The EMH clearly can hear and see. He doesn't have a sense of taste. Can he smell?
Yes, the Doctor is fully capable of olfactory detection.
In the episode Future's End, Part II, the Doctor smells a tree, as referenced in the linked article.
This is quite a sensible feature for a medical hologram to have, given that the capability exists. Many diseases have notable scents, and it would be useful for an emergency medical hologram to be able to use every conventional method of differentiation during triage.