My dad grew in a house of 3 chain smokers- he then smoked 2 packs a dayfor25 years himself. he has not smoked for 25 years. is he at risk of lung ca?

Yes: Although it is good that he has stopped smoking but past exposure remains a risk factor. He should consider getting a low-dose CT chest regularly to catch cancer in its early stage. He is also at risk for bladder cancer as well.

Yes he is!: Former smokers remain at risk for lung Cancer even after they stop smoking. However the risk diminishes with time off of smoking. He should get screened for lung Cancer to be sure that he doe snot have the beginings of early lung Cancer. Lung Cancer screening is now approved by various medical organizations.

Yes: Much less than if he were still smoking. There is nothing either of you can do about the cancer risk or the emphysema he probably has. You have and love one another. Thanks for writing

Mild to moderate: The risk is because of his smoking, not the prior exposure. The fact he stopped 25 years ago is to his benefit, but his risk is not minor. He should follow with screening CT scans on a regular basis.