From rare disease to new epidemic: Rethinking lung cancer’s causes

In this video, Jorge Nieva, M.D., professor at the Keck School of Medicine at the University of Southern California, traces how lung cancer evolved from being a medical rarity in 1919 to an epidemic driven first by machine-rolled cigarettes. He walks through how the disease's profile has changed dramatically over the past century, starting with the mass production of cigarettes in the early 20th century, which turned smoking into a widespread habit and lung cancer into a leading cause of cancer death.

Although smoking rates fell sharply after the 1980s for both men and women, lung cancer declined mainly in men, suggesting a new carcinogen more common in women but still affecting men. This divergence is central to Nieva's argument: if smoking cessation alone explained the drop in cases, the decline should have tracked evenly across both sexes. Instead, the data point to a separate, still-emerging risk factor disproportionately affecting women.

Nieva's environmental exposure study focused on patients diagnosed before age 50, whose cancers are usually driven by non–tobacco-related gene mutations. Because these younger patients rarely have a smoking history that explains their diagnosis, Nieva's team looked instead at lifestyle and environmental factors that might account for the mutations driving their disease.

They found that these young patients tended to eat "healthier" diets, meaning more fruits, vegetables and whole grains, which are associated with higher pesticide residues, and that women, who are more likely than men to eat this way, are now overrepresented among young lung cancer patients. The findings suggest an uncomfortable irony: dietary choices generally promoted as protective against disease may carry an overlooked risk tied to agricultural chemical exposure.

Nieva frames this as a call to rethink lung cancer's causes beyond tobacco, particularly as researchers work to explain why a growing share of cases now occurs in younger, non-smoking women.