For some of us, cells in our lungs mutate with age. These mutations seem perfectly healthy—until they come up against air pollution. The result is rapid changes in the cells that turn them cancerous, which could explain why people who've never smoked still develop lung cancer, according to Charles Swanton of the Francis Crick Institute in London, who says his team's findings will transform "our understanding of how tumors are initiated" and usher in a "new era" of molecular cancer prevention. They found mutations in the genes EGFR and KRAS "in 18% and 33% of normal lung samples, respectively," according to a release. These mutations—occurring in one in every 600,000 cells in the lungs of a 50-year-old, per the BBC—likely occur with aging.
"These mutations alone only weakly potentiated cancer in laboratory models," says Swanton, who presented the research Saturday in Paris, per CNN. When they were exposed to air pollutants, however, "we saw more cancers and these occurred more quickly ... suggesting that air pollution promotes the initiation of lung cancer in cells harboring driver gene mutations." In analyzing data on 463,679 people, researchers found a clear link between exposure to fine particulate matter (PM2.5), which come from vehicle exhaust and the burning of fossil fuels, and increased risk of non-small cell lung cancer in those with EGFR mutations. Inhaling PM2.5 triggers the release of a chemical alarm, interleukin-1-beta, which activates the mutated cells, per the BBC.
"This mechanism may be important in other cancers with carcinogens other than air pollution," Richard Smith, chair of the UK Health Alliance on Climate Change, adds in a BMJ opinion. It's "a wake-up call on the impact of pollution on human health," says Swanton. Amazingly, researchers who found the same link in mice with mutations in EGFR or KRAS were able to prevent cancers from forming by administering a drug that blocked the chemical alarm. It raises the possibility that in the future, we might "use lung scans to look for precancerous lesions in the lungs and try to reverse them with medicines such as interleukin-1-beta inhibitors," says Tony Mok of Chinese University of Hong Kong, who wasn't involved in the study. Yet "lowering the currently lethal levels of air pollution that affect most of the world's population" is the easier option, Smith writes. (Read more air pollution stories.)