Here’s how air pollution may trigger lung cancer

Air pollution may steer lung cells toward cancer ­— even in people who’ve never smoked a cigarette.

People living in high pollution areas may rack up DNA glitches that trigger lung cancer, scientists suggest July 2 in Nature. Those glitches can include mutations that hobble the very genes that protect cells from tumor development, says Ludmil Alexandrov, a cancer geneticist at the University of California, San Diego.

His team’s results are a “strong argument for why we really need to care about air pollution,” he says. Microscopic particles of dust and soot and chemicals in the air can actually mutate DNA. 

Worldwide, some 2.5 million new cases of lung cancer occur every year, and scientists predict the number could rise to more than 4.5 million by 2050. Smoking tobacco is the main driver of the disease, but up to 25 percent of cases crop up in people who’ve never smoked. Earlier studies have suggested air pollution might be to blame. In general, highly polluted areas tend to tally more lung cancer cases than less polluted areas. Alexandrov’s team wanted to find out how DNA mutations might factor in.

Along with scientists from the National Cancer Institute, the team analyzed lung cancer DNA from nearly 900 “never smokers.” The researchers also estimated each person’s overall air pollution exposure based on where they lived when they were diagnosed. They discovered that lung cancers from people in highly polluted cities like Milan and New York City carried substantially more mutations than those from rural areas. That’s a problem because mutations can wreak genetic havoc.

Inside a person’s cells, some six billion DNA letters make up the genome, the genetic instruction book of life. Changing, or mutating, too many letters can garble the book’s text and tamper with important tumor-fighting genes, like TP53. That’s one of the genes Alexandrov’s team identified as mutated in patients from high pollution areas. In fact, these people had many of the same mutations as those found in people who smoke. That suggests that inhaling tobacco smoke and inhaling air pollution can harm DNA in similar ways, he says.

Alexandrov’s team is now exploring how vaping and smoking marijuana could alter the genome. Those activities fall under risk factors that individuals can change ­— unlike exposure to air pollution.