On the one hand, the harmful gases in smoke cause damage and shortening of the cilia in the bronchial mucosa, which affects the clearing function of the cilia. In addition, smoking leads to hyperplasia and hypertrophy of the submucosal glands, causing increased sputum production.
On the other hand, smoking can indirectly cause increased sputum production by inducing primary diseases such as bronchitis and asthma, so quitting smoking is beneficial in reducing the amount of white sputum.