Can mould be leaking through pipes cracks/holes?
The pipe connected to the radiator has a deliberate space because it is really hot.
Can air leak through walls that has mold? Don’t want to scare you but just about every breath you take may have a mold or fungus spores, in the Forrest 100%  In  most living spaces.
Can you seal the pipes, I mentioned the radiator but there are special collars made to insulate and seal these, water pipes usually can be foamed to seal them. Make sure you know what you are sealing and use the proper material.