Is my husband infertile?

Patient: My husband and I have been trying to get pregnant for over a year now.. I have one child from a previous relationship and he has one from a previous relationship as well. My husband was a heroin addict for 12 years and has been clean for six years. His child is 9 and conceived at the beginning of his addiction. Could his past addiction be the cause of us not being able to conceive? If so, is there anything we can do to reverse this?