Air pollution leaves detectable blood markers years before lung cancer diagnosis

Researchers have found something that changes how we might think about lung cancer risk: measurable shifts in blood chemistry that appear years before someone gets sick. A study published this week in Nature Communications tracked 1,357 people who were cancer-free at the start and discovered that those exposed to long-term air pollution showed distinct molecular patterns in their blood—patterns that preceded a lung cancer diagnosis by several years.

The work was led by scientists at the American Cancer Society and Emory University's Rollins School of Public Health, and it zeroes in on a gap in our understanding. We have known for decades that air pollution causes lung cancer. What we haven't known is what actually happens inside the body in the years between exposure and disease. The researchers found that air pollution triggers changes in small molecules called metabolites—the chemical byproducts of normal body function. These changes involve inflammation, oxidative stress, the body's ability to detoxify itself, and how cells generate energy. All of these are connected to increased lung cancer risk.

Why this matters becomes clear when you look at who gets lung cancer in America. It is the leading cause of cancer death in the country. But here is the uncomfortable fact: more than half of all lung cancer cases occur in people who have never smoked or who smoked so little they don't qualify for current screening programs. Current guidelines recommend lung cancer screening only for adults between 50 and 80 with a substantial smoking history. That leaves a vast population—people breathing polluted air, living near highways or industrial zones, working in certain occupations—essentially invisible to the screening system.

Ying Wang, a senior epidemiologist at the American Cancer Society and one of the study's leaders, notes that the association between air pollution and lung cancer is often strongest in never-smokers. "That tells us something meaningful is happening biologically," she says, "but we still don't understand the mechanisms." This study is a step toward closing that gap. By identifying what changes in the blood years before diagnosis, researchers can begin to map the biological pathway from pollution exposure to disease.

Donghai Liang, an environmental health researcher at Emory's Rollins School, emphasizes the practical implications. More than half of lung cancers occur in people who fall outside current screening recommendations—either because they never smoked or because they smoked too little to meet eligibility criteria. Understanding non-smoking risk factors like air pollution is essential for prevention and early detection. Yet air pollution is not even mentioned in current lung cancer screening guidelines. "These environmental risk factors are not even considered," Liang says, "which highlights that there's still so much unknown about how air pollution contributes to lung cancer."

The next step is validation. If these blood metabolite patterns hold up in other populations and settings, they could become biomarkers—measurable signals that doctors could use to identify people at elevated risk. That would open the door to screening strategies that go beyond smoking history and account for environmental exposure. It would mean that someone living in a polluted city, or working in a job with high particulate exposure, could be identified as at-risk years before symptoms appear. It would mean lung cancer prevention could finally address the people who need it most.