Wan L. Lam and Stephen Lam from the British Columbia Cancer Agency took samples from the lungs of 24 current and former smokers, as well as from non-smokers who have never smoked. They used these lung samples to create libraries using a technique called serial analysis of gene expression, which helps to identify patterns of gene activity.

The study, published in the journal BMC Genomics, found about one-fifth of the genes in a cell are switched on at any given time but environmental changes such as smoking can result in changes to gene activity. The researchers found some changes that were irreversible and some changes were reversed by quitting smoking tobacco.

The researchers also identified a number of genes not previously associated with smoking that are switched on in active smokers.