Reductions in tobacco smoking have led to lower rates of lung cancer in many places. But people who have never smoked still get lung cancer. In fact, globally, their numbers are proportionally on the rise.
Scientists at UC San Diego wanted to learn why.
Working with colleagues at the National Cancer Institute, they found that air pollution is a prime suspect as a cause for lung cancer in people who have never smoked. Surprisingly, their study showed that second-hand smoke is not.
They studied gene mutations in lung cancer tumors that act as signatures to indicate the cause of cancers. One cancer risk they examined was in people, living in cities with strong particulate air pollution.
“In highly polluted places, we’re getting many more mutations in people, and (there are) very strong associations with the pollution likely causing the mutations needed for people to develop cancer,” said Ludmil Alexandrov, UCSD cellular medicine professor and a co-author of the study, published in the scientific journal Nature.
Researchers on Alexandrov's team also studied patients who were exposed to lots of second-hand smoke. Alexandrov said they expected to see strong evidence that passive smoking caused lung cancers.
“There’s more mutations. A bit more mutations in the cancers of passive smokers,” he said. “But it’s a very small elevation. And the specific things we thought that we would see, specific genes being mutated, we really didn’t see.”
Alexandrov said the lung cancers found in the 871 never-smokers they surveyed around the world are elevated among women, especially those in Asian countries. He said researchers now want to do further studies to learn what may be the risk of lung cancer that comes from smoking other things.
“Because we’re seeing the population changing their behavior from smoking tobacco cigarettes to vaping electronic cigarettes or smoking marijuana, and we want to understand the risk,” Alexandrov said.
