Scientists say the lungs have an almost "magical" ability to return to a healthy state from the smoking-induced changes that can lead to cancer. But that ability only works once a person stops smoking.

The changes smoking causes in the lungs, which raise the risk of cancer, were thought to be permanent and to persist even after a smoker quits.

But a report published in the journal Nature shows that a few lung cells not damaged by smoking later help bring the lungs back to normal. This was seen even in people who quit after smoking a packet of cigarettes a day for 40 years.

Thousands of chemicals in cigarettes alter the DNA of lung cells, slowly turning them from healthy to cancerous. The recent study found that smokers' lung cells change on a massive scale even before cancer is present.

Most cells taken from smokers' airways were found to have been altered by smoking, and some cells showed up to 10,000 genetic changes.

"You can compare these changes to mini time bombs. With the next hit, it may turn into cancer," said a researcher, Dr Kate Gowers.

Even in such cases, however, a small number of cells remain unchanged. How those cells escaped the genetic changes caused by smoking is not clear.

Source: BBC Bangla. First published in Bengali on The Agro News.