Pope Leo Has Lung Cancer. How Can a Non-Smoker Get Sick? (Exclusive)

Pope Leo XIV at St. Peter’s Square at the Vatican in October 2026Credit: Maria Grazia Picciarella/SOPA Images/LightRocket via GettyNEED TO KNOWThe Vatican said Pope Leo XIV had the lower lobe of his right lung removed due to lung cancer

Radon exposure, air pollution and age can raise lung cancer risk for people who never smoked

Doctors say early detection and complete surgical removal can offer a strong chance of long-term survival for the 71-year-old pontiff

The Vatican has announced that Pope Leo XIV has undergone surgery to remove the lower lobe of his right lung. The 71-year-old pontiff has been diagnosed with lung cancer, even though he is not a smoker.

While smoking is a leading cause of lung cancer, nonsmokers can, and do, develop the disease. And it's far from rare: "If lung cancer in never-smokers was classified as its own entity, it would be the fifth most common cause of cancer death worldwide and the seventh most common cancer overall," Dr. Sohaib Intiaz, Chief Medical Officer of PEOPLE Inc., says.

And an overwhelming majority of nonsmokers (60-80%) who get lung cancer develop the type of cancer Pope Leo has: lung adenocarcinoma.

"The disease arises from a combination of environmental exposures, inherited susceptibility, and endogenous (internal) mutational processes, though in a large fraction of individual cases no single cause can be identified," Imtiaz explains.

Pope Leo holds incense during Mass in October 2026Credit: Filippo MONTEFORTE / AFP via Getty

One of the hallmarks of adenocarcinoma is that it grows in the outer parts of the lungs. "That's where tiny airborne particles, like fine air pollution and radon breakdown products settle when we breathe them in," Imtiaz says. "It suggests the cause lies in pollution-type exposures and the body's own internal processes rather than the direct damage tobacco does."

In fact, Radon exposure is the leading environmental cause of lung cancer. It's a "colorless, odorless radioactive gas produced by the decay of uranium in soil and rock; it seeps into buildings through foundation cracks and accumulates in enclosed, poorly ventilated spaces, so exposure is predominantly residential," Imtiaz explains. As it decays, it emits radiation that damages the cells that line the lungs.

Another environmental factor involves breathing in outdoor air pollution or fine particulate matter. But there are indoor dangers, too, like secondhand smoke or high-temperature cooking oil fumes. When it comes to incense, like the type burned in a church, it is "biologically plausible as a carcinogen," but "incense-associated lung cancer risk was limited primarily to smokers. There's no association between incense exposure and disease, he says.

The Pope's age, Imtiaz says, "is itself the most quantitatively important non-smoking risk factor."

"Age is the single most powerful non-smoking determinant of lung cancer risk, and an older never-smoker carries meaningful absolute risk simply by virtue of age," he says, adding that lung cancer in nonsmokers "rises steeply across the decades of life, climbing markedly after roughly 60–70 years, so advancing age substantially raises the chance of disease even in someone who never smoked."

Pope Leo XIV presides over Mass at t. Peter's Basilica at the Vatican in October 2026Credit: Maria Grazia Picciarella/SOPA Images/LightRocket via Getty

The Vatican has not shared the pontiff's prognosis, or any further planned treatment. But catching it early and removing it surgically gives him the best chance of survival, according to Imtiaz. "Early-stage lung adenocarcinoma completely removed by lobectomy carries a favorable prognosis, with a realistic chance of cure."

"In practical terms, for an older never-smoker with an early-detected adenocarcinoma completely removed by lobectomy, it is reasonable to say the operation was likely curative and that the statistical odds strongly favor long-term, disease-free survival."

Plus, he adds, people who have never smoked often have "other things in their favor," like earlier cancer detection and better overall health.

In Pope Leo's case, "All this supports a strong outlook."