What Causes More And More Granulomas?

I am 49 years old, female. At the end of 2008, my chest x-rays showed some pulmonary nodules which prompted my doctor to order a CT scan. The scan showed 3 nodules, biggest of which was 6mm. A follow up scan about 5 months later revealed they were calcified granulomas but another 3 were found and too early to determine whether they were benign. So a follow up CT scan was ordered 6 months later and these too were found to be calcified granulomas. It's been 2 and 1/2 years since they first discovered the nodules, and the latest CT show a total of 16 nodules, all of which are calcified except for one (too early to tell). My question is why do I keep getting more and more granulomas?