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On a beautiful afternoon earlier this week, William & Mary geology professors Jim Kaste and Rick Berquist slowly meandered along the shoreline of Chippokes Plantation State Park in Surry.

At low tide, they alternated walking between the water’s edge and the nearby cliff, searching for shells, whale bones and other remnants of past eras that can provide clues for their research.

“We are looking at basically an old sea floor from millions of years ago,” Kaste says. “It's exposed because the James River has cut into it. This has given us the opportunity to look into the side of the Yorktown Formation.”

That formation is a stretch of sand, clay and other material that once covered much of Virginia’s coastal plain.

Millions of years ago, sharks, seals and walruses swam in a shallow sea a couple hundred feet above what is now Hampton Roads. The shoreline was around Richmond.

As local collectors and adventurers know well, there’s plenty leftover from that time: shells, megalodon teeth and more.

But some of those fossils can pose modern-day hazards as well, according to the new research out of William & Mary.

Researchers now say the fossils in the Yorktown Formation are fueling higher than usual levels of potentially cancer-causing radon gas.

The radon gas, they say, is coming at least in part to decaying uranium found in stuff like old marine mammal bones.

Exposure to radon over time can then increase people’s risk of lung cancer.

Both the researchers and state health officials emphasize there’s no reason to panic. But, they add, it's important that people are aware of the issue – and take appropriate precautions.

kaste berquist sized
Photo by Katherine Hafner. 

William & Mary geology professors Jim Kaste and Rick Berquist look at an exposed part of the Yorktown Formation at Chippokes Plantation State Park in Surry on Monday, April 25, 2022.

Berquist has been studying the relationship between the ancient formation and radon for decades.

Kaste got involved a few years ago after tripping over a whale bone while walking his dog in his neighborhood.

Knowing of Berquist’s research, out of curiosity he took it back to his lab and found “indeed it had very high uranium and radon gas production. And that deepened my interest.”

Radon isn’t a contaminant, Kaste said. It’s a colorless, odorless, naturally-occurring gas in the earth’s crust that can harm human health by adhering to lung tissue.

Over time, consistent exposure can increase people’s risk of developing lung cancer – especially when combined with other factors like smoking.

The William & Mary team found elevated levels in samples taken around the city. Some came from parts of the Yorktown Formation that are exposed, like the cliff at Chippokes and spots right on campus. Others came from drilling underground.

That was paired with on-site monitoring in Williamsburg homes. The team found that average radon levels in many exceed what the EPA deems safe. That was the case in up to about 40% of homes tested in some zip codes.

“We've been trying to use our knowledge of geology to help residents understand radon risk in this area,” Kaste said. “And then we're trying to expand that beyond Williamsburg.”

When Berquist started doing the work in 1989, he used only radon monitors in people’s homes, even dropping them into wells to find the gas’ source.

Newer technology has allowed for much more advanced data from a device that tests the samples for uranium in their small campus lab.

When outside, radon gas is harmless because it disperses into the air, Kaste said. But without proper ventilation – particularly in lower levels of a home like a basement – it can be dangerous.

Kaste said he wants to inform residents, not alarm them. The team made an online map where people can assess risk by typing in their address. Homes built below 58 feet of elevation are predicted to be at the greatest risk.

Radon exposure is also making it for the first time into the Hampton Roads Hazard Mitigation Plan, a regional document funded by the Federal Emergency Management Agency.

It cites the William & Mary research and notes it to watch and incorporate more in future planning work.

“Radon is a hazard, and it should be in there with hurricanes and floods,” Kaste said. “It doesn’t cost as much financial damage, maybe. But it does actually impact health a lot more than a lot of these other hazards that get a lot of attention. So we’re elevating it.”

shells sized
Photo by Katherine Hafner. 

Fossilized shells sit on a log at Chippokes Plantation State Park in Surry on Monday, April 25, 2022. Some come from a geological layer called the Yorktown Formation, which William & Mary researchers have linked to increased levels of radon gas.

Ryan Paris is the Virginia Department of Health’s one-man radon division.

He’s been aware of the William & Mary research for years and in touch with the geologists behind it as it progressed.

One big issue is a map on the state department’s website that displays radon risk by region. All of southeastern Virginia is listed as low risk, conflicting with the new research.

The map was made decades ago by the federal Environmental Protection Agency. Everyone agrees it needs updating, Paris said.

But the department doesn’t have the time, money or data to do so.

Paris emphasized that the William & Mary data doesn’t constitute a public health emergency and residents shouldn’t panic.

Most high readings happen only in the home’s lower levels. It would take a non-smoker many decades of constant exposure to potentially cause lung cancer.

Paris thinks the issue’s coming up more in Williamsburg because of newer housing developments.

“Instead of building the house on the surface … they're starting to build houses dug out of hillsides or in river valleys,” he said. “In doing that, they're encountering some deeper geologic layers, including the Yorktown Formation. And that's what's causing the radon problem.”

There are too many factors – how much laundry you do, how often you use exhaust fans, and so on – to predict any individual’s radon risk, he said.

However, Paris does recommend that all Virginians test their homes for radon – especially when first moving in, when buyers could more easily invest in mitigation measures.

Residents monitoring the element in their own homes would also help the state gather data about potential hotspots, Paris said. Those interested can visit to order a $3 home test kit from the department.