This question is for my 60 year old dad. is recurrent pneumonia dangerous? he has it for the second time in 6 months. can this lead to other problems such as cancer or anything that could become serious?

Your dad should see a lung doctor to see if there is a reason for his recurrent pneumonia. It is possible the diagnosis is incorrect-he could have X-ray changes that are due to some other etiology. If he smokes, he definitely needs to quit. His risk of cancer is based on many risk factors. Seeing a lung doctor will help to determine his risk. Good luck to you!