Radon is a colorless and odorless radioactive gas that can accumulate inside buildings, quietly putting millions of people at risk worldwide. It is known to cause between 3 and 14 percent of all lung cancer cases. This makes it the second-leading cause of the disease after tobacco smoking. Despite this, many non-smokers and former smokers remain unaware of their exposure, often missing the opportunity for early detection and treatment.
Scientists from the University of Calgary in Canada have recently made a new discovery. They found an innovative and surprisingly simple way to measure long-term radon exposure—through toenail clippings. Their new research suggests that toenails act as biological archives of environmental toxins. They preserve traces of radioactive elements. These elements can reveal how much radon a person has been exposed to over many years.
This breakthrough offers a promising new path to detect lung cancer risks in people who do not qualify for standard screening programs, including those who have never smoked or quit smoking long ago.
Radon: The Invisible Threat Lurking Indoors
Radon (Rn) is a naturally occurring radioactive gas formed when uranium in soil and rocks breaks down. It seeps up through the ground and enters homes and buildings through cracks in foundations, gaps around pipes, or poorly sealed floors. Outdoors, it disperses harmlessly into the air, but indoors, it can build up to dangerous levels, particularly in basements or areas with poor ventilation.
The problem is especially severe in colder regions where buildings are tightly sealed to conserve heat. This reduces airflow and traps radon indoors. Over time, breathing in radon gas allows radioactive particles to settle in the lungs, where they damage cells and increase the risk of lung cancer.
Radon exposure is difficult to detect without testing because the gas has no color, taste, or smell. Many people are unaware that their homes, workplaces, or schools contain elevated radon levels. The danger lies in prolonged exposure, as health risks increase with the length of time spent breathing radon-contaminated air.
A Simple, Scientific Discovery Hidden in Toenails
To address this hidden health threat, researchers led by biochemist Aaron Goodarzi and physicist Michael Wieser at the University of Calgary explored an unconventional idea: testing toenails for evidence of radon exposure.
Toenails, like hair and skin, grow slowly and incorporate trace elements from the body’s internal environment as they develop. Because they shed slowly, they serve as long-term biological records, preserving evidence of exposure to heavy metals and radioactive substances.
“When you inhale radon, it quickly transforms into a specific type of radioactive lead,” explains Goodarzi. “The body treats radioactive lead like ordinary lead, storing it in tissues such as hair, nails, and skin.”
Using advanced testing methods, the researchers measured the presence of lead isotopes in toenail clippings and discovered that they could reflect a person’s cumulative exposure to radon over time. Wieser notes, “We proved that toenail clippings can serve as a quantitative tool to reveal lifetime radon exposure at an individual level.”
Testing Toenails for Radioactive Lead Isotopes
In their study, the team analyzed toenail samples from 55 adults with known radon exposure histories. They specifically measured levels of the radioactive isotope lead-210 (210Pb), which forms as radon decays.
The results were remarkable. Researchers detected 210Pb in 71 percent of the toenail samples. People who had lived in homes with high radon levels for an average of 26 years had significantly higher concentrations of radioactive lead—about 0.298 femtograms of 210Pb per nanogram of stable lead—compared to just 0.075 femtograms in those with low exposure.
That represents a striking 397 percent difference, indicating that toenail clippings can provide an accurate, long-term record of radon exposure.
Even more interestingly, toenail samples from individuals who had taken steps to reduce radon levels in their homes still showed elevated traces years later. This demonstrates that toenails can retain evidence of past exposure long after mitigation efforts are complete.
Why Toenails Make a Reliable Diagnostic Tool
Toenails are uniquely suited for environmental testing because they are easy to collect, inexpensive to store, and less prone to contamination than hair or skin samples. They grow slowly, usually taking six to twelve months to fully replace, which means they can record long-term environmental exposure rather than short-term fluctuations.
This makes toenail testing an ideal, non-invasive screening method for identifying hidden health risks caused by environmental pollutants like radon. It could also help researchers better understand how long-term exposure impacts overall health, particularly among non-smokers who are often excluded from lung cancer screening programs.
Additionally, toenail testing could become a valuable public health tool in assessing population-level exposure, allowing governments and health organizations to identify high-risk areas and take action more effectively.
Modern Buildings and Lifestyle Changes Are Increasing Exposure
Although radon is a natural gas, modern construction and lifestyle habits have unintentionally made exposure worse. In colder regions like Canada, newer homes are designed to be energy efficient, using tight seals and insulation to conserve heat. Unfortunately, these features also trap air—and radon—inside.
“In regions of high geological radon potential, newer building practices have unintentionally worsened exposure,” the researchers wrote. Moreover, the shift toward remote work and indoor living means people are spending more time indoors, increasing their annual exposure.
Even building materials can emit small amounts of radon. Materials such as lightweight concrete made from alum shale, phosphogypsum, and volcanic rock tuff have been identified as minor but notable sources of indoor radon accumulation.
Radon can also dissolve in groundwater and be released during daily activities such as showering, cooking, or washing dishes, especially in rural areas where wells tap into uranium-rich soil.
Bridging the Gap in Lung Cancer Screening
Currently, lung cancer screening programs primarily target long-term smokers using low-dose CT scans. However, non-smokers and former smokers are often excluded, despite evidence that radon exposure significantly contributes to lung cancer in this group.
Since radon exposure cannot be self-reported—most people are unaware of their exposure levels—new testing methods like toenail analysis could help bridge this diagnostic gap. “Radon exposure isn’t something people can self-report because it varies with geology and building structure,” Goodarzi explains.
By identifying individuals with high levels of radon-related isotopes in their toenails, healthcare providers could offer early screening or preventive advice. This approach could save lives by catching lung cancer earlier, when treatment outcomes are far better.
Large-Scale Study and Future Applications
Encouraged by their promising initial findings, the University of Calgary team has launched a large-scale study involving 10,000 Canadian participants. Each volunteer will test their home’s radon levels and send in toenail clippings for analysis.
The goal is to validate the toenail method across a wider population with varying backgrounds, housing conditions, and geographic locations. If successful, the study could pave the way for toenail testing to become a routine part of environmental health monitoring.
Goodarzi says, “The data we gather could help expand early diagnostic access for patients whose lung cancers are not caused by tobacco smoke.” This research could also inform building regulations, radon awareness programs, and public health campaigns aimed at reducing environmental cancer risks.
The Importance of Testing Homes for Radon
Despite its dangers, radon exposure is entirely preventable. Simple home testing kits can detect elevated radon levels, and mitigation systems—such as improved ventilation, sub-slab depressurization, and sealing cracks—can drastically reduce indoor concentrations.
Public health authorities recommend testing every home, especially those in high-radon regions or older buildings without updated ventilation systems. Regular testing is crucial because radon levels can fluctuate seasonally and vary even between neighboring houses.
Raising awareness remains key, as many homeowners still underestimate radon’s health impact or assume it only affects smokers. The truth is, prolonged radon exposure poses a risk to anyone, regardless of lifestyle or background.
A Small Clipping With Big Potential
This study highlights how something as ordinary as a toenail can provide profound insights into our environment and long-term health risks. By transforming a simple biological sample into a diagnostic tool, scientists are opening new doors in personalized medicine and environmental health research.
As research continues, toenail testing could become an essential part of radon detection strategies, helping protect millions from an invisible yet deadly threat.
Ultimately, this innovative method could redefine how we understand and prevent lung cancer, ensuring that even those outside traditional screening programs receive the care and protection they deserve.
In the future, a few toenail clippings might not only tell us where we’ve walked but also how safely we’ve been breathing along the way.
