The leading cause of lung cancer among Americans is smoking. The second-leading cause, and the first among non-smokers, is radon — a naturally-occurring, invisible, odorless gas. Tompkins County falls under the Environmental Protection Agency’s highest risk zone for radon exposure, meaning that houses have an average indoor radon level above the threshold at which the EPA recommends mitigation.
Although radon testing and mitigation resources are available for county residents, health experts, local officials and housing professionals say that persisting financial, legislative and awareness barriers pose public health concerns.
Radon is naturally produced by the decay of uranium, a radioactive chemical element, in rocks and soil. Because it is released from the ground, it can travel through cracks or holes and accumulate in buildings, particularly basements and crawl spaces. This means that people who live in sub-grade residences may be especially vulnerable.
“We need as much awareness about radon as possible,” said Diana Crouch, education coordinator at Tompkins County’s Healthy Neighborhoods Program, which provides free home visits to test for hazards like radon and lead. “It’s [a] colorless, odorless, tasteless gas … and it can cause health problems.”
Being exposed to radon over time significantly increases a person’s risk for lung cancer, and the EPA lists the healthy limit for radon at four picocuries per liter. Being exposed to this level of radon for 15 years increased the risk for lung cancer by 50% among more than 1,000 people in Iowa, one study found.
In 2025, there were 1,384 radon-induced lung cancer cases in New York State, according to the Indoor Environments Association, a nonprofit that addresses radon and other indoor environmental hazards. Using data from the EPA and the Centers for Disease Control and Prevention, the organization estimates that these cases incurred more than $250 million in medical costs.
Among the nine towns that make up Tompkins County, 40% of 2,056 home basements tested by the county health department since 1987 have had radon levels above the 4 pCi/L threshold. In Ithaca, 450 basements out of the 1,245 tested have fallen in this category. This doesn’t include buildings tested by private home inspectors or property owners, or buildings that haven’t been tested.
High Radon Risk Due to Geology
Tompkins County’s high radon risk is due in part to the underlying geology of the Finger Lakes region, which is abundant in shale and glacial deposits, according to a U.S. Geological Survey report.
Shale, a type of sedimentary rock, can accumulate and release high levels of radon due to its geochemistry, according to Prof. Louis Derry, geological sciences.
Shale can contain high levels of organic carbon. When groundwater containing uranium — the precursor of radon — comes into contact with this organic carbon, the uranium precipitates out of the water due to a chemical reaction, Derry explained. Over time, uranium builds up and naturally decays, producing radon gas that can travel upwards and into buildings.
The Finger Lakes region sits atop the Marcellus Shale formation, a sedimentary rock layer formed 390 million years ago, which causes high indoor radon levels
Rock debris left behind by melting glaciers can also cause high radon, according to the report. The Finger Lakes region — which was carved out by glaciers millions of years ago — is also located near the Valley Heads Moraine, a large deposit of glacial debris, making it particularly at-risk.
Within a region, whether a specific building has high radon is highly variable depending on the specific geology of that area, as well as factors like groundwater flow.
“Two people could live not that far apart and have really different exposures,” Derry said. “You can’t just say everybody over here has it and everybody over here doesn’t. It's a little less simple than that.”
Testing and Mitigation Resources Available
Radon testing is available from a variety of sources for Tompkins County residents who want to test their homes for radon.
Funded by the New York State Department of Health, the Healthy Neighborhoods Program provides free radon testing. County property owners can request a free home visit from Healthy Neighborhoods that includes testing for various home safety hazards, including radon, lead, fire and asthma management.
“As far as we offer, everything is free and we deliver,” Crouch said. “We offer a radon test on every single visit to people that own their home.”
Crouch recommends that residents test their home for radon every five years due to this region’s high risk level. For people who have already installed mitigation systems, she recommends re-testing every two years.
If a building is found to have more than 4 pCi/L of radon, health agencies recommend installing a mitigation system, which typically costs around $2,500. This can pose a financial barrier for people who might be at risk for radon exposure.
“Some people pass on a free radon test … because they don’t want to know that they have high radon, simply because they can't afford mitigation,” Crouch said.
Ithaca Neighborhood Housing Services, a non-profit dedicated to affordable housing, can provide some financial assistance for low-income residents who want to install a radon mitigation system, but their funding is limited, Crouch said.
‘A Gap in Policy’
For Eric Rosario ’91, who served as Alderman for the City of Ithaca from 2008 to 2011 and as Acting Mayor in 2011, radon presents a policy issue — especially because there is no local or state level legislation surrounding radon testing, mitigation or disclosure.
Property owners can test for radon if they choose, but there are no legal mandates to do so. Regulations for landlords also do not require them to test for or mitigate radon in rental properties, which impacts the 74% of Ithaca residents who rent their homes, including Cornell students.
While in office, Rosario led the initiative to implement an outdoor smoking ban on public spaces including the Ithaca Commons and children’s playgrounds, his first foray into public health policy. During that same time, a local resident brought up the county’s high risk for radon at a town hall meeting, which he soon discovered was a relatively “invisible” issue.
“You can’t see it. But it’s around us,” Rosario said. “And there may be a way … for a gap in policy to be addressed, at least explored.”
Although there is no legislation surrounding radon in Tompkins County, several areas around the country have introduced mandates. Iowa City, Iowa requires radon testing as part of yearly inspections in rental homes, with mitigation mandated for levels above 4 pCi/L. New York City requires radon testing in below-ground residences before they are legalized for occupancy and for property owners to disclose the results of prior radon testing during sales.
Examples such as these can set a precedent for potential legislation in Tompkins County, which could help extend existing policies and resources, Rosario said.
“The current policy seems to be just to build awareness and encourage testing. And given how high-risk of a community we are … that is great,” he said. “But … those incentives may not be enough to address the public health hazard. You're relying on one, people seeing it, [then] two, people taking action.”
On the home inspection side, policy is underway. A proposed New York State bill seeks to require home inspectors to be educated and licensed in order to conduct radon testing.
The bill stems from issues raised in a 2024 state report on radon risks and prevention. One of the report’s main findings was that radon testing by home inspectors is being conducted incorrectly at high rates.
“Probably the biggest issue that we see [is] the testing is being done improperly,” said George Schambach, president of Central New York Coalition for Healthy Indoor Air, a group backing the bill, and owner of the company Professional Home Inspection Service.
Currently, New York State home inspector licensing policy explicitly excludes any rules about radon. If the bill is enacted into law, home inspectors in New York would need to obtain a license to be certified to test for radon. This would entail completing an educational course, passing an exam and completing additional training every two years.
“One of the reasons why we need legislation is to make sure that the people that are doing the tests are doing it correctly,” Schambach said. “And the standards are plain.”
The coalition plans to resubmit the bill this fall to be considered in next year’s legislative session, with hopes that it will become state law around 2028.
In Tompkins County, existing resources provide residents with access to radon information and testing, but health experts, local officials and housing professionals have raised questions about barriers related to awareness, cost and regulation.
“The exposure is real. The issue is real. And it’s hard to convince people of that sometimes,” Schambach said. “It doesn't matter whether the house is brand new, or whether the house is 200 years old. Radon knows no difference.”
Tania Hao is a member of the Class of 2028. She is a science editor for the 144th Editorial Board and can be reached at thao@cornellsun.com.
