I saw an ambulance in our building driveway today
Why were they there?
I don't know, but now I'm worrying about my health; I'm afraid I'll get cancer.
If they were not there for you, there is no need to worry about that right now. You should find out why they were there though.
I'm googling it now and I learned that our section of the building has mold and rats.
Mold and rats aren't good; both can affect your health. You should talk to your landlord about the condition of your home. And also your doctor to see if you've been affected, especially if you have reason to be worried about getting cancer.