Why Is Lung Cancer Rising in Non-Smokers?

Researchers point to several overlapping factors under active study, including air pollution, radon gas, secondhand smoke, and possibly genetic susceptibility, though no single cause has been established as the primary driver.

A 2026 genomic study published in Nature found mutational signatures in never-smoker lung tumors that resemble damage patterns associated with air pollution exposure, adding mechanistic evidence to a long-observed epidemiological association between fine particulate air pollution and lung cancer risk.

Radon gas, an invisible, odorless byproduct of soil and rock decay, is separately established as the second leading cause of lung cancer in the United States overall, and remains under study as a contributing factor in never-smoker cases specifically. Secondhand smoke exposure is estimated to raise lung cancer risk in never-smokers by roughly 20-25%.

Researchers caution that these factors likely interact rather than acting independently, and that a meaningful share of never-smoker lung cancer cases still have no clearly identified cause, which is why this remains one of the more actively funded areas of epidemiological lung cancer research.