tracing would be needed to distinguish drilling-related impacts from natural brine migration and other sources of salinity.

Why private-well testing still matters

A compliant result in this study does not establish the condition of every private well. Groundwater chemistry varies by location and can change over time. Owners concerned about radium, salinity, or nearby land use should use a certified laboratory and select tests appropriate to local geology and possible sources of contamination.

Want a practical starting point for understanding your drinking water? Get our Drinking Water Guide for Well Water & City Water for straightforward guidance on water quality, testing, and common concerns.

Related reading

• Could, Might, and Maybe: 91 Safe Wells and the Story That Refused to Match the Data
• Radium-226 and Radium-228 in Pennsylvania Groundwater
• Can Water Itself Be Radioactive?

Other Websites

• Know Your H2O
• B.F. Environmental Consultants
• Carbon County Groundwater Guardians
• Keystone Clean Water Team (Donate)

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